Sicista betulina Pallas 1779

10. Northern Birch Mouse Sicista betulina French: Siciste des bouleaux / German: \Waldbirkenmaus / Spanish: Ratén listado septentrional Taxonomy. Mus betulina Pallas, 1779, River terrace characterized by birch tree groves along Ishim River, Barabinsk Steppe, western Siberia, Russia. Northern Species Group. Sicista betulina has inhabited Europe (France, Germany, Hungary, and Romania) since the Middle Pleistocene as documented byJ. Rofes and colleagues in 2012, and it subsequently expanded its distribution in all directions. Specific status and cohesion among populations are supported by a chromosomal complement of 2n = 32, FN = 60-64, which has been verified in several locations in its distribution, with only a single discrepancy discovered. A population with 2n = 44 was identified in Ciscaucasia in Stavropol Krai, south-western Russia; this population was first recognized as S. betulina “form B” and then as separate subspecies strandi. V. E. Sokolov and colleagues in 1989 recognized it as a valid species, S. strandi. Sicista betulina resembles its sister taxon, S. strandi, in certain morphological characteristics but differs in karyotype and baculum and sperm morphology; however, T. Cserkész and colleagues in 2016 and 2017 revealed surprisingly low genetic divergence between these two species. Several isolated populations exist in the huge distribution of S. betulina. Sminthus i. tatricus named by L. Méhely in 1913 (nomen nudum) is a synonym of montana. Four subspecies are provisionally recognized herein, but phylogeography and biogeography of S. betulina have not been thoroughly investigated even though it is relatively well studied and is not rare in nature or museum collections. Four subspecies recognized. Subspecies and Distribution. S.b.betulinaPallas,1779—C&EEuropeEthroughEuropeanRussiaandSWSiberiatoNEAltaiMts;rangeextendsNabovetheArcticCircle(above68°N). S.b.montanaMéhely,1913—Alps(Switzerland,SGermany,andAustria),BohemianForest(CzechRepublic),andCarpathians(Slovakia,SPoland,SUkraine,andRomania). S.b.norvegicaChaworth-Musters,1927—Scandinavia. S. b. taigica Stroganov & Potapkina, 1950 — S Siberian uplands in S Russia between NE Altai Mts E to NE Lake Baikal in Irkutsk and Buryatia. Descriptive notes. Head-body 58-74 mm,tail 85-100 mm, ear 10-13 mm, hindfoot 15-17 mm; weight 6-:5-10-5 g. Dorsum of the Northern Birch Mouse is brownish pale yellow to reddish or rusty brown, with conspicuous black longitudinalstripe of solid black hairs extending from crown of head to base of tail along dorsal midline; stripes vary from 1-1-5 mm to 3-4 mm. Venter is white, with pale yellow or rusty tinge. Hindfootis ¢.24% of head-body length. Tail is bicolored, blackish-brown above, and whitish below. Tail is long, ¢.124% of head-body length, in northern populations of middle Yenisei River and proportionally longer, c.134% of head-body length, in Northern Ural populations. Condylobasal lengths are 17-2-18-8 mm, zygomatic breadths are 9-3—10 mm, interorbital breadths are 3-5-3-9 mm, and lengths of upper tooth rows are 2-8-3-2 mm. Diploid number is 2n = 32. External measurements were taken from adult mice collected in Bashkiriya Nature Reserve, Russia; cranial measurements were taken from adults captured near Ryazan, Russia, published by G. I. Shenbrot and colleagues in 1995 and 2008. Habitat. Glades in densely vegetated coniferous and deciduous montane forests, subalpine meadows, bogs, forest tundra, forest taiga, forest steppe, shrubland, and cultivated fields near forests from lowlands to mountains at elevations up to 2100 m. Northern Birch Mice require dense medium-tall grass or herbaceous vegetation, often in moist or wet soil conditions, as outlined by J. Kubik in 1952, J. Zejda in 1970, A. A. Cvetkova in 1978, and J. D. Mgller and colleagues in 2011. According to Kubik, there are no differences in habitat requirements of species of Sicista living in mountains versus lowlands. V. Pilats and D. Pilate in 2009 captured Northern Birch Mice 200 km north of the Arctic Circle in a river valley shrubland of Salix glauca (Salicaceae), typical of tundra vegetation; this record is generally regarded as the northern distributional limit of the Northern Birch Mouse. Food and Feeding. The Northern Birch Mouse eats invertebrates, berries, grass seeds, grain, and other vegetable matter. V. A. Popov in 1960 found a predominance of insects in 175 stomachs from the Volga-Kama Region. Insect remains were present in 