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![Figure 4. Hunter success ([alligators harvested/tags issued] × 100)...](profile/Mark-Merchant/publication/350111343/figure/fig2/AS:1016817757728770@1619439653924/Hunter-success-alligators-harvested-tags-issued-100-during-each-year-of-the_Q320.jpg)
Biologists with the Louisiana Department of Wildlife and Fisheries, Louisiana, USA, have managed statewide annual harvest of alligators (Alligator mississippiensis) for 35 years (1981–present). We collected and analyzed harvest data for Louisiana alligators to determine the effects of harvest on the population structure, focusing on the larger size...
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... cm/year, for an overall increase of 12.1 cm over the entire study period, or a 0.2% increase in average size of alligators harvested in Louisiana. Average annual size varied from 210.9 cm (1986) to 231.6 cm (2014; Fig. 2). The average of all skins measured (n = 870,028) during the entire time of the study was 233 cm, with a range of 120 to 430 cm (Fig. 3). The longest males and females harvested during the period were in the 400-430-cm and 270-290-cm size classes, respectively. An analysis of the total harvest during the study period revealed that 74.5% of the alligators were within the range of 153-244 cm (Fig. 3). Based on population size derived from nest surveys, the harvest records ...
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... during the entire time of the study was 233 cm, with a range of 120 to 430 cm (Fig. 3). The longest males and females harvested during the period were in the 400-430-cm and 270-290-cm size classes, respectively. An analysis of the total harvest during the study period revealed that 74.5% of the alligators were within the range of 153-244 cm (Fig. 3). Based on population size derived from nest surveys, the harvest records indicated that approximately 3% of the Louisiana alligator population was harvested ...
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... cm/year, for an overall increase of 12.1 cm over the entire study period, or a 0.2% increase in average size of alligators harvested in Louisiana. Average annual size varied from 210.9 cm (1986) to 231.6 cm (2014; Fig. 2). The average of all skins measured (n = 870,028) during the entire time of the study was 233 cm, with a range of 120 to 430 cm (Fig. 3). The longest males and females harvested during the period were in the 400-430-cm and 270-290-cm size classes, respectively. An analysis of the total harvest during the study period revealed that 74.5% of the alligators were within the range of 153-244 cm (Fig. 3). Based on population size derived from nest surveys, the harvest records ...
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... during the entire time of the study was 233 cm, with a range of 120 to 430 cm (Fig. 3). The longest males and females harvested during the period were in the 400-430-cm and 270-290-cm size classes, respectively. An analysis of the total harvest during the study period revealed that 74.5% of the alligators were within the range of 153-244 cm (Fig. 3). Based on population size derived from nest surveys, the harvest records indicated that approximately 3% of the Louisiana alligator population was harvested ...
Citations
... On the other hand, a well-regulated harvest of crocodilians in large wild populations can ensure that these populations do not decline over time (Velasco et al. 2003;Joanen et al. 2021). Joanen et al. (2021) showed that harvest quotas, set using current and recent population size indicators and environmental data, in combination with protection of breeding females and strict law enforcement, ensured that a wild American alligator population did not decline and in fact increased over a 35-year period, while at the same time realizing sizable economic benefit. ...
... On the other hand, a well-regulated harvest of crocodilians in large wild populations can ensure that these populations do not decline over time (Velasco et al. 2003;Joanen et al. 2021). Joanen et al. (2021) showed that harvest quotas, set using current and recent population size indicators and environmental data, in combination with protection of breeding females and strict law enforcement, ensured that a wild American alligator population did not decline and in fact increased over a 35-year period, while at the same time realizing sizable economic benefit. Length measurements were obtained from the harvested skins, which enabled size-class percentages to be calculated, and the data indicated that the average size of the harvested alligators increased over time without affecting the overall population size structure (Joanen et al. 2021). ...
... Joanen et al. (2021) showed that harvest quotas, set using current and recent population size indicators and environmental data, in combination with protection of breeding females and strict law enforcement, ensured that a wild American alligator population did not decline and in fact increased over a 35-year period, while at the same time realizing sizable economic benefit. Length measurements were obtained from the harvested skins, which enabled size-class percentages to be calculated, and the data indicated that the average size of the harvested alligators increased over time without affecting the overall population size structure (Joanen et al. 2021). Velasco et al. (2003) found that the harvest of large male caimans led to increases in the density and relative abundance of large males in harvested relative to nonharvested populations in most of the regions studied. ...
