No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Alligator diets in relation to marsh salinity
... At least 34 bird species were reported (Table 3). In four of these studies, birds were present in at least 20% of stomachs (Kellogg 1929, McIlhenny 1935, McNease and Joanen 1977, Elsey et al. 2004. ...
... Common Gallinule (Gallinula galeata) This study, Valentine et al. 1972, McNease and Joanen 1977, Delany 1986, Sloan 1987, Delany et al. 1988, Rice 1994 1 , Barr 1997, Delany et al. 1999, Saalfeld et al. 2011 American Coot (Fulica americana) Kellogg 1929, Valentine et al. 1972, Delany and Abercrombie 1986, Taylor 1986, Wolfe et al. 1987, Delany et al. 1988, Barr 1997 Great-tailed Grackle 2 (Quiscalus mexicanus) Giles and Childs 1949, Chabreck 1971, Valentine et al. 1972, McNease and Joanen 1977, Sloan 1987 Mottled Duck (Anas fulvigula) Kellogg 1929, Valentine et al. 1972, McNease and Joanen 1977, Sloan 1987, Elsey et al. 2004 Anhinga (Anhinga anhinga) Delany 1986, Rice 1994, Delany et al. 1999, Saalfeld et al. 2011 Rail (Clapper, King) (Rallus longirostris, R. elegans) Kellogg 1929, Giles and Childs 1949, Valentine et al. 1972, Wolfe et al. 1987 Cattle Egret (Bubulcus ibis) Delany 1986, Delany et al. 1988 Kellogg 1929 In addition to stomach contents studies and band recoveries, alligators have also been observed depredating birds. Folk et al. (2014) observed alligators preying on Whooping and Sandhill cranes and depredating crane nests in Florida. ...
... Common Gallinule (Gallinula galeata) This study, Valentine et al. 1972, McNease and Joanen 1977, Delany 1986, Sloan 1987, Delany et al. 1988, Rice 1994 1 , Barr 1997, Delany et al. 1999, Saalfeld et al. 2011 American Coot (Fulica americana) Kellogg 1929, Valentine et al. 1972, Delany and Abercrombie 1986, Taylor 1986, Wolfe et al. 1987, Delany et al. 1988, Barr 1997 Great-tailed Grackle 2 (Quiscalus mexicanus) Giles and Childs 1949, Chabreck 1971, Valentine et al. 1972, McNease and Joanen 1977, Sloan 1987 Mottled Duck (Anas fulvigula) Kellogg 1929, Valentine et al. 1972, McNease and Joanen 1977, Sloan 1987, Elsey et al. 2004 Anhinga (Anhinga anhinga) Delany 1986, Rice 1994, Delany et al. 1999, Saalfeld et al. 2011 Rail (Clapper, King) (Rallus longirostris, R. elegans) Kellogg 1929, Giles and Childs 1949, Valentine et al. 1972, Wolfe et al. 1987 Cattle Egret (Bubulcus ibis) Delany 1986, Delany et al. 1988 Kellogg 1929 In addition to stomach contents studies and band recoveries, alligators have also been observed depredating birds. Folk et al. (2014) observed alligators preying on Whooping and Sandhill cranes and depredating crane nests in Florida. ...
American alligators (Alligator mississippiensis) are opportunistic predators that prey upon or scavenge a wide variety of vertebrates and invertebrates. Fish and crustaceans are typically the most frequently encountered items in most diet analyses whereas birds are relatively uncommon in comparison. However, most alligator food habits analyses rely on stomachs collected from alligators legally harvested during short (one month in the fall) hunting seasons. Thus, these analyses may underrepresent the importance of birds because they provide data from a short period during which birds may not be readily available. In this paper we report on the frequency of birds found in a sample of over 500 stomachs collected by Louisiana alligator hunters and review published and unpublished accounts of alligator consumption of birds. In most cases, we could not tell whether the bird was caught and consumed alive or scavenged; however, several reports of direct observation of alligator depredation illustrate that alligators will prey on live birds when available. Considering all sources, we found evidence of alligators consuming at least 40 bird species, including two waterfowl species (Black-bellied Whistling-Duck [Dendrocygna autumnalis] and Blue-winged Teal [Anas discors]) not previously reported as alligator food. Among the most frequently recorded species were waterfowl and wading birds, two groups of birds that may be particularly susceptible to alligator depredation as flightless or naïve juveniles or as flightless adults during summer molt. Because alligator food habit studies typically do not occur during the summer when these groups of birds are breeding and population densities relatively high, their importance in alligator diets may be underestimated.
... In areas where alligators (Alligator mississippiensis) coexist with furbearing animals, commercial trappers perceive serious competition between themselves and these reptiles (personal communication; McNease and Joanen, 1977). Managers are aware that such problems may exist, but avai I able data provide a limited basis for informed decisions. ...
... In general, studies directed toward alligators of less than 1.5 m in length (Chabreck, 1971;Fogarty and Albury, 1968) have found mammals to be absent or unimportant in the diet. Studies which include larger alligators (Giles and Childs, 1949;Valentine et a/., 1972;McNease and Joanen, 1977) indicate that 'Present address: Archbold Biological Station, P.O. Box 2057, Lake Placid, FL 33852. ...
... We found the highest level of alligator predation on mammals ever reported, although Valentine et at. (1972) and McNease and Joanen (1977) also found mammals taken in substantial numbers. This may in part be due to the method of calculating weights, but our frequency of occurrence is also the highest on record. ...
... water bugs (Belostomatidae), whereas in alligators (>1.8 m total length) were saline habitats, the principal prey items described by Giles and Childs (1949), were red swamp crayfish, blue crabs Valentine et a/. (1972), McNease and (Callinectes sapidus), and fiddler crabs Joanen (1977), Taylor (1986), and Wolfe (Uca pugnax). Stomach contents of 36 eta/. ...
... Chabreck (1971) found that crayfish were utilized heavily by immature alligators in freshwater marshes, whereas blue crabs were frequently taken in more saline marshes. Other studies have also found crustaceans to be a major component of immature alligator diets (Giles and Childs 1949, Fogarty and Albury 1968, McNease and Joanen 1977, Delany and Abercrombie 1986. ...
... Size class comparisons revealed no differences in the utilization of prey items between larger juveniles (>0.9 m total length) and smaller individuals. Other alligator food habits studies have shown a progression from invertebrate to vertebrate prey utilization as the animal grows larger (McNease and Joanen 1977, Delany and Abercrombie 1986, Wolfe et a/. 1987. ...
Food habits of juvenile Alligator mississippiensis from an area in SW Louisiana were investigated. Crustaceans (crayfish; blue crabs Callinectes sapidus; grass shrimp Palaemonetes sp.), insects (hemipterans, coleopterans), and small fish (least killifish Heterandria formosa; mosquitofish Gambusia affinis) constituted the majority of prey items taken. -from Authors
... American Alligators (Alligator mississippiensis) have been described as opportunistic predators (McIlhenny 1935;Delany and Abercrombie 1986;Wolfe et al. 1987), considerable variation in food habits exists among size (or reproductive maturity) classes (Delany and Abercrombie 1986;Wolfe et al. 1987), between sexes (Delany et al.1988;Delany et al. 1999), among seasons (Delany et al. 1988), among habitats (Chabreck 1972;McNease and Joanen 1977;Taylor 1986;Delany et al. 1999), and among locations (Kellogg 1929;Chabreck 1972;McNease and Joanen 1977;Delany 1990;Platt et al. 1990). In addition, the importance of various prey items at a single location might vary over time as a result of habitat alterations, disturbance, or management activities (Giles and Childs 1949;Valentine et al. 1972). ...
... American Alligators (Alligator mississippiensis) have been described as opportunistic predators (McIlhenny 1935;Delany and Abercrombie 1986;Wolfe et al. 1987), considerable variation in food habits exists among size (or reproductive maturity) classes (Delany and Abercrombie 1986;Wolfe et al. 1987), between sexes (Delany et al.1988;Delany et al. 1999), among seasons (Delany et al. 1988), among habitats (Chabreck 1972;McNease and Joanen 1977;Taylor 1986;Delany et al. 1999), and among locations (Kellogg 1929;Chabreck 1972;McNease and Joanen 1977;Delany 1990;Platt et al. 1990). In addition, the importance of various prey items at a single location might vary over time as a result of habitat alterations, disturbance, or management activities (Giles and Childs 1949;Valentine et al. 1972). ...
... cit.), a region that encompasses 62% of Louisiana's coastal marsh habitat (Joanen and McNease 1987). Food habits of alligators from southeastern Louisiana have received little attention when compared to those from southwestern Louisiana (Chabreck 1972;Valentine et al. 1972;McNease and Joanen 1977;Wolfe et al. 1987;Platt et al. 1990). In particular, no food habits data have been published for alligators from coastal marsh habitats in the Barataria-Terrebonne region in southeastern Louisiana, where marsh loss rates are greatest (Gagliano et al. 1981;Barras et al. 1994. ...
American Alligators (Alligator mississippiensis) are opportunistic carnivores and scavengers. However, composition of alligator diets often differs geographically, presumably because of geographic variation in food availability. Diet influences alligator body condition, growth, and reproduction because energetic and nutritional content varies among prey items. Therefore, information on geographic, demographic, and temporal variation in alligator food habits is important for monitoring current population status and predicting possible impacts due to habitat alteration or disturbance. This study compares food habits of 448 alligators of three sex-size classes from coastal marshes of southeastern and southwestern Louisiana. Overall, remains of crustaceans were the most frequently encountered prey category, followed by fish, mammals, reptiles, and birds. Stomachs from large males were more likely to contain remains of mammals and reptiles than were stomachs from small males and from females. Stomachs from southwestern Louisiana were more likely to contain remains of fish and reptiles and less likely to contain remains of crustaceans than were stomachs from southeastern Louisiana. Because alligator food habits vary among geographic locations and among sex and size classes, demographic parameters might also vary among alligator populations and also among sex and size classes within populations. The relationship between demographic parameters and food habits in alligators needs more investigation. In addition, because alligators are the top consumer in their trophic chain, they could serve as an indicator species for monitoring responses of coastal systems following habitat loss or disturbances such hurricanes.
