Sicista caucasica, Vinogradov, 1925

Don E. Wilson, Russell A. Mittermeier & Thomas E. Lacher, Jr, 2017, Sminthidae, Handbook of the Mammals of the World – Volume 7 Rodents II, Barcelona: Lynx Edicions, pp. 9-48 : 40-41

4.

Caucasian Birch Mouse

Sicista caucasica

French: Siciste du Caucase / German: Kaukasus-Birkenmaus / Spanish: Raton listado del Caducaso

Taxonomy. Sicista caucasica Vinogradov, 1925 ,

“from distr. of Maikop , province of Kuban, Northern Caucasus, alt. 7000-9000 ft. [= 2134-2743 m],” Russia .

Western Montane Species Group. B. S. Vinogradov in 1925 described S. caucasica as aligned with S. concolor because of its uniformly colored dorsum that lacked a dark mid-dorsal stripe seen in some species of Sicista . In the 1980s, three additional species of unicolored Sicista were described from the Caucasus: two of these, along with S. caucasica , 1s endemic to the Greater Caucasus, S. kluchorica and S. kazbegica . The third species, S. armenica , is endemic to the Lesser Caucasus, and was described by V. E. Sokolov and M. I. Baskevich in 1988. G. I. Shenbrot and colleagues in 1995 and 2008 and Baskevich in 1996 grouped all four Caucasian endemics together based on chromosomal characters, uniform dorsal color, and similarities in male reproductive anatomy; this arrangement is followed here. The four species are thought to represent Pliocene relicts that were isolated from closely related Eurasian populations by contraction and fragmentation of forests with increased aridity during the mid-Pliocene. Studies by Baskevich and colleagues in 2004, 2015, and 2016 that included chromosomal banding data, genetic sequence data, and discriminant analysis of cranial measurements found the greatest genetic similarity between S. caucasica and S. kluchorica ; S. kazbegica was more similar to these two species than to S. subtilis (S. armenica was not sampled); morphological analysis yielded a similar arrangement, supporting grouping of the Caucasian endemics into their own species group. Because S. caucasica and S. kluchorica are virtually indistinguishable in external appearance and are extremely similar in cranial morphology, it is difficult to accurately outline geographical and elevational distribution of S. caucasica . As Shenbrot and colleaguesstated in 1995 and 2008, there are many museum specimens thatlikely represent S. caucasica , but they have not been positively identified. The IUCN Red Lust distribution map by K. Tsytsulina and colleagues in 2008 includes some of these specimens and other material, and is followed here. The Kizgich River, a tributary of Bolshoy Zelenchuk River, may be the eastern distributional boundary of S. caucasica according to Shenbrot and colleagues and T. Cserkész and colleagues in 2017. Monotypic.

Distribution. W Greater Caucasus in Russia and Georgia, on the N slopes from the Pshish River E to the N Kizgich River, and on the S slopes in Abkhazia and perhaps adjacent areas in Russia.

Descriptive notes. Head-body 43-6-68-9 mm, tail 84-105-8 mm, ear 9-2-12.8 mm, hindfoot 17-4-22 mm; weight 5:8-7-2 g. Dorsum of the Caucasian Birch Mouse is reddish ocher-brown, with scattered conspicuous black guard hairs and without middorsal stripes. Venter is grayish white, with yellowish tinge, or bright white. Sides of body and cheeks appear paler and brighter due to absence of black-tipped guard hairs. Hindfootis long, ¢.30% of head-body length. Tail is very long, ¢.150% of head-body length and bicolored, darker above and paler beneath. Condylobasal lengths are 17-5— 18-5 mm, zygomatic breadths are 9-2-9-7 mm, interorbital breadths are 3-4-3-6 mm, and lengths of upper tooth rows are 3-3-3-6 mm. Surface of glans penis of all four species of Sicista endemic to the Caucasus is covered with small keratinized spines but lacks larger spines or penile spikes jutting out of terminus that characterize species in the Northern and Steppe species groups. Diploid number is 2n = 32. External and cranial measurements were taken from adult males collected near Arkhyz, Karachay-Cherkessia, Russia, published by Shenbrot and colleagues.

Habitat. Subalpine meadows, glades in fir ( Abies , Pinaceae ) and coniferous-deciduous forests, and riverbanks with dense tall grass cover or herbaceous understory at elevations of 1400 m to at least 2100 m. Elevation at which type series was captured is undetermined; elevations near Maykop range at 2100-2700 m, according to V. G. Topilina in 1987, Baskevich in 2000, and A. Bukhnikashvili and A. Kandaurov in 2002. Cserkész and colleagues in 2017 reported that eight individuals were captured near type locality in 2014; most were captured in a small karst depression, densely vegetated with tall grass (c.70%) and tall nitrophilous herbs (¢.25%); others were captured near birch ( Betula , Betulaceae ) trees in rocky glade covered with greater amount of tall herbaceous vegetation (c.70%) than tall grass. Near Arkhyz, Cserkész and colleagues caught individuals in densely covered mesophilic grassland in Moon Valley at 1850 m. Individuals were caught in slightly grazed or degraded mesophilic grassland in a small pasture surrounded by forest in Sofiya Valley at 1720 m.

