ITHACA, N.Y. -- Every Feb. 2 has a special significance for researchers at Cornell University's College of Veterinary Medicine, and it's not because scientists think a sleepy rodent on Groundhog Day can predict winter's end.
Rather, the groundhog (also known as the woodchuck) is honored at Cornell for its indispensable contributions to the study of liver disease in humans. For more than 15 years, animals born at the world's only scientific source of disease-free woodchucks have led researchers to discoveries in treatment and prevention of hepatitis B infection and the liver cancer it can cause.
"A percentage of the wild woodchuck population in the United States is infected with a virus very similar to HBV, the human hepatitis B virus. Humans don't get hepatitis from woodchucks with WHV, the woodchuck hepatitis virus, but the virus and its effect on their liver is similar enough to make the woodchuck the best system we have for studying viral hepatitis in humans," explained Bud C. Tennant, D.V.M., the James Law Professor of Comparative Medicine who heads the woodchuck-research project.
Groundhogs in the Cornell program have been responsible for many advances in understanding liver disease (see accompanying chart), including the finding that immunizing against hepatitis B virus can prevent liver cancer. Woodchucks are the best-available animal model for hepatitis B studies, Tennant said, because the woodchuck virus has a nearly identical effect on woodchuck livers as does human hepatitis B virus on human livers -- except that time is compressed. Disease processes that take 30 to 40 years in humans occur in three to four years in woodchucks. The only other animal model for HBV studies is the chimpanzee, an endangered species.
An estimated 250 to 300 million people, mainly in sub-Saharan Africa and Asia, are carriers of HBV, and about 40 percent of those infected will develop chronic liver damage or cancer. Many babies are born infected with the virus in those regions of the world, and they carry the infection throughout their lives.
Most of the woodchuck studies are conducted at Cornell, in collaboration with researchers from the National Institutes of Health and from research centers supported by the NIH. The original woodchucks that formed the breeding stock for the Cornell colony were caught in the wilds of upstate New York, beginning in 1979.
Cornell raises the woodchucks indoors, under contract with the NIH, so the disease-free animals are essentially government employees. They must be considered "essential" because they continued to work and receive their pay -- in woodchuck chow -- during the recent federal government furloughs.
Besides a reliable source of food, shelter and veterinary care, the Cornell groundhogs have one advantage that their outdoor cousins do not: An unfailing knack for predicting weather. Even the most celebrated of wild groundhogs -- which folklore credits with indicating another six weeks of winter if they see their shadow on Groundhog Day -- are frequently and disappointingly wrong.
But not Shadow, the Cornell woodchuck colony mascot.
"By the time Shadow wakes up and comes out of her nestbox on Feb. 2, the indoor lights are on," Tennant revealed. "Not surprisingly, she always sees her shadow.
"And we're never surprised if spring is months away," he said. "After all, this is Ithaca and upstate New York." -30- Highlights of woodchuck (groundhog) research at Cornell ITHACA, N.Y. -- Cornell University research involving woodchucks -- at the only disease-free colony in the world, maintained for the National Institutes of Health -- has resulted in many advances in understanding liver disease. Among them:
" Proof that hepatitis B virus infection is the proximate cause of liver cancer.
" Demonstration that immunization against hepatitis B virus can prevent liver cancer.
" Confirmation that immunosuppressant drugs used for human liver transplants increase viral replication of HBV, leading to the loss of the transplanted liver.
Research now under way with woodchucks is expected to yield even more benefits. Among them:
" Determining the role of dietary factors in liver cancer, such as alcohol or the aflatoxins found in some cereal grains and peanuts.
" Identifying the viral genetic factors responsible for chronic infection by hepatitis B virus, an important step because the highest occurrence of liver cancer is seen in chronic carriers of the virus.
" Discovering, on the molecular level, exactly how the virus causes liver cancer, as well as how the viral genes responsible for replication of the virus function; interruption of the replication genes could be the best anti- viral strategy, some experts believe.
" Testing new and improved hepatitis B vaccines.
-30- Woodchuck Wisdom
Groundhog Day facts about Marmota monax
Groundhog, woodchuck -- what's the difference? Woodchuck and groundhog are common terms for the same animal, the rodent with the scientific name of Marmota monax. Most closely related to squirrels, woodchucks actually can climb trees and also swim. But they are more likely to be found in or around burrows that they excavate -- often at the edge of wooded areas. Their natural range stretches from southern Alaska to northern Georgia. For a wild woodchuck, "old" is around 6 years; in captivity, woodchucks can live 10-12 years. The average litter size is four pups, born in April or early May. By June, they are weaned and set off to establish their own burrows.
What's so special about Feb. 2?
Celestially speaking, Groundhog Day on Feb. 2 is a "cross- quarter" day, about halfway between the winter solstice in December and the vernal equinox in March, and is celebrated in some cultures as the midpoint of winter. It's not far from the time many groundhogs end their hibernation anyway, around the second week of February.
Who doesn't like woodchucks?
Their natural enemies are foxes and coyotes. Farmers destroy some because woodchuck burrows disrupt agriculture and endanger livestock. Others succumb to highway traffic or to parasitic diseases of the nervous system. Freshly excavated dirt is a sign of an occupied burrow, although the animals often maintain secretive "plunge holes" for a quick escape. Groundhogs show their affection by rubbing cheeks, where their scent glands are located.
What's going on in that woodchuck burrow? In the winter, not much. Groundhogs go into profound hibernation, greatly reducing their metabolic rate, and their body temperature drops to just a few degrees above ambient temperature. Because their hibernaculum, the deepest portion of the burrow where they hibernate, is below that frost line, that produces a body temperature as low as 39-40 degrees F.
What's the wake-up call?
The groundhog's internal clock is believed to be affected by annual changes in the amount of daylight. Hormonal responses to cyclic changes in production of melatonin, a sleep-related hormone, are thought by some to be the signal to wake up.
Why did groundhog fur coats go out of fashion? Groundhog fur never was in vogue, partly because it is not particularly thick and warm, and because the fur's grizzled grey-brown appearance is more appealing to others of their species than to people. Groundhog hairs are used for tying trout flies, such as the 'Chuck Caddis, and early American Indians once used sturdy woodchuck hides for soles of moccasins.
What's for dinner?
Groundhogs in the wild eat succulent green plants, such as dandelion greens, clover, plantain and grasses. They are also tempted by nearby garden vegetables. At Cornell, they dine on Agway Woodchuck Chow, a similar formulation to rabbit feed but in larger sized pellets. Woodchucks binge and purposefully put on weight in the summer, reaching their maximum mass in late August. They become lethargic and prepare for hibernation in October. By February, hibernating woodchucks have lost as much as half their body weight.
How much wood could a woodchuck chuck if a woodchuck could chuck wood?
About 700 pounds. Compared to beavers, groundhogs/woodchucks are not adept at moving timber, although some will chew wood. (At Cornell, woodchucks that gnaw their wooden nest boxes are given scraps of 2-by-4 lumber.) A wildlife biologist once measured the inside volume of a typical woodchuck burrow and estimated that -- if wood filled the hole instead of dirt -- the industrious animal would have chucked about 700 pounds' worth.
-30- Sources: College of Veterinary Medicine, Cornell University; New York State Department of Environmental Conservation; Mammals of the Eastern United States, Second Edition, William J. Hamilton Jr. and John O. Whitaker Jr.