|Scientific Name:||Microtus abbreviatus|
|Species Authority:||Miller, 1899|
|Taxonomic Notes:||Some authors have considered M. abbreviatus to be conspecific with M. miurus of the Alaskan mainland. Jones et al. (1992), Baker et al. (2003), and Musser and Carleton (in Wilson and Reeder 1993, 2005) recognize M. abbreviatus and M. miurus as distinct species.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Frey, J. & NatureServe (Garibaldi, A. & Hammerson, G.)|
|Reviewer(s):||Amori, G. (Small Nonvolant Mammal Red List Authority) & Chanson, J. (Global Mammal Assessment Team)|
Listed as Least Concern, although it is restricted to only two islands, these are not inhabited and are both totally under protection so there are no known threats to the populations at present, and the populations although fluctuating, are thought to be stable.
|Range Description:||This species is known from Hall Island (subspecies abbreviatus) and St. Matthew Island (subspecies fisheri), in the Bering Sea, Alaska, United States. Its range on each of the islands is not known.|
Native:United States (Alaska)
|Range Map:||Click here to open the map viewer and explore range.|
This species is represented by two occurrences or subpopulations on different islands. Populations fluctuate widely. Beals found the voles "abundant everywhere" in 1944 (Rausch and Rausch 1968). The population was apparently at near maximum density in 1954 but was "very low" in 1957 (Klein 1959). The numbers were also low, and concentrations dispersed, in 1963 (Rausch and Rausch 1968). On the mainland, Batzli and Henttonen (1990) reported moderate tundra vole densities of 4-50 per hectare. The total area of St. Matthew Island is approximately 31,475 hectares (this area includes Pinnacle Island) and the total area of Hall Island is 1,443 hectares (Brewer 1996). The estimated population based on these densities would be between 131,672 - 1,645,900 individuals.
The long-term population trend is unknown but appears to be stable. On a short-term basis, populations fluctuate from very low to very high (Rausch and Rausch 1968), but no predictable trend has been documented.
|Habitat and Ecology:||
On St. Matthew Island, this vole is most abundant in moist lowlands and on lower slopes; also in the Elymus community along beach ridges and the driftwood zone; it has been found up to about 240 m asl in moist, well-drained areas as well as around ponds and seepages. Burrows are in well vegetated rocky outcroppings. The species is not found in dry lowlands or in areas with much standing water (Rausch and Rausch 1968).
On Hall Island, limited data indicate a mean litter size of seven, with most females producing only one litter (Rausch and Rausch 1968). Diet on St. Matthew Island includes Deschampsia, Artemesia, Rumex, Salix, Sedum, and Saxifraga. Insular Voles are important prey for such predators as Long-tailed Jaeger, Snowy Owl, Glaucous Gull, and Arctic Fox, they are occasionally preyed on by Polar Bears.
No immediate threats are known, but the restricted range of this species increases its vulnerability to outside threats.
Fay noted that previously occupied habitat was destroyed by Reindeer introduced in 1944 on St. Matthew Island (Rausch and Rausch 1968). Reindeer population numbers increased to approximately 6,000 in 1963, but by the summer of 1966 only 42 remained and by the 1980s the population had completely died out.
The Arctic Fox (Alopex lagopus) is native to St. Matthew. According to Rausch, predation appears to take place during years of high vole populations rather than when vole numbers are low; however, additional studies are needed to verify this pattern (Rausch and Rausch 1968). Predation by Long-tailed Jaegers and Snowy Owls occasionally occurs (Rausch and Rausch 1968). In any event, such predation is unlikely to pose a significant threat to the long-term viability of the vole population.
Surveys are recommended to determine the nature and extent of any threats to the population of M. abbreviatus (Hafner et al. 1998). Populations on both islands are fully protected. Both St. Matthew Island and Hall Island are included in the Alaska Maritime National Wildlife Refuge.
The population is not currently being monitored. Factors affecting population size and distribution are unknown. Current research needs include: 1) population size and trend estimates 2) habitat preferences 3) reproductive capacity 4) long-term population viability assessment 5) further assessment of taxonomic status.
|Citation:||Frey, J. & NatureServe (Garibaldi, A. & Hammerson, G.) 2008. Microtus abbreviatus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 03 August 2015.|
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