In this thesis I examine reproductive patterns, test for effects of reproductive costs and winter food availability on female reproduction, estimate rates and causes of juvenile mortality, examine dispersal patterns and analyze population viability. Wolverine (Gulo gulo) females reached the reproductive stage no earlier than 3 years of age and the minimum average age at first reproduction was 3.4 years. Each year about every second female reproduced and produced an average of 0.8 kits per female. Reproduction incurred costs on females that affected reproduction the subsequent year. Experimental food-supplementation of females in early winter enhanced reproductive rates, even though all food-supplemented females had reproduced the preceding year. I therefore suggest that reproductive success of wolverine females is determined by the combined effect of reproductive costs and winter food availability. The survival rate of radio-marked juveniles from May to February was about 70%. Intraspecific predation was the most important cause of juvenile mortality (50%), and occurred in May-June when juveniles are dependent on their mother and in August-September after independence. Mean dispersal age was 13 (7-26) months for both sexes. All males (n = 11) and 69% of the females (n = 9) dispersed. Competition for resources apparently determined female dispersal pattern, while competition for mates seemed to explain male dispersal pattern. Population dynamics of wolverines are largely influenced by stochastic components. A population viability analysis suggest that the carrying capacity of a Scandinavian population should exceed 46 adult (≥3 years old) females to not be considered vulnerable according to IUCN (2000). This should be seen as a preliminary guideline as parameter estimates in the model are uncertain. The Swedish population averaged 100 adult females during 1999-2001, which is far above the carrying capacity recommended for a population to not be considered “vulnerable”. The recruitment rate to the next generation is primarily influenced by adult female survival, effects of reproductive costs and winter food availability on female reproduction, and intraspecific predation on juveniles. The recruitment shows a large variation among individuals and years, suggesting that wolverine population dynamics is strongly characterized by stochastic components. Wildlife managers should especially consider the importance of adult female survival.
展开▼
