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Our Latest Plague: Meadow Voles

I try to keep in touch with our custom grazing clients, maybe call them once a month or so during the winter months. This helps remind me to pay attention to forage conditions here on the ranch and lets them know that I’m thinking about them. Often, these calls include some personal conversations or potential troubles. Recently, I called Tom to tell him about some bad business bubbling up across my side of the State. His response made me think of the Bible.

“Well, what is this time? Fire? Flood? Locusts? Plague?”

“Nope. Voles.”

“What the heck is that?”

Meadow voles can grow to about 6 inches long (with a 2.5 inch tail) and usually weigh about 1.5 oz. They can swim, and use vocalizations and stamp their feet to protect themselves from predators and can become aggressive when trapped. The meadow vole consumes 60% of its body weight each day, eating grasses, sedges, seeds, tubers roots and the occasional insect. Under the cover of snow, the meadow vole may girdle trees and shrubs, consuming the inner bark. Breeding occurs year round. Females begin mating within 25 days of birth and have litters of 2 to 3, but sometimes as many as 9. With a gestation period of only 21 days, pastures can quickly be overrun by voles.

Actually, I’d received a couple of calls from friends over the past few months, telling me that they were very concerned about what seemed like a tidal wave of voles, entire fields covered by runways and burrows, all of the green disappearing from meadows and hay fields. Some folks were talking about the possibility of massive farming and re-seeding. This caused me to begin wandering around a bit, taking a more critical look at some of our pastures. Then I attended a Zoom meeting with my grazing group. When the topic of voles came up I mentioned that in some places I was seeing about one vole burrow per square foot. My pal Jon just laughed, telling the group that parts of his place were much worse than that. Shaken, I decided to take a closer look and visit several paddocks on each of our properties and see where we stood.

In Field Biology (no pun intended) we sample things on the ground by using a device called a quadrat. A quadrat has a known area and can be tossed randomly to capture a small survey. In this case, I intended to go out and toss my quadrat, count vole burrows, and calculate just how big the problem was. But as I began the project, it soon became clear that the nature of my project would make it very difficult.

Our grazing properties are very diverse: flat, steep, wet, dry, rocky, clay, loam, forest and swamp. As I wandered from place to place one thing became clear: the voles clearly preferred some places over others. They didn’t like the fields that were 100% saturated with ground water. What they really liked were fields that had suffered from heavy infestations of Tarweed and Queen Anne’s Lace (wild carrot) that I wrote about last summer. These paddocks were left covered with a “forest” of stiff, dead, brown weed stems. And the ground beneath those dead weeds was stripped bare of any green foliage. Burrows and rodent trails were everywhere. In terms of growing grass, I judged these paddocks to be…devastated.

Why are they choosing some sites over others? Perhaps it has to do with safety. Over the years I have noticed that the area directly beneath our single-wire fences always harbor large rodent populations. I assume this is because they are somewhat protected from raptor predators. It seems likely that this current phenomenon of voles populating the areas beneath the dead weed forests is related to the same thing: birds of prey do not like to dive into areas where they might be injured.

Ava, my bird dog, hunting voles. There are so many, she has given up eating them. Still, I notice my dog food bill has been markedly reduced this spring.

There are some things I really don’t know:

• What will these fields will look like in three months or six months?
• What effect will the voles have on total production on our different properties?

One thing I do know:

• The plant community on some of our paddocks looks terrible, and I worry about our carrying capacity this coming spring.

Later on, when I called Jon back to ask for his thoughts, the main question wasn’t about the current lack of forage, but about what was going on under the ground. Were the voles just harvesting foliage, or are they actually eating the roots and killing the plants? I’m not certain we have a good answer, but places look pretty scary.

At this point, I’m trying to remain positive but conservative. I have told my custom grazing clients that based on my observations I expect perhaps a 25 or 33 percent reduction in grazing this spring and summer. I will make that adjustment by working on plans to liquidate some of my own personal cattle as the grazing season unrolls. What is interesting about this approach is that it is exactly the same thing I would do in a drought: reduce stocking rate to accommodate a loss of growth and make those reductions before the rest of the ranching community recognizes the problem or floods the local market.

Hoping for the best, and also for happy grazing season here in the Calapooia valley.

John Marble
Crawfordsville, Oregon


This was written a couple weeks ago and John has continued to monitor the impacts of voles. He wrote me this week to say he’s updating his damage estimate to 50% loss of production. As he noted above, he’s now implementing the “vole” version of a drought management plan, reducing cattle numbers to match the remaining available forage.

John also talked about his management for voles being a lot like his drought management plan. If you don’t have one yet, download Drought Planning 101 from the Bonus Content provided for paying subscribers. Here’s what it includes:

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