... We compared the isotope ratios of C. acutus to those of 2 fully marine reptiles (marine iguanas Amblyrhynchus cristatus and Pacific loggerhead turtles Caretta caretta). We further compared C. acutus to the alligatorid Alligator mississippiensis, an obligate freshwater drinker (Laurén 1985), with similar opportunistic generalist feeding ecology (McNease & Joanen 1977, Thorbjarnarson 1988a) and similar home range requirements (Joanen & McNease 1989, Kushlan & Mazzotti 1989, Cherkiss et al. 2011, in both inland/freshwater and coastal ecosystems. Before presenting our analysis, we offer a brief overview of the isotopic systems we used and what aspects of animal ecology and physiology they record. ...
... Although several gut content studies have been done on coastal LA alligators (e.g. McNease & Joanen 1977, Wolfe et al. 1987, Elsey et al. 1992, comparisons of our isotopic data to the gut content analyses are not straightforward due to gut contents typically being binned by large phylogenetic rather than ecological groups (e.g. 'fish' may include freshwater and marine species). ...
... Gut content studies are wide ranging with respect to preferred prey items in their reported results. Elsey et al. (1992) and some surveys of McNease & Joanen (1977) would fall within our estimate's error envelope of percent reliance on marine prey (~65−70% and ~60%, respectively); other surveys from McNease & Joanen (1977) and Wolfe et al. (1987) would indicate much heavier reliance on aquatic mammals (specifically nutria) than marine fish or crustaceans. ...
Alligators and crocodiles differ in their physiological capacity to live in saline waters.
Crocodiles can tolerate high-salinity water, at least for limited timeframes, whereas alligators and
their close relatives cannot. Experiments have placed different crocodylians in various water
salinities to document physiological responses, but no study has estimated the extent to which natural
populations of crocodylids can live independent of fresh water. Here we estimated marine
food and perhaps seawater contributions to a population of American crocodile Crocodylus acutus
in southernmost Florida, USA. We evaluated the use of carbon, oxygen, and strontium isotopes as
tracers of marine versus terrestrial sources. We compared C. acutus isotopic values to those of
marine reptiles (marine iguanas and Pacific loggerhead turtles) and to American alligators, which
require fresh water. We found that freshwater reptiles can be discriminated from those that drink
seawater (or survive on metabolic and prey-included water in saline habitats) based on the magnitude
of population-level oxygen isotope variation in bioapatite, whereas mean carbon isotope
values discriminate between marine versus terrestrial food consumption. We used a 2 endmember
(seawater and fresh water) mixing model to calculate percentage of marine resources
used by C. acutus. Results indicate that adult C. acutus in southern Florida use marine food about
65% of the time and seawater or water gleaned from marine food about 80% of the time. This suggests
that behavioral osmoregulatory techniques (i.e. seeking fresh water specifically for drinking,
as suggested by other researchers) may not be necessary and that C. acutus is capable of being
largely ecologically independent of fresh water.
... To answer these questions we reviewed the literature on crocodilian diet, foraging ecology, digestive physiology and movement patterns. In addition to our literature review, we revisited a Louisiana Department of Wildlife and Fisheries (LDWF) dataset used in an earlier study (McNease & Joanen, 1977) that consisted of stomach contents recovered from 314 American alligators (Alligator mississippiensis) harvested during [1972][1973] (Taylor, Webb & Magnusson, 1978); J. C. Nifong also obtained stomach contents from a road-killed alligator and another that was euthanized after sustaining injuries in an aggressive intraspecific encounter. ...
... Second, if fruit consumption is infrequent, the apparent absence of fruit in the diet may simply be a consequence of the small number of animals sampled in some studies. Third and perhaps most importantly, because it is assumed that fruits make little energetic contribution to crocodilian diets (Neill, 1971;Coulson & Hernandez, 1983), those found in stomach contents or feces are considered anomalous and included in general categories such as 'nonfood items' (Platt et al., 2006a), 'vegetation' (Thorbjarnarson, 1993b) or 'plant material' (McNease & Joanen, 1977), rather than being mentioned specifically. For example, McNease & Joanen (1977) stated only that 'plant material' occurred in 84.3% of 314 Al. mississippiensis stomachs examined, yet we found fruits or seeds of at least 16 species listed on the original data sheets (Table 1). ...
... Third and perhaps most importantly, because it is assumed that fruits make little energetic contribution to crocodilian diets (Neill, 1971;Coulson & Hernandez, 1983), those found in stomach contents or feces are considered anomalous and included in general categories such as 'nonfood items' (Platt et al., 2006a), 'vegetation' (Thorbjarnarson, 1993b) or 'plant material' (McNease & Joanen, 1977), rather than being mentioned specifically. For example, McNease & Joanen (1977) stated only that 'plant material' occurred in 84.3% of 314 Al. mississippiensis stomachs examined, yet we found fruits or seeds of at least 16 species listed on the original data sheets (Table 1). Because seeds and fruits are often lumped into more inclusive categories, it is difficult to assess the prevalence of frugivory in most dietary studies. ...
Saurochory (seed dispersal by reptiles) among crocodilians has largely been ignored, probably because these reptiles are generally assumed to be obligate carnivores incapable of digesting vegetable proteins and polysaccharides. Herein we review the literature on crocodilian diet, foraging ecology, digestive physiology and movement patterns, and provide additional empirical data from recent dietary studies of Alligator mississippiensis. We found evidence of frugivory in 13 of 18 (72.2%) species for which dietary information was available, indicating this behavior is widespread among the Crocodylia. Thirty‐four families and 46 genera of plants were consumed by crocodilians. Fruit types consumed by crocodilians varied widely; over half (52.1%) were fleshy fruits. Some fruits are consumed as gastroliths or ingested incidental to prey capture; however, there is little doubt that on occasion, fruit is deliberately consumed, often in large quantities. Sensory cues involved in crocodilian frugivory are poorly understood, although airborne and waterborne cues as well as surface disturbances seem important. Crocodilians likely accrue nutritional benefits from frugivory and there are no a priori reasons to assume otherwise. Ingested seeds are regurgitated, retained in the stomach for indefinite and often lengthy periods, or passed through the digestive tract and excreted in feces. Chemical and mechanical scarification of seeds probably occurs in the stomach, but what effects these processes have on seed viability remain unknown. Because crocodilians have large territories and undertake lengthy movements, seeds are likely transported well beyond the parent plant before being voided. Little is known about the ultimate fate of seeds ingested by crocodilians; however, deposition sites could prove suitable for seed germination. Although there is no evidence for a crocodilian‐specific dispersal syndrome similar to that described for other reptiles, our review strongly suggests that crocodilians function as effective agents of seed dispersal. Crocodilian saurochory offers a fertile ground for future research.
... Opportunistic predators, alligators exhibit a varied diet, and are adept at exploiting local prey resources that encompass a wide diversity of sizes and taxa, ranging from small insects and crustaceans to large vertebrates (Chabreck 1971, Delany and Abercrombie 1986, Rice 2004, Valentine et al. 1972). Alligator diets vary by speci c geographic location, habitat, prey encountered, and prey vulnerability and size, as well as by alligator size (Barr 1994Barr , 1997; Delany and Abercrombie 1986; Dodson 1975; McNease and Joanen 1977; Platt et al. 1990; Wolfe et al. 1987). For example, smaller (juvenile) alligators typically consume invertebrates and small sh (Barr 1994, Chabreck 1971, Delany 1990, Dodson 1975, Fogarty and Albury 1967, Giles and Childs 1949, Platt et al. 1990, Valentine et al. 1972), whereas larger adults mainly consume vertebrates (Delany and Abercrombie 1986, Giles and Childs 1949, McNease and Joanen 1977, Shoop and Ruckdeschel 1990). ...
... Alligator diets vary by speci c geographic location, habitat, prey encountered, and prey vulnerability and size, as well as by alligator size (Barr 1994Barr , 1997; Delany and Abercrombie 1986; Dodson 1975; McNease and Joanen 1977; Platt et al. 1990; Wolfe et al. 1987). For example, smaller (juvenile) alligators typically consume invertebrates and small sh (Barr 1994, Chabreck 1971, Delany 1990, Dodson 1975, Fogarty and Albury 1967, Giles and Childs 1949, Platt et al. 1990, Valentine et al. 1972), whereas larger adults mainly consume vertebrates (Delany and Abercrombie 1986, Giles and Childs 1949, McNease and Joanen 1977, Shoop and Ruckdeschel 1990). Alligator diet studies have been concentrated in Louisiana (Platt et al. 1990, Taylor 1986, Valentine et al. 1972, Wolfe et al. 1987), north central and central Florida (Delany 1990, Delany and Abercrombie 1986, Delany et al. 1999, Rice 2004), and southern Florida (Barr 1994Barr , 1997 Fogarty and Albury 1967). ...
... As cannibalism was only documented at Dam B WMA after the drawdown, it likely resulted when low water levels and subsequent expansion of exotic invasive plant species led to unusually high concentrations of alligators of all size classes. Despite generally being opportunistic, alligators appear to shift diets from invertebrates to vertebrates as they increase in size, a phenomenon documented in many studies (Barr 1997, Chabreck 1971, Delany and Abercrombie 1986, Delany et al. 1999, Giles and Childs 1949, McIlhenny 1935, McNease and Joanen 1977, Taylor 1986, Valentine et al. 1972, Wolfe et al. 1987). Speci cally, within this study, mammals and amphibians/reptiles occurred most often in diets of larger alligators (>183.0 ...
American Alligator (Alligator mississippiensis) food habit data are important when establishing management strategies, as diet can directly in uence growth rates, body condition, behavior, and reproduction. Diets of American Alligators are hypoth-esized to vary among habitats as well as geographically; however, few diet studies have been conducted outside of Florida and Louisiana. To address this information gap, 62 diet samples were obtained from alligators ranging in size from 94.7 cm to 386.0 cm (total length) from June 2006–September 2008 in inland freshwater wetlands in East Texas. A total of 33 different prey items (comprising 670 individual prey items) and 1 parasite were identi ed. Irrespective of size class, sex, and study site, >85% of individual prey items were invertebrates. Nearly all diet samples contained some sort of organic by-catch and/or non-food items (i.e., woody debris, aquatic plants, seeds, rocks, shing tackle, etc.). Although alligator diets were similar between sexes, non-breeding (<183.0 cm in total length) alligators consumed more invertebrate prey items by biomass and percent occurrence than breeding-size alligators. In general, alligators forage opportunistically; therefore, most habitat-based, local, or geographic variability in food habits among popu-lations are most likely in uenced by food availability. As such, regional differences in food availability likely result in geographic variability in life-history characteristics such as growth rates and condition, important factors to consider when establishing manage-ment strategies.
