No place like home: an experimental comparison of reintroduction strategies using snakes.
Abstract
The practice of deliberately moving animals from one site to another for conservation is increasing as a tool to re-establish extirpated populations. Resource managers are faced with developing strategies for reintroduction attempts, but often lack experimentally derived evidence upon which to base decisions. Using the northern water snake Nerodia sipedon sipedon in the USA, we compared the behaviour and performance of resident snakes with that of individuals translocated directly from the wild to a nearby nature reserve or reared in captivity prior to translocation. Both translocated groups had low survivorship relative to resident snakes, but the proximal causes of their poor performance differed considerably. Captive-reared snakes exhibited restricted surface activity and movements and abnormal habitat use, and ultimately failed to maintain appropriate body temperature and body mass, with high mortality associated with the overwintering period. Wild snakes directly translocated to an unfamiliar site maintained body temperatures and growth comparable with residents, but their more extensive movements resulted in frequent excursions off reserve and high mortality. Synthesis and applications. We contend that an individual's prior experience is an important factor in determining their behaviour and performance during the phase of early establishment at an unfamiliar site. This suggests the existence of common underlying mechanisms influencing the outcome of reintroduction attempts, and provides a potentially useful framework for improving reintroduction efforts. Resource managers would likely improve success of reintroductions by matching habitats (and associated resources and conditions) between source and release sites, by temporarily confining animals in enclosures that force new associations to be made while limiting exploratory wanderings, or by enrichment of environmental conditions in captivity.