Factors affecting the success of an otter ( Lutra lutra) reinforcement programme, as identified by post-translocation monitoring

Abstract

Monitoring is essential to evaluate the success of translocations, but is frequently neglected. One exception has been the reinforcement of the otter ( Lutra lutra) population in the Derwent and Esk catchments in North East England, UK, between 1990 and 1993. Here, we use data on otter sprainting activity collected before, during and after translocations to identify relationships with vegetation, food resources and physical river characteristics. Sprainting activity increased significantly with trout density, stream order, and surrounding cover by woodland and semi-natural grassland vegetation, and decreased significantly with stream gradient. The form of these relationships was unimodal, sprainting activity peaking at intermediate levels of environmental variables. A logistic regression model including variables relating to fish density, the physical characteristics of the river and surrounding vegetation cover was able to predict the presence or absence of otter sprainting at different survey sites with an accuracy of 92%. Fish density and the physical characteristics of the river were the most important factors in the model. Models such as this are of practical use for assessing the likely success of future otter translocations, both in North East England and other regions of the UK and Europe.