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.
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.
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.
As the millennia-old Inuit saying goes...
“No one knows the way of the wind and the caribou”
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