... Most studies on crocodilians have had broad aims. There are many anecdotal lists of food, often from small samples in restricted areas, and detailed quantification of larger samples for Alligator mississippiensis (Kellogg 1929;Giles and Childs 1949;O'Neill 1949;Fogarty and Albury 1968;Chabreck 1971;Valentine et al. 1972;McNease and Joanen 1977), Caiman crocodilus crocodilus (Staton and Dixon 1975;Gorzula 1978), Crocodylus niloticus (Welman and Worthington 1943;Hippel 1946;Corbet 1959Corbet , 1960Cott 1961;Graham 1968), and Crocodylusporosus (Taylor 1979). ...
... It is thus affected by the energetic value of the food, the energy expenditure in gaining and assimilating the food, and the proportion of the population utilizing that food. Estimates of importance based on stomach contents usually assume equivalent calorific value and energy expenditure, and as indices of importance use: the proportion of animals utilizing a particular food source (occurrence method); the percentage of the total number of prey items made up by a particular taxon, or sometimes the proportion of the total food volume or weight made up by a particular prey (composition method); the proportion of animals in which a particular food is dominant, as indicated by approximate volumes in the stomach (dominance method); more complex analyses of dominance, in which points are assigned to each food depending on its estimated relative volume in the stomach (points method); analyses based on the ranking of food items on the basis of their approximate volumes in the stomach (ranking method) (Hynes 1950;Pollard 1973;McNease and Joanen 1977;Windell and Bowen 1978). These methods are sometimes combined; for example, Pinkas et al. (1971) used occurrence plus both numerical and volumetric measures of composition to form an index for tuna. ...
... The taxonomic range of prey eaten by C. johnstoni and other crocodilians is extensive (for example, see lists in : Corbet 1960;Cott 1961;Fogarty and Albury 1968;Graham 1968;Valentine et al. 1972;Staton and Dixon 1975;McNease and Joanen 1977;Gorzula 1978 andTaylor 1979), and includes invertebrates and vertebrates from both terrestrial and aquatic environs. In general terms, insects and crustaceans appear the most common prey of smaller crocodilians, fish being eaten by crocodiles from intermediate to large size. ...
The stomach contents of 153 C. johnstoni were examined by a modification of the method for stomach contents removal described by Taylor et al. (1978). Prey are analysed on the basis of taxonomy, although more emphasis is placed on prey equivalents, using a concept termed 'target size'. The relative importance of different taxa and prey equivalents is determined by a number of methods, and a ranking method is preferred. The most important prey are aquatic and terrestrial insects, fish and crustaceans. The most important sized organisms are target size 5, animals presenting a maximum area of 1.0-4.0 cm2. With regard to size of prey eaten, three size groups of C. johnstoni (16-25, 26-55 and 56-129 cm snout-vent length) were homogeneous within themselves but were significantly different from each other. With increased body size there was a significant increase in the proportion of aquatic prey eaten. Secondary ingestion did not appear a major bias. C. johnstoni ate appreciably more during the wet season than during the dry season, although seasonal comparisons were restricted due to the samples not coming from the same pools. Vegetation was found in 39.9% of crocodile stomachs, and its presence varied with season but not with crocodile size. Stomach parasites were present in 43.8% of animals, and the number of infected crocodiles varied with season and site. Stones were present in 88.2% of crocodiles; however, when compared with those of C. niloticus the stone loads were relatively small. Most data indicate that C. johnstoni is very much an opportunistic predator at the water's edge, which feeds primarily on small aquatic prey, although it may also take substantial numbers of terrestrial prey organisms. During the wet season there is a major shift in the importance of different prey taxa eaten, although the importance of prey equivalents remains largely unchanged.
... As apex predators, alligators prey on a variety of taxa including fish, mammals, amphibians, and other reptiles (Delany and Abercrombie, 1986;Elsey et al., 1992;Gabrey, 2010). Although snakes in general do not constitute a large proportion of the alligator's diet, both venomous (e.g., Cottonmouth, Agkistrodon piscivorus, Lacepede; hereafter 'Cottonmouth') and nonvenomous species are known prey (Valentine et al., 1972;McNease and Joanen, 1977;Wolfe et al., 1987;Saalfeld et al., 2011). Consequently, possible adaptations that enable alligators to prevent envenomation or counteract venom components following envenomation is a continued source of intrigue that requires further study. ...
... Partial resistance to Pit Viper venom may be a consequence of the fact that the American alligator is an opportunistic feeder. While previous studies reliably illustrate predation of Pit Vipers by alligators, other food items (e.g., crustaceans and fish) are often more readily consumed (Valentine et al., 1972;McNease and Joanen, 1977;Wolfe et al., 1987;Saalfeld et al., 2011). Inhibitors of SVMPs present in alligator sera may provide alligators with sufficient protection (i.e., enable survival) following possible Pit Viper envenomation during predation to prevent selection for hemolytic inhibitors (e.g., Perez and Sanchez, 1999;Arbuckle et al., 2017;Goetz et al., 2019). ...
American Alligators (Alligator mississippiensis) have been shown to consume pitviper snakes, apparently with no ill effects. Previous work failed to detect differences in how alligators handle venomous and nonvenomous snake prey indicating alligators may possess a physiological resistance to venom. In this study, we tested the ability of alligator blood sera to inhibit the activity of two of the primary toxins in Eastern Copperhead (Agkistrodon contortrix) venom, including hemolytic toxins and snake venom metalloproteinases (SVMP). Specifically, we compared relative venom activity following incubation with alligator sera to a venom-only control as well as venom incubated with serum from a species lacking venom resistance (House mouse; Mus musculus). In comparison to controls, alligator sera significantly reduced SVMP activity (p < 0.0001). There was, however, no effect of alligator sera on hemolytic activity (p = 0.822). Interestingly, we detected individual variation with respect to hemolytic activity such that inhibition was positively related with both alligator length (p = 0.015) and condition (p = 0.013). Our results provide evidence that alligator serum is capable of inhibiting at least one of the primary toxins present in pitviper venom.
... Although the selection of 10% plant matter in a diet is arbitrary, it allows for animals that rarely or accidentally consume plant matter to still be considered carnivores. For instance, it is well documented that crocodylians consume some plant and fruit material, but this definition still classifies them as carnivores, a dietary assignment that is not in debate (McNease and Joanen, 1977;Delany and Abercrombie, 1986;Magnusson et al., 1987;Tucker et al., 1996;Pauwels et al., 2003;Pauwels et al., 2007;Saalfeld et al., 2011;Laverty and Dobson, 2013). Omnivorous diets include a percentage of vegetation varying between 10% and 90%, and therefore, herbivores are animals where plants make up over 90% of the diet (Cooper and Vitt, 2002). ...
... This result gives confidence that the OPCR-analysis can detect phenotypic differences in tooth complexity even in closely related species. Additionally, many crocodylians (e.g., Alligator mississippiensis, Caiman crocodilus, Crocodylus moreletii, Osteolaemus tetraspis, Paleosuchus trigonatus) have mixed diets (McNease and Joanen, 1977;Delany and Abercrombie, 1986;Tucker et al., 1996;Pauwels et al., 2003;Pauwels et al., 2007;Saalfeld et al., 2011;Laverty and Dobson, 2013), and this may be reflected in their somewhat high complexity, 5.23-6.8 PPT at 25 RPT. ...
Living saurian reptiles exhibit a wide range of diets, from carnivores to strict herbivores. Previous research suggests that the tooth shape in some lizard clades correlates with diet, but this has not been tested using quantitative methods. I investigated the relationship between phenotypic tooth complexity and diet in living reptiles by examining the entire dentary tooth row in over 80 specimens comprising all major dentigerous saurian clades. I quantified dental complexity using orientation patch count rotated (OPCR), which discriminates diet in living and extinct mammals, where OPCR-values increase with the proportion of dietary plant matter. OPCR was calculated from high-resolution CT-scans, and I standardized OPCR-values by the total number of teeth to account for differences in tooth count across taxa. In contrast with extant mammals, there appears to be greater overlap in tooth complexity values across dietary groups because multicusped teeth characterize herbivores, omnivores, and insectivores, and because herbivorous skinks have relatively simple teeth. In particular, insectivorous lizards have dental complexities that are very similar to omnivores. Regardless, OPCR-values for animals that consume significant amounts of plant material are higher than those of carnivores, with herbivores having the highest average dental complexity. These results suggest reptilian tooth complexity is related to diet, similar to extinct and extant mammals, although phylogenetic history also plays a measurable role in dental complexity. This has implications for extinct amniotes that display a dramatic range of tooth morphologies, many with no modern analogs, which inhibits detailed dietary reconstructions. These data demonstrate that OPCR, when combined with additional morphological data, has the potential to be used to reconstruct the diet of extinct amniotes. J. Morphol., 2017.
... Percent occurrence is an appropriate metric when individual prey items cannot be quantified (Rosenberg and Cooper, 1990). While fresh prey mass is occasionally used in analyses of crocodilian diet, studies comparing this variable to percent (or frequency) of occurrence note a general agreement between the two measures (McNease and Joanen, 1977;Elsey et al., 1992;Thorbjarnarson, 1993). Because bone, flesh, and mollusk shell are digested rapidly, whereas chitinous remains, fish scales, hair, and feathers are more persistent, differential digestion of prey types is a common source of bias in studies of crocodilian diet (Jackson et al., 1974;Garnett, 1985a;Magnusson et al., 1987). ...
