The Delta Farmland and Wildlife Trust
The dreaded Townsend Vole
This suspicious fellow is under investigation as the culprit in the destruction of thousands of berry plants over the past few years. BCIT instructor Bill Ransome is heading the first-ever long-term examination of the impact of the Townsend Vole on agriculture, and particularly on berry crops.
At first glance, the blueberry farm in Ladner, BC seemed just fine, other than some discoloured leaves. Then the farm owner went out and tugged on one of the bushes.
To his shock, the bush came right out of the ground with no resistance at all ... and no roots!
Bill Ransome, of the BC Institute of Technology, says while everything looked fine above ground, below the farmer’s feet hundreds of tiny but voracious Townsend Voles were devouring the roots of his blueberry bushes.
“He lost so much that he had to put poison out,” says Ransome. “It’s in the several thousands or tens of thousands of dollars, and he just can’t handle that level of damage.”
Last year Ransome presented some of his preliminary findings at the Pacific Agriculture Show from a pilot program of research into fruit damage from the Townsend Vole.
That initial research showed a serious enough problem that Ransome, an instructor at BCIT, is now leading a five-year, in depth study into Voles and berry damage. Ransome was the lead investigator in a previous study which focused on the Microtus genus of Vole, which primarily goes after tree roots in the BC Interior.
“Our studies have gone back over a long period of time,” Ransome says. “Voles can cause millions of dollars damage in forested areas around Kelowna and Kamloops. There was an outbreak of voles there, and they ate a large proportion of the trees on tree farms in that area.”
In the berry farms of the Lower Mainland Ransome has again donned his detective’s cap, investigating the activities of the Townsend Vole. Very little is known about this species, and even less about its long-term impact on berry crops.
“We know there is damage, and that some producers are seeing a huge amount of damage,” he says. “But, why do some producers have high amounts of damage and other producers right next door have low amounts of damage? Why are some years worse than others, and what drives the vole to go after berry crops some years and not other years? “These are some of the questions we don’t yet have answers for, and so far, no one has really studied these voles in an agricultural setting.”
Townsend voles live underground and are not often seen above ground. The best evidence of their presence are the entrances to vole tunnels, and the ‘runways’ or trails that lead from one tunnel to another. But despite the scant evidence on the surface, below ground there may be an entire vole city.
“There have been plots done where it was revealed there were up to 800 voles on a single hectare, and there was one in the forest with 1200 voles per hectare,” says Ransome. “The fact is, we really don’t know what’s going on under the ground, but we need to find out.”
Among the goals of this study is finding out whether Townsend voles have a ‘cycle’ in which their population waxes and wanes, and also why they go after berry bush roots in some years and not others.
It’s believed this happens in years when there is more competition for food sources, and the voles are driven to eat foods they might normally ignore.
It’s an important study for farmers, who will be able to use this information to better control the pests, but it’s important for other species who live in the same area.
“Farmers like the one we talked to in Ladner don’t want to use poison, but sometimes they have no choice, and this has an impact on other species,” Ransome points out. “For example, there are far more deer mice present than there are voles, and they don’t cause any damage at all, but they will obviously be impacted by poisons put out to control the voles.
“We hope our research will help find better ways to control the vole population so this isn’t necessary.”