U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Herpetological Conservation and Biology (2023) 18(3): 488–499


United States government work


Differential predation was observed in a population of 59 translocated juvenile desert tortoises (Gopherus agassizii) of known sex during a juvenile translocation survival study between September 2012 and November 2017. The main source of mortality was attributed to coyote (Canis latrans) and kit fox (Vulpes macrotis) predation. Predation was skewed with higher female mortality than male mortality. We tested the hypothesis that juvenile females smell different than males, which leads to increased canid predation. We also explored differences in chemical signatures of resident adult female and male desert tortoises. We collected oral, cloacal, and chin/forelimb swabs from translocated juvenile and resident adult tortoises during fall 2015 and fall 2017 and analyzed them using headspace gas chromatography/mass spectrometry to determine potential differences in the chemical signatures of volatile compounds. Standardized chromatographic peak responses were subjected to analyses of variance (ANOVA). For development of artificial scents, mean responses were calculated for each juvenile tortoise from standardized responses representing all collections, and grand means were determined for males and females. Collections of volatiles differed significantly according to age and/or sex depending on the body location of collection. Among the plausibly endogenous volatiles that differed by age, many of them are alcohols. We conducted two field trials using captive coyotes and one field trial partially within the translocation area to test if coyotes showed a preference for female or bias against male synthesized scent. No consistent preference or bias was shown, suggesting that no innate preference for female odor was evident.