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Marine turtle populations on the west-central coast of Florida: Results of tagging studies at the Cedar Keys, Florida, 1986-1995
Abstract
Large-mesh tangle nets were used to collect marine turtles in Waccasassa Bay, near the Cedar Keys, Florida, from June 1986 to October 1995. Tagging records were analyzed to determine the species composition, population structure, and seasonal occurrence of Kemp's ridley, Lepidochelys kempii, loggerhead, Caretta caretta, and green, Chelonia mydas, turtles. Additional information on local movements, morphometrics, growth, population estimation, and diet was provided for Kemp's ridley turtles. Subadult green turtles dominated the catch on the seagrass shoals of Waccasassa Reefs. Subadult Kemp's ridley turtles and, to a lesser degree, subadult and adult loggerhead turtles were primarily captured near the oyster bars of Corrigan Reef. Marine turtles were caught in these nearshore waters from April to November. Recaptures indicate that some Kemp's ridley turtles remain in the vicinity of Corrigan Reef during their seasonal occurrence and return to this foraging area annually. Seasonal and annual size distributions of Kemp’s ridley turtles were investigated and regression equations were developed for carapace morphometrics. Carapace growth averaged 4-5 cm/yr for Kemp's ridley turtles, but growth analyses were confounded by the extrapolation of annual estimates from short-term recaptures. Population estimates for the Kemp's ridley mark-recapture data indicated a mean annual population size of 159 turtles at Corrigan Reef with presumably high rates of immigration and emigration by larger subadult turtles. Examination of fecal samples indicated that crabs were the primary food items of Kemp's ridley turtles captured near oyster bars.
... About 2 decades following the end of the sea turtle harvest in Florida waters, Schmid (1998) sampled turtles near Cedar Key between 1985 and 1996, and found that captures were dominated by Kemp's ridleys. Similarly, Barichivich (2006) also found that Kemp's ridleys dominated captures from 1996-1999 in Deadman Bay, about 100 km north of Cedar Key. ...
... Comparing these results to historical data from the region highlights possible demographic shifts. Green turtle capture efforts by Schmid (1998) from 1986-1995 at a location just north of our study site resulted in only 10 green turtles, all > 40 cm SSCL, with the majority > 60 cm SSCL. In contrast, about 92% of green turtles in our study were < 50 cm SSCL. ...
... In contrast, about 92% of green turtles in our study were < 50 cm SSCL. We are cautious in drawing conclusions about this apparent shift toward smaller (younger) green turtles because the large-mesh tangle netting method used by Schmid (1998) favored capture of larger turtles. Our observations are that the hand-capture method we used was equally successful for all turtle sizes. ...
Coastal waters of Florida’s Big Bend, Gulf of Mexico (GOM) once supported one of the largest sea turtle fisheries in the United States. To fill an information gap in this region on abundance and distribution of sea turtles, we used vessel—based distance sampling and active capture methods to characterize current foraging aggregations near the St. Martins Marsh Aquatic Preserve. Over 10 sampling periods between 2012—2018, we completed 513 km of transects and recorded 819 turtles among 4 species—green turtle (Chelonia mydas, n = 624), Kemp’s ridley (Lepidochelys kempii, n = 147), loggerhead (Caretta caretta, n = 47), and a single hawksbill (Eretmochelys imbricata). Turtle densities in 4 study plots within the 200 km2 study site ranged from 57—221 immature green turtles/km2, 16—56 immature Kemp’s ridleys/km2, and 1—14 juvenile—to—adult loggerheads/km2. Of 200 green turtles captured, 67.5% showed skin tumors consistent with fibropapillomatosis, a frequency similar to that from urbanized estuaries of Florida’s east coast. The largest green turtles (> 60 cm straight standard carapace length), abundant in the southern portion of our study area, are of note because this size class is uncommonly recorded within US territorial waters. Analyses of green turtle mtDNA haplotypes found contributions from rookeries in the western GOM, Mexican Caribbean, and Costa Rica. Although Big Bend protected areas were principally designed to conserve marine and coastal habitats, these regulatory zones have also effectively encompassed a hotspot for foraging sea turtles.
