Physiological consequences of captive conditions in water voles (Arvicola terrestris)

Abstract

Re-introductions of captive-bred animals are increasingly common in wildlife conservation and it is important that they fulfil their potential. To foster this goal we examined variations in stress levels in a captive-bred population of water voles Arvicola terrestris in response to housing conditions and radio-collaring, using weight loss and leukocyte coping capacity (LCC) as measures of relative stress, to investigate the impacts of housing conditions, handling and radio-collaring on this species. Thirty-eight water voles (22 males and 16 females) were used in the investigation, 25 housed in outdoor enclosures and 13 in laboratory cages. During the 6-week study, LCC, body weight and urine refractive index (URI, an indicator of hydration levels) were recorded once a week for each individual in weeks 1, 2, 4 and 6. After the first sample, radio-collars were attached to 20 individuals (10 males and 10 females) taken from both housing types. Throughout the experiment laboratory-cage housed voles weighed less, had lower LCC scoresindicating a reduced ability to combat infection -and had higher URIs than outdoor-enclosure voles. This suggests that the laboratory-cage voles were more stressed and dehydrated than the outdoor-enclosure voles. Weights and LCC scores of both housing groups decreased as the study progressed, suggesting that elements of the study, such as repeated handling, may have caused stress to both groups. Evidence suggested a short-term effect of radio-collaring on immunocompetence. We conclude that captive housing conditions, repeated manipulation and radio-collaring had demonstrable physiological effects on the water voles studied. We recommend that the effects of husbandry and tagging practices upon captive-bred mammals be closely studied as part of the quest to improve the success of the re-introductions to which they contribute.

Post-release survival of orphaned wild-born polecats Mustela putorius reared in captivity at a wildlife rehabilitation centre in England

“…Reintroductions did appear to be more successful when source animals were wildborn (31% versus 13%), but other factors such as the number of animals released and persistence of the original reason for the species decline were also shown to be important (Fischer & Lindenmayer 2000). Although the use of wild-born animals in restoration projects may be more successful than using captive-bred individuals (Fischer & Lindenmayer 2000, Hayward et al 2007, Jule et al 2008, translocating wild animals to unfamiliar habitats or territories may affect their welfare (Molony et al 2006, Moorhouse et al 2007, PinterWollman et al 2009). Sub-optimal habitat and naivety to the local environment may lead to competitioninduced stress, exposure to disease and vulnerability to predation.…”

“…This could potentially result from poor diet in captivity (less than appropriate milk replacers for example), lack of opportunity to learn or develop social skills resulting in inappropriate social responses to conspecifics (particularly if imprinted on humans), lack of opportunity to learn how to hunt, lack of familiarity with local prey, and the possibility that rescued wildlife may be poor quality in relation to other individuals in the population. Captivity itself may result in increased cumulative effects of stress (Moorhouse et al 2007). However, the effect of stress is rarely considered in translocation, reintroduction or wildlife rehabilitation programmes (Teixeira et al 2007, Linklater et al 2010).…”

The importance of chemical communication studies to mammalian conservation biology: A review

“…Captive breeding and reintroduction are vital tools in single species conservation. However, captive conditions, the associated handling stress and monitoring of released individuals can have negative physiological effects and thereby affect reintroduction success (Moorhouse et al, 2007). Detailed understanding of the use and behavioural effects of chemical signals could serve to increase welfare and health status of captive animals as well as encourage settlement of newly released or translocated animals into suitable habitats.…”

“…Collection of whole family groups maintains important social bonds, behaviours and can increases survival (Shier, 2006). Capture, handling and transportation can have negative physiological consequences to animal welfare, which in turn can affect the success of reintroductions (Moorhouse et al, 2007). The inclusion of an animal's scent in transport containers or living quarters can aid settlement, reduce stress, aggression and the display of over scent marking behaviours (Swallow et al, 2005;Veillette and Reebs, 2010).…”

Who ends up in the eagle owl pellets? A new method to assess whether water voles experience different predation risk

“…Although some studies used information from radio-collared prey (Keith et al 1984;Temple 1987;Rohner and Krebs 1996;Murray 2002), radiocollaring itself could affect prey vulnerability and bias the results. For instance, in water voles radio-collaring was correlated both with lower survival and immuno-competence and altered offspring sex ratio (Moorhouse and Macdonald 2005;Moorhouse et al 2007). …”