Jennifer Schultz Nelson
Extension Educator, Horticulture
The topic of groundhogs seems more appropriate for early February and predictions of spring's arrival, but if one has moved into your garden this summer, this is definitely a timely topic.
The U of I Extension Master Gardeners in Macon County maintain a display garden of vegetables and flowers that is used for a gardening segment on WAND-TV that airs on Mondays during the noon news. Viewers see all the successes and failures in the garden throughout the season. This season has presented a lot of challenges.
Spring and summer was full of unusual weather patterns that delayed planting much of the garden, and affected how well the plants grew. Then the local deer population became a nuisance and threatened to destroy much of the garden.
A fishing line fence combined with strategically placed Irish Spring soap and commercial deer repellent has kept the deer at bay to date. Recently though, Master Gardeners that were working out in the garden noticed a few of the bars of soap hanging in the garden had what appeared to be two big front teeth marks in them. We had a new visitor in the garden, probably a groundhog.
The problem was he was not just visiting. He saw the garden and thought it was the perfect place to live, with an all-you-can-eat buffet open 24 hours a day. Soon what looked like a truckload of black dirt appeared at the edge of the garden. Excavation had begun on a deluxe groundhog dream home under the garden. This was not news I wanted to hear.
Groundhogs, a.k.a. woodchucks or whistle pigs, are pretty tough to evict once they decide to move in. They are stubborn and strong, and can be dangerous if cornered.
Groundhogs are very common across Illinois. They are rodents, and members of the squirrel family. They have large incisors which they will use to grind, chatter, and make a shrill whistle when threatened-- hence the common name "whistle pig". Typically they are about 17 to 26 inches long and weigh anywhere from 7 to 14 pounds. Given an abundant food supply though, some sources say they can grow up to about 32 inches long and weigh a whopping 30 pounds!
As we were witnessing first hand at the WAND-TV garden, groundhogs are burrowing animals. They have powerful, clawed front legs that are well-adapted for digging. If they are cornered, they can use these same strong front legs to defend themselves. When digging a new burrow, it is estimated that a groundhog moves about 35 cubic feet of soil!
Groundhogs typically dig at least two burrows over the course of a year-- one or more summer burrows and a winter burrow. They live alone except during the breeding season in early spring. Usually only one or two adults will occupy an acre of land, unless the habitat is exceptionally good.
The summer burrow is the most extensive, containing up to 45 feet of tunnels that may be as deep as 5 feet underground. Groundhogs prefer to situate the summer burrow on a grassy slope in an area with sandy, well-drained soil. There is one main entrance with soil piled next to it, and one or more other entrances which provide the groundhog quick access to his burrow should a predator threaten.
The summer burrow contains a main chamber for sleeping, and a chamber the groundhog uses as a bathroom. Groundhogs are diurnal, meaning they are active during the day, so they are typically found outside the summer burrow during the day.
It's where he is found outside during a typical summer day that annoys gardeners. Groundhogs are primarily herbivores, feeding on local vegetation. They especially love fruits and vegetables, though they will occasionally eat insects, snails, and birds' eggs. A home orchard or vegetable garden is truly a smorgasbord for a groundhog. He will eat about one to one and a half pounds of vegetation each day.
Groundhogs are unique in that they are one of the only true hibernating animals in Illinois. In about October, they begin hibernation in a separate winter burrow. This burrow is typically in a wooded area and is much shorter, has only one opening, and contains one nest chamber at the end that the groundhog blocks off with soil when he is inside.
During hibernation, the groundhogs body temperature drops from about 97 ˚F to 34 ˚F. It takes a breath about once every six minutes, and its heart beats only four times per minute. In a process that is not completely understood, the groundhog's internal clock tells it when to wake up in the spring. Scientists believe the outdoor temperature is a factor involved in the waking process.
While some would consider the groundhog to be an interesting and fascinating creature, I find him considerably less fascinating as he destroys our garden at WAND-TV. What do we do now? Many homeowners are probably asking themselves the same question this time of year.
The only control method for groundhogs that can be utilized without a permit is exclusion, finding a way to keep the groundhogs away from a particular area. This is not as easy as it may sound. A simple fence will not work. Not only are groundhogs excellent diggers, they are good at climbing too.
A fence for a groundhog needs to be at least three feet tall, with the top portion angling outward at a 45 degree angle to prevent the groundhog from climbing over the fence.
That same fence needs to extend underground 12 to 14 inches with the lower two to four inches angled out at a 90 degree angle to prevent the groundhog from burrowing under the fence.
As an additional deterrent, place an electrified wire four to five inches above the ground outside the fence.
That is a lot of work for most gardeners. I have heard some anecdotes about placing highly "fragrant" materials like fresh manure near the burrow entrance to encourage the groundhog to move elsewhere. While I haven't found any research to back up this method, if you can stand the smell, it certainly wouldn't hurt anything, so why not try it?
Groundhogs do not venture very far from their burrows-- only about 50 to 150 feet. If they have burrowed into material that can be removed from the site, they may move on if that material is removed. I have seen situations where groundhogs have moved into piles of junk and brush on a property, and getting rid of the piles also got rid of the groundhogs.
Groundhogs prefer areas that don't have a lot of human activity. Increasing human activity in an area, or using props like scarecrows, as long as they are moved often, may help encourage the groundhogs to find a new home.
A common question we receive is about trapping. A person may not use any type of trap, even a live trap, to capture a groundhog without an animal removal permit from an Illinois Department of Natural Resources (IDNR) District Wildlife Biologist.
A groundhog caught in a live trap must be released or euthanized within 24 hours of capture. To release the animal on property other than your own, you need written permission from the landowner in addition to the permit from IDNR. As with all other mammals, it is not permitted to release groundhogs in public parks, forest preserves, or natural areas.
There are carbon monoxide gas cartridges available that effectively kill groundhogs. But again, you still need to obtain a permit from the Illinois Department of Natural Resources to use them.
Homeowners may also choose to hire a nuisance wildlife control operator to trap and remove the animal. If you can tolerate the animal's presence on your property, it is also a valid choice to just leave the groundhog alone.
University of Illinois Extension has recently released a new website called "Living with Wildlife in Illinois" that answers many common questions, including how to obtain permits to remove nuisance animals. Check it out at: http://web.extension.uiuc.edu/wildlife/.