Sicista loriger

14.

Nordmann’s Birch Mouse

Sicista loriger

French: Siciste de Nordmann / German: Nordmann-Steppenbirkenmaus / Spanish: Raton listado de Nordmann

Taxonomy. Sminthus loriger Nathusius, 1840,

Odessa, Ukraine.

Steppe Species Group. The first specimen of this taxon was trapped by A. von Nordmann between 1833 and 1837 close to Odessa, and it was described by W. E. von Nathusius in 1840, based on material from Odessa in south-eastern Ukraine. Later in the same year, A. Keyserling and J. H. Blasius described the same specimens under the name of Sminthus nordmanni. As pointed out byJ. L. Chaworth-Musters in 1934, Keyserling and Blasius in 1840 subsequently published a letter in which they stated that their name (nordmanni) was a synonym of S. loriger, and they only became aware of the error after their description of nordmanni had been printed. G. S. Miller in 1912 and I. Zagorodnyuk in 2009 correctly listed nordmanni as a synonym of S. loriger. S. 1. Ognev in 1935 treated Sicista loriger as a subspecies of S. subtilis, citing differences in color of fur. Subspeciesstatus of loriger was upheld by V. E. Sokolov and colleagues in 1986 and 1987, who studied chromosomes of individuals from Kherson and Donets regions of Ukraine and compared them with other taxa associated with S. subtilis, such as subspecies vaga, sibirica, and severtzovi. They documented considerable differences among chromosomes of loriger (2n = 26), severtzovi (2n = 18-20), and other taxa linked to S. subtilis (2n = 24) and outlined distributional limits of these subspecies for the first time. Yu. M. Kovalskaya and colleagues in 2011 also noted that S. loriger and S. subtilis could be distinguished by unique karyotypes indicating reproductive isolation. Sicista loriger has a stable diploid number of 2n = 26, which clearly distinguishesit from S. subtilis sensu stricto. It shares an identical 2n and autosomal fundamental number (FNa) with a chromosomal race (2n = 26, FNa = 46) of S. subtilis severtzovi and is unique among the Steppe Species Group in its Gand C-banded karyotypes. All these features prompted Kovalskaya and colleagues to recommend that loriger be treated as a valid species. T. Cserkész and colleagues in 2016 studied phylogeny of S. loriger with molecular markers, and found thatit is closely related to S. trizona. These two species form the western clade of the Steppe Birch Mice. This clade is highly divergent from the eastern clade, including the S. subtilis complex. Based on genital morphology and cytogenetic differences between these two clades and between S. trizona and S. loriger, Cserkész and colleagues supported separate specific status of S. subtilis and S. longer. Length of long penile spike can be used to identify species: short (less than 1 mm) spike is characteristic of S. trizona, medium length spike (1-2 mm) is found in S. subtilis, and longest penile spike (greater than 2 mm) is found in S. loriger. Craniometrical and external measurements of S. loriger were significantly greater than those of S. trizona but overlapped with S. s. severtzoui, as documented by Cserkész and colleagues in 2009. Discriminant function analysis incorporating five cranial and seven dental characteristics clearly separated S. trizona and S. loriger. Monotypic.

Distribution. Known only from ten locations in E Romania, S & E Ukranie, and SW Russia (W Belgorod Region). Distribution poorly known and it certainly occurs at more localities than are currently documented; status unknown in Moldova and Bulgaria.

Descriptive notes. Head-body 53-78 mm, tail 60-90 mm, ear 10-5—14 mm, hindfoot 12-5—17 mm; weight 7-6-12-1 g. Nordmann’s Birch Mouse is one of the smallest species of Sicista in bodysize. It is similar in size and appearance to the Southern Birch Mouse (S. subtilis) and the Hungarian Birch Mouse (S. trizona). Dorsum of Nordmann’s Birch Mouse is yellowish gray or brownish gray, with bold, black mid-dorsal stripe. Two slightly diffuse and broader beige stripes are often present on each side of mid-dorsalstripe and extend from shoulder to rump; these stripes are well developed in most individuals. Venter is usually whitish or, less often, slightly yellowish gray. Condylobasal lengths are 17-9-18-5 mm, and lengths of upper tooth rows are 3-3-4 mm. External and cranial measurements are based on specimens captured in Romania and reported by D. Auslinder and S. Hellwing in 1957.

