Social Network Formation in Translocated Gopher Tortoises (Gopherus polyphemus)

Abstract

The gopher tortoise is a fossorial species native to the coastal plain of the southeastern United States. The species occurs spatially in colonies, or aggregations of individuals on the landscape, which were recently found to exhibit a complex social structure. Within a social network, individuals interact with known conspecifics, actively seeking out some individuals while avoiding others and groups of interacting individuals have been termed social cliques. Social cliques therefore are behaviorally isolated from other cliques while still sharing overlapping geographical space within a colony. While it is thought that these social cliques develop over long periods of time within colonies, clique formation has not yet been studied. Moreover, gopher tortoises are frequently translocated, often in mixed colony groups, and the effect of translocation practices on these cliques is unknown. To address questions about clique formation, I tracked 53 adult gopher tortoises from June – October 2017 that were translocated to Nokuse Plantation in Walton County, Florida. The study individuals were from seven source populations across Florida released into an 8.32 ha enclosure and located via radio telemetry four times per week. Forty-five of the 53 tracked adults engaged in 155 social interactions. Interactions were recorded as passive (n=27), mate choice (n=108), or aggressive (n=20) behaviors and classified as positive (passive, mate choice) or negative (aggressive) interactions. Then, a positive interaction matrix was developed and Girvan-Newman subgroup analysis of the matrix revealed the presence of eight social cliques (Q-score = 0.430), of which seven (87.5%) contained individuals from multiple source populations. Mean number of individuals per social clique was 5.63 (SD±3.12) and mean number of source populations per clique was 3.38 (SD±1.58). Thus, it appears that the gopher tortoise can form novel social cliques in a short timeframe, and that source populations do not remain socially isolated following translocation (χ2=65, P<0.001, df=7).