Voles have become a significant threat to Idaho agriculture, particularly to alfalfa crops. With some farmers reporting losses of up to 60% or more, understanding the vole life cycle, their resilience and innovative control methods has become critical.
Voles are prolific breeders, capable of producing five to 10 litters per year, with each litter containing three to six young. Their rapid reproductive rate allows populations to explode under favorable conditions. Voles can live up to two years, however, most never make it to their first birthday. Their short lifespan is counterbalanced by their high birth rate. They thrive in environments with ample ground cover, which provides protection from predators and harsh weather.
Voles are often mistaken for gophers or ground squirrels. Voles can make burrows but usually use these underground dens for hiding and nesting. The majority of their foraging happens above the ground, unlike gophers. They prefer to feed above the surface under some kind of cover, such as grass or alfalfa plants in the summer and snow in the winter. If they have a good snow cover, they don’t bother with digging deep tunnels. Instead, they will make their tunnels between the snow and the dirt, where it's easier to dig and they still feel protected. Without any cover, they tend to dig deeper and be much more leery of the open sky. To really thrive, they need some kind of protection, which makes them less visible to predators and much harder to target. They are also very adaptive, figuring out shortcuts around common control methods and becoming skeptical of repeated applications of rodenticides.
Voles tend to do well in northern states, such as Idaho and Montana. My father-in-law is an alfalfa farmer in central Utah, and he doesn’t even know what a vole looks like. The bane of his operation is pocket gophers. Why don’t they have any voles? It seems they thrive better where it’s colder in the winter. In fact, it seems they do much better with a thick snow cover than without one. The difficulty of applying a rodenticide during the winter only exacerbates this problem, often leading to six months or more between chemical applications.
It has been said many times that 100 years ago when everyone used millboard plows and flood irrigated, there were no problems with voles. It seems that as we have improved our soils, we have inadvertently improved the habitat for voles to thrive. I would never advocate reversing all of the great progress we have made in the way of soil health, but we do need to ask ourselves why voles are getting worse. Why is it a specific problem for northern states, such as Idaho and Montana? And more importantly, how can understanding their biology help disrupt this endless cycle?
The desperation of Idaho farmers has led to some great innovations. Several farmers are getting creative trying to stop them in their tracks. One promising approach involves rolling and harrowing over snow-covered fields. Rolling compresses the snow and underlying soil, making it more challenging for voles to dig new tunnels. Harrowing, on the other hand, effectively disrupts existing tunnels, collapsing the intricate networks that voles rely on for safety and mobility. Without a network of burrows, the only option for the vole is to go up to the surface. Their thick brown hair stands out against the bright white snow, where they are quickly picked up by hawks, owls, eagles, crows or any other predator in the area. Farmers are optimistic that these practices will help keep the populations down through the winter months, denying the vole populations they need to explode through the winter.
There are still more questions than answers. What effect will this have on the alfalfa stand? Will it actually impede vole population growth? Is it worth it? All these questions will be answered by those willing to take the risk. Unfortunately for Idaho hay growers, there is less and less to lose with each year of high vole populations. The important takeaway is that farmers continue to educate themselves on vole biology to figure out how to disrupt it. While these cultural techniques show promise, understanding vole biology and behavior remains critical to developing long-term, sustainable solutions. By blending traditional knowledge with scientific research, farmers can better disrupt the vole life cycle and mitigate future crop damage.
