Sorex minutissimus Zimmermann 1780

8.

Eurasian Least Shrew

Sorex munutissimus

French: Musaraigne minuscule / German: Knirpsspitzmaus / Spanish: Musarana minima de Eurasia

Other common names: Least Shrew, Least Siberian Shrew, Lesser Pygmy Shrew, Miniscule Shrew

Taxonomy. Sorex minutissimus Zimmermann, 1780, Mariinsk (= Kiiskoe), (Kemerovo Region), bank of Kiya River, Siberia, Russia.

Data from karyotypes and mtDNA, and nDNA sequences place S. minutissimus in the S. minutissimus group, although this group may be better included under the S. minutus group; further studies of all Sorex taxa are needed. An isolated population on the eastern slope of the Qinghai-Tibet Plateau, in the Gansu, Sichuan, and Yunnan provinces of China, needs further investigation to confirm that it belongs to this species. Eleven subspecies recognized.

Subspecies and Distribution.

S.m.minutissimusZimmermann,1780—WSiberianPlain.

S.m.abnormisStroganov,1949—NKazakhstanandW&CAltai.

S. m.barabensisStroganov,1956—forest-steppeandsteppeofWSiberia.

S. m.caudataYudin,1964—KuznetskAlatau,Salair,andNWAltai.

S. m.karelicusStroganov,1949—FennoscandiaandKarelia(Russia).

S. m.neglectusOgnev,1921—EastEuropeanPlain.

S. m.stroganoviYudin,1964—TuvaandSEAltaiMts.

S. m.tscherskitOgnev,1913—lowlandoftheKhankaLake,PrimorskyKrai,RussianFarEast.

S. m.tschuktschorumStroganov,1949—ESiberiaandChuckchiandKamchatkapeninsulas.

S.m.ussuriensisOgnev,1921—Sikhote-AlinMts,PrimorskyKrai,RussianFarEast.

S. m. yukonicus Dokuchaev, 1997 — Alaska.

Also present in W Kazakhstan, Mongolia, NE China, Korean Peninsula, Japan (Hokkaido), and most of Russian Far East, but subspecies involved not known.

Descriptive notes. Head—body 30-53 mm, tail 17-33 mm, hindfoot 7-9 mm; weight 1-4-4 g. Pregnant females can weigh more than 3 g. The Eurasian Least Shrew is one of the smallest species of Sorex. Rostrum is very short blunt. Tail is no longer than 50% of headbody length and is covered with rare long hairs that stick out;it is bicolored, with indistinct boundary between dark upper and light lower sides. Pelage is bicolored, usually without distinct demarcation; back is grayish brown; and belly is light gray. Chromosomal complement has 2n = 38 and FN = 74 in Finland and 2n = 42 and FN = 74 in Siberia and Hokkaido (Japan). X-chromosome is large acrocentric, and Y-chromosome is small acrocentric.

Habitat. Eurytopic, often in ecotones, such as edges of forests, borderlines between bogs and forests, etc. The Eurasian Least Shrew is often found in habitats unsuitable for other species of shrew, such as raised bogs, rock slides devoid of vegetation, sand dunes, and sea shores, avoiding rich habitats, such as floodplains.

Food and Feeding. Diets of Eurasian Least Shrew include mostly small beetles (adults) and arachnids in Karelia, small beetles (leaf beats most commonly) in western Siberia, and similar foods in Yenisei taiga. Arachnids and myriapods prevail in the diet in Primorsky Krai. Myriapods, arachnids, and adult small beetles were main foods on Hokkaido, with lepidopteran larvae and adults often eaten in sand dunes. Common feature of diets from different regions is that they do not include earthworms and dipteran larvae, that is, prey dig out ofsoil.

Breeding. In western Siberia, breeding of the Eurasian Least Shrew lasts from May to mid-August, and average numbers of embryos/female are 4-5. Breeding season is longer in most other Siberian regions and is the longest on Hokkaido from late March to mid-autumn, with four embryos found in the only pregnant female captured there. Embryo numbers/female are 4-9 in north-eastern regions of European Russia. Cases of female young-of-the-year reproducing were observed; e.g. a young female with eight embryos was captured in northern Yakutia (= Sakha Republic), and two young females with well-developed breasts were captured in northern regions of European Russia. A female has at least two litters/season.

Activity patterns. Daily activity of the Eurasian Least Shrew is multiphasic; activity periods occur mostly (up to 60%) during the day in Primorsky Krai.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Eurasian Least Shrew’s distribution is the widest in the genus Sorex, but abundance is typically low throughout the distribution. It is usually one of the least abundant in the shrew community. The Eurasian Least Shrew is on 18 regional Red Lists in Russia.

Bibliography. Anufriev et al. (1994), Churchfield & Sheftel (1994), Churchfield et al. (1999), Dokuchaev (1997a), Dolgov (1985), Grigoriev & Bashilov (1988), Gureev (1979), Ivanter & Makarov (2001), Nesterenko (1999), Ohdachi, Ishibashi et al. (2009), Ohdachi, Yoshizawa et al. (2012), Okhotina (1974), Sheftel & Hanski (2002), Sheftel et al. (2017), Sulkava (1990a), Volpert & Shadrina (2002), Yudin (1962), Zaitsev et al. (2014), Zima et al. (1998).