Social dynamics and behavior of zoo-housed red-footed tortoises at different housing densities

Within zoos, it is common for animals that are considered solitary to be housed with conspecifics. This may be due to a variety of factors such as spatial constraints within zoos, difficulties associated with transferring animals, breeding goals, and/or other management challenges. However, the welfare implications of housing solitary animals with conspecifics are not well understood. This opportunistic study examined the impact of different housing densities (two versus four individuals) on red-footed tortoise social dynamics and behavior. Agonistic behaviors, primarily mounting, were significantly higher when four tortoises were present. Additionally, the tortoises utilized more of their enclosure when four tortoises were present. Social network analyses revealed that the tortoises had a dominance hierarchy, with high asymmetry and unidirectionality between tortoise dyads. Further, social inactivity decreased when only two tortoises were present. Collectively, the results of this study provide valuable information about the relationship between housing density and behavior in these tortoises, which can inform future study design and management strategies at other institutions that house reptiles socially.