Crocodile social environments dictated by male philopatry

Few studies have examined the social behaviors of solitary animals, due to the rarity of observing interactions in the wild. We demonstrate how animal telemetry can be used to characterize individual social environments among a wild population of estuarine crocodiles. We discovered that crocodiles were more social than previously thought, where an individual's sex, degree of site-fidelity and proximity to the mating season influenced the degree of spatial overlap between potential mates and conspecifics. Examining the social behaviors of solitary species can be challenging due to the rarity in which interactions occur and the large and often inaccessible areas which these animals inhabit. As shared space-use is a prerequisite for the expression of social behaviors, we can gain insights into the social environments of solitary species by examining the degree of spatial overlap between individuals. Over a 10-year period, we examined how spatial overlap amongst 105 estuarine crocodiles Crocodylus porosus was influenced by season, sex, and movement tactic. We discovered that crocodiles displayed highly consistent spatial overlaps with conspecifics between months and across years. Furthermore, male crocodiles that exhibited a greater degree of site fidelity displayed more stable social environments, while females and males that were less site-attached had more dynamic social environments with spatial overlaps between conspecifics peaking during the mating season. Our results demonstrate how long-term tracking of multiple individuals within the same population can be used to quantify the spatial structure and social environment of cryptic and solitary species.