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Mammals Ecology Behavior

Ecology and Behavior of Woodchucks

Opposition Research on My Garden’s Greatest Nemesis

Even if a woodchuck could chuck wood, it would still rather eat your garden!

As a relative newcomer to somewhat-rural New England, my disappointment at no longer living in a major city was offset by the opportunity to finally have the big vegetable garden of my dreams. This spring I built a raised bed and planted rows and rows of salad greens. I was pretty naïve about the local wildlife—I hadn’t seen any deer in the area, so I thought my plants would be fine.

Well. Lesson humbly learned! The first sprouts were chomped immediately. I wised up and built a haphazard fence using thin wooden slats and some plastic bird netting. I planted more seeds, figuring I’d done a pretty good job.

I was so, so wrong.

Within days of the next leaves unfurling, ferocious incisors had sheared through the plastic fence in a dozen places and laid waste to the tender greens inside. Careful observation from my front porch led me to the culprit, a rotund animal that became my gardening nemesis: the woodchuck.

While the woodchucks devouring my garden were a nuisance, they weren’t causing any harm and have as much right to live on the property as I do. But with so much other vegetation in the area, why did they have to target my home-grown lettuce? When I saw one individual barge through the wreckage of the plastic fence and lay down to sun himself, I knew I had to investigate this formidable foe. I hoped that learning about their ecology and behavior would help me build a woodchuck-proof fence—the kind of fence that says, “I support your right to exist on this planet but stay OUT of my garden.”

First: what is a woodchuck?

Marmota monax UL 04.jpg
By Cephas - Own work, CC BY-SA 3.0, Link

Figure 1. The woodchuck or groundhog, Marmota monax, is related to squirrels, chipmunks, and marmots.

A woodchuck (also called a groundhog or whistlepig) is a large ground squirrel and a member of the squirrel family of rodents. Unlike its closest relatives, the alpine marmots, the woodchuck lives in lowland areas ranging across eastern North America[1]. They are stocky mammals with short bushy tails, and, in my professional opinion, adorably grouchy expressions.

What do they eat?

Even if a woodchuck could chuck wood, it probably won’t when there’s an easier source of food available. Woodchucks feed during the day and are mostly herbivorous, preferring to eat grasses and low ground cover plants such as alfalfa, clover, or dandelions. They probably think my garden is a delicious buffet. However, they will also eat the leaves and bark of trees, insects, and even bird eggs to help them pack on body fat for their winter hibernation [1]. Like all rodents, woodchucks have large incisor teeth at the front of their jaws. They use these to gnaw wood, to clip grass and leaves while eating, and to decimate plastic fences. Furthermore, the bones in their skull and jaw are very strong and accommodate large chewing muscles, which help them grind up tough plant material.

Woodchuck up a tree.jpg
By D. Gordon E. Robertson - Own work, CC BY-SA 3.0, Link

Figure 2. They are technically ground squirrels and don’t look particularly graceful, but woodchucks can climb trees pretty well. I was worried they would also be able to climb a fence!

How do they get around?

Although they on the chunky side, woodchucks can definitely climb trees to escape from predators or to feed on leaves [2].

However, woodchucks are more at home underground than in trees. Woodchucks are semi-fossorial mammals who burrow and dig dens to use as shelter from predators and as a place to raise their young. Woodchucks are scratch-diggers, meaning they use their forelimbs and claws to burrow and remove soil. They display traits that are well-adapted for digging, including rounded ears that keep out soil when underground and short, muscular forelimbs. However, one study of the forelimb muscle strength in woodchucks found that they generate relatively low forces while digging, meaning they are less-specialized burrowers than other digging animals such as moles [3].

Research conclusions:

After learning about my rodent neighbors, I realized that planting more vegetables would be useless without a serious investment in materials. The fence had to withstand both attempts to scale the sides and tunneling attacks below ground, so plastic netting and mostly-rotten wood was not going to be enough.

I bought some sturdy wood, chicken wire, and a staple gun, and used what I had learned about the chewing, digging, and climbing abilities of the chucks to construct a fence. I made the chicken wire three feet high and loose at the top, so that it would be too wobbly to climb. I also dug a trench around the garden bed and buried two feet of chicken wire to deter digging. Then I planted some beans, crossed my fingers, and waited.

20161114_vander

Figure 3. Successful woodchuck-proof garden! Due to my lack of expertise with the staple gun and chicken wire, the fence is pretty loose up top, which makes it hard to climb. The buried portion makes it hard to dig under, too. Nice try, rodents! Image source: Abby Vander Linden

One month later, I can report success! I’ve seen a woodchuck try to climb the fence only to be dumped by the wobbly wire. I found holes dug around the garden, none of them deeper than the buried chicken wire. Best of all, there’s no sign of rodent incisor damage to any of my healthy plants! After my frustration-fueled research, I now enjoy watching the woodchucks chow down on the dandelions in my yard. I like to think we’ve come to a mutual understanding.

References:

[1] Kwiecinski, Gary G. “Marmota monax.” Mammalian Species 591 (1998): 1-8.

[2] Swihart, Robert K. and Peter M. Picone. “Arboreal foraging and palatability of tree leaves to woodchucks.” American Midland Naturalist 125 (1991): 372-274.

[3] Rupert, Joseph E., Rose, Jacob A., Organ, Jason M. and Michael T. Butcher. “Forelimb muscle architecture and myosin isoform composition in the groundhog (Marmota monax).” Journal of Experimental Biology 218 (2015): 194-205.

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