Groundhogs (Marmota monax) are the largest rodents of the Sciuridae family, and they belong to a group of ground squirrels also known as marmots. They are solitary animals, best known for their excellent burrowing abilities. Widely distributed in North America, groundhogs are also commonly referred to as: chucks, woodchucks, thickwood badgers, groundpigs, whistlepigs, whistlers, Canada marmots, monax, moonacks, weenusks, or red monks. To a lot of people, groundhogs are pests, because they build burrows close to homes, eat fruits and vegetables from gardens, and chew through anything, from wood to electrical cables.
Description and distribution of groundhogs
Being the largest mammals of their family, they generally measure around 40 – 65cm in length and weigh around 2 – 4kg. In areas where predators are scarce and food is plentiful, however, they can grow up to 80cm in length and 14kg in weight.
A groundhog’s body is therefore well-adapted to its environment and its lifestyle. They have a flat head, small, round eyes and ears, as well as a nose that presents a highly developed sense of smell. The mouth also presents 2 long incisors that continue to grow all throughout the groundhog’s life. Overall, they have a rounded shape, with short, powerful limbs and strong, curved claws, which are very useful in digging; unlike other members of the Sciuridae family, they have curved spines and short tails. Because they live in temperate habitats, groundhogs are covered with 2 coats of fur, generally of a brown-grey colour.
Groundhogs are lowland animals, widely distributed in North America (the United States and Canada), where they can be found as far north as Alaska and as far south as Georgia. Habitat-wise, they live in open plains, preferable at the edges of woodlands, where they can still benefit from protection against predators.
Behaviour and lifespan
Groundhogs are diurnal animals, often active, from spring to fall, early in the morning or late in the afternoon. They are the most solitary of all marmots, seeking out one another only when they need to mate. Between themselves, groundhogs are territorial, generally resorting to skirmishes to establish dominance, but not aggressive. They are still relatively social animals, who alert each other to danger using a high-pitched whistle — hence the names “whistlepigs” and “whistlers”.
The thing that defines groundhogs the best is the tendency and excellent ability to build burrows. These are large, buried up to 1.5m underground (in dry, well-drained soil), with multiple chambers and with up to 14m worth of tunnels. They are so complex that each burrow even has its own “bathroom” chamber. It is inside these burrows that groundhogs spend most of the time; it is here that they sleep, hibernate during the cold months, retreat into to pass bad weather, raise younglings, and hide in case of danger. If a predator manages to enter a burrow, the groundhog is usually prepared to escape through one of the 2 – 5 entrances.
Groundhogs are one of the only animals that hibernate in the real sense of word, entering a dormant state where body temperature and heart rate fall dramatically — i.e. below 20 degrees Celsius and to about 5 beats per minute, respectively. To gain an understanding of what this means, a bear’s body temperature only drops to 30 degrees Celsius when it hibernates. However, this does not mean that groundhogs sleep all through the winter. Instead, they will be asleep (with a body temperature of 5 degrees Celsius) for around a week, wake up for roughly 3-4 days, and then go back to sleep. In cold areas, they hibernate from October to March/April, although in more temperate areas, they will hibernate less, for as little as 3 months. Interestingly, some species of groundhogs build completely separate burrows to hibernate in. These are usually in a wooded or bushy area and are dug below the frost line — both attributes that enable them to remain at a stable temperature, well above freezing, during the winter. Before entering hibernation, groundhogs are at their maximum weight, which allows them to survive the cold months, and immediately following hibernation, they have only enough remaining body fat to live on until the warm spring weather produces the necessary plant materials for them to eat.
Common predators of groundhogs include: bears, bobcats, cougars, coyotes, dogs, eagles, foxes, and wolves. Young groundhogs also have snakes to defend themselves from, since these can very easily enter burrows, where younglings may be left unattended during the day. When it comes to defence mechanisms against these predators, most groundhogs choose to flee and hide, which is the main reason why they always tend to remain within close distance to their burrows. If these burrows are invaded, however, adults are capable of defending themselves using their incisors and their front claws. Despite their heavy-set appearance, groundhogs are also capable of swimming, as well as climbing trees — both of which are abilities that are often used when trying to escape predators.
