Sorex daphaenodon Thomas 1907

21.

Siberian Large-toothed Shrew

Sorex daphaenodon

French: Musaraigne a dents foncées / German: Sibirische GroRzahnspitzmaus / Spanish: Musarana de dientes grandes de Siberia

Other common names: Large-toothed Siberian Shrew

Taxonomy. Sorex daphaenodon Thomas, 1907,

“ Dariné, 25 miles [= 40 km] N.W. of Korsakoft [= Korsakov], Saghalien [= Sakhalin Island],” Russia.

Evidence from mtDNA and nDNA sequences classifies S. daphaenodon in the araneus group. Four subspecies recognized.

Subspecies and Distribution.

S.d.daphaenodonThomas,1907—RussianFarEast(KhabarovskKrai,AmurRegion,andSakhalinI).

S.d.oriiKuroda,1933—ParamushirI(NKurilIs).

S.d.sanguinidensG.M.Allen,1914—C&ESiberiaandChukchiandKamchatkapeninsulasStoNAmurRegion.

S. d. scaloni Ognev, 1933 — W Siberia.

Also present in N Mongolia, NE China, S Russian Far East (Primorsky Krai), and NE North Korea, but subspecies involved not known. Descriptive notes. Head-body 54-78 mm, tail 25-39 mm, hindfoot 10-13 mm; weight 6-10-3 g. Tail of the Siberian Large-toothed Shrew is relatively short and very rarely exceeds 50% of head-body length. Its base is bicolored, and it is dark on its distal part. Pelageis bicolored. Back is brown to dark brown in young individuals and black-brown to almost black in adults. Sides are slightly lighter than back. Belly is dark gray. Demarcation in color of sides and belly is always clear. Chromosomal complement has 2n = 26/27 in Krasnoyarsk Krai and 2n = 28/29 in vicinities of the Lake Baikal, Russian Far East, and Mongolia and FN = 46 everywhere. Trivalent of sex chromosomes consists of large metacentric X-chromosome, small acrocentric Y-chromosome, and medium-sized acrocentric Y-chromosome. There are 16-18 metacentric and 8-10 acrocentric autosomes.

Habitat. The Siberian Large-toothed Shrew prefers well-moistened meadow habitats in floodplains. It almost never dominates shrew communities and is often low in abundance. Shrub floodplains are often inhabited, but forest habitats and subalpine meadows are avoided. It is not found in mountains other than the Transbaikal and the Khentii highlands (northern Mongolia) where wet valley meadows and shrubs are main habitats. There are only a few regions where the Siberian Large-toothed Shrew is common, including Baraba steppe (southern western Siberia), Selenga River delta (Baikal Basin), Khankan lowland (the lowland near Khanka Lake), Omolon River floodplain (Kolyma River Basin), middle reach of the Lena River, and valley of the Epoo River in western Khentii (northern Mongolia).

Food and Feeding. Insects are more abundant than earthworms in diets of Siberian Large-toothed Shrews, and coleopterans are the most common insect component. Food items vary in different regions, seasons, and even months. For example, earthworm percentagesin gastric contents increased from 11:1% in July to 35-5% in August in north-western Asia (Magadan Region and Chukchi Peninsula). Seasonal variations were even greater; e.g. earthworms were absent in winter diets that included vertebrate tissues (occurrence 26%), not detected in June-September. Species of Homoptera were most often found in winter diets. Larch seeds were always observed (incidence 100%) in diets in September, being released at a peak rate during this month. Dipterans and caterpillars are more often found in summer diets in central Yakutia (= Sakha Republic), in contrast to north-eastern Asia. Low proportion of arachnids in the diet is common ofall regions and is probably typical of the Siberian Large-toothed Shrew.

Breeding. Juvenile Siberian Large-toothed Shrews first appear in the second one-half ofJune; similar periods were observed in southern and central Yakutia and Chukchi Peninsula. Reproduction stops in mid-September, after females have two,rarely three, litters. Young-of-the-year rarely reproduced in the region of the Omolon River (Kolyma River Basin), but male young-of-the-year participated in reproduction in central Yakutia in some years. Reproductive rate is relatively high and seems to increase northward. For example, number of embryos/female was 6-5 in the middle reach of the Lena River, 7-7 in the Kolyma River region, and 7-9 in the Omolon River region.

Activity patterns. No information.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Siberian Large-toothed Shrew is not abundant throughoutits distribution. It has decreased in abundance in the western part ofits distribution and western and central Siberia over the past decade.

Bibliography. Dokuchaev (1990), Glotov et al. (1978), Nesterenko (1999), Revin (1989), Sheftel (1983), Shvetsov (1977), Volpert & Shadrina (2002), Yudin (1975, 1989), Yudin et al. (1976), Zima et al. (1998).