Wallin, K., Bergström, R. & Vikberg, M. 1995: Population density and inbreeding effect on moose Alces alces reproduction. - Wild. Biol. 1: 225-231.
The relationship between reproduction, age-structure, inbreeding and population density was analysed in an enclosed moose Alces alces population in Sweden. There was a strong negative relationship between the yearly average number of calves produced per cow and population density. Other variables, such as the average age of the cows and inbreeding also covaried with density. Taking these variables into account, a relationship remained between density and reproductive rate. An inbreeding index of three-year-old cows was negatively related to their calf production. Inbred, old (≤ 4 years) cows had a significantly lower calf production than old, outbred cows. Taking density into account, the effect of inbreeding remained. Even though inbreeding had a measurable effect at the individual level, the impact at population level was small and insignificant. During the early growth phase of the founder population, inbreeding remained low and had no negative effect on early population dynamics. The reason for this is that the first inbred individuals did not appear until the third generation. Therefore, a founder population can grow for a fairly long time and reach high population numbers before the effect of inbreeding appears. This means that the negative effects of inbreeding may increase in importance beyond our 12 years of study.
Key words: density dependence, reproduction, inbreeding, moose, Alces alces, founder population
Kjell Wallin*, Department of Animal Ecology, Swedish University of Agricultural Sciences, S-901 83 Umeå, Sweden
Roger Bergström, Swedish Hunters' Association, Research Unit, P.O.Box 7002, S-750 07 Uppsala, Sweden
Mats Vikberg, Swedish Hunters' Association, Research Unit, Box 3365, S-820 20 Ljusne, Sweden
*Present address: University of Göteborg, Department of Environmental Science and Management, Medicinaregatan 20B, S-413 90 Göteborg, Sweden
Received 19 June 1995, accepted 7 November 1995
Associate Editor: Bernt-Erik Sæther