Kluane grizzly bears are a very diverse lot, but do not expect to figure this out just by looking at them. It took the use of something called nuclear microsatellite markers to come to this conclusion.

Researchers at the University of Alberta looked at genetic diversity among grizzly bears across North America, ranging from Yellowstone in the south to the Arctic Coast in the north. Of the populations that they studied, the Kluane bears were the most genetically diverse of them all.

Their genetic health reflects their connections with other populations of bears across the North for the Kluane bears tend to be travelers; they range between the Alaskan Panhandle and the shores of Kluane Lake, ensuring that their genes are spread far and wide.

Researchers figured this out by using the same technique of DNA fingerprinting that has helped to bring criminals to justice and to release people wrongfully convicted of crimes. Just as with humans, the identities of the bears were sometimes established with evidence as minute as a hair.

The study was prompted by concerns that the loss of genetic diversity can be a factor in the decline of populations of large carnivores such as grizzly bears. These animals need huge home ranges to survive, and the carving up of their habitat has led to their demise in most of the United States.

The researchers also wanted to determine what happens to populations that lose their genetic diversity. Most conservation biologists consider the degree of genetic diversity found in an endangered population as a key indicator of its overall health. They point to the importance of measuring genetic diversity as an effective aid in managing populations of endangered species.

The researchers used a technique called microsatellite fingerprinting on tissue or hair samples taken from 678 different grizzly bears. David Paetkau, a doctoral student at the time of the study, perfected this technique for use on bears.

Paetkau describes microsatellites as "repetitive pieces of DNA." They have been used to identify genetic diversity in everything from pilot whales to ants.

Biologists supplied the researchers with tissue or hair samples, which were most often plugs of ear tissue taken when the biologists put ear tags on sedated animals. The DNA was extracted and purified, and then analyzed using a technique called polymerase chain reaction.

Eight different nuclear markers were studied. Paetkau says that the resulting data gives "a numeric description of the animal. What that means is that for each animal you have eight pairs of numbers that describe the animal."

The data can then be used in a number of different ways. Genetic analysis was first used on wildlife in 1989 to determine the paternity of certain birds. It was used for the first time to compare different populations of animals in 1994.

Now genetic analysis is becoming a relatively common tool in the field of conservation biology. Researchers also like this approach because even hairs from an animal can supply the necessary sample; tissue samples are not essential.

Hair traps are set up by wrapping a single strand of barbed wire around several trees at a height of about a half metre. Some sort of scent is placed in the middle of the trap to attract bears. When the bear walks under the barbed wire to investigate the scent, the barbed wire snags some of its hair.

"It is a traditional mark and recapture approach, but you never have to physically handle the animal, and there are lots of good reasons for minimizing handling," says Paetkau.

Since the days of Darwin, biologists have believed that in-breeding threatens the health of a population of animals. The Alberta researchers wanted to look at the genetic diversity of two isolated populations of bears to see whether any effects of in-breeding could be measured.

They studied two different sorts of island populations: the grizzlies in the Yellowstone region are geographically cut off from any other populations of grizzly bears; on Kodiak Island, the bears have been isolated from the mainland since the end of the last Ice Age.

Genetic diversity among the Kodiak Island bears was so low that several animals had identical genotypes, a phenomenon found nowhere else. The Yellowstone bears also had a low level of genetic diversity.

While the survival of the Kodiak bears shows that a population can survive with a low level of genetic diversity, the researchers are not concluding that genetic diversity is unimportant. The Kodiak bears have had 10,000 years to adapt to their isolation.

The Yellowstone bears are more of a concern because they have lost genetic diversity in a relatively short period of time. The researchers concluded that an influx of new blood, and new genes, is needed to guarantee the long-term health of this group of bears.

"Variation in Genetic Diversity across the Range of North American Brown Bears" by Paetkau et al can be found in the Journal of Conservation Biology. David Paetkau now works for Wildlife Genetics International in Alberta and can be contacted at wgi@telusplanet.net.