Habitat. Sand, shrub, and forest steppes, unmowed grasslands with herbaceous vegetation, and pastures. According to V. M. Izdebskii in 1962, Nordmann’s Birch Mice prefer areas with sandy soil in the vicinity of Kherson, Ukraine, and were more often found in open habitats rather than forest margins. In the Black Sea Biosphere Reserve, they were reported to be more common in sand steppe versus dry forest steppe by D. C. Berestennikov in 1977. In the same reserve, they were most often encountered in shrub steppe, herbaceous vegetation, and forest steppe, in which density peaked at 1-2 ind/100 trapdays, according to Z. V. Selyunina in 2005. N. Antonets and M. Shumkova in 2008 noted that afforestation of sand steppe has led to loss ofrare species, particularly Nordmann'’s Birch Mouse. They concluded thatits distribution in the Dnipropetrovsk region has been significantly reduced, and it is now known only in the Dnieper-Oril Nature Reserve and its buffer zone. A. I. Dulitskiy in 2001 considered habitat preferences of Nordmann’s Birch Mice to range from virgin steppes with sparse vegetation to cultivated fields. In his study, 43-4% was recorded in virgin steppe, 32:7% in forest, 11-2% in agricultural fields, 9-6% in roadside weed patches, and 3-1% in other habitats. In Romania, Auslander and Hellwing in 1957 trapped these birch mice in alfalfa and barley fields. In Crimea, individuals were captured in the steppe zone, most often in undisturbed places and cultivated fields. Cserkész and colleagues in 2014 and 2016 reported captures in Iasi, Romania, in primary steppe dominated by dense and high feather grass and fescue, and in Borisovka, Russia, in steppe dominated by common meadow-grass (Poa angustifolia, Poaceae) and woodland sage (Salvia nemorosa, Lamiaceae). Cserkész and colleagues also trapped two specimens in secondary sandy steppe that had regenerated after deforestation ofartificially planted black pine close to Kherson, Ukraine; vegetation was sparse and provided c.40% cover. Nordmann’s Birch Mouse is most often detected in virgin steppes but can quickly colonize other suitable habitats.

Food and Feeding. Stomachs and intestines of 22 Nordmann’s Birch Mice collected in Romania by Auslinder and Hellwing in 1957 contained, almost exclusively, arthropod remains. Nine orders were identified: Lepidoptera (mostly Noctuidea), Coleoptera (especially Curculionidae, then Scarabeidae, Carabidae adults and larvae), and Arachnidae (most common); Heteroptera, Orthoptera, Dermaptera (Forficula larvae), Formicidae, and Myriapoda were present but sparse. Hairy caterpillars were ignored, and Nordmann’s Birch Mice hunted only for nocturnal hairless owlet moths (Noctuidae). Remains of crickets (Gryllidae) were not present in stomach and intestines. Most food was well chewed, and only Diptera larvae were swallowed intact.

Breeding. Mating season of Nordmann’s Birch Mouse in Crimea begins after hibernation in April. First pregnant female was trapped in late April and the last one in late August, but most pregnant females were recorded in May and early June and comprised 15-54-5% of the individuals trapped during that period. One litter is produced per year, and only overwintered females reproduce. Litters contain 2-8 young (average 5-5) in Crimea, according to Z. S. Khodikina in 1965.

