Impacts of the season and reproductive status on fecal reproductive and adrenocortical steroid metabolites in zoo Cuban crocodiles (Crocodylus rhombifer)

Abstract

Conservation strategies for crocodilians often include captive breeding to create stable assurance populations. Evaluating adrenal and gonadal hormone patterns can provide animal managers with data to more effectively monitor animal welfare and reproductive status. This study evaluated the effects of season (breeding, nesting, or off), sex (male and female), and reproductive status of females (egg-laying/housed with a male or non-laying/housed solo) on concentrations of fecal glucocorticoid metabolite (FGM), fecal androgen metabolite (FAM), and fecal progestogen metabolite (FPM) in seven Cuban crocodiles, Crocodylus rhombifer, at the Smithsonian's National Zoological Park. Overall, seasonal changes in FGM and FPM concentrations were only observed in egg-laying females; FGM and FPM concentrations were both higher during the nesting season compared to the breeding and off seasons. Seasonal changes in FAM concentrations were only observed in males; males had higher FAM concentrations during the breeding and nesting seasons compared to the off season. Future studies investigating the use of fecal hormone metabolites in crocodilians are necessary to understand differences between individuals and species, to further elucidate the interactions between hormones and environmental factors, such as social housing, and to develop long-term datasets for the management of this species. K E Y W O R D S crocodilians, fecal hormone metabolites, zoo management 1 | INTRODUCTION Crocodilians are often propagated ex situ for sustainable population management and to create assurance colonies for species conservation as recommended by the IUCN SSC Crocodilian Specialist Group. These managed animals are often critical to the preservation of species, particularly those for which the in situ populations are experiencing drastic declines due to loss of habitat and illegal hunting. The Association of Zoos and Aquariums manages sustainable populations of seven crocodilian species in North America to promote conservation through species management, education, and research. While space is the limiting factor in many of these programs, the consistent reproduction of some species remains a challenge (e.g., the Indian Gharial, Gavialis gangeticus). Hormone monitoring in crocodilians can provide valuable data on the reproductive status of individuals and the external factors (stressors) that may be negatively impacting reproductive success in captive populations; however, blood collection can be difficult for many species and can produce skewed results due to the effects of capture

Investigating Welfare Metrics for Snakes at the Saint Louis Zoo

“…Although we found that increased FGM was associated with increased levels of disturbance in these snakes, we urge caution in the design of studies using FGM to assess welfare in reptiles. Gastrointestinal passage time in reptiles makes it difficult to assess real-time stress responses, as it represents an average value pooled in the gut of the animal over a more prolonged period than is typically the case in mammals or birds [59,64]. In this study, there was a significant positive association between the number of days since the last feeding and FGM concentrations.…”

“…Snakes respond to stress by activating the hypothalamic-pituitaryadrenal (HPA-) axis, which releases corticosterone into the blood [55]. Fecal glucocorticoid metabolites (FGM) can be measured non-invasively in animal feces [49], a technique that is becoming increasingly popular as a tool for evaluating reptile welfare [48,49,[56][57][58][59][60][61][62][63][64]. Many factors can influence FGM levels, such as diet and metabolic rate [51,65,66].…”

Hot and bothered: alterations in faecal glucocorticoid metabolite concentrations of the sungazer lizard, Smaug giganteus, in response to an increase in environmental temperature

“…The use of non-invasive endocrine monitoring techniques, through the collection of faeces, urine and hair, hold several advantages above the commonly used, invasive blood collection, including (1) minimal human-animal interaction, (2) the ability to collect repeated samples over prolonged periods with minimal effort (Whitham and Wielebnowski 2013) and (3) hormone metabolite concentrations assessed in faeces are less affected by episodic fluctuations in hormone secretions due to the pooling of metabolites within the gut prior to excretion (Kersey and Dehnhard 2014;Russell et al 2012). Several studies have used noninvasive faecal glucocorticoid metabolite (fGCM) monitoring to assess the level of physiological stress experienced by reptiles in response to direct human-animal interaction (Borgmans et al 2018;Kalliokoski et al 2012;Rittenhouse et al 2005) or seasonal changes in social and reproductive parameters (Augustine et al 2020;West and Klukowski 2018).…”

Monitoring the stress physiology of free-ranging mugger crocodiles (Crocodylus palustris) across diverse habitats within Central Gujarat, India

“…However, for the crocodilians, only two studies have been done so far to measure fGCM concentrations: one on Nile crocodiles ( Ganswindt et al. , 2014 ) and the other on Cuban crocodiles ( Crocodylus rhombifer ) ( Augustine et al. , 2020 ).…”