Part of a series of articles titled Alaska Park Science - Volume 16 Issue: Science in Alaska's Arctic Parks.
Article
Caribou: Nomads of the North
By Kyle Joly, National Park Service
Caribou (Rangifer tarandus) are an iconic Arctic species. With a circumpolar distribution ranging from the temperate rain forest to polar deserts, the species is highly adaptable both physiologically and behaviorally. Yet, caribou populations face many challenges, such as climate change and industrial development, and are in decline in many portions of their range.
Caribou (Rangifer tarandus) are an iconic Arctic species. With a circumpolar distribution ranging from the temperate rain forest to polar deserts, the species is highly adaptable both physiologically and behaviorally. Yet, caribou populations face many challenges, such as climate change and industrial development, and are in decline in many portions of their range.

NPS Photo / Kyle Joly
It remains unclear which of these drivers is most important in the decade-long decline of the WAH; particularly difficult winters may have contributed. Population crashes and irruptions in the WAH have been linked to a long-lasting, large-scale climate cycle known as the Pacific Decadal Oscillation (PDO; Joly et al. 2011). Declines are associated with the “negative” phase of the PDO (colder years), while increase with the “positive” phase (warmer years; Figure 1).

Harvest of WAH caribou is dominated (>90%) by subsistence hunters that live within the range of the herd. Hunting likely had limited impact on the herd when it numbered 500,000 caribou, however, as the herd continues to decline, its influence has increased. High numbers of harvested cows could accelerate the herd’s decline. Cautious management of the harvest is essential until the trajectory of the herd reverses.

NPS/Kyle Joly
While tolerant of an extreme range of temperature, climate change could negatively impact caribou in myriad of ways. Warmer temperatures could lead to more wildfires, reducing the abundance of lichens, the primary winter forage of caribou (Joly et al. 2012). Warmer temperatures combined with early successional habitats promoted by increased fire may also allow for more shrubs and moose (Alces alces), and thus predators such as wolves (Canis lupus), which could affect caribou populations (Joly et al. 2012). These conditions may also enhance insect populations that torment caribou during the short Arctic summer. Not all impacts of climate change may be detrimental to caribou. Warming temperatures could lengthen the growing season in the Arctic and increase the abundance of summer forage.

NPS Photo / Kyle Joly
As the millennia-old Inuit saying goes...
“No one knows the way of the wind and the caribou”
References
Alaska Department of Fish and Game (ADFG). September 2016.
Alaska Fish and Wildlife News: Western Arctic Caribou Herd Update. Available at: http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=794 (accessed November 18, 2016)
Gunn, A. 2003.
Voles, lemmings and caribou – population cycles revisited? Rangifer Special Issue 14:105-111.
Hasselbach, L., J. M. Ver Hoef, J. Ford, P. Neitlich, E. Crecelius, S. Berryman, B. Wolk, and T. Bohle. 2004.
Spatial patterns of cadmium and lead deposition on and adjacent to National Park Service lands near Red Dog Mine, Alaska: NPS Final Report. National Park Service Technical Report NRTR-2004-45. 59 pp.
Joly, K. and M. D. Cameron. 2015.
Caribou vital sign annual report for the Arctic Network Inventory and Monitoring Program: September 2014-August 2015. Natural Resource Report NPS/ARCN/NRR—2015/1090. National Park Service, Fort Collins, Colorado. 25 pp.
Joly, K., P. A. Duffy, and T. S. Rupp. 2012.
Simulating the effects of climate change on fire regimes in Arctic biomes: implications for caribou and moose habitat. Ecosphere 3(5):1-18. Article 36.
Joly, K. and D. R. Klein. 2011.
Complexity of caribou population dynamics in a changing climate. Alaska Park Science 10(1):26-31.
Joly, K., D. R. Klein, D. L. Verbyla, T. S. Rupp and F. S. Chapin III. 2011.
Linkages between large-scale climate patterns and the dynamics of Alaska caribou populations. Ecography 34(2):345-352.
Messier, F., J. Huot, D. le Henaff, and S. Luttich. 1988.
Demography of the George River Caribou Herd: Evidence of Population Regulation by Forage Exploitation and Range Expansion. Arctic 41:279-287.
Wilson, R. R., L. S. Parrett, K. Joly, and J. R. Dau. 2016.
Effects of roads on individual caribou movements during migration. Biological Conservation 195:2-8.
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Last updated: October 23, 2021