This work was conducted by Lance Craighead, Research Director of CERI, in collaboration with Harry Reynolds, David Paetkau, Ernie Vyse, and Curt Strobek at the Strobeck Genetics Lab at the University of Alberta, Edmonton, and at Ernie Vyse's Genetics Lab at Montana State University.

Field work was supported by the Alaska Dept. of Fish and Game and the National Park Service. Lab work supported by Montana State University, University of Alberta, Parks Canada, Alberta Fish and Wildlife Service, and donations from private foundations.

The demographics of an Arctic grizzly bear population were studied for 17 years in the foothills of the Western Brooks Range in Alaska under the direction of Harry Reynolds of the Alaska Department of Fish and Game. During that time 489 captures of 256 individual bears resulted in detailed observations of maternal/offspring relationships. We used DNA microsatellite analysis to examine paternity and male reproductive success. The genetic research resulted in Lance Craighead's PhD dissertation in Biological Sciences at Montana State University.

Bears were darted from helicopters and immobilized using Telazol at 8-9 mg per kg body weight. 152 individuals were sampled for genetic analysis. 75 of these were males, 75 females, and 2 whose sex was not recorded.

Particular emphasis was placed on radio-collaring adult females and their offspring which were radio-collared just before dispersing. Grizzlies grow slowly in the Arctic and cubs generally stay with their mothers for 3-5 years. Litter size averaged about 2 cubs per litter and the reproductive cycle was about 6 years.

 Blood samples were collected for genetic analysis. If bears were ear-tagged, a small plug of ear tissue was removed and also saved for genetic analysis. Total DNA was extracted from all samples. The DNA microsatellite analysis was based upon the amplification of distinct genes using the polymerase chain reaction (PCR) technique. A sample of the individual's DNA was used as a template to make millions of copies of alleles at 8 different loci. Each copy was labeled with a fluorescent marker. The amplified allele products were run on a polyacrilamide gel in an automated sequencing apparatus.

David Paetkau, a doctoral candidate at the University of Alberta developed the primers for the grizzly bear loci and perfected this technique. Our study examined 8 loci, 4 of which could be run in a single lane on the gel. David's system now allows 10 loci to be run in each lane. A single gel can now analyze 36 individual bears. A laser device scans the gels, and identifies the marker dyes. This data is recorded as a digital image. Each allele can be visualized as a high peak on a graph. The exact size (in number of base pairs) is determined by comparison with a known standard that is also run in each lane on the gel.

Efforts were made to capture and sample mother-offspring pairs where the female's breeding behavior had been observed during the previous year. For example, this female, #1479 gave birth to this cub, #1758, in 1992. She had not been observed the previous year, but in years before that she had been observed breeding with 4 different males. DNA analysis showed that none of them was the father. Although almost all resident males were sampled, the father of this cub was not among them.

By examining known family groups, we were able to identify 12 fathers for 36 of 57 known offspring. The remaining 21 offspring were sired by males for which we had no genetic sample. The mother of this large family group is in the upper right; 2 of her cubs were sired by one known male, and the third was sired by a different, unsampled male.

This is a pedigree diagram of this family group with multiple paternity. Male 1453 fathered cubs 1480 and 1481. The probability of a different male having a correct genotype to also be the father is greater than 1 times 10,000,000. Male 1453 was excluded as the father of 1482. Three paternal alleles were found in the offsprings' genotypes which indicates unequivocally that more than one male fathered this family. No other sampled male had the necessary alleles to be a possible father of 1482. A hypothetical genotype for the father of 1482 was deduced from 1482's genotype, subtracting the alleles that came from the mother.

In a similar manner, a minimum of 7 hypothetical males were deduced as sires in this population. Including these in calculations of reproductive success demonstrated that no single male was reponsible for more than 11% of the offspring sampled. No males under 9 years of age were successful breeders although they exhibit breeding behavior at age 5.

It is evident that males from a large surrounding area are breeding successfully with the females in our study area, and competing with males who center most of their activities here. Since females tend to be strongly philopatric, male behavior is thus the primary mechanism for maintaining genetic diversity in grizzly bear populations.

This study helped establish a baseline for measures of genetic diversity in wild grizzly populations. These data can be used to measure the relative degree of diversity in more isolated populations like the Greater Yellowstone or Northern Continental Divide Populations. Currently David Paetkau and colleagues are In Press with manuscripts that compare the genetics of over 667 grizzlies across the U.S. and Canada, 72 of which were from Yellowstone.

Publications resulting from this work, and related genetics studies, are listed in the grizzly bear genetic bibliography and carnivore genetics bibliography.