Serum concentrations of corticosterone and sex hormones and their relationship in farmed Morelet’s crocodile (Crocodylus moreletii)

Abstract

31 Background: Crocodile farming aims to produce high-quality skins from captive 32 crocodilians. Captivity usually exposes the animals to stressful conditions, resulting in 33 increased serum corticosterone (CORT) levels that correlate negatively with those of sex 34 hormones and reproductive success. Objective: To evaluate serum concentrations of CORT 35 and sex hormones and their relationship in farmed Morelet’s crocodiles ( Crocodylus 36 moreletii ), in the non-breeding (NBS) and breeding (BS) seasons. Methods: The study 37 included 59 adult crocodiles (29 females, 30 males). One blood sample was collected in 38 NBS (n = 31) and BS (n = 28) from each crocodile to determine serum concentrations of 39 CORT, estradiol (E 2 ), progesterone (P 4 ), and testosterone (T). Throughout the study, 40 crocodiles were kept in mixed-sex groups and were fed once or twice a week. Results: In 41 females, CORT was higher (p<0.05) in NBS, but had no correlation (p>0.05) with E 2 or P 4 42 in any season. In males, CORT was similar (p>0.05) in NBS and BS, and had no correlation 43 (p>0.5) with T. Conclusion: Levels of CORT had no effect on sex hormones perhaps 44 because CORT was low as a result of farming conditions that did not expose the animals to 45 severe or chronic stress.