Wolf-caribou dynamics within the central Canadian Arctic

Abstract

The severity of recent declines of barren‐ground caribou (Rangifer tarandus groenlandicus) across the central Canadian Arctic has led to harvest restrictions and concerns about population recovery. Wolves (Canis lupus) are the main predator of barren‐ground caribou; however, the extent that wolves influence the decline and recovery of caribou herds is unknown. Such uncertainty confounds management responses (e.g., reducing harvest, predator control). We investigated wolf–caribou dynamics on the summer range of barren‐ground caribou in the Northwest Territories and Nunavut, Canada (i.e., Bathurst caribou herd). Our primary objective was to test for a numerical response of wolves to changes in the abundance and spatial distribution of caribou. Caribou experienced a >90% decline in abundance over the study period (1996–2014). Using long‐term data sets (1996–2012), we developed regression models to investigate relationships between abundance indices of wolves and range‐use patterns of caribou. We monitored the movements of adult female wolves fitted with global positioning system (GPS) collars representing individual packs throughout the 2013 and 2014 denning periods. We also investigated pup recruitment, an index of population decline, at a time of low caribou abundance. Finally, we developed a series of stochastic population models to understand how pup recruitment influenced wolf densities on the Bathurst range over the period of caribou decline. As caribou abundance decreased, the late‐summer distribution of the Bathurst herd contracted toward the calving ground. These movements correlated with low rates of wolf pup recruitment and high den abandonment, suggesting a regulatory mechanism whereby wolf reproductive success was limited by the low availability of caribou within the denning areas. Furthermore, these data suggested a numerical response, where wolf densities decreased as caribou numbers declined. In 2014, wolf density was estimated at <4 wolves/1,000 km2. Our results suggest that these wolves exhibited a relatively strong numerical response to a single, declining prey base. Given the continued decline in the Bathurst caribou herd, the tundra wolf population on the Bathurst range has likely declined below our 2014 estimate. © 2016 The Wildlife Society.

Observed and predicted effects of climate change on Arctic caribou and reindeer

“…Wolves that follow and prey on migratory barren-ground caribou typically den near the tree line and give birth to pups in late May and early June (Heard and Williams 1992). During the denning period wolf movements are limited because pups cannot travel long distances from their dens (Klaczek et al 2016). Reduction of predation risk from wolves, particularly to vulnerable calves, has thus been suggested as one of the drivers of caribou migrations to calving grounds on the tundra (Bergerud 1988(Bergerud , 1996.…”

Efficacy and ethics of intensive predator management to save endangered caribou

“…Second, predator management will be most effective in systems where the population dynamics of the primary predator has been decoupled from the abundance or availability of the prey. For example, if the decline of caribou regulates the predator population then there is little risk of a high density of predators and resulting predation leading to the extirpation of the caribou population (Klaczek et al, 2016). Although, any asynchrony in the population dynamics of the predator or prey, slow or limited reproductive output from the prey, or the availability of other prey species (i.e., apparent competition) could lead to extirpation.…”

“…In some Arctic and northern boreal ecosystems, caribou is the major source of prey. Thus, declines in caribou result in concurrent declines in the abundance of their major predator, wolves (Klaczek et al, 2016; Neufeld et al, 2021). Given those ecological circumstances, predator management would be much less effective and lead to outcomes that are not comparable to the more southern distribution of woodland caribou where moose and deer are the primary source of prey biomass for predators (Latham et al, 2011; Serrouya et al, 2011).…”

Polar Regions

“…Summer warming is changing the composition of tundra plant communities, modifying the relationship between climate, forage and Rangifer (Albon et al, 2017), which also impacts other Arctic species such as musk ox (Ovibos moschatus) (Schmidt et al, 2015). As polar trophic systems are highly connected (Schmidt et al, 2017), changes will propagate through the ecosystem with effects on other herbivores such as geese and voles, as well as predators such as wolves (Hansen et al, 2013;Klaczek et al, 2016).…”