Monitored populations of the Nile crocodile Crocodylus niloticus at the southern end of its distribution, in the KwaZulu-Natal province of South Africa, are largely in decline. Trophy hunting of wild Nile crocodiles is only permitted at Pongolapoort Dam in the province, and monitoring of this population is required to enable the setting of annual hunting quotas. The aims of this study were to determine the feasibility of using drones to count and measure Nile crocodiles in the inlet to the dam and evaluate the utility of photo mosaics, individual photographs and videos for this purpose. A total of 16.5 km of shoreline was surveyed and 183 sub-adult and adult crocodiles observed, averaging 10.74 crocodiles per kilometer. The use of drones was cost-effective compared to traditional survey methods even though a higher number of person hours were required for data collection and processing. We recommend that drones be used to acquire video footage, supplemented by photo mosaics in areas where large aggregations of crocodiles occur, to regularly monitor this crocodile population.
... It is therefore technically possible to estimate the number of individual crocodylians in a population without human intervention in the analysis, and indeed without knowing the identities of individuals (e.g. based on passive bioacoustics monitoring). As the conservation methods of American alligators involve alligator farming (Frechette, 2001) and sustainable harvest of wild populations (Grigg & Kirshner, 2015), being able to accurately estimate population densities is vital to preventing overharvesting (Joanen et al., 2021). Currently, the method for monitoring alligator populations is the eye-shine survey, involving the counting of alligators at night via the reflections of light from their eyes, which does not sufficiently discriminate between age classes (Subalusky et al., 2009). ...
Identity cues in animal calls are essential for conspecific vocal individual recognition. Some acoustically active species mainly show reliable identity cues in their vocalizations because of variation in anatomy and life history. Long and strenuous-to-produce vocalizations may be particularly effective for showing identity cues because sustaining such calls may reveal individual anatomical differences in sound production. It is largely unknown whether reptiles possess acoustic individuality despite some groups being vocal. We analysed 814 bellows from 47 American alligators, Alligator mississippiensis, extracting spectral characteristics and manually corrected contours of the fundamental frequency. Recognition was up to 66% correct with a supervised classifier (random forest) and 61% with unsupervised clustering (chance = 2.1%), indicating that individual alligators have highly distinct bellows. Alligators were distinguished primarily based on the call spectrum, fundamental frequency contour and amplitude modulation, which also provided information about the animal's size. Neither manual supervision of acoustic analyses nor supervised training on labelled data was necessary to achieve reasonable accuracy, which has promising potential for identification of individuals via passive acoustic monitoring for research and conservation purposes. Additionally, our results highlight the importance of studying the utilization of acoustic individuality in the social lives of crocodylians.
... In these examples, catch quotas are based on population data, with monitoring ensuring that quotas can be adapted to address unforeseen impacts on populations (Gaston and Robertson, 2010). Other examples of sustainable trade are known, with crocodilians (e.g., Alligator mississippiensis) showing population growth despite offtakes, but this is contingent on well-enforced management and regulation (Joanen et al., 2021). These examples also reveal how models can support and manage populations and set offtake levels (Eversole et al., 2018), although these species are generally valuable and funds exist to facilitate genuinely sustainable management on a local basis ('t Sas-Rolfes et al., 2022; Weaver and Pieterse, 2019), whereas the necessary volume of data is unavailable for most traded species. ...
Exploitation of wildlife represents one of the greatest threats to species survival according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Whilst detrimental impacts of illegal trade are well recognised, legal trade is often equated to being sustainable despite the lack of evidence or data in the majority of cases. We review the sustainability of wildlife trade, the adequacy of tools, safeguards, and frameworks to understand and regulate trade, and identify gaps in data that undermine our ability to truly understand the sustainability of trade. We provide 183 examples showing unsustainable trade in a broad range of taxonomic groups. In most cases, neither illegal nor legal trade are supported by rigorous evidence of sustainability, with the lack of data on export levels and population monitoring data precluding true assessments of species or population-level impacts. We propose a more precautionary approach to wildlife trade and monitoring that requires those who profit from trade to provide proof of sustainability. We then identify four core areas that must be strengthened to achieve this goal: (1) rigorous data collection and analyses of populations; (2) linking trade quotas to IUCN and international accords; (3) improved databases and compliance of trade; and (4) enhanced understanding of trade bans, market forces, and species substitutions. Enacting these core areas in regulatory frameworks, including CITES, is essential to the continued survival of many threatened species. There are no winners from unsustainable collection and trade: without sustainable management not only will species or populations become extinct, but communities dependent upon these species will lose livelihoods.
