Functional Responses of Coyotes and Lynx to the Snowshoe Hare Cycle

Abstract

Coyotes and lynx are the two most important mammalian predators of snowshoe hares throughout much of the boreal forest. Populations of hares cycle in abundance, with peaks in density occurring every 8-11 yr, and experimental results suggest that predation is a necessary factor causing these cycles. We measured the functional responses of coyotes and lynx during a cyclic fluctuation of hare populations in the southwest Yukon, to determine their effect on the cyclic dynamics. We used snow-tracking and radio telemetry to examine changes in the foraging behavior of the predators.Coyotes and lynx both fed mostly on hares during all winters except during cyclic lows, when the main alternative prey of coyotes was voles, and lynx switched to hunting red squirrels. Both predators showed clear functional responses to changes in the densities of hares. Kill rates of hares by coyotes varied from 0.3 to 2.3 hares/d, with the most hares killed one year before the cyclic peak, while those of lynx varied from 0.3 to 1.2 hares/d, with the highest one year after the peak. Maximum kill rates by both predators were greater than their energetic needs. The functional response of coyotes was equally well described by linear and type-2 curves, and that of lynx was well described by a type-2 curve. Kill rates by coyotes were higher during the increase in density of hares than during the cyclic decline, while the reverse was true for lynx. Coyotes killed more hares early in the winter, and cached many of these for later retrieval. Lower densities of hares were associated with longer reactive distances of both predators to hares, but with little apparent change in time spent searching or handling prey. In summary, our data show that the two similarly sized predators differed in their foraging behavior and relative abilities at capturing alternative prey, leading to different patterns in their functional responses to fluctuations in the density of their preferred prey.

The Costs of Carnivory

“…Our aim here was to broadly characterize these differences in the model. For carnivores hunting small prey (invertebrate and small vertebrates), there was no consistent differences in travel speeds or time budget across prey types or by predator sizes, so we used fixed average for travel speed of 1.19 km/h ( v = 0.33 m/s) [14,46,47] and for time hunting T h , 9.8 h [13,14,47]. For the large-prey feeders, estimating the costs of hunting was more difficult because many activities contribute to hunting costs, including search, pursuit, capture, and killing large prey [19].…”

Reconsidering the Specialist-Generalist Paradigm in Niche Breadth Dynamics: Resource Gradient Selection by Canada Lynx and Bobcat

“…Previous research at smaller scales suggests that these two species may differ in their ability to use dietary and habitat resources; Canada lynx are specialist predators of snowshoe hare [30], while bobcats prey on a wide variety of food sources from hares, rodents, and even ungulates (e.g., [31]–[34]). Canada lynx tend to select boreal and montane coniferous forested areas that are more suitable to their primary food source [35], [36], whereas bobcats exploit a range of ecotypes including subtropical swamps, arid landscapes and temperate forests [37].…”

Complex dynamics and phase synchronization in spatially extended ecological systems

“…This might arise when there are alternative food sources available for the predator 22 , and is modelled by linearizing the predators' growth rate in equation (1) about the equilibrium by using the term (w Ϫ w ‫ء‬ ). These equations might, for example, outline the principal ecological transfers involved in the Canadian lynx-hare-vegetation foodweb, whose dynamics are dependent on three vertical trophic levels 3,28 and where alternative prey (such as the red squirrel) are considered to be important for the lynx population 29 .…”