... In 1984, the National Marine Fisheries Service initiated long-term tagging studies to characterize the aggregations of Kemp's ridleys occurring in Apalachicola and western Apalachee Bays, Franklin and Wakulla counties Rudloe et al., 1991) and Waccasassa Bay, Levy Co. Ogren, 1990, 1992;Schmid, 1998). Other tagging studies have resulted in a small number of captures in Tampa Bay, Hillsborough Co., and Charlotte Harbor, Charlotte Co., in west-central Florida (Manire and Foote, 1995), and Florida Bay, Monroe Co., in southwestern Florida (B. ...
... Barichivich (1998) emphasized the importance of the shallow seagrass flats in Deadman Bay as developmental habitat for Kemp's ridleys. Schmid (1998) suggested that Kemp's ridleys in Waccasassa Bay were preferentially utilizing an oyster (Crassostrea virginica) reef complex and the mud bottom adjacent to the reefs. However, none of these studies have quantified habitat use and habitat availability, both of which are necessary to test for habitat preferences and subsequently determine essential developmental habitat for this species. ...
... Kemp's ridleys were captured in the former west Florida turtle fishery in April through November (Carr and Caldwell, 1956;Carr, 1980). Recent tagging studies have confirmed this pattern of seasonal occurrence Ogren, 1990, 1992) and have determined that turtles occur in these shallow waters when water temperatures are above 20ºC (Schmid, 1998). However, sightings and captures have also been reported in December and March during periods of unseasonably warm water temperatures (Barichivich, 1998;Schmid and Barichivich, 2005). ...
Kemp’s ridley, Lepidochelys kempii, is a critically endangered species of sea turtle that is common in Florida waters. It is the smallest sea turtle species and is recognizable by its circular carapace, olive gray coloration, and relatively large head with a parrot-like beak. Kemp’s ridleys are distributed throughout the Gulf of Mexico and western North Atlantic Ocean. A few nesting females of this species have been observed on Florida beaches; however, the primary nesting beach is along the Gulf coast of Tamaulipas, Mexico. Historic records, incidental captures, and tagging data were compiled to provide a detailed distribution of live, wild Kemp’s ridleys inhabiting coastal waters of Florida. Seagrass beds and mud bottom have been identified as the benthic habitats used by subadult turtles, but quantitative analyses of habitat associations have determined that live bottom is also an important developmental habitat. The near-shore waters of Florida’s west coast provide important summer foraging grounds, while the offshore waters of the east coast are an important overwintering area. Seasonal north-south migrations have been documented on both coasts. Kemp’s ridleys establish restricted foraging ranges along the Florida Gulf coast and may return to these areas for at least 4 years. Kemp’s ridleys feed primarily on decapod crustaceans and a possible ontogenetic shift in prey and habitat has been suggested for subadult turtles in northwestern Florida. Egg harvest and capture in shrimp trawls were identified as the primary causes for the rapid decline of the Kemp’s ridley population. However, protection of the nesting beaches and regulations imposed on the shrimp fishery (primarily use of turtle excluder devices [TEDs]) has presumably led to the increasing number of nests over the past 20 years. Florida’s coastal waters provide essential developmental habitat for Kemp’s ridleys and these areas must be conserved to ensure the viability of the species.
... Little is known about the function of nearshore reefs in the life history of the Kemp's ridley sea turtle. More is known about their behavior and habitat-use in Gulf of Mexico waters (Schmid et al. 1998;Gregory and Schmid 2001;Seney andLandry 2008, 2011;Shaver et al. 2016). Believed to prefer muddy estuarine and bay habitat, radio and sonic telemetry studies conducted on the west coast of Florida revealed that subadult and adult Kemp's ridleys were frequently utilizing nearshore hardbottom habitat (Schmid 1998). ...
... More is known about their behavior and habitat-use in Gulf of Mexico waters (Schmid et al. 1998;Gregory and Schmid 2001;Seney andLandry 2008, 2011;Shaver et al. 2016). Believed to prefer muddy estuarine and bay habitat, radio and sonic telemetry studies conducted on the west coast of Florida revealed that subadult and adult Kemp's ridleys were frequently utilizing nearshore hardbottom habitat (Schmid 1998). While further habitat selection and behavioral data are needed, results from Kemp's on the Gulf coast of Florida (Schmid et al. 2003) and limited tracking (1 adult and 2 juvenile Kemp's; Gitschlag 1996) of turtles released in Georgia waters suggest that nearshore rock resources in southeast Florida may be important habitat for these turtles. ...