... Presumably our results in part reflect the overall availability of crustaceans in marine habitats. Similarly, the percent occurrence of crustaceans in the diet of American Alligators (Alligator mississippiensis) inhabiting coastal marshes was positively related to water salinity, with the highest level of consumption found in brackish habitats (McNease and Joanen, 1977). Crabs also contain large amounts of calcium and phosphorous (Webb et al., 1991), two minerals involved in a wide range of physiological and biological processes (Robbins, 1983). ...
We studied diet and size-related dietary patterns among American Crocodiles (Crocodylus acutus) in marine habitats of coastal Belize (1996-1997). Prey items recovered from crocodile (N = 97) stomach contents included insects, mollusks, crustaceans, fish, amphibians, reptiles, birds, and mammals. Based on an overlapping group analysis of percent occurrence, we concluded that hatchlings and small juveniles feed largely on insects and crustaceans, larger juveniles broaden their diet to include fish and nonfish vertebrates, subadults consume increasing amounts of crustaceans with lesser amounts of insects and nonfish vertebrates, and adults subsist primarily on marine crustaceans. Dietary diversity was uniformly low across all size classes but greatest among small and large juveniles. Conversely, hatchlings, subadults, and adults had the most specialized (least diverse) diet owing to reliance upon a limited selection of prey, largely insects (hatchlings) or crustaceans (subadults and adults). Dietary overlap was greatest between adjacent size classes and lowest between the largest and smallest size classes. The high prevalence of freshly ingested prey among all size classes indicates frequent, regular feeding by C. acutus in coastal habitats, perhaps driven by the relatively small size of frequently consumed prey such as crabs. Because crabs have a blood salt content equivalent to the external medium and comprise a large portion of the diet, these prey likely impose a high osmoregulatory burden on C. acutus inhabiting hyperosmotic coastal environments. Contrary to earlier assertions that salt glands in C. acutus lack the excretory capacity to balance salt and water, we suggest populations in coastal Belize rely on these glands in addition to behavioral strategies to maintain osmotic homeostasis.
... The magnitude and influence of cannibalism in crocodilian populations is difficult to assess (Cott, 1961;Messel and Vorlicek, 1986;Neill, 1971;Richards and Wasilewski, 2003). The occurrence of American Alligator (Alli-gator mississippiensis) remains and marking tags in alligator stomachs may evince intraspecific predation (Delany and Abercrombie, 1986;Rootes and Chabreck, 1993), consumption as carrion (Giles and Childs, 1949), ingestion after agonistic encounters (Valentine et al., 1972), or oophagy after nest opening (McNease and Joanen, 1977). Cannibalism among American Alligator populations may be demographically important. ...
... The absence of alligator remains (other than tags) in our sample and their infrequency (,1% occurrence) in other studies (Barr, 1997;Delany and Abercrombie 1986;Delany et al., 1999;McNease and Joanen, 1977;Valentine et al., 1972) may not accurately reflect the incidence of cannibalism. Alligator digestion of prey is rapid (Barr, 1997;Delany and Abercrombie, 1986), and compared with other prey taxa (especially turtles and mammals), alligators may be underrepresented in stomach contents. ...
Mortality of juvenile (<122 cm total length; TL) American Alligators (Alligator mississippiensis) attributed to cannibalism on Orange Lake, Florida was examined. Alligator web tags used in markrecapture studies were found in 12% of 267 stomachs sampled from alligators >168 cm TL. Captive alligators retained 76% of force-fed tags during a 588-d tag-retention trial. Models relating the probability of tag recovery to the annual probabilities of juvenile survival, cannibalism, tag retention, adult survival, and adult harvest suggested that cannibalism may on average remove 6-7% of the juvenile alligator population annually. Vulnerability continued to 140 cm TL (age 6-8 yr). Cannibalism of juveniles may serve to regulate the alligator population on Orange Lake. Alligator cannibalism may vary widely among populations, depending on demography and environmental conditions. The role and importance of cannibalism in alligator population dynamics should be more fully assessed and environmental and population factors that influence cannibalism identified to better evaluate management programs.
... The magnitude and influence of cannibalism in crocodilian populations is difficult to assess (Cott, 1961;Messel and Vorlicek, 1986;Neill, 1971;Richards and Wasilewski, 2003). The occurrence of American Alligator (Alli-gator mississippiensis) remains and marking tags in alligator stomachs may evince intraspecific predation (Delany and Abercrombie, 1986;Rootes and Chabreck, 1993), consumption as carrion (Giles and Childs, 1949), ingestion after agonistic encounters (Valentine et al., 1972), or oophagy after nest opening (McNease and Joanen, 1977). Cannibalism among American Alligator populations may be demographically important. ...
... The absence of alligator remains (other than tags) in our sample and their infrequency (,1% occurrence) in other studies (Barr, 1997;Delany and Abercrombie 1986;Delany et al., 1999;McNease and Joanen, 1977;Valentine et al., 1972) may not accurately reflect the incidence of cannibalism. Alligator digestion of prey is rapid (Barr, 1997;Delany and Abercrombie, 1986), and compared with other prey taxa (especially turtles and mammals), alligators may be underrepresented in stomach contents. ...
Mortality of juvenile (,122 cm total length; TL) American Alligators (Alligator mississip-piensis) attributed to cannibalism on Orange Lake, Florida was examined. Alligator web tags used in mark– recapture studies were found in 12% of 267 stomachs sampled from alligators $168 cm TL. Captive alligators retained 76% of force-fed tags during a 588-d tag-retention trial. Models relating the probability of tag recovery to the annual probabilities of juvenile survival, cannibalism, tag retention, adult survival, and adult harvest suggested that cannibalism may on average remove 6–7% of the juvenile alligator population annually. Vulnerability continued to 140 cm TL (age 6–8 yr). Cannibalism of juveniles may serve to regulate the alligator population on Orange Lake. Alligator cannibalism may vary widely among populations, depending on demography and environmental conditions. The role and importance of cannibalism in alligator population dynamics should be more fully assessed and environmental and population factors that influence cannibalism identified to better evaluate management programs. CANNIBALISM occurs among a wide range of taxa and can have important ecological implications (Elgar and Crespi, 1992). Con-sumption of conspecifics can sustain a popu-lation by providing an alternative food if other sources are scarce, remove potential compet-itors, and serve to regulate population size and age structure (Dong and Polis, 1992; Fox, 1975; Polis, 1981; van den Bosch et al., 1988). Although usually considered facultative and beneficial at the individual predator and population levels, cannibalistic behavior has some implicit costs. Cannibals may sustain injury during predation, lose inclusive fitness if they consume relatives, and risk increased exposure to pathogens and parasites (Dong and Polis, 1992; Fox, 1975; Polis, 1981). Cannibalism appears to occur opportunisti-cally during predatory behavior of reptiles (Polis and Myers, 1985) and may be density dependent (Mitchell, 1986). The magnitude and influence of cannibal-ism in crocodilian populations is difficult to assess (Cott, 1961; Messel and Vorlicek, 1986; Neill, 1971; Richards and Wasilewski, 2003). The occurrence of American Alligator (Alli-gator mississippiensis) remains and marking tags in alligator stomachs may evince intra-specific predation (Delany and Abercrombie, 1986; Rootes and Chabreck, 1993), consump-tion as carrion (Giles and Childs, 1949), ingestion after agonistic encounters (Valentine et al., 1972), or oophagy after nest opening (McNease and Joanen, 1977). Cannibalism among American Alligator populations may be demographically important. For example, Nichols et al. (1976a) predicted annual mortality rates of 2–6% due to cannibalism among alligators in Louisiana, and Rootes and Chabreck (1993) estimated that cannibalism accounted for $50% of the total annual mortality of alligators on their study area in Louisiana. Cannibalism was suspected as a cause of some mortality of juvenile (,122 cm total length; TL) alligators on Orange Lake, Flor-ida, USA (Woodward et al., 1987). Our objective in this study was to estimate the rate of cannibalism among American Alliga-tors on Orange Lake, Florida by analyzing the recovery probabilities of marking tags from alligator stomachs sampled during harvests.
... American Alligators (Alligator mississippiensis Daudin, 1802) are ubiquitous top predators in the southeastern US that have been studied using SCA (Chabreck, 1971;Valentine et al., 1972;McNease and Joanen, 1977;Delany and Abercrombie, 1986;Barr, 1997;Rice, 2004;Gabrey, 2010). Most studies, however, involved sacrificing individuals (i.e., Chabreck, 1971;Valentine et al., 1972;McNease and Joanen, 1977;Delany and Abercrombie, 1986;Gabrey, 2010). ...
... American Alligators (Alligator mississippiensis Daudin, 1802) are ubiquitous top predators in the southeastern US that have been studied using SCA (Chabreck, 1971;Valentine et al., 1972;McNease and Joanen, 1977;Delany and Abercrombie, 1986;Barr, 1997;Rice, 2004;Gabrey, 2010). Most studies, however, involved sacrificing individuals (i.e., Chabreck, 1971;Valentine et al., 1972;McNease and Joanen, 1977;Delany and Abercrombie, 1986;Gabrey, 2010). Fitzgerald (1989) evaluated three different crocodilian stomach flushing techniques. ...
Stomach contents analysis (SCA) provides a snap-shot observation of a consumer's diet. Interpretation of SCA data can be complicated by many factors, including variation in gastric residence times and digestion rates among prey taxa. Although some SCA methods are reported to efficiently remove all stomach contents, the effectiveness of these techniques has rarely been tested for large irregular shaped prey with hard exoskeletons. We used a controlled feeding trial to estimate gastric residency time and decomposition rate of a large crustacean prey item, the Blue Crab (Callinectes sapidus), which is consumed by American Alligators (Alligator mississippiensis), an abundant apex predator in coastal habitats of the southeastern United States. The decomposition rate of C. sapidus in the stomachs of A. mississippiensis followed a predictable pattern, and some crab pieces remained in stomachs for at least 14 days. We also found that certain portions of C. sapidus were prone to becoming caught within the stomach or esophagus, meaning not all crab parts are consistently recovered using gastric lavage techniques. However, because the state of decomposition of crabs was predictable, it is possible to estimate time since consumption for crabs recovered from wild alligators. This information, coupled with a detailed understanding of crab distributions and alligator movement tactics could help elucidate patterns of cross-ecosystem foraging by the American Alligator in coastal habitats.
