Movements, habitat use, and predation on pronghorn fawns in Alberta

Sixty-two pronghorn (Antilocapra americana) neonates were fitted with radio collars in southeastern Alberta and located daily for 58 days or until death. The mean distance between bedded siblings was 73.4 m; they were first seen bedded together at 7 days of age and after 24 days they were together habitually. Mean daily movements and home ranges of fawns increased (P < 0.001) with age. Bedding-site selection and vegetation used by fawns did not change markedly during the 58-day observation period. Fawns preferred heavy native vegetation and under-used cultivated land. Predation by coyotes (Canis latrans) and bobcats (Felis rufus) caused the death of at least 43.5% of 62 marked fawns. Predation was highest on 4-15-day-old fawns, but remained important for animals between 16 and 57 days of age. During the past 10 years in Alberta, annual fawn mortality has approximated 50%. This rate of fawn mortality has not limited the growth of the provincial pronghorn population. J. WILDL. MANAGE. 48(2):542-550 Since the advent of miniaturized telemetry systems (Mech 1967) researchers have shown that predation can be a locally important cause of mortality for pronghorn fawns (Beale and Smith 1973, Barrett 1978, Beale 1978, Bodie 1978, Von Gunten 1978). Beale and Smith (1973) observed that radio collars did not alter the behavior of marked fawns nor change their mortality rate when compared with unmarked animals. Bromley (1978) theorized that bed-site selection by fawns was influenced by predation pressure and habitat structure. In Alberta, the mean mortality of fawns in the first 60 days following parturition approaches 50% (Barrett 1978). Mitchell (1980:139) and Barrett (1981) suggested that increased survival of fawns was a reflection of larger quantities of forb and browse cover. In Idaho, Bodie (1978) related differences in predation rates on fawns to cover type. This paper reports the spatial and behavioral relationships of free-ranging pronghorn fawns for 58 days after birth until they have been integrated into doefawn summer groups. The relationships of fawns to key habitat components of their environment and the effect of predation are also examined. Many individuals of the Alberta Fish and Wildlife Division assisted with fieldwork. Particular thanks go to E. H. Bruns, R. J. Clark, A. R. Cook, K. R. Froggatt, L. D. Gudmundson, D. E. Hofman, H. G. Vriend, and L. A. Windberg. J. P. Chenier, Computing Serv., Univ. of Alberta, assisted with statistical analyses. G. A. Chalmers, Anim. Health Div., Alberta Dep. of Agric., assisted with fieldwork, necropsies, and reviewed the manuscript. G. L. Langford, of G. L. Langford and Associates, Edmonton, assisted with the digitizing and analyses of occupied areas. W. M. Samuel, Univ. of Alberta, Edmonton, B. W. O'Gara, Univ. of Montana, Missoula, and M. J. Dorrance and A. W. Hawley of the Alberta Environ. Cent. reviewed the paper. STUDY AREA AND METHODS The study was conducted during 1975 and 1976 in a 1,054-km2 area of southeastern Alberta. The study area was in the Brown soil zone in part of the mixed-grass prairie region. Mean annual precipitation 542 J. Wildl. Manage. 48(2):1984 This content downloaded from 157.55.39.102 on Mon, 03 Oct 2016 05:11:50 UTC All use subject to http://about.jstor.org/terms PRONGHORN FAWN BEHAVIOR AND MORTALITY * Barrett 543 (1941-70) was 327 mm as measured by the Agriculture Canada research substation at Onefour. Western wheatgrass (Agropyron smithii), blue grama (Bouteloua gracilis), and needle-and-thread (Stipa comata) were the dominant grass species. The primary shrub was silver sagebrush (Artemisia cana), but western snowberry (Symphoricarpos occidentalis) and rose (Rosa spp.) were present in bottomlands and along the many intermittent water courses that transect the area. Topography varied from gently rolling plains to limited hills at an altitude of <1,100 m. This general area has been described by Coupland (1950, 1961) and Mitchell and Smoliak (1971). The study area was divided into large pastures by conventional threeor fourstrand barbed-wire fence and by a few roads. Domestic cattle ranged throughout the area during the summer grazing sea-