... While Kemp's ridley turtles may occupy the east Florida coastal waters, whether they are transient or resident is still a mystery. The capture of turtles entrained through cooling water intake pipes at the St. Lucie Nuclear Power Plant (n = 34 between 1976 and1998;Bresette et al. 1998) suggests that Kemp's utilize the shallow nearshore rock reefs off St. Lucie County. ...
Green, loggerhead, hawksbill, and, less frequently, Kemp’s ridley turtles are observed in east Atlantic Florida waters on nearshore reefs. These species have one or more fundamental developmental requirements supplied by nearshore hardbottom reefs (e.g., food, shelter, predator avoidance, migratory corridor). While there is still much to be discovered concerning the juvenile life stages of all species of sea turtles, based on current data, there is strong evidence that at least juvenile green turtles initially recruit to nearshore hardbottom reefs off east-central Florida (i.e., sabellariid reefs in Brevard, Indian River, and St. Lucie counties) and primarily forage on macroalgae. The subadult and adult life stages of loggerheads are generally observed on deeper offshore hardbottom reefs with adults being particularly abundant during mating and inter-nesting periods. Juvenile and subadult hawksbill turtles are mostly observed in South Florida waters (Jupiter and further south) on both nearshore and offshore reefs. Kemp’s ridley turtles are infrequently sighted but there is evidence that supports use of hardbottom reefs. All four of these species found on nearshore reefs in Florida were previously exploited to a mere fraction of their historic numbers throughout the Atlantic and Caribbean. Protected today, some populations are recovering. Tasks lie ahead, however, as we seek to understand the critical ecological role of sea turtles in shaping healthy marine ecosystems and prevent or reverse habitat loss due to anthropogenic activities (e.g., coastal construction, sedimentation from dredge-and-fill projects, fisheries interactions, and pollution).
... The postlarvae of many decapod species select complex habitats for metamorphosis (Wolcott & DeVries 1994, Stevens & Kittaka 1998, Pardo et al. 2007, Webley et al. 2009); and high turbidity can deter aquatic predators that rely on visual prey recognition (Reustle & Smee 2020), as well as those that do not (Ortega et al. 2020). The cannibalistic nature of stone crabs of all sizes (Yang & Krantz 1976, Krimsky 2008) and susceptibility of YOY stone crabs to predation by other animals (Frick & Mason 1998, Schmid 1998, Scharf & Schlicht 2000, Shervette et al. 2004, Reeves et al. 2019 suggests that, as in other species (Kurihara & Okamoto 1987, Fernandez 1999, Luppi et al. 2001, Pirtle & Stoner 2010, refuge from predation is important in habitat selection by stone crab megalopae and PS-juveniles. Complex shelters with small openings have been shown to reduce interspecific and intraspecific competition and predation on YOY Menippe adina and enhance the density and survival of all sizes of juveniles (Gibbs 1994). ...
Knowledge of juvenile recruitment (defined here as the quantitative addition of early benthic life stages to a local population) is important for conserving heavily harvested species and their critical habitats. Stone crabs (genus Menippe) are commercially and ecologically important throughout the Gulf of Mexico nearshore waters off Florida, but very little is known about their recruitment. Using standard commercial stone crab traps, megalopal and postsettlement juvenile (collectively, young-of-the-year, “YOY”) stone crabs were sampled at multiple spatial scales and for multiple stone crab generations to characterize geographical, seasonal, and interannual variation in their distribution and relative abundance (numbers collected on traps) in the Gulf of Mexico off peninsular Florida and north of the Florida Keys (the “Florida Gulf”). The influences of potentially relevant oceanographic and biological variables [temperature, salinity, benthic community on the traps (trap fouling community), depth, distance from shore] on YOY stone crabs were investigated at locations distributed throughout the study area. Trap fouling communities had never been analyzed in detail prior to this study; an importance index was developed to quantify the seasonality, commonality, and density of the fouling communities and organisms composing the communities. Continuous, long-term data from the Tampa Bay location allowed investigation of the effects of biological relationships [relative abundance of female Menippe carrying eggs (ovigerous), occurrences of red tide (Karenia brevis, a toxic dinoflagellate) blooms] and meteorological events [tropical cyclones, El Niño Southern Oscillation (ENSO) occurrences] on temporal patterns of variation in recruitment. High relative abundances of YOY stone crabs were collected off peninsular Florida from dense, complex benthic biota that grew on crab traps located off large, pristine estuaries in relatively turbid water less than 5 m deep, where salinity ranged 24–36 and water temperature averaged 29°C–32°C. Two major recruitment locations, stable through decades, consistently accounted for approximately 50% of the YOY stone crabs