Changes in social groups across reintroductions and effects on post‐release survival

Abstract

Reintroductions, essential to many conservation programmes, disrupt both abiotic and social environments. Despite growing recognition that social connections in animals might alter survival (e.g. social transmission of foraging skills, or transmission of disease), there has thus far been little focus on the consequences of social disruption during reintroductions. Here we investigate if moving familiar social groups may help a threatened species to adjust to its new environment and increase post-release survival. For a reintroduction of 40 juvenile hihi Notiomystis cincta (a threatened New Zealand passerine), we observed social groups before and after translocation to a new site and used social network analysis to study three levels of social change: overall group structure, network associations and individual sociality. We also tested alternate translocation strategies where birds were kept temporarily in aviaries in either a familiar group, or where their prior association was mixed. Although social structure remained similar among juveniles that remained at the source site, we detected significant changes in translocated birds at both the group-and individual-level post-release. However, our holding treatments did not affect these social bonds so we remain unable to maintain or manipulate social groups during translocation. Crucially, there was a small tendency for translocated juveniles that gained more associates during re-assortment of social groups to be more likely to survive their first year post-release. We suggest that prior sociality may not be important during translocations, but rather individuals that are most able to adapt and form associations at a new site are most likely to be the surviving founders of reintroduced populations.

The phenotypic costs of captivity

“…Reintroduced hihi Notiomystis cincta that gained more associates post‐release tended to show higher survival, suggesting that social individuals are more likely to found reintroduced populations (Franks et al ., 2020). Post‐release dispersal distance of captive river otters Lontra canadensis was predicted by prior history of positive social interactions in captivity (Hansen et al ., 2009).…”

Understanding and applying biological resilience, from genes to ecosystems

“…48,86 ), and can also be conducted alongside interventions to mitigate species decline or change in ecosystem function (e.g. conservation actions including introductions of individuals or translocations of populations 87 ), if the selection of individuals or species to be moved is designed to test the relative resilience of different characteristics (e.g. social behaviour 88 , genetic diversity 67 ).…”

The nuthatch and the hare: Slow explorers dominate in a re-established population of the Brown-headed Nuthatch (Sitta pusilla) two decades later

“…In the early years of a restoration effort when conspecific densities are low, dispersal-averse, slow-exploring individuals that remain near the release site benefit from group vigilance and defense, transmission of social information such as resource location, and are able to form social bonds necessary for reproduction and survival (Cote et al 2010, Reale andDingemanse 2010). For example, juvenile Hihis (Notiomystis cincta; another cooperative breeder) that broadened their social affiliations following translocation were more likely to survive their first year than individuals that did not make this adjustment (Franks et al 2019). The loss of fastexploring individuals also results in decreased behavioral (and likely genetic) diversity of the founding population (Reale and Montiglio 2020), which could explain the predominance of slow explorers in EVER today.…”