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Article Excerpt
ABSTRACT. The Peary caribou (Rangifer tarandus pearyi) is an endangered species in Canada, having been in an overall decline since 1961. Sightings of Peary caribou were compared from two aerial searches, in 1993 and 1998, on Bathurst and its neighbouring islands, western Queen Elizabeth Islands in the Canadian High Arctic. The comparison indicated a near-total (98%) cataclysmic decline in the number of Peary caribou seen per unit of search effort. In summer 1993, 2400 caribou were counted during 33.8 h of low-level helicopter searches. In contrast, in summer 1998, only 43 caribou were seen within the same area during 35.2 h of low-level helicopter searches. The frequency of observation was markedly different: 118.3 caribou/100 min in 1993, but only 2.0 caribou/100 min in 1998. The number of carcasses indicated that the decline resulted from deaths and not from mass emigration. Males died at a disproportionately higher rate than females among all 1+ yr old caribou, and bulls (4+ yr) compared to cows (3+ yr) had died at an even greater rate. Widespread, prolonged, exceptionally severe snow and ice conditions from 1994-95 to 1996-97 caused the die-off. Trends in snowfall are consistent with predictions for global warming in the western Canadian High Arctic. Future climate change may increase the frequency of years with unfavorable snow and ice conditions, which could prevent or at least impede future recovery of Peary caribou populations on the western Queen Elizabeth Islands, particularly to sizes that would support subsistence harvesting.
Key words: Peary caribou, Rangifer tarandus pearyi, cataclysmic die-off, western Queen Elizabeth Islands
RESUME. Le caribou de Peary (Rangifer tarandus pearyi) est une espece en peril au Canada, vu qu'elle a connu une diminution globale depuis 1961. On a compare des observations du caribou de Peary faites lors de deux recherches aeriennes menees en 1993 et 1998 sur l'ile de Bathurst et les iles avoisinantes, celles de la Reine-Elisabeth occidentales dans 1'Extreme-Arctique canadien. La comparaison a revele un declin cataclysmique quasi-total (98 %) du nombre de caribous de Peary apercus par unite d'activite de recherche. En ete 1993, on a denombre 2400 caribous durant 33,8 heures de recherches par helicoptere volant a basse altitude. En revanche, durant l'ete 1998, on n'a apercu que 43 caribous dans la meme zone durant 35,2 heures de survol a basse altitude en helicoptere. La frequence des observations etait nettement differente: 118,3 caribous/100 min en 1993, mais seulement 2,0 caribous/100 min en 1998. Le nombre de carcasses a demontre que le declin etait du a la mort des animaux et non a une emigration massive. Les males mouraient a un taux superieur a celui des femelles de facon disproportionnee parmi tous les caribous ages de plus d'un an, et, en comparaison avec les femelles de plus de trois ans, les males de plus de quatre ans avaient peri a un taux encore plus eleve. La mortalite massive etait due a des conditions d'enneigement et de glace generalisees et persistantes extremement rudes. Les tendances dans les chutes de neige rejoignent les predictions concernant le rechauffement global dans 1'ouest de l'Extreme-Arctique canadien. Il se peut que de futurs changements climatiques augmentent la frequence des annees ou les conditions d'enneigement et de glace ne sont pas favorables, ce qui pourrait empecher ou du moins entraver le retablissement des populations du caribou de Peary dans les iles de la Reine-Elisabeth occidentales, en particulier a des niveaux qui pourraient permettre les prelevements de subsistance.
Mots cles: caribou de Peary, Rangifer tarandus pearyi, mortalite cataclysmique, iles de la Reine-Elisabeth occidentales
Traduit pour la revue Arctic par Nesida Loyer.
INTRODUCTION
The Peary caribou (Rangifer tarandus pearyi) was first listed as 'threatened' in 1979 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) because of a decline between 1961 and 1974 (Gunn et al., 1981). Then, as the decline continued, COSEWIC reclassified Peary caribou on the Queen Elizabeth Islands (QEI; Fig. 1) as 'endangered' in 1991 (Miller, 1990).
The first systematic, range-wide measure of abundance was obtained by aerial survey in summer 1961, when Tener (1963) estimated 24 363 Peary caribou on the western QEI (WQEI) and 25 845 on the entire QEI. By summer 1973, the estimated number of Peary caribou on the WQEI was only about a quarter of the 1961 estimate (Miller et al., 1977). However, the precise timing, cause and pattern of that decline were not investigated. The first investigation of winter and spring die-off of Peary caribou on the WQEI was in 1973-74 (Parker et al., 1975; Miller et al., 1977). In that one 'caribou-year' (1 July 1973 to 30 June 1974), the estimated number of Peary caribou on the WQEI declined by 49% and that of muskoxen (Ovibos moschatus) by 35% (Miller et al., 1977). Thus, in summer 1974, the estimated number of Peary caribou was down by 89% from the 1961 estimate.
Recovery after the 1973-74 die-off was slow, at least during the first three years, and then varied among islands across the WQEI. However, we are hampered by having relatively little information except for Bathurst Island and the neighboring islands of Vanier, Cameron, Alexander, Massey, and Marc (Fig. 1). On Bathurst Island and those 3000 by summer 1994 (Miller, 1995).
Subsequently, the 20-year recovery in abundance of Peary caribou on Bathurst and its neighboring islands was virtually lost in two years, as aerial surveys revealed a sharp 85% decline from 3000 in summer 1994 to only 452 in summer 1996 (Miller, 1998). The magnitude of that two-year decline led to an aerial survey across the entire WQEI in summer 1997 (Gunn and Dragon, 2002). The results indicated that the caribou on Bathurst and its neighboring islands had plum-meted a further 83% from summer 1996 to only 78 caribou in summer 1997--down 98% from the 3565 caribou estimated there in 1961 (Tener, 1963). The 1997 survey recorded an alltime known low of only 1086 Peary caribou throughout the WQEI. This low point represents a 96% decline throughout the WQEI over 36 years, 1961-97 (Tener, 1963; Gunn and Dragon, 2002). Thus, the number of Peary caribou on the WQEI was in an overall decline during the last four decades of the 20th century.
Die-offs are usually uneven in their effects on sex and age classes (e.g., Parker et al., 1975; Gunn et al., 1989). Sex and age composition, as well as the number of survivors of a die-off (effective population size), will determine the initial rates of recovery. As we had data on the sex and age composition of the caribou population before the 1994-97 die-off, we returned to the Bathurst Island complex in 1998 to record the sex and age class of surviving caribou and of carcasses. We recorded these data to document further the extent of the 1994-97 decline, and we used them, along with data from caribou carcasses obtained during that decline, to gain insight into the proportional loss of male vs....
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