collected; two secondary recruitment locations similarly accounted for another 25%. Relative abundance of YOY stone crabs was highest nearshore at the major recruitment locations, particularly during years of high relative abundance. Approximately 65%–75% of the recruits were collected August to October; however, the timing of both peak relative abundance and lowest relative abundance shifted to later in the year as latitude decreased. Patterns of change among months in relative abundance differed among locations within years and among years within locations. Water temperature, salinity, and trap fouling community were the important determinants of temporal and spatial variation in YOY stone crab relative abundance; depth and distance from shore were also important in areas where they varied notably among stations within locations and across broader expanses of the study area. At Tampa Bay, a sharp increase in relative abundance of ovigerous females in spring was followed by a similarly sharp increase in YOY stone crab relative abundance (principally stage 3–5 crabs) 3 mo later; whereas a sharp decrease in ovigerous female relative abundance in autumn was followed by a similarly sharp decrease in YOY stone crab relative abundance 1 mo later. Coincidence of the normal autumnal decrease in YOY stone crab relative abundance with red tides and tropical cyclones prevented assigning clear relationships between seasonal change in relative abundance and these potential external influences. Annual decreases in relative abundance were significantly related to the occurrence of tropical cyclones that came near Tampa Bay during the previous year. Twice, confluences of multiple hurricanes, timely red tides, and ENSO events were followed by nearly complete, 1- to 2-y recruitment collapses. In contrast, a single meteorologically and oceanographically highly anomalous year coincided with exceptionally high abundances of both YOY and ovigerous female stone crabs. A relationship between YOY stone crabs and subsequent fishery harvest was not evident, possibly due to a variety of fishery practices. Because stone crabs are subjected to intense fishing pressure throughout the Florida Gulf, the YOY stone crab recruitment grounds and their associated estuaries should be protected from the effects of development, agriculture, aquaculture, and commercial and recreational crabbing.
... In summer, the center of green turtle abundance remains within their winter range, although green turtles are known from waters as far north as Massachusetts. In Florida, summer foraging extends north in the Gulf of Mexico from Tarpon Springs to Yankeetown (Caldwell and Carr, 1957;Carr, 1967;Schmid, 1998) and within St. Joseph Bay (E. ...
... Visual transect survey data indicate that juvenile green turtles are more abundant in intertidal and shallow subtidal areas than in deeper subtidal areas, and hawksbill turtles are infrequently encountered north of Palm Beach County (see Chap. 6 for detail). While little is known concerning the latitudinal distribution of the Kemp's ridley turtle off the Florida Atlantic coastal region, this species likely uses Florida southeast NHRs based on habitat-use patterns of Kemp's on nearshore hardbottom in southwest Florida (Schmid 1998). The current paucity of capture and tagging data for Kemp's turtles constrain attempts to assess trends in water depth and micro-habitat preferences along the Florida coast. ...
Nearshore reefs of mainland east Florida function as habitat for a diverse assemblage of marine organisms. This chapter provides an overview of multiple attributes (e.g., latitude and water depth, habitat use, feeding, disturbance processes, and connectivity) that shape shelter and trophic level functions for these communities. Reef structure and hard substratum provide shelter and attachment sites for invertebrates fishes, algae, and cyanobacteria. Some of these species, particularly the polychaete, Phragmatopoma lapidosa, and macroalgae, modify reefs and provide shelter that supports substantial invertebrate and fish assemblages. The abundance and diversity of organisms based on trophic status differs among latitude and depth gradients along nearshore reefs. For example, the numbers of herbivorous fishes decline with increasing latitude while the density of juvenile green turtles appear to be higher in east-central Florida. The type and availability of macroalgae, as well as competition among herbivores, may play a key role in these observed patterns. Natural disturbances in the form of wind and wave events, and periodic sand burial and scour, often affect recruitment and survival of sessile organisms and their faunal associates. Numerous macroalgal, invertebrate, and fish species are adapted to intermediate levels of disturbance, using these reefs for reproduction, as well as feeding sites and refuge from predators. The high abundance of newly settled and early juvenile fishes suggests these habitats serve important functions for settlers that grow out and emigrate to other environments. Such diverse inflows and outflows of propagules and nutrients suggest semi-continuous connectivity among nearshore reefs and other habitats of the larger east Florida coastal seascape.
