Lynx-Prey Interactions in Central Alberta

A lynx (Lynx canadensis) study was conducted in central Alberta in 1964-68. Population densities on 57 square miles in winter decreased from 11 in 196>6S to 3 in 1966-67, then increased to 9 in 1967-68. The winter diet was comprised of 76 percent snowshoe hare ( Lepus americanus), 9 percent ruffed grouse (Bonasa umbellus), 3 percent red squirrel ( Tamiasciutus hudsonicus), 10 percent carrion, and other less important items. The relative importance of the major food items did not change significantly between years, but use of carrion was higher in 196S67 than in the previous two winters. Daily food requirements in winter were 600 and 400 grams for adult and juvenile lynxes, respeotively. From December through MarcAh, lynxes removed six, six, two, and three percent of the December hare population; they accounted for 10, 24, 8, and 37 percent of the December to April decline in hare numbers in 196465 through 1967-68, respectively. Lynxes removed less than six, two, one, and two percent of the fall ruffed grouse population during these same winters. Between one and two percent of the fall red squirrel population was taken by lynxes over winter. Kittens were produced in all years, but only those born in 1967 survived through their first winter. Ages of autopsied lynxes also indicated that no young were added to the population in 196>66-the years of lowest hare numbers. Thus, annual productivity of lynxes appears to be direcKy related to abundance of snowshoe hares. We believe that some critical minimum density of hares is necessary for female lynxes to raise kittens. 320 Journal of Wildlife Management, Vol. 36, No. 2, April 1972 ogy and control of the Engelmann spruce beetle in Colorado. U. S. Dept. Agr. Circ. 944. 35pp. MITCHELL, H. H. 1964. Comparative nutrition of man and domestic animals. Vol. a. Academic Press, New York and London. 840pp. OTVOS, I. S. 1965. Studies on avian predators of Dendroctonus brevicomis LeConte ( Coleoptera: Scolytidae ) with special reference to picidae. Canadian Entomol. 97(11 ) :11841199. PORTER, W. P., AND D. M. GA12;S. 1969. TheImodynamic equilibria of animals with environment. Ecol. Monographs 39 ( 3 ): 227-244. VAN DYNE, G. M. 1962. Micro-methods for nutritive evaluation of range forages. J. Range Mgmt. 15 ( 6 ): 303-314. YEAGER, L. E. 1955. TWO woodpecker populations in reladon to environmental change. Condor 57 ( 3 ): 148-153. Received for p2Iblication April 30, 1971. Lynx populations exhibit marked fluctuations that are associated with the well1 A contribution of the Department of Wildlife Ecology, College of Agriculture and Life Sciences, and Research Committee of the Graduate School, University of Wisconsin; the Research Council of Alberta; the Alberta Departnent of Lands and Forests, Fish and Wildlife Division; the Alberta Department of Agriculture, Veterinary Services Branch; the National Science Foundation (Grants GB-6156 and GB-7744); and the Wildlife Management Institute. 2Present address: College of Forest Resources, University of Washington, Seatt]e. 3 Present address: P. O. Box lS9, Happy Valley, Labrador. known 10-year cycle of snowshoe hares as reviewed by Keith ( 1963:6) . The present paper examines some relationships between the lynx and its chief winter prey during a trough (1964 to 1968) in the hare cycle in central Alberta. We thank H. O. Johnson, D. H. Wood, and the late C. H. Browning for assistance with fieldwork. Other students at Rochester were also helpful, especially E. C. Meslow and D. H. Rusch. We are also grateful to H. W. Mossman for help in reading reproductive tracts and to R. D. Taber for reading the manuscript. This content downloaded from 157.55. 39.162 on Thu, 11 Aug 2016 06:09:26 UTC All use subject to http://about.jstor. org/terms LYNX-PREY INTERACTIONS * Nellis et al. 321 METHODS AND MATERIALS The main study area was a 57-squaremile block located at Rochester, 60 miles north of Edmonton, Alberta. In 1964, the area was approximately 31 percent open farmland, 34 percent aspen ( Populus tremuZoides ) -dominated upland forest, 16 percent spruce (Picea mariarla and P. glst4ca) forest, 13 percent bog with bog birch ( Betula glandulosa) and willow (Salix spp.) predominating, 2 percent marsh, 2 percent open water, and 3 percent scattered brush on burned-over land. Jack pine ( Pinus banksiana ) was scattered throughout the forested uplands and, on some light soils, formed nearly pure stands. Nine lynx carcasses were also collected from other localities, where the habitat varied from 90 percent cultivated farmland to undisturbed forest. Lynxes were captured in steel traps, immobilized with Sernylan (a phencyclidine hydrochloride from Parke, Davis and Company), marked, and released. Marking devices used were ear tattoos, ear tags, springbronze collars, and Nyanzol D dye in patterns that allowed recognition of individuals. Ear tags and collars were engraved with a number, our address, and notice of a $2 reward for return of the tag and $4 for both tag and carcass. Trailing three lynxes in winter provided estimates of home range size. Activity centers-separate areas containing lynx sign immediately after fresh snows were located by winter tracks and yielded estimates of lynx densities on the study area. Food habits were determined from analysis of 35 digestive tracts and 123 scats and from records of 261 miles of winter trailing. The data from winter trailing were previously reported (Nellis and Keith 1968). The food from the stomachs was stored in 10 percent formalin until examined; the total volume was determined by water displacement. Food items were separated by species, and the volume and number of individuals of each species were determined. For the number of individuals, the characteristic (teeth, bones, feet, tails) that gave the highest count was utilized.