The next few years could be tough for arctic ground squirrels; they have an even higher chance than normal of ending up as dinner for a lynx, coyote or other predator.

Populations of arctic ground squirrels are part of the natural cycle that affects many of the animals living in the boreal forest. Over the course of a decade, the numbers of lynx, coyotes, red squirrels and other animals will rise and fall.

The snowshoe hare cycle is the most dramatic of them all as hare numbers can increase 300 fold between the bottom and the top of this cycle. The hare cycle peaked last winter, meaning that the animals that eat them will soon be looking around for other food sources.

Predators will turn to arctic ground squirrels as tasty alternatives to hares, and the numbers of ground squirrels will start to decline. Ground squirrel populations can change three fold between the low and high points of their cycle.

But biologists do not think that predation is the only factor driving their numbers down. Tim Karels, a doctoral student at the University of Toronto, has studied arctic ground squirrels in the Kluane area since 1990.

His research was part of the Kluane Boreal Forest Ecosystem Project, a massive ten-year undertaking in which biologists studied the interactions between different animals and the food they eat in a 350-square-kilometre area near Kluane Lake. The Arctic Institute coordinated the project, which ended in 1996.

While predation certainly drives the decline in the population of ground squirrels, Karels' study showed that food seems to be the key to maintaining their numbers. He determined this by monitoring several study areas in which different factors were controlled.

In one study area, the population of ground squirrels doubled when predators were kept out. In another area, where the ground squirrels had no protection from predators but researchers gave them extra food, the population rose four to seven times higher than in the control area.

The biggest increases occurred in the test area where there were no predators and the ground squirrels also had extra food. In those areas the numbers of ground squirrels increased to 20 times the average density.

Karels suspects that there are links between food and predation that the researchers have not yet teased out. For example, the ground squirrels might forage less when there are predators around, so they produce fewer offspring and have a lower overall survival rate. Or the stress of having predators around could affect the immune systems of the ground squirrels and their ability to reproduce.

In the areas where predators were excluded, 50 percent more of the ground squirrels had litters. "We don't know why. It could be that there is lower stress or they are able to forage more often or they are living in areas where there is a higher risk of being eaten," he says.

Whatever the reasons, arctic ground squirrels are one of many northern species that must pack a lot of living into a short period of time. When they come out of hibernation in late April or early May, they mate immediately. About four weeks later the babies are born, and four weeks after that the young emerge from the burrow.

From that point -- in middle or late June -- the adults have only four weeks to pack on enough weight to last them through the winter before they crawl into their burrows again for hibernation.

While the adults can head for their deep sleep as early as late July or early August, their offspring will spend another four weeks or so fattening up.

Why would any animal that spends so little of its time in the light of day head for darkness when the summer sun is still relatively high in the sky? Karels says it could be because once the squirrels are fat enough to last through the winter, they choose the burrow because it is safer.

"The advantage is that there is less chance of being eaten when they are hibernating, so they spend 80 to 90 percent of their time below ground," he says.

But all of that time underground still cannot completely buffer ground squirrels from the natural cycles of the boreal forest. While their populations will not crash as dramatically as those of snowshoe hares, far fewer ground squirrels will pop their heads out of their burrows over the next few years.

Karels is now studying at the University of British Columbia, and can be contacted there at karels@zoology.ubc.ca.