... (GILES & CHILDS 1949; McNEASE & ] OANEN 1977) and, at least occasionally, ingests carrion (VALENTINE et al. 1972; McNEASE & ]OANEN 1977). Our study provides informati on on the natural feeding behavior of alligators insofar as it sugges ts their use of chemoreception in locating carrion and injured prey. ...
... Alligators do not ordinarily consume horses, although they may attack them (KELLOG G 1929). Stomach-content analyses indicate that alligators occasionally consume raccoons (GILES & CHILDS 1949; McNEASE & ]OANEN 1977). Horse meat was p resented to alligators duri ng fo ur overnight trials conducted over 10 d. ...
American alligators (Alligator mississippiensis) were offered raw meat or animal carcasses under water or on land in experiments where only chemoreception could be used to discriminate between these and control materials. Alligators also were presented with aqueous extracts and airborne chemicals from meat. Juvenile alligators, tested in indoor tanks, opened more cheesecloth packets containing meat than control packets when these materials were placed under water and on platforms above the water surface. Adult alligators, tested in outdoor semi-natural enclosures, removed more cheesecloth-wrapped meat presented under water, and more of both meat and raccoon (Procyon lotor) carcasses placed under perforated baskets on land, than control materials. Juvenile alligators, tested in tanks partially filled with water, exhibited more lateral head movements and mouth-openings to an aqueous beef extract than to water alone. Juvenile alligators, tested in an olfactometer, exhibited more gular pumps to airborne chemicals from beef than to distilled water. These experiments indicate that alligators may use chemical cues to locate food both on land and under water, and that they detect both water- and airborne chemicals from meat.
... Alligators are carnivorous so it is highly unlikely that they would consume vegetable rodenticide baits placed for nutria; hence, no primary hazard is expected. However, because alligators consume nutria as part of their diet (Elsey et al. 1992;McNease and Joanen 1977;Valentine et al. 1972), a secondary hazard may exist. ...
... The area is important because alligator food habits vary by marsh type. In freshwater marshes (more inland), the frequency of occurrence of nutria in alligator stomachs was 64%; this dropped to 42% in intermediate salt-water marshes, and dropped even further (23%) in more coastal, brackish marshes (McNease and Joanen 1977). Crustaceans and fish become more important in the alligator diet as one moves southward to the coast where the brackish marshes are located (Elsey et al. 1992). ...
Nutria, Myocastor coypus, populations must be reduced when they cause substantial wetland damage. Control can include the rodenticide zinc phosphide, but the potential impacts to American alligators, Alligator mississippiensis, must be assessed. The mean amount of zinc phosphide per nutria found in nutria carcasses was 50 mg. Risk assessment determined that a conservative estimate for maximum exposure would be 173 mg zinc phosphide for a 28 kg alligator, or 6.2 mg/kg. Probit analysis found an LD(50) for alligators of 28 mg/kg. Our studies suggest that the use of zinc phosphide to manage nutria populations would pose only a small risk to alligators.
... As "true carnivores" farmed crocodilians are fed a variety of meats which presents several problems to the crocodilians captive breeding, including availability, transportation, storage, handling, and a lack of control over nutrition (McNease & Joanen, 1977;. Food formulation and elaboration for these animals are complicated by several nutritional peculiarities that have been attributed to them. ...
A specific diet for broad‐snouted caiman, Caiman latirostris has not been designed despite the value of farm‐raised caiman as an aquaculture product. To fill this gap, the objectives of this study were to evaluate the performance dietary replacement of ground chicken carcasses by of soybean meal (SM) as diet complement for C. latirostris . We conducted a 3‐month growth trial to determine effects of graded levels of dietary SM on caiman growth as measured by increase in body length, body weight gain, food consumption (FC) and food conversion rate (FCR). Forty‐eight hatchling caimans were fed with diets, composed primarily of practical feed ingredients, with 0, 25, or 40% dietary SM. Diets were fed three times per week for 90 days under temperature controlled. Body lengths and body weights were measured at 30‐day intervals, and FC samples were taken between the 31–60‐day interval. The results of this study indicate that the inclusion of SM in the diet of C. latirostris at levels of 25% increases in body length, body weight gain, FC and improve the FCR indicated that a concentration of 25% dietary SM (as fed) was adequate for growth of caimans under the conditions of this study. Results suggest that SM have a real nutritional contribution in the diet of broad‐snouted caiman and can be used as an ingredient of the diet of the crocodilians raised in captivity, reducing production costs for sustainable use and conservation programs of this species.
... Predator abundance Valentine et al., 1972McNease and Joanen, 1977Stutzenbaker, 1988Elsey et al., 2004Carethers, 2011Rigby and Haukos, 2012 Variation in precipitation Stutzenbaker, 1988Wilson, 2007Bielefeld et al., 2010 Habitat loss, degradation, or change Chabreck and Linscombe, 1982Moulton et al., 1997Wilson, 2007Bielefeld et al., 2010 Lead Exposure Stutzenbaker, 1988Merchant et al., 1991Merendino et al., 2005McDowell et al., 2015Hybridization Stutzenbaker, 1988Sea-Level Rise Leatherman, 1984Park et al., 1986Michener et al., 1997Twilley et al., 2001Bindoff et al., 2007Meehl et al., 2007Twilley, 2007Day and Templet, 2008Urbanization Stutzenbaker, 1988Wilson, 2007Haukos, 2012Moon, 2014 Davis 2012;Wehland, 2012). A second set of transects were established parallel to but 10 km west of each perpendicular oriented transect (set 2, Davis 2012; Wehland, 2012). ...
Coastal wetlands along the Gulf of Mexico support a wide diversity of wildlife, are important nurseries for sport and commercial fisheries, provide erosion and flood control, and serve many other ecological functions and services. These marshes have been declining in area and degrading at alarming rates since the 1930s. Effective conservation planning is vital to protect these ecosystems, but decision makers often lack knowledge of expected future conditions to strategically target conservation actions. To address this issue, we focus on a species of conservation concern, the mottled duck (Anas fulvigula), that resides year-round in the coastal marshes of the Gulf of Mexico. We used location data collected from radiomarked hen mottled ducks from 2006 to 2011 to create an ensemble model of habitat selection for 2010. We then projected future habitat states using models of sea-level rise and human development. By combining future predictions with our ensemble model, we predict future habitat for mottled ducks through 2100, in 20-year time steps beginning with 2020. Sea-level rise models predicted reductions in coastal marsh habitats and our ensemble model predict corresponding declines in overall habitat quantity and quality for mottled ducks, with the largest rate of habitat loss predicted within the Chenier Plain of Louisiana, USA at 71%. In some areas, particularly the Texas Mid-Coast, USA, future urbanization and human development is expected to reduce the ability of wetland habitat to migrate inland with rising sea-levels. Our results also highlight areas of coastal marsh particularly vulnerable to sea-level rise; and conversely, identify areas most likely to persist into the future that could be targeted for habitat conservation to help mottled ducks persist on the landscape.
... In freshwater systems, A. mississippiensis have been documented to prey upon several freshwater turtle species within the genera Apalone, Deirochelys, Kinosternon, Pseudemys, Sternotherus, and Trachemys (Barr 1997;Delany and Abercrombie 1986;Gabrey 2010;McNease and Joanen 1977;Wolfe et al. 1987). In three Florida lakes, Delany and Abercrombie (1986) found turtles to be the most common prey type recovered from the stomachs of adult male alligators greater than 3.0 m total length. ...
... The predatory interactions and food habits of Alligator mississippiensis Daudin (American Alligator) have been thoroughly studied across multiple populations inhabiting various inland freshwater ecosystems (i.e., lakes, rivers, and marshes) throughout their native range in the southeastern coastal plain of the United States (e.g., Delany and Abercrombie 1986, Delany et al. 1999, Rice 2004, Wolfe et al. 1987. Documentation and characterization of the food habitats and predatory interactions of coastal-inhabiting American Alligator populations, which have the ability to cross-ecosystem forage in nearshore marine and estuarine ecosystems, however, was until recently, marginalized due to the lack of salt-secreting glands in alligatorids and the associated paradigm that American Alligators do not habitually use these ecosystems (Boggs et al. 2016, Chabreck 1971, Gabrey 2010, McNease and Joanen 1977, Nifong 2016, Nifong and Silliman 2013, Nifong et al. 2012, Rosenblatt et al. 2015, Tamarack 1989, Tellez and Nifong 2014, Wheatley 2010. American Alligators, while lacking salt secreting-glands (Taplin et al. 1982), are now known to frequent brackish and estuarine (5-25 ppt salinity) habitats as well as perform repetitive long-term (days to weeks) travel into marine (> 25 ppt salinity) habitats (Elsey 2005, Mazzotti and Dunson 1989, Nifong and Silliman 2017, Nifong et al. 2015, Rosenblatt and Heithaus 2011, Tamarack 1989. ...
The food habits and predatory interactions of Alligator mississippiensis (Ameri-can Alligator) have been thoroughly studied within populations inhabiting inland freshwater ecosystems; however, it is increasingly evident that coastal populations habitually forage in estuarine and nearshore marine ecosystems inhabited by other top predators. While few studies have been performed, data reported thus far from marine-foraging populations indicate individuals chiefly consume small-bodied prey such as crustaceans, fish, and wading birds. Nonetheless, capture and consumption of large-bodied marine prey such as multiple species of sea turtles and a single species of Elasmobranchii (sharks and rays) have been documented. Here, we examine evidence regarding reciprocal intraguild predation between American Alligators and elasmobranchs. We provide the first evidence of American Alligator depredation of 4 Elasmobranchii species and review putative evidence for Elas-mobranchii depredation of American Alligators. We discuss the ecological significance of these interactions, draw comparisons to similar interactions experienced by other crocodil-ians, and recommend further avenues for research on the subject.