... Nutria comprise a significant portion of adult alligator diets throughout coastal Louisiana (Keddy et al., 2007). Through a harvest management program implemented in 1981 by the LDWF, alligator nest counts have doubled from 1985 to 2015 (Joanen et al., 2021). Warming from climate change coupled with management may further increase alligator populations in coastal Louisiana (Ryberg & Lawing, 2018). ...
Climate change, interacting with and exacerbating anthropogenic modifications to the landscape, is altering ecosystem structure and function, biodiversity, and species distributions. Among the most visible short-term impacts are the altered ecological roles of foundation species—those species, native or non-native—that create locally stable environmental conditions and strongly influence ecosystem services. Understanding the future of these species is crucial for projecting impacts on ecosystem services at both local and regional scales. Here we present foundation species by ecoregion study cases across the US South-Central Region (Louisiana, New Mexico, Oklahoma, and Texas), including C4 grasses, mesquite, and northern bobwhite in the Southern Great Plains, mangroves and nutria in coastal Louisiana wetlands, tiger salamanders and sandhill cranes in wetlands of the Southern Great Plains, and post and blackjack oaks and eastern redcedar in the Cross Timbers ecoregion. These case studies explore the impacts of climate change on foundation species and the consequences for ecosystem services, the outlook for climate adaptation efforts, and the sustainability of restoration in these systems. We underscore risks and vulnerabilities that stakeholders should consider when managing or restoring natural resources and conserving ecosystem services in an increasingly extreme and variable climate. We show that past management, through a lack of understanding or implementation of actions, has exacerbated shifts in invasive species, resulting in significant changes in ecosystem structure and function. These changes, interacting with landscape fragmentation and shifting land use and exacerbated by climate change, can result in critical losses of biodiversity. Unfortunately, lack of public understanding may hinder political support for restoration efforts and climate adaptation strategies crucial for the continued supply of traditional ecosystem services. Furthermore, the resulting invaded systems may provide opportunities for income via new ecosystem services valued by society that may reduce support for restoration to historical baselines, thus further shifting management priorities. These priorities should be informed by an understanding of past and ongoing ecological trends in region-specific situations, such as those we present, to highlight the immediacy of climate change impacts on the environment and society and provide evidence for the critical nature of informed management decisions.
... Nutria comprise a significant portion of adult alligator diets throughout coastal Louisiana (Keddy et al., 2007). Through a harvest management program implemented in 1981 by the LDWF, alligator nest counts have doubled from 1985 to 2015 (Joanen et al., 2021). Warming from climate change coupled with management may further increase alligator populations in coastal Louisiana (Ryberg & Lawing, 2018). ...
Climate change, interacting with and exacerbating anthropogenic modifications to the landscape, is altering ecosystem structure and function, biodiversity, and species distributions. Among the most visible short-term impacts are the altered ecological roles of foundation species—those species, native or non-native—that create locally stable environmental conditions and strongly influence ecosystem services. Understanding the future of these species is crucial for projecting impacts on ecosystem services at both local and regional scales. Here we present foundation species by ecoregion study cases across the US South-Central Region (Louisiana, New Mexico, Oklahoma, and Texas), including C4 grasses, mesquite, and northern bobwhite in the Southern Great Plains, mangroves and nutria in coastal Louisiana wetlands, tiger salamanders and sandhill cranes in wetlands of the Southern Great Plains, and post and blackjack oaks and eastern redcedar in the Cross Timbers ecoregion. These case studies explore the impacts of climate change on foundation species and the consequences for ecosystem services, the outlook for climate adaptation efforts, and the sustainability of restoration in these systems. We underscore risks and vulnerabilities that stakeholders should consider when managing or restoring natural resources and conserving ecosystem services in an increasingly extreme and variable climate. We show that past management, through a lack of understanding or implementation of actions, has exacerbated shifts in invasive species, resulting in significant changes in ecosystem structure and function. These changes, interacting with landscape fragmentation and shifting land use and exacerbated by climate change, can result in critical losses of biodiversity. Unfortunately, lack of public understanding may hinder political support for restoration efforts and climate adaptation strategies crucial for the continued supply of traditional ecosystem services. Furthermore, the resulting invaded systems may provide opportunities for income via new ecosystem services valued by society that may reduce support for restoration to historical baselines, thus further shifting management priorities. These priorities should be informed by an understanding of past and ongoing ecological trends in region-specific situations, such as those we present, to highlight the immediacy of climate change impacts on the environment and society and provide evidence for the critical nature of informed management decisions.
