Relationships between boldness and fecal steroid hormone levels in captive alpine musk deer (Moschus chrysogaster) in China

Animals adapt to environmental changes through behavioral and physiological regulation, and there are individual differences in their ability to adapt to the environment, which are associated with individual personality. Boldness is a fundamental axis of animal personality, characterizing an animal's response to unfamiliar environments and threats. From June 1 to July 28, 2023, a personality assessment experiment utilizing a novel stimulus test with an unfamiliar human was conducted on 39 captive alpine musk deer (Moschus chrysogaster) at the Zhuanglang Musk Farm in Gansu Province, China. We recorded avoidance reaction indicators of musk deer in the presence of an unfamiliar human, and measured the level of the musk deer's boldness, influencing factors, and the relationships with fecal steroid hormone levels. Based on cluster analysis, 39 captive musk deer could be divided into bold (boldness score, BSS = 0.994 ± 0.008, n = 3) and shy groups (BSS = 0.327 ± 0.145, n = 36) and the average BSS in 39 musk deer was 0.378 ± 0.228. Factors such as age, sex, and density of enclosures did not have a significant effect on the boldness of musk deer. There was a significant negative correlation between the musk deer's boldness and the level of fecal cortisol metabolites. However, the correlations between boldness and testosterone levels in males and estradiol levels in females were not significant. Based on the results of our study, in the practice of musk deer farming, the measurement of the boldness can help predict the individual's adaptation to environmental stress, and it can also provide a new research perspective for the study of the boldness of solitary animals that are forced to live in groups.