Wolverine Gulo gulo populations have a low reproductive potential and are thus relatively sensitive to changes in survival rates. Consequently, knowledge about survival and mortality causes in juvenile wolverines is important for a sound management of the species. We estimated survival rates for juvenile wolverines and evaluated the relative importance of intraspecific predation compared to other mortality causes in northern Scandinavia during 1993–2001. We monitored 80 radio-marked juvenile wolverines from May to February. Intraspecific predation was the most important cause of juvenile mortality and occurred during two periods. First, seven juveniles were killed in May-June when still altricial, i.e. infanticide. Second, four juvenile females were killed by conspecifics outside their mothers' territories after independence in August–September. The survival rate of radio-marked juveniles during May-February was 0.68. There was a strong tendency for survival to be lower during the summer when juveniles were altricial, than after they became independent. The estimates of survival rates and mortality causes provided by this study are important for the understanding of wolverine population dynamics. Currently, our data are too weak to suggest an explicit explanation for infanticide in spring/early summer. Still, in the light of the available information on wolverine life history and infanticide patterns in other species, we suggest two, not mutually exclusive, hypotheses to consider for further investigation: 1) males kill non-related juveniles to increase their reproductive success, and 2) females kill non-related juveniles to reduce competition for resources. In addition, attention should be given to the alternative hypothesis that infanticide in wolverines is non-adaptive. Finally, we suggest that independent juvenile females were killed by resident females in territorial defence.
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Vol. 9 • No. 4