Long-Term Control of Peary Caribou Numbers by Unpredictable, Exceptionally Severe Snow or Ice Conditions in a Non-equilibrium Grazing System

Abstract

The number of Peary caribou (Rangifer tarandus pearyi) on the Queen Elizabeth Islands, Canadian High arctic, is at an all-time known low. yet some populations are still hunted, and there is no adequate monitoring program in place to determine the consequences. We evaluate information from the Peary caribou population on the south-central Queen Elizabeth Islands as a standard for an accurate and realistic assessment of what controls Peary caribou population dynamics. Between 1973 and 1997, major population crashes related to severe winter or spring weather are known to have occurred on the south-central Queen Elizabeth Islands in four caribou-years (i.e., 1 July-30 June). Population losses were 67% in 1973-74, 33% in 1994-95, 78% in 1995-96, and 83% in 1996-97. There is no evidence for direct density-dependent responses during either the favorable weather years of population growth or during any one of the years with a disastrous die-off. It appears that Peary caribou on the Queen Elizabeth Islands are living in a non-equilibrium grazing system driven mainly by abiotic factors (emergent properties), particularly by exceptionally unfavorable snow or ice conditions. Changing levels of predation by the High arctic gray wolf (Canis lupus arctos) compound the uncertainty. In this High arctic ecosystem, non-equilibriumgoverned population dynamics plus wolf predation represents an appropriate conceptual model for Peary caribou populations on the Canadian High Arctic islands. The application of our findings to decision making, together with an adequate monitoring program by the responsible agencies, would promote the biological management and ecological conservation of Peary caribou on the Queen Elizabeth Islands. key words: arctic Canada, population dynamics, Rangifer tarandus pearyi, weather-related density-independent population crashes rÉSUMÉ. Le nombre de caribous de Peary (Rangifer tarandus pearyi) répertoriés dans les îles de la reine-Élisabeth, Extrême-arctique canadien, se trouve au niveau le plus bas à n'avoir jamais été enregistré. Pourtant, certaines populations font toujours l'objet de la chasse et il n'existe aucun programme de surveillance adéquat pour en déterminer les conséquences. Nous évaluons ici des données relatives à la population de caribous de Peary des îles centre-sud de la Reine-Élisabeth afin d'aboutir à une norme d'évaluation précise et réaliste pour déterminer ce qui influence la dynamique de population des caribous de Peary. Entre 1973 et 1997, d'importants déclins de population attribuables aux hivers ou aux printemps rigoureux ont été enregistrés dans le centre-sud des îles de la reine-Élisabeth sur une période de quatre années-caribous (c'est-à-dire du

Climate, icing, and wild arctic reindeer: past relationships and future prospects

“…B. Hansen and R. Aanes, unpublished data) but may still represent a partial buffer against icy winters on the recently occupied Sarsøyra and Kaffiøyra, where the flat lowlands are often coated with ice. Increased icing nevertheless reduced the population growth rates, which is in line with previous indications from our study area (Kohler and Aanes 2004) and elsewhere (Parker et al 1975, Solberg et al 2001, Miller and Gunn 2003, Tveraa et al 2007, Helle and Kojola 2008, Miller and Barry 2009.…”

“…This leaves us with only indirect evidence for the ruling hypothesis that arctic ungulates will be negatively influenced by warmer and rainier winters owing to icing and more impenetrable snowpacks (Parker et al 1975, Aanes et al 2000, Solberg et al 2001, Miller and Gunn 2003, Kohler and Aanes 2004, Helle and Kojola 2008, Miller and Barry 2009. Recently, Tyler (2010) hypothesized that warmer winters may rather be beneficial to Rangifer owing to increased snowmelt and improved vegetation accessibility (see also Tyler et al 2008).…”

Multiple Effects of Changes in Arctic Snow Cover

“…Ice crusts, ice layers and rain-on-snow events have been implicated in population crashes of reindeer on Svalbard (Aanes et al 2000), the near extirpation of Peary's caribou (Rangifer tarandus pearyi) in High Arctic Canada (Barry et al 2007), population crashes in caribou on the Queen Elizabeth Islands, Canadian High Arctic (Miller and Barry 2009) and the deaths of 20 000 musk ox on Banks Island in October 2003 (Rennert et al 2009). The Sámi (Moen 2008;Helle and Kojola 2008) and Nenets (e.g.…”

Local and regional variability in snow conditions in northern Finland: A reindeer herding perspective

“…Although the structure of snow cover is highly significant for reindeer and other northern animals, studies on snow structural properties are very limited in the circumpolar area. Further, earlier studies have mainly focused on the impacts of snow and ice on reindeer and caribou populations in treeless high-latitude regions (Miller and Barry 2009;Tyler 2010;Hansen et al 2011;. In this work, weather station measurements were used to force the SNOWPACK snow model and combined with reindeer herders' experiences to study the local and regional variations in snow conditions in boreal and subarctic zones in northern Finland over the past 30 years.…”