Emigration and Density Dependence in Yellowstone Bison


Our study area was in northeastern Dalarna County and neighboring Gdivleborg and Jdimtland counties, south- central Sweden (610N, 18’E). The area was hilly, with elevations ranging from about 200 m to 950 m, but only a very small part of the area was above timberline, approx- imately 750 m. Lakes and bogs covered large areas, but most of the area was covered with coniferous forest dominated by

Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Besides moose, the major source of protein for the bears was

ants (Formica spp. and Componotus herculeanus; Swenson et al. 1999a). The last brown bears killed during the extermination

campaign in Sweden were in 1897 in Dalarna County and 1895 in Giivleborg County. Following protection and effective conservation measures, bears returned to these

counties in the 1920s and 1960s, respectively (Swenson et al. 1995). Bear density in the study area was estimated to be 30/ 1,000 km2 by a combination of a mark-recapture technique and fecal DNA sampling (Solberg et al. 2006). Moose

1 E-mail: jon.swenson@umb.no 2 Present address: Department of Biology, University of Oslo, P.O. Box 1066 Blindern, NO-0316 Oslo, Norway 3 Present address: Agriculture Ministry, SE-103 33 Stockholm, Sweden

4 Present address: Ldnstyrelsen i Dalarna, P.O. Box 86, SE-790 91 Idre, Sweden 5 Present address: Norwegian Nature Inspectorate, NO-9321 Moen, Norway 6 Present address: Swedish Game Management, P.O. Box 5260, SE-711 98 Ramsberg, Sweden

Swenson et al. * Brown Bear Predation on Moose Calves 1993

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Table 1. Total mortality among unmarked calves of radiomarked female

moose from birth to the beginning of the fall moose-hunting season in mid- September in south-central Sweden, 1988-1998.

Yr No. of calves Disappeared % mortality

1988 22 6 27

1994 9 2 22

1995 13 6 46 1996 16 7 44

1997 13 2 15

1998 18 10 55 Total 91 33 36

density in winter averaged 920/1,000 km2, based on aerial sampling in the area where moose were radiomarked (Cederlund and Wallin 1998).