Captive housing during water vole (Arvicola terrestris) reintroduction: does short-term social stress impact on animal welfare?

Merryl Gelling,Tom P Moorhouse,David W Macdonald,Iñigo Montes

doi:10.1371/journal.pone.0009791

Abstract

BackgroundAnimals captive bred for reintroduction are often housed under conditions which are not representative of their preferred social structure for at least part of the reintroduction process. Specifically, this is most likely to occur during the final stages of the release programme, whilst being housed during transportation to the release site. The degree of social stress experienced by individuals during this time may negatively impact upon their immunocompetence.Methodology/Principal FindingsWe examined two measure of stress - body weight and Leukocyte Coping Capacity (LCC) - to investigate the effects of group size upon captive-bred water voles destined for release within a reintroduction program. Water voles were housed in laboratory cages containing between one and eight individuals. LCC scores were negatively correlated with group size, suggesting that individuals in larger groups experienced a larger degree of immuno-suppression than did individuals housed in smaller groups or individually. During the course of the study mean body weights increased, in contrast to expectations from a previous study. This was attributed to the individuals sampled being sub-adults and thus growing in length and weight during the course of the investigation.Conclusions/SignificanceThe reintroduction process will inevitably cause some stress to the release cohort. However, for water voles we conclude that the stress experienced may be reduced by decreasing group size within captive colony and/or transportation housing practises. These findings are of significance to other species' reintroductions, in highlighting the need to consider life-history strategies when choosing housing systems for animals being maintained in captivity prior to release to the wild. A reduction in stress experienced at the pre-release stage may improve immunocompetence and thus animal welfare and initial survival post-release.

Highlights

The maintenance of animals in captivity as part of a larger program to ensure a particular species’ survival is becoming increasingly commonplace [1]
Animals are often housed under conditions which may not be representative of their preferred social structure, and this is likely during transportation to the release site [2]
Effects of group size on Leukocyte Coping Capacity (LCC) LCC scores were negatively correlated with the number of water voles in each cage (MANOVA F7,21 = 2.506, P = 0.049)

Summary

Introduction

The maintenance of animals in captivity as part of a larger program to ensure a particular species’ survival is becoming increasingly commonplace [1]. Animals are often housed under conditions which may not be representative of their preferred social structure, and this is likely during transportation to the release site [2]. Animals captive bred for reintroduction are often housed under conditions which are not representative of their preferred social structure for at least part of the reintroduction process. This is most likely to occur during the final stages of the release programme, whilst being housed during transportation to the release site. The degree of social stress experienced by individuals during this time may negatively impact upon their immunocompetence

Methods

Results

Conclusion