Scientists investigate dietary quirks of captive caribou

Got nitrogen?

Posted: Friday, January 26, 2001

This is the warm and fuzzy side of wildlife biology -- nine little caribou calves clustered around Alaska Department of Fish and Game Wildlife Techni-cian John Crouse.

The youngsters, with their gangly legs and Bambi eyes, live in a pen at the Kenai Moose Research Center, in the Kenai National Wildlife Refuge near Swanson River. They share lodgings with 26 moose and a lone Dall sheep lamb.

But this is no petting zoo. The people and the animals are there for scientific research purposes.

As much as Crouse enjoys the fuzzy fawns, what he's really after is their urine.

"Caribou are a little different," he said. "Nothing seems to subsist on a diet so low in nitrogen as caribou."

During the winter in the wild, he explained, the animals subsist on lichens. The specialized plants, which thrive in harsh arctic and subarctic climates, are rich in carbohydrates but lack nitrogen, one of the basic building blocks of life.

Dietary nitrogen is necessary for animals to make protein, the biochemical basis of muscles, enzymes and other essential bodily ingredients. As a body functions, it builds up and breaks down diverse proteins, excreting discarded nitrogen as urea in urine.

Most animals, including people, waste away without protein in the diet. But caribou survive.

"The question is, how does an animal maintain its muscle on a diet with no protein?" Crouse said.

Biologists are discovering intriguing eccentricities in the way caribou use nitrogen.

"Rather than excrete the urea, they can recycle it," he said. "But we don't know to what extent they do it."

Tom Stephenson, who directs research at the center, said scientists are finding clues to the puzzle.

For one, the structure of caribou's kidneys differ from those of other mammals. For another, the caribou and other deer are ruminants, a large group of vegetarian mammals, including cattle and sheep, that have extra stomachs and chew cuds. Ruminants make and swallow lots of saliva, and reabsorb an unusually high amount of nutrients in their digestive tracts.

The Kenai Peninsula researchers want to understand more about how caribou use nitrogen and how it affects the welfare of wild herds. Across the state, caribou populations sometimes fluctuate wildly. People are concerned about human impacts on them through development, hunting and wildlife management.

To get their questions answered, the biologists feed the caribou controlled diets with manipulated protein levels. Then they monitor the animals' urine and blood looking for traces of metabolites, the biochemical remnants of reactions in cells.

Along the way, the researchers plan to experiment with varieties of artificial feeds for keeping caribou and reindeer, the domesticated Old World breed of caribou, healthy while in captivity.

The project ties in with the broader goals of the research center. It uses semi-tame animals in large, naturally vegetated pens to approximate how wild animals interact with their environment, especially with respect to their nutrition.

One challenge is keeping wild species in natural habitat yet getting close enough to them to study such intimate details of their lives.

The center was founded in 1968. The first caribou were moved there in 1991 from the Nelchina herd, but the biologist who planned to study them left the center, and for years the little herd loafed around. In 1995, Stephenson began the current project.

But the caribou, more skittish and high strung than moose, proved difficult to work with. Getting samples from them usually involved tranquilizer darts or wrestling them to the ground, stressful for humans and deer alike.

A couple of years ago, when the caribou project moved into high gear, the research team hit upon a better way. They resolved to domesticate calves from an early age.

"We wanted to bottle-raise them so we would have a herd that was more tractable, less excitable around people," Stephenson said.

Two years ago, they captured a caribou calf to make sure they could care for it. Last spring, the biologists traveled to the Interior and stole nine more from their mothers and transported them to the Kenai Peninsula. The youngsters have been fed, coddled and taught to wear halters.

"We're trying to halter train them so we can load them in and out of trailers," Crouse said.

Now, 10 of the center's 23 caribou grew up there with extensive handling. The researchers plan to collect more calves in May.

It will be a few years before they will know if the behavior experiment succeeds. How the caribou will act after they pass through the changes of puberty is unclear, but so far the calves are docile and friendly.

Crouse said his great hope is that in years to come, all he will have to do to collect their urine samples is to have a cup handy at the right moment.

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