IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| O'Donoghue, M.; Boutin, S.; Krebs, C.J.; Zuleta, G.; Murray, D.L.; Hofer, E.J. | |
| Functional responses of coyotes and lynx to the snowshoe hare cycle | |
| 1998 Ecology (79): 1193-1208 | |
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. |
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