Vole problem may be overrated
Researcher finding minimal damage in cultivated fields from Townsend’s Vole, which ismuchmore at home in grasslands.
By Judie Steeves D
oug Ransome is playing detective. A biologist specializing in small
mammals, Ransome is head of the ecosystem restoration program at the B.C. Institute of Technology, and he’s investigating the presence of Townsend’s Voles in Fraser Valley blueberry fields.
Although his initial research in four fields didn’t show much damage as a result of their presence, he noted that the mulch commonly used provides cover for them. The material is loose so it’s easy for the little rodents to tunnel in under the bush and burrow into cavities within the root structure. Ransome says they have eaten roots in some spots, but although there is lots of tunnelling in some areas, there isn’t a lot of damage evident.
“For years, we’ve heard of voles in blueberry fields,” he noted. However, normally the Townsend’s Vole prefers grassland habitat where it can exist at the highest density of any vole in B.C. They’ve been known to inhabit grassy
Townsend’s Vole trapped as part of study effort in the Fraser Valley to determine just how prevalent and destructive they are in blueberry fields.
fields at a density of 800 per hectare, while other species of voles only get to a density of 50 to 100 per hectare. The Townsend’s Vole is also the largest vole in North America, at 50 to 90 grams in weight, compared to most other species, at 20 to 50 grams in weight.
He believes damage occurs through winter, although he admits there is sparse information about the vole, except in forest settings where they are known to occur in a three to five- year cycle.
There the highest populations are in October, when they stop breeding and they overwinter poorly, so populations are slow to start up in spring, he says.
They are native to the areas of Vancouver Island and the Lower
Mainland where the young females can bear litters of one to nine young in their first summer.
Normally their diet is tender marsh or grassland vegetation, although they also consume the bark of shrubs, some stems and some roots. Since there is good control of grass in most berry fields, Ransome is not sure why the voles have chosen to inhabit berry farms.
When farms are located beside grassy areas, he feels there could be a spillover of vole populations from those areas.
“They’re very territorial. They’ll kick out the youngsters to find their own territory,” he said.
Townsend’s Voles have strong teeth, and they sometime have a bit of an attitude, Ransome added.
British Columbia Berry Grower • Summer 2012 17
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