Post-release movements of captive-born European mink Mustela lutreola

Abstract

Naïve captive-bred animals often make excessive movements when released into the wild, which may increase vulnerability to predation, take animals into unsuitable habitat and/or increase the probability of conflict with humans. We analysed the post-release movements of captive-bred European mink Mustela lutreola reintroduced to Hiiumaa Island, Estonia. We tested the effect of pre-release enclosure type, sex, generations in captivity, pregnancy and age on post-release movements, investigated the settlement process and explored the relationship between post-release movements and survival. We found no effect of enclosures on post-release movements in the first 2 wk following release (except that individuals from large naturalistic enclosures spent less time close to water than did animals from standard zoo enclosures) but some evidence of a slight effect at 1 mo post-release. Males moved further at 3 d (but not 2 wk) postrelease than did females, and juveniles appeared to move further in the first 3 d post-release than did 1 yr olds. We were unable to detect a relationship between post-release movements and survival. The largest known cause of mortality was predation, but it was not clear why mink were vulnerable to predation, and the locational data presented here were unable to shed light on this issue. Individual variation also made it difficult to define patterns. These are common problems in reintroductions, and we suggest that in future releases of captive-bred animals, more detailed post-release behavioural observations and investigation of personality types might be insightful.