An individual’s foraging ecology can affect its growth and survival. Stable isotope analysis has been commonly used to investigate the foraging ecology of marine turtles. However, only a few studies have provided isotopic values for the critically endangered Kemp’s ridley turtle (Lepidochelys kempii). This study presents the first characterization of δ¹³C and δ¹⁵N values from Kemp’s ridley epidermal tissue in the coastal Gulf of Mexico, Florida, USA (28.834953°N, 82.761966°W) and investigates potential size-related differences in foraging ecology. Samples were collected from 64 neritic individuals between 2016 and 2021 and divided into two groups based on straight carapace length (SCL): a smaller (< 40 cm, n = 17) and a larger (> 40 cm, n = 47) size class. When analyzing all the data together, significant correlations were found between SCL and δ¹³C, but not SCL and δ¹⁵N. However, significant differences were found between size classes, with the larger size class exhibiting higher δ¹³C and lower δ¹⁵N values than the smaller size class, which may indicate niche partitioning between size classes. To compliment these findings, an animal-borne camera was deployed on a Kemp’s ridley, and its foraging activity was documented. These results provide insights into the trophic and spatial dynamics of an understudied population and can be used to facilitate future research. Continued stable isotope analysis of Kemp’s ridley epidermis, coupled with dietary studies and satellite telemetry, can expand on these findings to elucidate more about the foraging ecology of Kemp’s ridleys and explore how dietary preferences may differ by individual size, which can guide conservation initiatives for foraging areas.
This Region comprises 48 parties, amongst countries and territories (Anguilla, Antigua & Barbuda, Aruba, Bahamas, Barbados, Belize, Bermuda, Bonaire, British Virgin Islands, Canada, Cape Verde, Cayman Islands, Colombia, Costa Rica, Cuba, Curacao, Dominica, Dominican Republic, French Atlantic & Channel coasts, French Guiana, Grenada, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Martinique, Mexico, Monserrat, Nicaragua, Panama, Portugal, Puerto Rico, Saba (Dutch West Indies), Saint Barthélemy, Saint Vincent & The Grenadines, Saint Eustach, Saint Maarten, Saint Kitts & Nevis, Saint Lucia, Saint Pierre & Miquelon, Suriname, Trinidad & Tobago, United Kingdom [U.K.], the United States [U.S.], U.S. Virgin Islands, Venezuela). The present report includes a total of 19 parties (39.5%, Belize, Canada, Colombia, Cuba, Curacao, France Atlantic, French Guiana, Guadeloupe, Guatemala, Martinique, Mexico, St. Bartholome, St. Eustach, St. Lucia, St. Martin, St. Pierre et Miquelon, UK-Ireland, the U.S., and Venezuela).
It demands a large and constant effort to bring together the detailed information from all the parties, and although there are still several parties to include in this document, as it stands it is intended to provide panorama of the complete information on the reproductive ecology and status for sea turtle populations in the North Atlantic.
For species of conservation concern, somatic growth and age at maturation are key
parameters in models used to evaluate population dynamics, as spatial and temporal variability in growth rates may be particularly important for predicting population recovery. Following an oceanic juvenile developmental stage, endangered Kemp’s ridley sea turtles Lepidochelys kempii occupy neritic habitats in 2 primary regions, the Gulf of Mexico (GoM) and along the US Atlantic coast. Results of prior studies suggest that somatic growth rates differ between these groups, which has the potential to influence maturation trajectories and relative reproductive contributions. To determine the nature and extent of potential regional differences, we conducted skeletal growth mark analysis (skeletochronology) with complementary annual bone growth increment-specific stable nitrogen isotope analysis that allowed delineation of oceanic-to-neritic habitat shifts for turtles stranded from 1993 to 2016. Results demonstrate that in the GoM, the oceanic-to-neritic habitat transition is associated with younger ages and faster somatic growth rates than in US Atlantic waters. Overall, US Atlantic somatic growth response was depressed relative to that in the GoM throughout all juvenile life stages, and this disparity persisted for more than 20 yr. This discrepancy translated into regional divergence in size-at-age relationships and maturation trajectories, with the prediction that US Atlantic Kemp’s ridleys would mature on average 2 to 3 yr later than their GoM counterparts. These analyses provide important baseline information on somatic growth rates and predicted age at maturation that can facilitate the evaluation of factors contributing to recent fluctuations in reproductive output for this endangered population.