... The second strategy (hunting of adults) generated problems in the past because it was poorly controlled and carried out at unsustainable rates. However, there are currently successful programs of this type, i.e., Caiman crocodilus fuscus in Venezuela (since 1983, Velasco andAyarzagüena 2010), and Alligator mississippiensis in the United States (since 1971, Elsey and Woodward 2010;Joanen et al. 2021). In both cases, hunting mainly males at low rates has maintained stable or increased populations. ...
... In crocodilians, it is considered that the capture of males is not harmful to the population (Joanen et al. 2021). Based on this, our model represents the tolerance of natural populations to occasional extractions of females. ...
... Such a differential prey selection, however, requires a hunting method that confirms the sex of the animal before harvesting (e.g., spinel, and capture from a boat, instead of long-distance shooting). In addition, hunting sites can be established based on the different spatial distribution between males and females, allowing hunting mostly where it is known that there is a preponderance of males (Joanen et al. 2021). Therefore, our model provides a conservative value for any female-or male-focused management scenario. ...
We created a matrix model structured by stages (divided into 5 stages) to evaluate the populationdynamics of Caiman latirostris and the population behavior at different management intensities throughranching and hunting of adult individuals. We generated 5000 matrices by sampling the mean andvariance values of survivals (pi) and hatching for each stage. For each matrix, we obtained the growthrate λ and performed elasticity analyses. Modifying the mean matrix obtained from the previousanalysis, we evaluated different scenarios of ranching, reintroduction, and hunting of adult females ofthe last two stages (E) raised here (class III animals, > 60 cm snout-vent length, divided into two: E4and E5). We obtained a mean λ of 1.035 (range 0.88 − 1.12), and 11.9% of the simulations had λ < 1.The vital rate with the highest elasticity and variance was that of the adult females of the last stage.Natural populations can tolerate a maximum of 5% adult female hunting, and ranching can extract55% of nests from the wild without reintroduction or 80% of nest harvest, returning to the wild at least3% of hatched animals in the ranching programs. Our model showed that hunting and ranching withreintroduction are feasible strategies to be applied without threatening natural populations. Increasingreintroduction makes it possible to extract more adult individuals and maintain the species’ populationsat sustainable levels.
... Proportion of undersized skins by its time allow learning the proportion of misdoing and how this is affected by other factors, such as increase in the required hunting effort [7,39,46]. Together, these parameters allow us to better understand anaconda populations, just as they do for other species under older and more well-established management initiatives, such as the American alligator [47]. ...
Sustainable wildlife management is necessary to guarantee the viability of source populations, but it is rarely practiced in the tropics. The yellow anaconda (Eunectes notaeus) has long been harvested for its leather. Since 2002 its harvest has operated under a management program in northeastern Argentina, which relies on adaptive management practices, that limit the minimum body length permitted for harvesting, the number of active hunters and the length of hunting seasons. Here we investigated the effects of yellow anaconda harvest on its demography based on 2002-2019 data and show that exploitation levels are sustainable. The gradual reduction in annual hunting effort, due to a decrease in the number of hunters and hunting season duration, reduced the total number of anacondas harvested. Conversely, captures per unit effort increased across the study period. The body size of anacondas was not influenced by the harvesting, and more females than males were caught. We also found that a decrease in mean temperature positively influenced anaconda harvest and the capture of giant individuals. Because sustainable use is a powerful tool for conservation, and anacondas are widespread in South America, these discoveries are highly applicable to other species and regions.
... In these examples, catch quotas are based on population data, with monitoring ensuring that quotas can be adapted to address unforeseen impacts on populations (Gaston and Robertson, 2010). Other examples of sustainable trade are known, with crocodilians (e.g., Alligator mississippiensis) showing population growth despite offtakes, but this is contingent on well-enforced management and regulation (Joanen et al., 2021). These examples also reveal how models can support and manage populations and set offtake levels (Eversole et al., 2018), although these species are generally valuable and funds exist to facilitate genuinely sustainable management on a local basis ('t Sas-Rolfes et al., 2022; Weaver and Pieterse, 2019), whereas the necessary volume of data is unavailable for most traded species. ...