... Stomach content analyses carried out on A. mississippiensis have shown several of the aforementioned species to be prey items including Atractosteus spatula (Gabrey 2010), unidentified gar species (Overstreet et al. 1985), and Lepisosteus spp. (McNease and Joanen, 1977). Thus, parasitological examinations of potential second intermediate hosts species, particularly of the genera Lepisosteus and Atractosteus, are needed to identify additional hosts, provide a more detailed morphological description of the metacercariae, and to carry out histopathological analyses of in females with metacercariae being found encysted chiefly in the ovaries. ...
Based on specimens collected from harvested American alligator Alligator mississippiensis Daudin, 1801 in Mississippi, USA, novel molecular data for both nuclear ribosomal genes (18S, ITS1-5.8S, ITS2, and 28S) and mitochondrial genes (cytochrome c oxidase subunit 1 and nicotinamide adenine dinucleotide dehydrogenase subunit 1) are provided for Odhneriotrema incommodum (Leidy, 1856), a trematode of the family Clinostomidae Lühe, 1901 infecting A. mississippiensis and the Florida spotted gar Lepisosteus platyrhincus DeKay, 1842. This represents the first sequencing data available for the genus Odhneriotrema and the subfamily Nephrocephalinae Travassos, 1928. Additionally, the results of phylogenetic analyses, additional morphometric data, a photomicrograph, and a line drawing supporting the present identification of O. incommodum are provided. These data will aid in elucidating the life cycle of O. incommodum through molecular identification of larval stages as well as understanding the evolutionary history of Clinostomidae and its subfamilies. Implications for the currently accepted organization of the Clinostomidae are discussed.
... Factors potentially contributing to mottled duck declines in Texas, in addition to habitat loss and degradation, include predation (McNease and Joanen 1977, Stutzenbaker 1988, Elsey et al. 2004, Carethers 2011, Rigby and Haukos 2012, hybridization (Stutzenbaker 1988), and inter-annual variation in precipitation and landscape habitat changes (Stutzenbaker 1988, Moulton et al. 1997, Wilson 2007, Bielefeld et al. 2010. Contemporary lead exposure and anthropogenic disturbance may also be contributing to mottled duck population declines (Stutzenbaker 1988, Merchant et al. 1991, Merendino et al. 2005, McDowell et al. 2015. ...
The mottled duck (Anas fulgivula) is a non-migratory duck dependent on coastal habitats to meet all of its life cycle requirements in the Western Gulf Coast (WGC) of Texas and Louisiana, USA. This population of mottled ducks has experienced a moderate decline during the past 2 decades. Adult survival has been identified as an important factor influencing population demography. Previous work based on band-recovery data has provided only annual estimates of survival. We assessed seasonal patterns of female mottled duck survival from 2009 to 2012 using individuals marked with satellite platform transmitter terminals (PTTs). We used temperature and movement sensors within each PTT to indicate potential mortality events. We estimated cumulative weekly survival and ranked factors influential in patterns of mortality using known-fate modeling in Program MARK. Models included 4 predictors: week; hunting and non-hunting periods; biological periods defined as breeding, brooding, molt, and pairing; and mass at time of capture. Models containing hunt periods, during and outside the mottled duck season, comprised essentially 100% of model weights where both legal and illegal harvest had a negative influence on mottled duck survival. Survival rates were low during 2009–2011 (12–38% annual rate of survival), when compared with the long-term banding average of 53% annual survival. During 2011, survival of female mottled ducks was the lowest annual rate (12%) ever documented and coincided with extreme drought. Management actions maximizing the availability of wetlands and associated upland habitats during hunting seasons and drought conditions may increase adult female mottled duck survival.
... Epstein et al. (1983) reported that Alligators preyed upon radio-collared fawns but that none had been wholly consumed. Other studies have noted White-tailed Deer hair or skeletal remains in the stomachs or feces of Alligators (McNease andJoanen 1977, Shoop andRuckdeschel 1990). Shoop and Ruckdeschel (1990) found parts of White-tailed Deer carcasses in Alligator holes but indicated consumption of the carcasses had occurred over an extended period. ...
An unusually large Alligator mississippiensis (American Alligator) was harvested in Alabama in 2014. We report on the animal's length and mass, and document the techniques used to obtain those measurements. We compare our measurements to other extreme lengths and weights reported for the species. We show that the size of the American Alligator is consistent with known allometric relationships of head length, total length, snout-vent length, tail girth, and weight. The specimen's straight-line total length of 450.0 cm (14 ft 9.25 in) makes it the longest officially measured American Alligator for Alabama and arguably the longest credible record for the species. We recommend using standardized techniques, particularly the straight-line total-length measurement, for documenting record-length or near-record-length American Alligators.
... POSSIBLE CONSUMPTION OF CORN BY AMERICAN ALLIGATORS AT WILDLIFE FEEDERS IN LOUISIANA, USA. American alligators (Alligator mississippiensis) are generally assumed to be obligate carnivores, although plant materials such as fruits, seeds and vegetation have been found among stomach contents (Dowler 1846;Kellogg 1929;Chamberlain 1930;McNease and Joanen 1977;Platt et al. 1990;Forkner 1996). The presence of these items is usually attributed to accidental ingestion during prey capture or secondary ingestion [ie the acquisition of items contained in the gut of primary prey (Neill 1971)]. ...
... Diet may be the cause for the lack of relationship between C. c. crocodilus Hg concentration and size. Several species of crocodilians include more terrestrial vertebrates, especially mammals, in their diet when they attain large sizes (Blomberg 1977;Giles and Childs 1949;Medem 1981;McNease and Joanen 1977;1979). C. c. crocodilus could be feeding more on terrestrial vertebrates when they are adults, which would explain why Hg concentrations were the same or greater in smaller individuals. ...
Total mercury (Hg) concentrations of muscle, liver, blood, and epidermal keratin were measured in typically consumed, economically and culturally important species of turtle (Podocnemis unifilis and Podocnemis expansa) and caiman (Melanosuchus niger and Caiman crocodilus) from the Rio Purus in the Amazon basin, Brazil. Methylmercury (MeHg) concentrations were also measured in muscle tissue, representing the first analysis of MeHg concentrations in Amazonian reptile species. In muscle tissues Hg was mostly MeHg (79–96%) for all species. No correlations existed between animal size and total Hg or MeHg concentrations for any species other than M. niger, possibly as a result of growth dilution or the evolution of efficient Hg elimination mechanisms. Significant linear correlations were found between total Hg concentrations in all pairs of nonlethally sampled tissues (keratin and blood) and internal tissues (muscle and liver) for M. niger and between keratin and internal tissues for P. expansa, indicating that nonlethally sampled tissues can be analyzed to achieve more widespread and representative monitoring of Hg bioaccumulation in Amazonian reptiles. Although mean Hg concentrations in muscle for all species were below the World Health Organization guideline for safe consumption (500 µg kg–1), mean concentrations in caiman liver were above the safe limit for pregnant women and children (200 µg kg–1). No significant differences were found between total Hg and MeHg concentrations in tissues from wild-caught and farm-raised P. expansa, suggesting that farming may not reduce Hg exposure to humans. Environ Toxicol Chem 2015;9999:1–11. © 2015 SETAC
... Large alligators are capable of preying upon adult feral hogs (Sus scrofa) and mature cattle (McIlhenny 1935, Neill 1971, Wood and Brenneman 1977, species which are larger and more mobile than young fawns. Nonetheless, McNease and Joanen (1977) found deer hair in only 1 of 314 alligator stomachs and did not speculate as to whether or not it was carrion. Valentine et al. (1972) found no evidence of deer remains in 413 alligator stomachs, nor have other researchers studying alligator food habits (Kellogg 1929, Giles and Childs 1949, Chabreck 1972. ...
Forty-eight white-tailed deer fawns (Odocoileus virginianus) were marked during the spring and early summer of 1981 and 1982. Forty-one (85.4%) of these fawns died, 26 (63%) due to predation. In 18 of the 26 predator-caused deaths, the species of predator could be determined. Bobcats (Felis rufus) accounted for 12 deaths, while red foxes (Vulpes vulpes) , gray foxes (Urocyon cinereoargenteus) and alligators (A lligator missis-sipptensis) were responsible for a total of at least 6 fawn deaths. Criteria for determining predator damage are discussed. Foxes and alligators have not previously been documented as predators on white-tailed deer fawns. Proc. Annu. Cont. Southeast. Assoc. Fish and Wildl. Agencies 37:161-172
... MANY studies of crocodilians have described resource partitioning in terms of food (Cott, 1961;Magnusson et al., 1987), space (Chabreck, 1971;McNease and Joanen, 1977), time (Valentine et al., 1972;Taylor, 1979;Webb et al., 1991), or their interaction. Despite these examples, crocodilians are not represented in reviews of resource partitioning among amphibians and reptiles (Toft, 1985) for two reasons. ...
We examined size-related dietary patterns in a Queensland population of the Australian freshwater crocodile (Crocodylus johnstoni). In three consecutive dry seasons, we stomach flushed crocodiles (n = 324) to record the numerical frequency and percent occurrence of prey items. Prey included spiders, aquatic insects, terrestrial insects, shrimp, fish, anurans, turtles, snakes, mammals, and birds. The diet of C. johnstoni showed ontogenetic shifts as the cranium broadened and once body size exceeded 60 cm SVL. With increasing crocodile size, the ingestion of spiders, insects, and anurans declined strongly whereas the consumption of fish, turtles, and snakes increased strongly. Shrimp were eaten at low and variable levels by all size classes of crocodile. The low overall prevalence of mammals and birds suggested that they were consumed opportunistically by the larger crocodiles. With increasing crocodile size, there were overall increases in prey richness and significant declines in realized dietary niche, dietary breadth, and mean number of prey items per crocodile. There were no significant changes in dietary diversity, evenness, or number of equally common prey species.
... In freshwater systems, A. mississippiensis have been documented to prey upon several freshwater turtle species within the genera Apalone, Deirochelys, Kinosternon, Pseudemys, Sternotherus, and Trachemys (Barr 1997;Delany and Abercrombie 1986;Gabrey 2010;McNease and Joanen 1977;Wolfe et al. 1987). In three Florida lakes, Delany and Abercrombie (1986) found turtles to be the most common prey type recovered from the stomachs of adult male alligators greater than 3.0 m total length. ...
