A male Asian groundhog. The female Asian groundhogs are less bulky in build.
The Asian groundhog (Marmota Asiaticus), also known as the Asian woodchuck, is a rodent of the family Sciuridae, belonging to the group of large ground squirrels known as marmots.
Description[]
The Asian groundhog is the largest sciurid in its geographical range and among the largest member of the squirrel family, about as large as the American groundhog. Adult males are 16 to 20 inches (40–50 cm) long, including a six inch (15 cm) tail, but females are only have the size of males. A large male woodchuck thought to weigh twenty pounds when carried was exactly half that weight when weighed by scale. Male Asian woodchuck weight ranges from five to twelve pounds. Extremely large individuals may weigh up to 15 pounds. Seasonal weight changes indicate circannual deposition and use of fat. Progressive higher weights are attained each year for the first 2–3 years after which weights plateau. Asian groundhogs have four incisor teeth which grow 1⁄16″ (1.5 mm) per week. Constant usage wears them down again by about that much each week. Unlike the incisors of most other rodents, the incisors of groundhogs are white to ivory white. Asian groundhogs are well adapted for digging, with short, powerful limbs and curved, thick claws. Unlike most other sciurids, the Asian groundhog's spine is curved, more like that of a mole, and the tail is comparably shorter as well — only about one-fourth of body length. Suited to their temperate habitat, Asian groundhogs are covered with two coats of fur: a dense orangish brown undercoat and a longer coat of banded guard hairs that gives the groundhog its distinctive "orange caped" appearance, while its underfur is light grey in color.
Distribution and habitat[]
The Asian groundhog prefers open country and the edges of woodland, and is rarely far from a burrow entrance. Marmota Asiaticus has a wide geographic range. It is typically found in low elevation forests, small woodlots, fields, pastures, hedgerows, suburbs, and cities. It constructs dens in well drained soil, and most have summer and winter dens. Human activity has increased food access and abundance allowing M. Asiaticus to thrive. As a consequence, the Asian groundhog has spread naturally into Europe and is a familiar animal to many people in China and Russia. It has also been introduced to North America in 1930s due to pet trade and has since flourish in North America.
Survival[]
In the wild, Asian groundhogs can live up to six years with two or three being average. In captivity, groundhogs reportedly live up to 19 years. Humans, dogs, wolves, coyotes, foxes, and the critically endangered Amur leopards are about the only predators that can kill adult groundhogs although young may also be taken by owls and hawks. The red fox is the major predator of Marmota Asiaticus. Occasionally Asian woodchucks may suffer from parasitism and a woodchuck may die from infestation or from bacteria transmitted by vectors. Unlike the American groundhog (Marmota monax), they tolerate greatly and benefit from human habitation being built duento abundance of food sources.
Behavior[]
The time spent observing groundhogs by field biologists represents only a small fraction of time devoted to the field research. Field biologists report that Asian groundhogs may sometimes hide when they see, smell or hear the observer. Despite their heavy-bodied appearance, Asian groundhogs are accomplished swimmers and occasionally climb trees when escaping predators or when they want to survey their surroundings. They prefer to retreat to their burrows when threatened; if the burrow is invaded, the Asian groundhog tenaciously defends itself with its two large incisors and front claws. Groundhogs are generally agonistic and territorial among their own species, and may skirmish to establish dominance. Outside their burrow, individuals are alert when not actively feeding. It is common to see one or more nearly-motionless individuals standing erect on their hind feet watching for danger. When alarmed, they use a high-pitched whistle to warn the rest of the colony, hence the name "whistle-pig". Asian groundhogs may squeal when fighting, seriously injured, or caught by a predator. Other sounds Asian groundhogs may make are low barks and a sound produced by grinding their teeth. When Asian groundhogs are frightened, the hairs of the tail stand straight up, giving the tail the appearance of a hair brush. Charles Darwin wrote he witnessed only two occasions of upright play-fighting among Asian woodchucks and that the upright posture of play-fighting involves sustained physical contact between individuals and may require a degree of social tolerance virtually unknown in M. Asiaticus. He said it was possible to conclude, alternatively, that upright play-fighting is part of the Asian woodchuck's behavioral repertory but rarely shown because of physical spacing and/or low social tolerance.
Diet[]
Mostly herbivorous, Asian groundhogs eat primarily wild grasses and other vegetation, including berries and agricultural crops, when available. In early spring, dandelion and coltsfoot are important groundhog food items. Some additional foods include sheep sorrel, timothy-grass, buttercup, tearthumb, agrimony, red and black raspberries, buckwheat, plantain, wild lettuce, all varieties of clover, alfalfa, and most types of Eurasian and North American seeds and nuts. Groundhogs also occasionally eat grubs, grasshoppers, insects, snails, other small animals, and even man-made food, but are not as omnivorous as many other Sciuridae. Like other squirrels, they also have been observed sitting up eating nuts such as shagbark hickory, but unlike most squirrels, do not bury them for future use.