52-78% of all stomachs depending on season, with the greatest percentage in June. This is consistent with results of E. V. Ivanter in 1975 who found insects (adults and larvae) in 50-79% of 75 stomachs from central Siberia and an analysis of specimens from Peresvet (= Novostroyka), European Russia, by N. M. Okulova and colleagues in 1980 who found insects in 80% of 90 stomachs. Z. Pucek in 1958 showed that a lack of insects in diets of female Northern Birch Mice could inhibit embryo development. Percentage of stomachs containing plant parts varied among different investigations: Popov found green parts in 46-52% of stomachs (most individuals caught in autumn), Ivanter recorded 38-74%, and Okulova and colleagues reported 50%. The latter authors offered different parts (stems, leaves, flowers, and fruits) from various plants to captive Northern Birch Mice and found a lower preference for leaves than other plant parts tested. Other food items identified in stomach content analysis by Popov included mammal hair (present in 32% of 175 stomachs), remains of caterpillars (7-4%), ants (5-1%) and mollusks (4%). Ivanter also found mollusks (2:5-6-2%) and earthworms (7-5-12-5%). Breeding. Reproduction of the Northern Birch Mouse begins shortly after emergence from hibernation, usually toward the end of May and beginning of June, depending on environmental factors, sex, and age of individuals. In Karelia, reproductive season begins c.1 month later than in more central and southern regions. Onelitter per year is typical, with litters of 2-11 young. Gestation lasts ¢.30 days. Young are born without fur and unpigmented. They lie immobile in the nest for c.5 days, developing slowly and nursing from day six until weaning at about day 37. Females do not reproduce until their second year of life and produce young only twice during their lifetime. Northern Birch Mice often excavate shallow burrows for nesting so soil must not be overly compacted; burrows are often constructed under logs, stumps, moss, hay piles, and other protective cover. Breeding and wintering nests in Denmark are typically 20-40 cm deep. Activity patterns. Northern Birch Mice are nocturnal and crepuscular, but in northern latitudes, activity patterns can shift to include more daylight hours. Temperatures below 10°C correspond to a sharp decrease in activity. Nevertheless, on a frigid day with ambient temperature of only =3°C in May 2015, an individual was recorded by trail camera, as reported byJ. van der Kooij and colleagues in 2016; this suggests that Northern Birch Mice are not always as sensitive to cold as is commonly accepted. They hibernate 6-8 months of the year, usually from late October through the beginning of May, in burrows under moss or under or inside rotting logs and stumps, and emerge after snow recedes and warmer temperatures stabilize. Like other species of Sicista, the Northern Birch Mouse can enter torpor in summer in the event of unfavorable environmental conditions. Seasonal migration from wet habitats such as meadows in summer to drier habitats such as forests during hibernation has been reported, although Mgller and colleagues in 2011 did not find evidence of migration. During a study in Denmark by T. S. Jensen and Mgller in 2006, one of 22 Northern Birch Mice fitted with miniature radio transmitters had inactive periods lasting a couple of days,interspersed by single nights of activity. On 27 October 2002, it was radio-tracked to an underground location adjacent to a mouse hole. When soil around the hole was removed, a second Northern Birch Mouse was hibernating in a grass nest. Known predators include several species of owls (Strigiformes) and diurnal raptors (Falconiformes) such as kestrels (Falco). Where Northern Birch Mice are common, they may comprise more than 30% of remains in owl pellets. Movements, Home range and Social organization. Northern Birch Mice move by scampering and jumping and leap when startled; they climb bushes and shrubs, aided by their semi-prehensile tail and by grasping twigs and stems with their outer digits. They may dig shallow burrows lined with leaves, moss, dry grass, or other vegetation, or construct nests in rotting logs, stumps, driftwood, or burrows of other animals. Nests are spherical, with diameters of 5-8 cm. A burrow contains a nest chamber and another chamber beneath the nest filled with excrement and remnants of food. Northern Birch Mice are thoughtto be solitary in the wild. Home ranges of males and