Scent-marking behavior by female sloth bears during estrus

Abstract: The sloth bear (Melursus ursinus) is one of the least studied bears. Important aspects of sloth bear biology and ecology, such as reproductive physiology and behavior, are largely unknown. Increased scent-marking by anogenital rubbing during breeding season has been recorded in other bear species. We studied the genital rubbing behavior of 37 captive female sloth bears (2–18 yr of age) at the Agra Bear Rescue Facility, India, for 4 breeding seasons over a period of 3.5 years (1 Jun 2015 to 31 Dec 2018). Data on changes in vulva visibility and presence of genital rubbing behavior were collected daily during the breeding period and twice per week for rest of the year, throughout the study period. Vulva visibility was scored as 0 (not visible), 1 (slightly visible), and 2 (fully visible), and a female was considered to be in estrus if the vulva was slightly or fully visible. Presence of genital rubbing was recorded as 1 and its absence as 0. Occurrence of genital rubbing coincided with estrus, as defined by vulva visibility scores. Statistical analysis indicated that female age and the number of males with physical proximity (i.e., in the same enclosure) were significantly correlated with the occurrence of genital rubbing behavior. The number of females in physical proximity and the number of females in the vicinity without physical proximity (i.e., not in the same enclosure but sharing a fence) did not significantly affect this behavior. The results of our study suggest that the genital rubbing behavior by female sloth bears in estrus is likely a form of scent-marking, serving a communicative function, and could be influenced by male presence. This behavior may be a key factor in attracting a mate during the breeding season in the wild.