... Diet may be the cause for the lack of relationship between C. c. crocodilus Hg concentration and size. Several species of crocodilians include more terrestrial vertebrates, especially mammals, in their diet when they attain large sizes (Blomberg 1977;Giles and Childs 1949;Medem 1981;McNease and Joanen 1977;1979). C. c. crocodilus could be feeding more on terrestrial vertebrates when they are adults, which would explain why Hg concentrations were the same or greater in smaller individuals. ...
Mercury (Hg) concentrations in the Amazon are generally high, but no studies have been published on Hg concentrations in caimans (Alligatoridae) from the region. Aiming for sizes representative of caimans traded for food in the Amazon, we measured Hg concentration in tail muscle of spectacled caiman (Caiman crocodilus crocodilus) and black caiman (Melanosuchus niger) from the Purus River basin. The information on Hg concentration in caimans from this area is important because of the potential health risk to humans and other animals that eat them as well as the potential use of these top-level predators as bioindicators. There were no significant interspecific or sex differences in Hg concentrations. The mean Hg concentration was 291.2 μg/kg in C. c. crocodilus and 193.9 μg/kg in M. niger. A significant positive correlation between Hg concentration and size was found for M. niger (p = 0.005) but not for C. c. crocodilus. Our Hg sample from M. niger corresponded to the size of M. niger collected for commercial trade, but our Hg sample from C. c. crocodilus turned out to be significantly smaller than the trade samples (p = 0.004), but this difference is not pertinent in the absence of a correlation between size and Hg concentration for this species. Although there are no standards for reptile meat, both species had mean Hg concentrations lower than the maximum allowable level of 500 μg/kg Hg recommended by the World Health Organization and by the Brazilian Health Ministry for fish. However, by calculating daily consumptions limits and number of meals per month that can be safely consumed, we found that consumers who eat caimans frequently may be at risk for Hg-related health problems.
... Finally, seasonal changes in population density mediate indirect behavioural effects on crocodile growth owing to an individual's status in a size-ranked hierarchy (Lang 1987; Tucker et al. 1998). Together, such mechanisms account for substantial variation in growth processes of crocodilians at broad geographic scales (Chabreck and Joanen 1979; Jacobsen and Kushlan 1989; Cooper-Preston 1992; Wilkinson and Rhodes 1997), among seasons (Magnusson and Taylor 1981; Hutton 1987), for different habitats within a region (McNease and Joanen 1977; Rootes et al. 1991; Elsey et al. 1992), between sexes (Webb et al. 1983) and for different resource availabilities (Webb et al. 1978; Delany and Abercrombie 1986). Reptile growth patterns can be fitted by various fixed parameter models including the von Bertalanffy, logistic by length, logistic by weight, Gompertz and Richard's growth models (Kaufmann 1981; Andrews 1982; Brisbin 1987; Abercrombie 1992). ...
We analysed growth models for a population of Australian freshwater crocodiles (Crocodylus johnstoni). Competing growth models were tested with two data sets: individuals of known-age, and growth interval data from capture-recapture records. A von Bertalanffy function provided the best empirical fit of several growth models. The estimated asymptotic lengths (snout–vent length of males = 125.3 cm; females = 97.4 cm) agreed well with average lengths of the ten largest males and females in the population. Sexual size dimorphism in this species resulted from a combination of smaller mean length at maturity for females and a subsequent decline in female growth rate. Size dimorphism may result from individual trade-offs in age v. length at maturity as a consequence of sexual selection. Yes Yes
Cross-ecosystem movements of mobile consumers are a primary mechanism by which energy and nutrients are exchanged between disparate ecosystems. While factors influencing variation in bottom–up subsidies between ecosystems have been well studied, much less is known regarding how biotic and abiotic factors influence the dynamics of mobile consumer-driven connectivity. In a literature survey, we found only 14% of studies examined factors contributing to variation in cross-ecosystem marine foraging by freshwater-adapted consumers. Here, we examine the relationships between abiotic factors and cross-ecosystem movements of a highly mobile freshwater-adapted top predator, Alligator mississippiensis (American alligator). As alligators lack physiological adaptations to survive in marine environments, we predict this linkage would be affected by factors that modify the ability to cope with high salinities. Our results reveal that multiple abiotic factors (e.g., relative humidity, temperature, total precipitation) are key explanatory variables of the duration of cross-ecosystem foraging trips by alligators, and that the absence of salt glands does not preclude them from performing long forays into marine environments. More broadly, our results expand our understanding of mobile consumer-driven ecosystem connectivity at the land–sea interface by demonstrating connectivity is highest when physical stressors are relaxed, and access to and availability of resources are maximized.
Found only in the United States, the American alligator ranges in Texas through 120 counties, from the Sabine River to the Rio Grande, across a swath of river drainages and coastal marshes that include both the backwater swamps of the Big Thicket and the urban bayous of greater Houston. From its beginning in a pile of eggs buried in a meticulously constructed nest to its possible end as an alligator burger or a pair of boots, an alligator's habitat preferences sometimes coincide with the favorite haunts of boaters, hunters, and coastal residents. In Alligators of Texas, biologist Louise Hayes and photographer Philippe Henry bring readers up close to this cryptic reptile's food choices, parenting skills, communication techniques, and responses to natural events such as freezes and hurricanes. They also relate some Texas "alligator tales"; discuss alligator farming, hunting, and live capturing; and examine how people can successfully co-exist with this predator. They end by telling readers where they can view alligators, both in the wild and in captivity. Although not as often, as easily, or perhaps as happily observed as white-tailed deer or armadillos, the American alligator is an iconic Texas animal, and knowing more about its life and habits can help Texans better understand its rightful place in the landscape. © 2016 by Louise Hayes and Philippe Henry. All rights reserved.
Fifty American alligators (Alligator mississippiensis) were obtained from southeast Texas from September 1992 to September 1995. A total of 8,861 parasites were recovered from 46 infected alligators (92%). Necropsy revealed the presence of 1 species of pentastome (Sebekia mississippiensis), 3 species of nematodes (Brevimulticaecum baylisi, B. tenuicolle, and Dujardinascaris waltoni), and 8 species of trematodes (Acanthostomum coronarium, A. loossi, A. pavidum, Archaeodiplostomum acetabulatum, Crocodilicola pseudostoma, Dracovermis occidentalis, Polycotyle ornata, and Pseudocrocodilicola georgiana). Prevalence, mean intensity, and abundance of infection were higher in adult (≥ 1.80 m) alligators. There was no significant difference (P > 0.05) in mean intensity or abundance between male and female alligators. Infracommunity structure, based on species richness, intensity of infection, and diversity of endohelminths, is considered depauperate when compared to homeothermic hosts. However, alligator endohelminth communities are relatively rich and diverse compared to other reptilian hosts. Broadened feeding preferences, as related to maturity, are suggested as the main factor that determines endohelminth community structures in alligators.
Nile crocodiles and American alligators belong to a group of reptiles called broad-nosed crocodilians. In the warmer parts of the world, broad-nosed crocodilians are the largest predators to walk on land. They are living fossils in the sense that they resemble ancient forms in the shapes and the ruggedness of their heads and bodies.
As part of an ongoing study on growth and sexual maturation of Alligator mississippiensis (American Alligator) on Rockefeller Wildlife Refuge, LA, 3601 specimens, ranging in total length from 28 to 361 cm, were captured from June 2000 through August 2004. Additionally, 70 alligators were collected opportunistically as part of a teaching exercise in August 2005, and 248 more were collected in 2006 (and one in January 2007) as part of a study evaluating the effects of Hurricane Rita on alligators. Representative samples from size classes greater than 60 cm were collected in most months of the year between 2000 and 2004. Each animal was tagged, measured, sexed, and released immediately at the site of capture. A large number of these marked alligators were recaptured outside the refuge boundaries during annual alligator hunts in September. Of the 286 recaptured alligators, 214 were males, 68 were females, and four were of undetermined sex. From each recaptured alligator, total body length and date of recapture were recorded, and minimum distance from initial capture site estimated. From these preliminary data, we calculated the time interval between captures, and plotted minimum distance moved. The number of days between first capture and recapture ranged from 29 to 3336 days (9.1 years). Distance moved from initial capture site to final capture site ranged from 0.3 to 90.2 km. Eleven alligators moved between 30.0 and 39.9 km, and eight moved >= 40 km. Six of these moved between 40.0 and 49.9 km, and the others moved 87.4 and 90.2 km. These results greatly extend previous estimates of long-distance movement by alligators and demonstrate that both sub-adult and sexually mature animals move considerable distances. These data also showed that smaller alligators moved greater distances than larger alligators (P = 0.0002), and that the longer the time between captures, the greater the distance moved (P < 0.0001).
RESUMEN Dentro de los estudios realizados sobre los aligatóridos presentes en el ámbito del Proyecto de Asentamiento Rural Integral Jenaro Herrera, se realizaron análisis del contenido estomacal de 11 ejemplares juveniles de lagarto blanco (Caiman sclerops, Schneider). Los resultados obtenidos coinciden con los reportados en estudios de otras especies como el yacaré sudamericano o el aligator de Florida. El tipo de alimento más consumido por los individuos juveniles de la especie en estudio fueron artrópodos como crustáceos e insectos. El consumo de vertebrados a este nivel de edad fue casi nulo pero siempre mayor en los individuos más grandes. SUMMARY In the studies performed on alligatoridae present in the Integral Rural Settlement Project of Jenaro Herrera area, analysis of the stomachal contents of 11 Spectacled Caiman (Caiman sclerops, Schneider) juvenile individuals were made. Results obtained coincide with those reported in studies of other species such as southamerican yacare and american alligator. The type of nourishment consumed in largest amounts by juvenile individuals of the species studied was arthropoda, such as croustaceous and insects. The consumption of vertebrates at this age was almost null, but always greater in the larger individuals.
We used data from carcasses found in a natural population of nine-banded armadillos (Dasypus novemcinctus) to assess the sources and age structure of mortality. Juveniles (young of the year) made up approximately 33% of the living population, but constituted about 60% of all carapaces collected. Circumstantial evidence indicated that most juvenile, but not adult, mortality was probably due to predation. Increased adult mortality was associated with a period of prolonged drought.
