We report data from analyses of microsatellite loci of 30 grizzly bear family groups which demonstrate that each cub in a litter can be sired independently, and we derive estimates of maximum reproductive success for males, from an Arctic population in northwestern Alaska that is minimally affected by human activities. These analyses were made possible by the use of single-locus primers that amplified both of an individual's alleles at eight microsatellite loci and by detailed knowledge of maternal/offspring relationships that allowed the identification of paternal alleles. No single male was responsible for more than approximately 11% of known offspring, and no more than 49% of breeding-age males successfully bred. These data contribute to an understanding of the genetic and demographic basis of male reproductive success, which is of vital importance in the maintenance of small, isolated grizzly bear populations.

M. C. S., NAGY, J. A., and REYNOLDS, H. V. 1988. Growth in length and weight of northern brown bears: differences between sexes and populations. Can. J. Zool. 66: 98 1 -986. Growth curves were fitted to data on age, length, and spring weight for individuals from three populations of the brown bear, Ursus arctos, in northern Canada and northwest Alaska. Females reached 90% of asymptotic length before sexual maturity and before the age of first production. Their weight remained approximately in proportion to the cube of their length. Males reached 90% of asymptotic length 0.7 to 1.7 years later than females, and had asymptotic lengths 10-15% greater. Males continued their growth in weight even longer, and reached asymptotic weights 80-100% greater than females. Variation between these populations was small compared with the total range of variation in the species. KINGSLEY, M. C. S., NAGY, J. A., et REYNOLDS, H. V. 1988. Growth in length and weight of northern brown bears: differences between sexes and populations. Can. J. Zool. 66 : 98 1 -986. Des courbes de croissance ont kte ajustees a des donnkes sur l'ige, la longueur et la masse au printemps chez trois populations d'Ours bruns (Ursus arctos) dans le nord du Canada et le nord-ouest de ]'Alaska.Les femelles atteignent 90% de la longueur a l'asymptote avant la maturitC sexuelle et avant l'ige de la premikre reproduction; leur masse reste a peu prks proportionnelle au cube de leur longueur. Les miles atteignent 90% de leur longueur 0,7 a 1,7 ans plus tard que les femelles et leur longueur a l'asymptote est de 10 a 15 % plus grande. Les miles continuent leur croissance en masse encore plus longtemps et leur masse a l'asymptote est de 80 a 100% plus ClevCe que celle des femelles. La variation entre ces trois populations est faible comparativement a la variabilitk totale qui existe chez I'espkce.[Traduit par la revue]

Knowledge of genetic diversity and population structure is critical for conservation and management planning at the population level within a species’ range. Many brown bear populations in Central Asia are small and geographically isolated, yet their phylogeographic relationships, genetic diversity, and contemporary connectivity are poorly understood. To address this knowledge gap, we collected brown bear samples from the Gobi Desert (n = 2360), Altai, Sayan, Khentii, and Ikh Khyangan mountains of Mongolia (n = 79), and Deosai National Park in the Himalayan Mountain Range of Pakistan (n = 5) and generated 927 base pairs of mitochondrial DNA (mtDNA) sequence data and genotypes at 13 nuclear DNA microsatellite loci. We documented high levels of mtDNA and nDNA diversity in the brown bear populations of northern Mongolia (Altai, Sayan, Buteeliin nuruu and Khentii), but substantially lower diversity in brown bear populations in the Gobi Desert and Himalayas of Pakistan. We detected 3 brown bear mtDNA phylogeographic groups among bears of the region, with clade 3a1 in Sayan, Khentii, and Buteeliin nuruu mountains, clade 3b in Altai, Sayan, Buteeliin nuruu, Khentii, and Ikh Khyangan, and clade 6 in Gobi and Pakistan. Our results also clarified the phylogenetic relationships and divergence times with other brown bear mtDNA clades around the world. The nDNA genetic structure analyses revealed distinctiveness of Gobi bears and different population subdivisions compared to mtDNA results. For example, genetic distance for nDNA microsatellite loci between the bears in Gobi and Altai (F ST = 0.147) was less than that of the Gobi and Pakistan (F ST = 0.308) suggesting more recent male-mediated nuclear gene flow between Gobi and Altai than between Gobi and the Pakistan bears. Our results provide valuable information for conservation and management of bears in this understudied region of Central Asia and highlight the need for special protection and additional research on Gobi brown bears.

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We investigated grizzly bear (Ursus arctos) use of caribou (Rangifer tarandus) as carrion and prey in 3 areas: 2 areas were in or adjacent to the traditional calving grounds of large caribou herds, and 1 area that did not include caribou calving grounds. The western Brooks Range study area was located in the mountains and foothills near the calving grounds of the Western Arctic Caribou Herd (est. 200,000 in 1985); the Arctic National Wildlife Refuge study area was in the coastal plain and foothills of the eastern Brooks Range in the calving grounds of the Porcupine Caribou Herd (est. 150,000 in 1985); and the Canning River study area was in the mountains and foothills of the eastern Brooks Range, 80 km southwest of the calving grounds of the Porcupine Herd. Predation or scavenging was determined from direct observation, locating radio-collared bears feeding on caribou, and from blood on the muzzles of captured bears. The Canning River bear population was distant from calving grounds, showed little use of caribou, and was characterized by low population density and productivity. Caribou were used as carrion and prey by the 2 grizzly bear populations for which calving caribou were available. Bear population density and productivity were higher when caribou were available, even though patterns of caribou use by bears differed between the 2 areas. Near the calving grounds of the Western Arctic Herd, western Brooks Range grizzly bears stayed within their established seasonal home ranges and used caribou as the caribou migrated through their home ranges. In contrast, on the Porcupine Herd calving grounds, some Arctic Refuge bears left seasonal home ranges in the mountains to take advantage of the caribou on the coastal plain, staying only as long as the calving caribou were available. In addition, some bears that preyed on Porcupine Herd animals apparently traveled long distances following the path of migrating caribou to the calving grounds. No bears from the Canning River study area were observed to leave their home ranges to reach the calving grounds. The proportion of caribou that were killed by bears vs. those that were scavenged was not determined. Although most caribou killed by bears were calves, adults were also preyed upon. Grizzly bears of all sex and age classes fed on caribou.