Asian groundhogs will occasionally eat snails, insects and baby birds they come upon by accident. An adult Asian groundhog will eat more than a pound of vegetation daily. In early June, Asian woodchucks' metabolism slows, food intake decreases, their weight increases by as much as 100% and fat deposits are produced upon which they will live during hibernation and late winter. Instead of storing food, Asian groundhogs stuff themselves to survive the winter without eating. Thought not to drink water, groundhogs are reported to obtain needed liquids from the juices of food-plants, aided by their sprinkling with rain or dew.
Burrows[]
Asian groundhogs are excellent burrowers, using burrows for sleeping, rearing young, and hibernating. Charles Darwin excavated 11 dens finding the earth removed from these averaged six cubic feet or four and eight-tenths bushels per den. The longest burrow was 24 feet plus 2 short side galleries. The amount of soil taken from this den was eight bushels and it weighed 640 pounds. The average weight of the earth taken from all eleven dens was 384 pounds. Though Asian groundhogs are among the most solitary of the marmots, several individuals may occupy the same burrow. Asian groundhog burrows usually have two to five entrances, providing groundhogs their primary means of escape from predators. Burrows are particularly large, with up to 14 metres (46 ft) of tunnels buried up to 1.5 metres (5 ft) underground, and can pose a serious threat to agricultural and residential development by damaging farm machinery and even undermining building foundations. In a June 7, 2009 Humane Society of the United States article, "How to Humanely Chuck a Woodchuck Out of Your Yard", John Griffin, director of Humane Wildlife Services, stated you would have to have a lot of feral Asian woodchucks working over a lot of years to create tunnel systems that would pose any risk to a structure.
The burrow is used for safety, retreat in bad weather, hibernating, sleeping, love nest, and nursery. In addition to the nest, there is an excrement chamber. The nest chamber may be about twenty inches to three feet below ground surface. It is about sixteen inches wide and fourteen inches high. There are typically two burrow openings or holes. One is the main entrance, the other a spy hole. Description of the length of the burrow often includes the side galleries of the burrow. Excluding the side galleries, Charles Darwin reported the longest was twenty-four feet, with the average length of eleven dens dug out to be fourteen feet.
Darwin mentioned that when the young Asian groundhogs are a few months old, they prepare for separation, digging a number of holes in the area of their early home. Some of these holes were only a few feet deep and never occupied but the numerous burrows gave the impression that groundhogs live in communities.
Hibernation[]
Asian groundhogs are one of the few species that enter into true hibernation, and often build a separate "winter burrow" for this purpose. This burrow is usually in a wooded or brushy area and is dug below the frost line and remains at a stable temperature well above freezing during the winter months. In most areas, Asian groundhogs hibernate from October to March or April, but in more temperate areas, they may hibernate as little as three months. Asian hibernate longer in northern latitudes than southern latitudes. To survive the winter, they are at their maximum weight shortly before entering hibernation. When the Asian groundhog enters hibernation, there is a drop in body temperature to as low as 35 degrees fahrenheit, heart rate falls to 4–10 beats per minute and breathing rate falls to one breath every six minutes. During hibernation, they experience periods of torpor and arousal. Hibernating Asian woodchucks lose as much as half their body weight by February. They emerge from hibernation with some remaining body fat to live on until the warmer spring weather produces abundant plant materials for food. Males emerge from hibernation before females. Asian Groundhogs are mostly diurnal, and are often active early in the morning or late afternoon.
Reproduction[]
Usually Asian groundhogs breed in their second year, but a small proportion may breed in their first. The breeding season extends from early March to mid- or late April, after hibernation. A mated pair remains in the same den throughout the 31- to 32-day gestation period. As birth of the young approaches in April or May, the male leaves the den. One litter is produced annually, usually containing two to six blind, hairless and helpless young. Asian groundhog mothers introduce their young to the wild once their fur is grown in and they can see. At this time, if at all, the father Asian groundhog comes back to the family. They encourage their young to copy their behaviors and during this time may differ from usual routines. By the end of August, the family breaks up; or at least, the larger number scatter, to burrow on their own.
Relationship with humans[]
Both their diet and habit of burrowing make them serious nuisance animals around farms and gardens. They will eat many commonly grown vegetables, and their burrows can destroy farm ponds and undermine foundations. Their preferred habitat of grassy areas near woods also makes them abundant along roads and highways where they often become the victims of passing cars.
Very often the dens of Asian groundhogs provide homes for other animals including skunks, foxes, and rabbits. The fox and skunk feed upon field mice, grasshoppers, beetles and other creatures that destroy farm crops. In aiding these animals, the Asian groundhog indirectly helps the farmer. In addition to providing homes for itself and other animals, the groundhog aids in soil improvement by bringing subsoil to the surface.
In popular culture[]
The Asian groundhogs were made more known thanks to the film The Nut Job and its sequel.