Food and Feeding. Little is known, but captive Caucasian Birch Mice consumed insects, seeds, and berries, according to Shenbrot and colleagues.

Breeding. Mating activity of Caucasian Birch Mice begins shortly after females emerge from hibernation in mid-May and continues through earlyJune, although local weather can shift timing of mating and reproductive activity by up to two weeks. Reproductively mature males with sperm present in testes were captured in late June, with testes lengths of 4-2-5-3 mm. Pregnant females were captured in late June through late July, and litters contained 4-6 young, according to Sokolov and colleagues and Topilina in 1987. Young-of-the-year do not seem to be reproductively active. Wild Caucasian Birch Mice live up to c.3 years; Topilina reported that young-of-the-year and 1-2year-olds comprised more than 76% of individuals captured in Caucasus Nature Reserve.

Activity patterns. Caucasian Birch Mice are crepuscular and nocturnal and possibly diurnal at high elevations. Ambient temperatures below 0-1-5°C seem to correspond to a notable decrease in activity; they hibernate 8-9-5 months out of the year, usually from midto late August through May. Peak activity occurs in June—July. There is no information about burrows and nests of the Caucasian Birch Mice, but closely related species burrow under moss and under or inside rotting logs and stumps, emerging after snow recedes and warmer temperatures stabilize.

Movements, Home range and Social organization. Caucasian Birch Mice are solitary. Several authors report that Caucasian Birch Mice may be common in certain Russian localities and densities might depend on suitability of microhabitat and elevation. Topilina in 1982 reported that Caucasian Birch Mice in the Urushten Valley of Caucasus Nature Reserve comprised 25-5% of small mammal captures in subalpine vegetation at elevations of ¢.1500 m, 12:5% in the tall grass offorest glades at ¢.1450 m, and 2-4% in subalpine meadow at c¢.1850 m. Individuals were captured in five different habitats but were most abundant in subalpine tall grass at 1500 m. When temperatures drop below 1-5°C in summer, they are much less active according to Topilina in 1987, and estimates of relative frequency may be affected by fluctuations in ambient temperature.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. This classification is due to few positively identified records of the Caucasian Birch Mouse from a small number of localities, and habitat threats such as overgrazing and loss oftall grass and herbaceous cover in agricultural areas. Its distribution might be smaller than 20,000 km?, and its area of occupancy might be less than 2000 km? Growing tourism in this region has resulted in increased development and threatens critical habitat. Although Shenbrot and colleagues, Baskevich in 2000, and Cserkész and colleagues reported Caucasian Birch Mice to be common in optimal, undisturbed habitat in the western Greater Caucasus, positive identifications based on genotype and karyotype have not been determined for many specimens. Estimates of capture frequency are thus tentative in some localities. Caucasian Birch Mice are estimated to be far less abundant outside protected areas, and degradation of mesophilous habitat by human activities (e.g. overgrazing) has likely negatively impacted local population sizes. Despite conservation concerns and listings, populations of Caucasian Birch Mice are not monitored in protected areas. International collaborative action plans such as the Ecoregion Conservation Plan for the Caucasus published in 2012 have developed goals to conserve and protect habitats, fauna, and flora in the Caucasus due to its designation by Conservation International and other groups as a biodiversity hotspot based on high levels of diversity and endemism.

Bibliography. Baskevich (1996, 2000, 2016), Baskevich, Okulova et al. (2004), Baskevich, Potapov & Mironova (2015, 2016), Bukhnikashvili & Kandaurov (2002), Cserkész, Fulop et al. (2017), Holden & Musser (2005), KryStufek & Vohralik (2005), Okulova & Baskevich (2003), Shenbrot et al. (1995, 2008), Sokolov & Baskevich (1988), Sokolov, Baskevich & Kovalskaya (1981, 1986a), Sokolov, Baskevich, Lukyanova et al. (1987), Topilina (1982, 1987), Tsytsulina et al. (2008), Vinogradov (1925), Zazanashvili et al. (2012).

Figures

1. Long-tailed Birch Mouse (Sicista caudata), 2. Chinese Birch Mouse (Sicista concolor), 3. Tian Shan Birch Mouse (Suwcsta ttanshanica), 4. Caucasian Birch Mouse (Sucsta caucasica), 5. Kluchor Birch Mouse (Sicista kluchorica), 6. Kazbeg Birch Mouse (Sicista kazbegica), 7. Armenian Birch Mouse (Sicista armenica), 8. Altai Birch Mouse (Sicista napaea), 9. Gray Birch Mouse (Sicista pseudonapaea), 10. Northern Birch Mouse (Sicista betulina), 11. Strand’s Birch Mouse (Suwcista strandi), 12. Southern Birch Mouse (Sicista subtilis), 13. Hungarian Birch Mouse (Sucista trizona), 14. Nordmann’s Birch Mouse (Sicista loriger)

Distribution. W Greater Caucasus in Russia and Georgia, on the N slopes from the Pshish River E to the N Kizgich River, and on the S slopes in Abkhazia and perhaps adjacent areas in Russia.