In the wild, groundhogs can live up to 6 years, with most living between 2 – 3 years. In captivity, groundhogs have been reported to live between 9 – 14 years.
Breeding and dietary information
In the case of groundhogs, the breeding season starts once they emerge from hibernation; thus, it lasts from early March to mid/late-April. Interestingly, there is evidence that the males wake up earlier than the females in order to determine where the potential mates are. Usually having a territory that includes more than one female burrow, the male will go from burrow to burrow to ascertain that the female is still there, before returning to his own burrow to continue his hibernation for around another month. Following mating, both the male and the female will live together in the same den until the gestation period (which lasts 31 — 32 days) ends. The males leave just before the younglings are to be born, in late April/May.
On average, a pair will have 1 litter per year, containing 2 – 6 younglings, which are born blind, hairless, and helpless. They are only introduced to the wild (by their mother) once they can see and have grown fur. It is around this time that the father may return to the family, but this does not always happen. In the following weeks, the mother (and sometimes father) encourage the younglings to copy, and in this way learn, behaviours. Generally, the time period that the pups spend with the mother is of about 2 months. In August, the family breaks up, with the younglings scattering to build their own burrows. Groundhogs usually start breeding at 2 years of age, although some may be capable of breeding at only 1 year of age.
When it comes to food, it is important to realize that groundhogs are not as omnivorous as other members of the Sciuridae family. They are primarily herbivorous, feeding on various forms of vegetation, such as grass and agricultural crops, and particularly enjoying alfalfa, clover, coltsfood, and dandelion. They will also eat fruit (such as berries, watermelon, cantaloupe, etc.), nuts, as well as many commonly grown vegetables (such as peas, lettuce, etc.). On occasion, they will eat grubs, grasshoppers, snails, insects, as well as other small animals. Each day, groundhogs eat approximately 1/3 of their weight in vegetation, an amount that increases as the time comes closer to winter, and they have to start accumulating fat reserves. As far as water is concerned, groundhogs get most of it from plant juice or dew and rain.
Groundhogs as pests
Common as they are in the region, groundhogs are familiar animals to a lot of people in North America, and, more often than not, these people are bothered by their presence. This is because of 3 main reasons: burrowing, eating, and chewing. Because of these actions with which the groundhogs can affect your property, preventive measures need to be taken in time. You can find such examples in our article which details ways in which to “Prevent infestations with groundhogs”
First of all, the large, intricate burrows that groundhogs dig are problematic when it comes to agriculture, seeing as they can upset seedlings and damage farm machinery. Equally, they can be problematic when it comes to residential development, seeing as they can undermine building foundations.
Secondly, groundhogs will most happily eat any fruits, vegetables, or flowers that you may have in your garden and that they may find appealing. In fact, there is evidence to indicate that groundhogs actively search for gardens to settle in, seeing as they provide 2 very important things: abundant food and protection from predators. Furthermore, groundhogs will gnaw and chew on any wood that you may have lying around, be it the firewood you have cut in preparation for winter or the shed that you built to hold your tools.
Finally, like most rodents, groundhogs will not only chew on crops and wood, but also on tubing and electrical wires, which can be both a nuisance and a serious problem.
From a different perspective, however, groundhogs can also be useful to humans. This is mainly because, by bringing soil to the surface, they aid in its improvement. Furthermore, groundhogs burrows are often used by animals such as skunks, foxes, and rabbits, which can indirectly aid farmers by getting rid of other creatures that damage crops, such as grasshoppers, beetles, field mice, etc.
With regards to other types of relationships that groundhogs may have with humans, it is important to know that they are often hunted as a sport, which helps maintain populations in check. Due to the clearing of forests in recent decades, these populations are higher than they used to be. A less well-known, but equally interesting, fact is that groundhogs are also used in medical research on hepatitis B-induced liver cancer.