Overwinter survival and post-release movements of translocated water voles: implications for current mitigation guidance

Abstract

Translocation is currently used as a last resort mitigation strategy for water voles (Arvicola amphibius) in the UK (Dean et al. 2016, The Water Vole Mitigation Handbook), where populations have undergone widespread declines during the past century Q214 (Strachan and Jefferies1993, Preliminary report on the changes in the water vole as shown by the National Surveys of1989-1990 and 1996-1998). To increase the chances of success, current guidance suggests translocation of voles during autumn should not be carried out as individuals may be at higher risk of overwinter mortality, and instead should be overwintered in captivity for release the following spring (Dean et al. 2016). To verify this guidance, we carried out a mark recapture and radio tracking study of an autumn translocated and resident population in lowland England. Whilst we found translocated voles undertook longer exploratory movements than residents and those previously recorded in spring, there was no evidence from our study that translocated voles suffered higher mortality rates compared to the resident individuals. The turnover in both populations was high with 25% and 8% of the translocated and resident individuals being recaptured in spring. Younger voles that were not collared had a significantly higher chance of being recaptured in spring and their survival and settlement on the receptor channel is considered important as this is the age class that will produce most of the following years' young. Mean weekly distances moved by collared voles showed no pattern of stabilisation, in either sex, over the 10-week monitoring period and combined dispersal from both study populations accounted for 26% of those that were not recaptured in spring. However, due to low sample size, we were unable to distinguish between the effects of dispersal and mortality. We conclude that where individuals or populations will be negatively impacted by planned development, autumn translocations in lowland England may offer a feasible alternative to housing animals in captivity, given the high financial cost and additional health and welfare risks associated with a captive environment. The receptor site and adjacent habitat (> 1 km) would need to support a seasonal abundance of food and cover, be connected to existing populations and be part of a wider landscape that is mink free and under an effective mink control programme to help secure long-term population viability. We advise, however, that due to our small sample size, further studies are undertaken to confirm our findings.

Space use, habitat selection and daily activity of water voles Arvicola amphibius co-occurring with the invasive American mink Neovison vison

“…Moreover, Moorhouse & Macdonald (2005) concluded that female water voles exhibit drifting territoriality, and the degree to which territories drifted was smaller at higher densities. Results of recent studies conducted in U.K. showed, similarly to our results, that activity of resident water vole males was about twofold higher than activity of resident females (Baker et al 2018). Mean weekly distance between two locations was about 30 m in males and 15 m in females, and maximum weekly distance was about 315 m in males and 70 m in females.…”

Putting rakali in the spotlight: innovative methods for detecting an elusive semi-aquatic mammal

“…For a semi-aquatic mammal, focusing on methods within their main foraging medium appears highly beneficial. Traps mounted to floating platforms have been successful in trapping water voles (Arvicola amphibius), muskrats (Ondatra zibethicus and Neofiber alleni), South American water rats (Nectomys squamipes), water opossums (Chironectes minimus), mink (Neovision vison) and spot-legged turtles (Rhinoclemmys punctularia) (Schooley and Branch 2005;Ahlers et al 2010;Harrington et al 2012;Leite et al 2016;Lima et al 2016;Baker et al 2018;Garcia-Passos et al 2018). However, the use of cameras overlooking such platforms has not been previously reported and provides a successful novel method.…”

“…However, camera traps have successfully detected semi-aquatic species when positioned at a distance from the water, at haul-out areas, and latrine sites (Day et al 2016;Findlay et al 2020;Gil-Sánchez and Antorán-Pilar 2020). Other specialised methods are often adopted to detect semi-aquatic mammals, such as pressure-plate activated camera traps, or cage traps adapted to be deployed in the water (Lerone et al 2015;Baker et al 2018). The use of environmental DNA sequencing has also been demonstrated as a powerful tool in detecting semi-aquatic mammals, particularly in comparison with alternate methods (Sales et al 2020;Brunt et al 2021).…”

Home ranges of fossorial water voles (Arvicola amphibius) in urban grasslands.

“…Studies on fossorial voles are needed to characterise male and female home ranges in both early spring prior to breeding and when breeding, and across a range of habitats and seasons to fully understand spatial use. Furthermore, urban open space is often redeveloped for housing and relocation of water voles to donor sites is used to mitigate impacts on local populations (Dean et al 2016;Baker et al 2018). Future research should therefore consider tracking water voles in response to development in other urban areas where water voles occur.…”