We documented 15 cases of Grus americana (Whooping Crane) mortality in 6 Florida counties during 1997-2010 that may have been associated with Alligator mississippiensis (American Alligator; hereafter Alligator) predation or scavenging. In four cases; Whooping Crane remains were identified within Alligator mouths or stomachs. The latter is a first in the literature. Other cases were less conclusive but suggestive that Alligators were involved with predation or scavenging of Whooping Cranes, An Alligator was videotaped eating the eggs of G. canadensis pratensis (Florida Sandhill Crane); plus Alligators were implicated in the depredation of eggs from another Sandhill Crane nest and a Whooping Crane nest; the latter was the first record of Alligators depredating Whooping Crane eggs. All 4 populations of Whooping Cranes and 4 populations of Sandhill Cranes in the southeastern United States spend at least part of the year within the range of Alligators. To improve survival of cranes in areas where water management is practiced, water depths should be maintained at optimal levels (10-20 cm) for crane nesting and roosting to discourage intrusion by larger Alligators and to allow the cranes to detect approaching Alligators.
Large-bodied apex predators (e.g., sharks, wolves, crocodilians) are believed to regulate food web structure and drive ecosystem processes, but there remains relatively little experimental evidence. Here we use field surveys and a mesocosm experiment to evaluate the cascading effects of an apex predator (American alligator) on a salt marsh food web. Consistent with previous studies (n. = 10), field surveys revealed blue crabs (Callinectes sapidus Rathbun 1896), an important marsh mesopredator, were a frequent component of estuarine-occurring alligators' diet (mean. ±. SD, 47. ±. 20%, n. = 1384). In mesocosms, we examined potential consequences of this interaction in a simplified salt marsh community. We experimentally isolated alligator effects on the abundance (consumptive effect) and behavior (non-consumptive effect) of blue crabs and on blue crab consumption of plant-grazing snails and ribbed mussels. Alligators reduced blue crab abundance by ~. 40% over 3. days and induced behavioral changes, resulting in decreased foraging activity and increased refuge use by blue crabs. The combined effects of reduced crab abundance and altered behavior translated into increased survival of both a keystone grazer (snails) and a mutualist (mussels) within the salt marsh food web. Our findings experimentally demonstrate that a large-bodied, apex predator has the potential to 1) generate a trophic cascade, 2) elicit behavioral changes (i.e., non-consumptive effects) in mesopredator prey, and 3) indirectly affect the potential for both grazing and mutualism to occur in this food chain. Our results generate testable hypotheses regarding the broad-scale effects of alligator presence and top-down forcing in salt marsh ecosystems.
Eggs produced by farm-reared alligators have lower fertility and hatchability than eggs collected from wild alligators and incubated under identical conditions. To assess the effect of diet on trace elements essential for reproduction, plasma samples from farm-reared alligators fed fish (Micropogon undulatus) or nutria (Myocastor coypus) meat, and from wild alligators caught during the reproductive cycle (April–July) were assayed for vitamin E, selenium, calcium, magnesium, zinc, copper, iron, total protein, cholesterol, and estradiol-17β. Calcium, magnesium, zinc, iron, total protein, cholesterol, vitamin E, and estradiol-17β all showed significant increases in females during vitellogenesis (April–May), and all returned to levels not significantly different from males by July. There were no significant differences between the captive alligators fed fish or nutria, or between either group and wild alligators for any of these plasma constituents. Selenium and copper did not increase during egg production and were similar in males and females. There were significant differences due to diet in plasma selenium and vitamin E in female alligators. Fish-fed alligators had significantly higher plasma selenium and significantly lower vitamin E levels than nutria-fed and wild females which were not significantly different from one another.
SUMMARY In order to determine the growth rate of C. crocodilus crocodilus in several conditions of captivity, 137 newborn specimens were raised to 10 old months in four experimental circular tanks, with 28.26 m 2 of surface area and a volume of 62.17 m3 in each tank. The tanks were built with solid concrete walls and guarded blocks covered internaly with sheets of myrrhlike resin, and roof of galvanized sheets. One tank was covered partially with the galvanized sheets, the other tanks were protected totally from the sun. Three different diets were used for three groups of animals. Group I was raised in the partially covered tank and fed with 70% of fresh fish, 30% of chicken meat and a mixture of minerals. The other two groups
In southern Louisiana, high population densities of exotic Myocastor coypus (Nutria) have been implicated in causing significant coastal marsh damage through extensive herbivory. Wildlife officials instituted a Nutria removal program in 2002 to reduce this marsh loss. Because Alligator mississippiensis (American Alligator) frequently consume Nutria, concern arose regarding the program's impacts on alligator food habits. Therefore, we conducted our study to determine if the Nutria removal program affected the frequency of occurrence of Nutria remains in alligator stomachs collected from five parishes in southern Louisiana. Three parishes had high Nutria densities and removal programs; two parishes had low Nutria densities and no Nutria removal. We collected >550 alligator stomachs during three September trapping seasons and examined the contents of each. We used logistic regression to model effects of year (1 year prior to the removal program compared to two years during removal) and parish (three with Nutria removal programs compared to two without) on the probability that an alligator stomach contained Nutria remains. Overall, about one-third of the alligator stomachs contained Nutria remains. Nutria removal appeared to have no effect on the probability of a stomach containing Nutria remains even after two years of Nutria removal. In addition, the probability that an alligator stomach contained Nutria remains was similar among all parishes regardless of whether Nutria removal occurred or not. We recommend that continuance of the Nutria removal program be based on its effectiveness in reducing marsh damage and not on perceived impacts to alligator food habits.
Mottled Ducks (Anas fulvigula) are widely distributed in southeastern coastal marshes, as are American Alligators (Alligator mississippiensis). Although the alligator has been noted to prey upon Mottled Ducks, evidence of Mottled Duck consumption is rare in numerous studies of alligator food habits. This may be due to the season and habitat from which alligators were collected for evaluation (often autumn samples from deep water habitats preferred by adult alligators). We examined stomach contents of alligators in summer (when Mottled Duck broods and molting adults are flightless) from shallow water habitats preferred by Mottled Ducks. Mottled Duck remains were found in 20.9% of 43 alligator stomachs examined, far more than the highest frequency occurrence previously reported (1.27%). Unexpectedly, three relatively small alligators (1.51–1.70 m total length) consumed Mottled Ducks and the sixteen largest alligators did not. This study underscores the importance of season and location of collections when evaluating stomach content data.
In 4 experiments, alligators were presented with paper bags containing beef, nutria, rattlesnake meat, or an aqueous meat extract. Bags containing meat or meat extract were removed more often than control bags. While there were no differences in the latencies with which Ss contacted experimental and control bags, they tended to contact experimental bags first, suggesting that they detected water- or air-borne chemicals from materials presented to them. Contact chemoreception was important to Ss for food recognition. Ss grasped and released 30 control bags but released bags containing meat or treated with meat extracts only 11 times. Gustation was probably involved in the contact chemoreception of food. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
We described the types of anatomical damage exhibited by a population of nine-banded armadillos (Dasypus novemcinctus) in northern Florida USA, and quantify the extent and frequency of occurrence of damage among different subgroups of animals. Anatomical damage included tail loss, missing portions of the carapace (notches), torn or missing ears, scarring of the carapace, and band abnormalities. Damage accumulated with age : adults exhibited significantly more damage than either juveniles or yearlings, and, among adults, the amount of damage increased over time. There were few sex differences in the extent or incidence of any type of damage, nor was there any evidence that damage affected reproductive success, although lactating females did exhibit more damage than non-lactating females. Body weights of damaged and undamaged animals did not differ for juveniles or yearlings, but damaged adults were significantly heavier than non-damaged individuals. Possible causes of damage included predators, conspecific aggression, the physical environment, and developmental instability.
The growth dynamics of the American alligator (Alligator mississippiensis) were studied in the subtropical Florida Everglades using extensive mark-recapture data from over 2000 recaptures of known-aged and unknown-aged animals. A model based on the power curve best describes growth of Everglades alligators. The nonasymptotic character of this curve leads to rejection of the hypothesis that alligator growth is determinate. A model consisting of piece-wise linear equations better described growth in the first year, and suggested a period of arrested growth occurred in the first winter. A comparison of predictions from growth models derived from several populations indicated that Everglades alligators grew more slowly than did those in more temperate areas, leading to the rejection of the hypothesis that growth rates in subtropical Florida would be elevated because of the long growing season. We attribute this result to a combination of increased maintenance costs and a limited resource base in the Everglades.
Analyses considered the extent to which growth model evaluation and use can be affected by data selection. Mathematical constraints posed by negative growth data can be alleviated by including growth records over combined recapture intervals to achieve a positive growth increment. However, periods of no to negative growth may be real, and such deviations are obscured by fitting growth data to monotonically increasing models.
A comparative study of American alligator (Alligator mississippiensis) growth rates was made in estuarine and palustrine wetlands in southwestern Louisiana. In the estuarine wetlands, where characteristic
salinity levels were ≤5%, alligators grew faster and therefore reached sexual maturity earlier than did those in palustrine
wetlands, which are characterized by shallow, freshwater marsh vegetation. Slower growth rates in palustrine wetlands appeared
to be related to prey density, indicated by previous studies to be lower than in estuarine wetlands. Males grew faster than
females and therefore reached sexual maturity at an earlier age in both habitats. This study revealed a major limitation in
using total lengths as an index upon which population age structure can be based even when alligators are in the same geographic
region.
The architecture of the jaw muscles and their tendons of Alligator mississippiensis is described and their function examined by electromyography. Alligator grabs its prey with forward lunges or rapid lateral movements of the head. It does not engage in regular masticatory cycles. Prey is manipulated by inertial movements and the tongue does not appear to play any role in transport. The Mm. adductor mandibulae externus, adductor mandibulae posterior, and pterygoideus activate bilaterally and simultaneously during rapid closing or crushing. The M. pterygoideus does not act during prey holding whereas the Mm. adductor mandibulae externus, adductor mandibulae posterior continue to be active. The Mm. depressor mandibulae and intramandibularis are variably active during both jaw opening and closing.
ResearchGate has not been able to resolve any references for this publication.