Subadult Kemp's ridley turtles(Lepidochelys kempi) were captured and tagged at Cape Canaveral, Florida, from 1986 to 1991 (n = 113) and at Cedar Key, Florida, from 1986 to 1995 (n = 251). Subsequent recapture data at Cape Canaveral (n = 12) and Cedar K ey (n = 24) were combined and von Bertalanffy growth equations were fitted with respect to recapture interval duration. Asymptotic carapace length was either underestimated (Cape Canaveral) or overestimated (Cedar
Key) for each source database when compared to the known mean length of nesting females. Differences in asymptotic length estimates were attributed to differences in intrinsic growth rates and the inverse correlation of these two parameters. The von Bertalanffy equation for all recaptures in the combined database yielded age to maturity estimates between 8 and 13 years, based on the minimum and mean carapace lengths of nesting Kemp's ridley turtles. A duration of approximately 8-9 years was calculated for the coastal-benthic, subadult stage ofdevelopment. Recapture data for adult-size turtles are needed to increase the precision of Kemp's ridley turtle growth models.
Determined seasonal occurrence, size composition and movement patterns. -from Authors
The full text of this paper can be downloaded from: http://www.galvestonlab.sefsc.noaa.gov/publications/pdf/104.pdf
The author describes the history of US sea turtle fisheries and summarizes the commercial sea turtle landings reported in Federal fishery documents for the continental United States, Puerto Rico and Hawaii. These records provide useful ecological information regarding species composition, relative abundance, and temporal and spatial distributions of the five species commonly harvested (green, Chelonia mydas; loggerhead, Caretta caretta; Kemp's ridley, Lepidochelys kempi; hawksbill, Eretmochelys imbricata; and leatherback, Dermochelys coriacea). The conservation strategies now in place to ensure sound management of these species are briefly discussed.
Immature green turtles Chelonia mydas in Mosquito Lagoon grew at a much slower rate than would be expected from studies of captive specimens. Lagoonal loggerhead turtles Caretta caretta were also of slower growth than expected, though not to the same degree. -P.J.Jarvis
Digestive tract contents were examined from 101 dead Kemp's ridley turtles, Lepidochelys kempi, found stranded on south Texas beaches from 1983-1989. Fifty turtles were wild and 51 had been head-started (captively-reared) for 6-9 months. Fifty-one were found on bay (inshore water) and 50 on Gulf of Mexico (offshore water) shorelines. Ogren (1989) stated that juveniles (<20 cm carapace length) are surface feeders and consume a variety of food items, while subadults (20-60 cm carapace length) and adults (>60 cm carapace length) are predominately benthic feeders and eat mostly crabs. It appears, from analysis of gut contents, that wild and head-started turtles are foraging in water depths of less than 50 m and that they will consume items discarded from shrimp trawls and smaller trawls fishing for bait items. Significant differences occur between various dietary parameters measured for wild and post-release head-started turtles. However, there are similarities between the diets of both groups and head-started turtles appear to be adapting to feeding in the wild. Size and habitat differences are primary causes of dietary divergences among L. kempi.
Von Bertalanffy, logistic-by-length, and logistic-by-weight models of individual growth for 2 populations of Sceloporus merriami were estimated from 3 yr (1974-1976) of mark-recapture data using nonlinear regression. The logistic-by-weight model was found to provide the best fit to observed growth rates. Abundance of arthropod prey was estimated by 2 techniques and found to be serially correlated with seasonal precipitation. Prey abundance was correlated with annual precipitation. Individual foraging success was found to be correlated with estimated prey abundance. Parameters of logistic-by-weight growth models were compared for the 3 yr of the study and revealed that variation in food availability resulted in predictable variation in individual growth rates. Individual growth rates were positively correlated with active-season and annual precipitation and with estimates of food availability. The limitations of using stationary growth models to describe a potentially nonstationary process such as individual growth are discussed.