Activity patterns. Nordmann'’s Birch Mice are crepuscular and nocturnal. Khodikina in 1962 captured an individual on 8 April in Crimea after a night of heavy frost— the earliest recorded date of capture in spring. In southern part of its distribution in Crimea, they are first encountered in the first half of April when mean daily temperature exceeds 5°C. Males emerge from hibernation first, and females awaken two weekslater. Ajuvenile (weight 6 g) was trapped in mid-Septemberafter 15 mm ofrain at an average of 18°C in Iasi by Cserkész and colleagues in 2013. These observations demonstrate that Nordmann'’s Birch Mice are sometimes active after rainfall and are not as sensitive to humidity and cold weather as was previously believed. In Romania, Auslander and Hellwing trapped 30 individuals in 1955-1956; 25 were collected in May when activity was higher due to the mating season. In April, only two individuals were caught; ambient temperatures were 10-16°C. The authors speculated that low number of captures in April indicated that most individuals were still hibernating, and likely awakened during in the second half of April. In July, they captured only three individuals and ascribed this to decreased activity after the mating season.

Movements, Home range and Social organization. Nordmann’s Birch Mice are probably solitary. They easily climb vertical stalks, using their semi-prehensile tail to aid in balance. They are very agile, moving in small jumps. They use burrows of other rodents and holes among stones and tree roots. Selyunina in 2003 and 2005 presented results of a population survey carried out in 1977-2003. She detected short-term cycles with amplitudes of 2-3 ind/100 trap-nights and found a correlation between density and weather factors such as annual precipitation, ambient temperature, and snow cover. High rainfall generates well-developed herbaceous vegetation, which is advantageous because dense vegetation provides more food and shelter and thus potentially increases reproduction rate. A similar correlation was observed in Hungary.

Status and Conservation. Not assessed on The [UCN Red List due to recent elevation to species level. Original distribution of Nordmann’s Birch Mouse included all of southern and eastern Ukraine, small areas in western Russia in the Belgorod region, Moldova, north-eastern Bulgaria, and eastern and southern Romania. At present, distribution is highly fragmented into small, isolated areas. Zagorodnyuk and Selyunina in 2009 reviewed distribution in Ukraine, where it occurs in some protected (and unprotected) grasslands and sand steppes in the southern part of the country. In Bulgaria and Moldova, there are no recent occurrences of Nordmann’s Birch Mouse, and in Romania, it is only found in a single locality. A classification of Vulnerable on The IUCN Red List is probably most appropriate. Nordmann’s Birch Mouse is endangered in Romania, vulnerable in Ukraine and Russia, data deficient in Moldova, and critically endangered or extinct in Bulgaria. If a population still survives in Bulgaria, it may be restricted to a small coastal area where it would likely be negatively impacted by wind turbine development and tourism. Unprotected primary steppe is fragmented in Romania, Ukraine, and Russia. In Ukraine, Nordmann’s Birch Mouse occurs in the Black Sea Biosphere Reserve, Luhansk Nature Reserve, Ukrainian Steppe Nature Reserve, and Dnieper-Oril Nature Reserve, but no action plans or special management strategies are being implemented. Status of Nordmann’s Birch Mouse in Moldova is unknown, but it occurs in some sites that are very close to Moldova (Iasi in Romania and Tarutyne in Ukraine). Additional field surveys are required to obtain more data on extant populations of Nordmann’s Birch Mouse, but even without additional surveys, western members of the Steppe Species Group warrant intense conservation attention. Plowing and deforestation of virgin steppes, overgrazing, and destruction of ravines threaten existence of Nordmann’s Birch Mouse.

Bibliography. Antonets & Shumkova (2008), Auslander & Hellwing (1957), Barkasi & Zagorodnyuk (2016), Berestennikov (1977), Chaworth-Musters (1934), Cserkész, Aczél-Fridrich et al. (2015), Cserkész, Kitowski et al. (2009), Cserkész, Rusin & Sramké (2016), Dulitskiy (2001), Izdebskii (1962), Keyserling & Blasius (1840a, 1840b), Khodikina (1965), Kovalskaya et al. (2011), Méhely (1913), Miller (1912), von Nathusius (1840), Ognev (1935), Pucek (1999), Selyunina (2003, 2005), Sokolov, Baskevich & Kovalskaya (1986b), Sokolov, Kovalskaya & Baskevich (1987), Vinogradov (1937), Zagorodnyuk (2009a), Zagorodnyuk & Selyunina (2009).