Increase in Red Voles and Gray Shrews

Gary Nielsen writes:

For about 3 years there wasn't very many Red Voles and Gray Shrews . This year there is a lot.

LEO says:

According to the Alaska Fish and Wildlife News article titled, "Voles in Alaska," there are two main types of vole in Alaska. One is the red-backed vole (Myodes rutilus), which typically live in forested environments in small groups. The other type are meadow voles (Microtus pennsylvanicus), which prefer open meadow or tundra, and are found in larger groups. Vole populations will fluctuate. Every four or five years, the vole population "might be 50 to 100 times higher than usual." Additionally, in warmer winter years, with adequate snow cover and food, voles may continue to breed throughout the winter, increasing the population. While fluctuations in shrew populations are more difficult to pinpoint (according to the ADFG Wildlife Notebook Entry), a notable change in shrew population can be seen in their distribution. As the tundra warms, the masked shrews (Sorex cinereus) common in boreal foreast areas expand their range, while the population of tundra-dwelling shrews (Sorex tundrensis) shrink. Read more about shrew and climate research here.

ANTHC Consult: Dr. James Berner writes: "The red-backed vole is known to be susceptible to infection with Echinococcus multilocularis (EM), a parasite which the voles, and other rodent species, can acquire by consuming vegetation contaminated by dogs as well as foxes, wolves and coyotes that can carry the parasites for many years in their gastrointestinal tract, excreting parasite eggs in their feces. Alaska Arctic regions, and northern regions of the central US and adjacent Canadian provinces have also had EM parasites identified in dogs and rodent populations. EM causes a slowly developing liver and lung infection in humans, and is often fatal If not treated. In the mid-1940, EM was found to be infecting many residents of St Lawrence Island, and was transmitted to them by the feces of domestic dogs, which had been infected by consuming local voles. The EM infection in humans can take years to become symptomatic. Note: there is no evidence of new human cases of EM. It is however a topic of interest in the context of the warming trend in Alaska. The possibility that EM is spreading in rodent populations in western and northwest Alaska will be investigated by the UAF Department of Veterinary Medicine, in conjunction with funding and other activities supported by ANTHC and regional corporations, starting this spring. The results of these surveys will be shared with villages, regional corporations, as well as human and wildlife health agencies."

See also reference (p.28) from State of Alaska Section of Epidemiology Bulletin Assessment of the Potential Health Impacts of Climate Change in Alaska, "Echinococcosis is a zoonotic infection caused by tapeworms from the genus Echinococcus. Echinococcosis occurs sporadically in Alaska and reported cases have decreased in recent decades. Cystic echinococcosis, caused by infection with Echinococcus granulosus, has been reported in all regions in Alaska except the Aleutians. Alveolar echinococcosis, caused by infection with E. multilocularis, has only been reported in Alaska in the North Slope region and St. Lawrence Island. Warmer temperatures could support the expansion of foxes and voles, which are common carriers of E. multilocularis, though warmer temperatures might also make it harder for E. multilocularis eggs to survive (Parkinson and Evengård, 2009; Rausch, 2003; Jenkins et al., 2013)."

Resources:

The UAF Cooperative Extension provides information on how to identify and remove rodents if they are causing damage to a building or home. See their publication "So You Have Mice- Now What?".