Range-body mass interactions of a northern ungulate - a test of hypothesis

Abstract

Summer diet, summer temperature, length of the growth season and animal density appeared to best explain annual and regional differences in calf and yearling body mass in moose from southeastern Norway. In general animals inhabiting steep, alpine landscapes had less body mass than animals using flat, low-altitude habitats. Autumn body mass of calves and yearlings decreased with increasing snow depth during the preceding winter and spring. However, calf body mass was more influenced by the summer range and less by the winter range than was body mass of yearlings. There was no indication that the effect of snow depth on autumn body mass was greater in moose living on poor than on good summer ranges. Body mass decreased with increasing competition for summer forage, while the winter range mainly had an density-independent effect. Habitat quality, expressed as regression lines between calf and yearling body mass and animal density (hunting yield), differed between regions. On ranges of medium and high altitude where birch (Betula spp.) rowan (Sorbus aucuparia) and bilberry (Vaccinium myrtillus) dominated moose summer diet, body mass decreased at a rapid rate with increasing animal density. Body mass decreased at a slower rate at low-altitude ranges and at high-altitude ranges where willow (Salix spp.) and forbs dominated the diet. Body mass of lactating cows decreased with increasing animal density, but animal density did not affect body mass of non-lactating cows. There was no indication that the decrease in autumn body mass with increasing moose density over the last 25 years has caused a decrease in animal condition (ability to survive the winter). The results are discussed in relation to the effect of summer and winter range on population regulation in moose. It is concluded that a density-dependent effect is apparent on the summer range even at low and intermediate population densities. On the winter range, on the other hand, density-dependence is likely to occur only at high levels of population density.

Performance of hunting statistics as spatiotemporal density indices of moose (Alces alces) in Norway

“…For more information on the study areas, Fig. 1 Saether and Heim (1993), Solberg and Saether (1993), Saether et al (1996), Gangsei (1999), Hjeljord and Histøl (1999), and Solberg et al (2006).…”

Summer Diet of Two White-tailed Deer, <em>Odocoileus virginianus</em>, Populations Living at Low and High Density in Southern Québec

“…At high density, forage competition can modify feeding habits of ungulates, in particular for small, selective species (Kie and Bowyer 1999) and reduce body size in cervids (Ashley et al 1998;Crête et al 1993;Hjeljord and Histol 1999;. In mid-latitude deer, forage competition during the growing season likely determines adult body We investigated summer diets of two White-tailed Deer (Odocoileus virginianus) populations through rumen content analyses.…”

“…size because growth and replenishment of body reserves occur during this period of the year (Hjeljord and Histol 1999;Lesage et al 2001;Boucher 2004).…”

Scale-dependent effects of summer density on autumn mass in reindeer

“…Skogland, 1985;Loison et al, 1999;Kumpula & Colpart, 2003;Tveraa et al, 2007) as well as cost of locomotion (Fancy & White, 1985). Several studies have also shown negative summer density-dependent effects on body mass of large temperate and northern herbivores (Hjeljord & Histøl, 1999;Stewart et al, 2005;Herfindal et al, 2006), including reindeer (Lundqvist, 2007). The main suggested mechanism being intraspecific competition for forage, which may operate at multiple spatial scales (Senft et al, 1987).…”