The southern birch mouse Sicista loriger (Dipodoidea) in the Crimea: distribution, habitats, seasonal ac-tivity, and abundance

Abstract

The southern birch mouse is a rare and non-abundant species of small mammals of the fauna of the Crimean Peninsula. Its geographic range has gradually reduced during the 20th century. Initially, the southern birch mouse occupied almost the entire territory of the steppe and foothills of the Crimea. As the area of virgin and unploughed lands decreased, the species disappeared from the most part of the peninsula. Whereas the species had been recorded in 11 administrative districts in the middle of the twentieth century, now it is known only in three districts, in two of which it is extremely rare. Currently the southern birch mouse exists in two isolated populations—a western (Tarkhankut) and an eastern (Kerch)—separated by 200 km of anthropogenic landscapes. Census of small mammals has been carried out on trap-lines for the past 40 years. In a total of 667100 traps-nights, 144 birch mice were collected. Additionally, remains of 56 birch mouse specimens were found in 16862 pellets of the long-eared owl. The birch mouse population in the Tarkhankut Peninsula is small (12 specimens were trapped and 39 specimens were identified in pellets), and its range is largely restricted. The species’ population in the Kerch Peninsula is larger (132 birch mice were trapped and 17 specimens were identified in pellets of birds of prey) and its range occupies the entire area of the Kerch Peninsula. Data of long-term epidemiological surveys showed that the ratio of trapped birch mice in the whole of the Crimea is 0.21 %, whereas their ratio in the steppe zone is 0.29 % at a relative abundance of 0.03 specimens per 100 trap-nights. Birch mice are active from mid-April to mid-November. The peak of activity occurs in April, when 49.9 % of animals were trapped. Among natural enemies, the red fox (Vulpes vulpes) can pose a real threat to birch mice, as well as the long-eared owl (Asio otus) to local micropopulations, especially during the breeding season. In our opinion, despite the generally low abundance of birch mice in the Crimea and the fragmentation of its geographic range, extinction does not threatens this species in the peninsula (especially its Kerch population) under the current management system. Conservation of the southern birch mice populations in the Crimea requires a detailed study of the species’ ecology, especially of limiting factors.