Exploitation of wildlife represents one of the greatest threats to species survival according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Whilst detrimental impacts of illegal trade are well recognised, legal trade is often equated to being sustainable despite the lack of evidence or data in the majority of cases. We review the sustainability of wildlife trade, the adequacy of tools, safeguards, and frameworks to understand and regulate trade, and identify gaps in data that undermine our ability to truly understand the sustainability of trade. We provide 183 examples showing unsustainable trade in a broad range of taxonomic groups. In most cases, neither illegal nor legal trade are supported by rigorous evidence of sustainability , with the lack of data on export levels and population monitoring data precluding true assessments of species or population-level impacts. We propose a more precautionary approach to wildlife trade and monitoring that requires those who profit from trade to provide proof of sustainability. We then identify four core areas that must be strengthened to achieve this goal: (1) rigorous data collection and analyses of populations; (2) linking trade quotas to IUCN and international accords; (3) improved databases and compliance of trade; and (4) enhanced understanding of trade bans, market forces, and species substitutions. Enacting these core areas in regulatory frameworks, including CITES, is essential to the continued survival of many threatened species. There are no winners from unsustainable collection and trade: without sustainable management not only will species or populations become extinct, but communities dependent upon these species will lose livelihoods.
... American alligators are an important economic resource in the southeastern USA. In particular, in Louisiana, alligators are sustainably farmed and hunted for the production of both meat and skin products (e.g., Joanen et al. 2021). Because alligators are long-lived, top trophic carnivores, capable of accumulating high amounts of certain toxicants (e.g., Finger et al. 2017a, b;Tuberville et al. 2016), including Hg (e.g., Jagoe et al. 1998;Nilsen et al. 2019), consumption of alligator meat represents a possible exposure risk to humans in certain areas of their range. ...
Total mercury (THg) concentrations were measured in wild alligators inhabiting a coastal marsh in southern Louisiana, to determine the tissue distribution of THg among various body organs and tissue compartments. Concentrations of THg in claws and dermal tail scutes were compared to those in blood, brain, gonad, heart, kidney, liver, and skeletal muscle to determine if the former tissues, commonly available by non-lethal sampling, could be used as measures of body burdens in various internal organs. Mercury was found in all body organs and tissue compartments. However, overall, THg concentrations measured in alligators were below the FDA action level for fish consumption and were comparable to previous data reported from southwestern Louisiana. Our results suggest consumption of meat from alligators found in this region may be of little public health concern. However, the extended period of time between sampling (in this study) and the present-day highlight the need for continuous, additional, and more recent sampling to ensure consumer safety. Total mercury concentrations were highest in the kidney (3.18 ± 0.69 mg/kg dw) and liver (3.12 ± 0.76 mg/kg dw). THg levels in non-lethal samples (blood, claws, and dermal tail scutes) were positively correlated with all tissue THg concentrations (blood: R 2 = 0.513-0.988; claw: R 2 = 0.347-0.637, scutes: R 2 = 0.333-0.649). Because THg concentrations from blood, claws, and scutes were correlated with those of the internal organs, non-lethal sampling methods may be a viable method of estimating levels of THg in other body tissues.
... This is problematic because in many cases whether trade-driven harvest is detrimental to populations remains an open question requiring further research. While some species may be threatened by modest levels of trade, others can be traded in large volumes without trade posing a threat to the survival of the species in the wild (e.g., reticulated python Malayopython reticulatus and American Alligator Alligator mississippiensis; Joanen et al., 2021;Natusch et al., 2016). ...
Overexploitation is a key driver of biodiversity loss but the relationship between the use and trade of species and conservation outcomes is not always straightforward. Accurately characterizing wildlife trade and understanding the impact it has on wildlife populations are therefore critical to evaluating the potential threat trade poses to species and informing local to international policy responses. However, a review of recent research that uses wildlife and trade‐related databases to investigate these topics highlights three relatively widespread issues: (1) mischaracterization of the threat that trade poses to certain species or groups, (2) misinterpretation of wildlife trade data (and illegal trade data in particular), resulting in the mischaracterization of trade, and (3) misrepresentation of international policy processes and instruments. This is concerning because these studies may unwittingly misinform policymaking to the detriment of conservation, for example by undermining positive outcomes for species and people along wildlife supply chains. Moreover, these issues demonstrate flaws in the peer‐review process. As wildlife trade articles published in peer‐reviewed journals can be highly influential, we propose ways for authors, journal editors, database managers, and policymakers to identify, understand, and avoid these issues as we all work towards more sustainable futures.
