Translocations of European ground squirrel (Spermophilus citellus) along altitudinal gradient in Bulgaria – an overview

Abstract

The European ground squirrel (Spermophilus citellus) is a vulnerable species (IUCN) living in open habitats of Central and South-eastern Europe. Translocations (introductions, reintroductions and reinforcements) are commonly used as part of the European ground squirrel (EGS) conservation. There are numerous publications for such activities carried out in Central Europe, but data from South-eastern Europe, where translocations have also been implemented, are still scarce. The present study summarises the methodologies used in the translocations in Bulgaria and analyses the factors impacting their success. Eight translocations of more than 1730 individuals were performed in the period 2010 to 2018. These included 4 reinforcements, 3 reintroductions and 1 introduction. Two of the translocations are still ongoing. Five of the completed six (83%) translocations were successful, although in two cases the number of individuals was critically low. The relatively higher success in Bulgaria than in Central Europe is probably due to using the gained experience. Most of the translocations (6) used a soft release approach. In 6 cases, the animals settled 100 to 720 metres away from the release site, implying management and protection of suitable habitat beyond the translocation area. In 7 of the translocations, the altitude between the donor colony and the release site varied from 470 to 1320 m which could have a hindering effect on the adaptation of animals due to the specific conditions in the mountains. The main reasons for failure are probably poorly selected and maintained habitats and bad climatic conditions (rainy and cool weather) during the translocation action. European funds are of critical importance for translocations, with only two translocations funded by other sources. Based on the gathered data, the current paper also gives some recommendations for improvement in translocation activities.