Delineating Canadian and Greenland polar bear (Ursus maritimus) populations by cluster analysis of movements

Within their circumpolar range, polar bears (Ursus maritimus) are not subject to absolute barriers. However, physiographic features do cause discontinuities in their movements. These discontinuities in distribution can be used to delineate population units. Based on satellite telemetry of the movements of female polar bears carried out in 1989- 1998, we used cluster analysis to identify 6 regions within the Canadian and western Greenland Arctic in which move- ments appear to be restricted enough to identify distinct populations. These regions generally correspond to manage - ment units that have been previously identified as Viscount Melville Sound, Lancaster Sound, Norwegian Bay, Kane Basin, Baffin Bay, and Davis Strait. A north-south substructure was identified for the Baffin Bay population, but it was weaker than the structure identified for the 6 primary units. The 6 units were consistent with genetic information, ex - cept for the Baffin Bay - Kane Basin separation, and with mark-recapture observations and the traditional knowledge of Inuit hunters. Only 2 of 65 bears that provided telemetry information for more than 1 year were classified in differ - ent populations in different years. However, annual rates of exchange, measured as the percentage of locations outside the population boundary, ranged from 0.4 to 8.9%. Analysis of mark-recapture movements indicated no difference in large-scale movements between the sexes or long-term movements with age. Although our validation criteria for demo- graphic closure were satisfied, the observed rates of exchange between adjacent populations suggest that population dynamics in adjacent populations may not be completely independent. Resume : Il n'existe pas de barrieres absolues aux mouvements des Ours blancs (Ursus maritimus) dans leur reparti- tion ciricumpolaire; cependant, des caracteristiques physiographiques peuvent entrainer des discontinuites dans leurs de- placements, discontinuites qui peuvent servir a etablir les limites d'unites demographiques. Grâce a la telemetrie par satellite, nous avons suivi les deplacements de femelles de 1989 a 1998; une analyse de groupements a permis d'identifier 6 regions arctiques au Canada et dans l'ouest du Groenland ou les deplacements semblent suffisamment restreints pour identifier des populations distinctes. Ces regions correspondent aux unites d'amenagement identifiees precedemment : le detroit de Melville, le detroit de Lancaster, la baie Norwegian, le bassin de Kane, la baie de Baffin et le detroit de Davis. La population de la baie de Baffin compte en outre une sous-structure nord-sud qui est cepen- dant plus faible que la structure qui delimite les 6 unites primaires. Les 6 unites correspondent aux informations gene - tiques, sauf en ce qui concerne la separation baie de Baffin - bassin de Kane, et s'accordent aussi avec les donnees de capture-recapture et avec les connaissances traditionnelles de chasse des Inuit. Seulement 2 ours sur les 65 qui ont fourni des donnees telemetriques pendant plus de 1 annee ont ete classifies dans des populations differentes d'une annee a l'autre. Cependant, les taux annuels d'echange equivalant au pourcentage de sites au-dela des limites de la po - pulation, se situaient entre 0,4 et 8,9 %. L'analyse des donnees capture-recapture n'indique pas de difference entre les mâles et les femelles quant a leurs deplacements sur une grande echelle, ni entre individus d'âges differents quant a leurs deplacements a long terme. Bien que ce systeme reponde aux criteres de validation d'un systeme ferme, les taux d'echanges observes entre les populations adjacentes indiquent que la dynamique de chacune de ces populations n'est probablement pas totalement independante. (Traduit par la Redaction) Taylor et al. 709

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