females overlap. In Denmark, a radio-tracking study by Mgller and colleagues found that individuals moved an average of 227 m/night, and mean home range was 8080 m®. In the breeding season, males’ home ranges are much larger than average, and males can be found in unusual habitats and areas. There is an overall trend of higher densities in the eastern part of the distribution. Cyclic fluctuations have not been recorded, and changes in density from year to year is less than tenfold. High relative capture frequency of the Northern Birch Mouse was detected by A. V. Bobretsov and colleagues in 2005 in forests on western slopes of the Northern Urals: 9-6 ind/10 trench-days on average compared to 1 ind/ 10 trench-days in lowlands. In some years, obvious population increases were recorded. In 1996, for example, when densities of many species of small mammals were low, average relative capture frequency of Northern Birch Mice and its proportion in catches reached 31-5 ind/10 trench-days and 50-1%, respectively. They dominated in all habitats but were captured more frequently (50 ind/10 trench-days, 64-7% in catches) in fir (Abies)spruce (Picea, both Pinaceae) forests with herbaceous ground cover. Status and Conservation. Classified as Least Concern on The IUCN Red List. The Northern Birch Mouse has a large distribution and is abundant in certain areas, especially in eastern parts ofits distribution. In western parts of its distribution, it is often considered rare, and certain populations are geographically isolated. The Northern Birch Mouse is listed in Appendix II of the Bern Convention and Annex IV of the EU Habitats Directive and included in national Red Lists of many countries. Population status and trends in some areas (e.g. Romania) are poorly documented. The Northern Birch Mouse is thought to be difficult to detect and trap, and thus, abundance or population estimates are likely underestimated. Intense efforts are needed to detect it using a variety of techniques. Use of pitfall traps and dissection of owl pellets are most effective in estimating densities and trends, but trail cameras also produce reliable occurrence data. Potential threats include habitat destruction and deforestation and increases in intensive agriculture. Trends in climate change are predicted to negatively impact or even decimate certain western isolated populations. While the Northern Birch Mouse is not considered at risk or threatened throughout most of its distribution, monitoring of populations, especially in western parts of its distribution, is recommended. Active conservation measures have been accomplished only in Denmark, outlined by Mgller in 2012, where authorities carried out a project to create habitat improvements for the Northern Birch Mouse, such as establishment of earthen banks in moist areas where nesting localities seemed scarce, modifications of intensive grazing to extensive grazing in areas of occurrence, and other measures. In Denmark, Northern Birch Mice were captured in or near stream valleys, and these areas should be protected from intensive human activity. Adjacent hibernation areas such as earthen banks, slopes, and hedges also should be preserved. Because the Northern Birch Mouse has a patchy occurrence in Denmark,it is also important to secure corridors such as stream valleys with suitable grass and hedge vegetation on moist earthen banks. Bibliography. Barkasi & Zagorodnyuk (2016), Baskevich (2016), Bobretsov et al. (2005), Bolshakov et al. (1977), Borkenhagen (2012), Cserkész, Fulop et al. (2017), Cserkész, Rusin & Sramké (2016), Cvetkova (1978), Fedyk et al. (2011), Flgjgaard et al. (2009), Hable & Spitzenberger (1989), Holden & Musser (2005), Ivanter (1972, 1975), Ivanter & Kukhareva (2008), Jensen & Maller (2006), van der Kooij (2012a, 2012b), van der Kooij et al. (2016), Kubik (1952), Kulik et al. (1968), Makarov & Korosov (1996), Méhely (1913), Meinig et al. (2016), Meller (2007 2012), Meller et al. (2011, 2012), Okulova et al. (1980), Pilats & Pilate (2009), Popov (1960), Pucek (1958, 1999), Rofes et al. (2012), Schulz (2012), Schulz et al. (2012), Shenbrot et al. (1995, 2008), Sokolov et al. (1989), Stroganov & Potapkina (1950), Vakhrusheva & lichenko (2012), Zejda (1970).Published as part of Don E. Wilson, Russell A. Mittermeier & Thomas E. Lacher, Jr, 2017, Sminthidae, pp. 9-48 in Handbook of the Mammals of the World – Volume 7 Rodents II, Barcelona :Lynx Edicions on pages 44-45, DOI: 10.5281/zenodo.660355