THE EFFECT OF SUMMER FEEDING ON JUVENILE ARCTIC FOX SURVIVAL - A FIELD EXPERIMENT

The arctic fox Alopex lagopus L. population in Sweden is small and its numbers fluctuate widely with food availability, i.e. rodent populati ons. This fluctuation is mediated through differences in recruitment r ates between years. The recruitment can be divided into three phases: number of litters born, number of cubs per litter and cub survival rat es. The number of litters and their sizes have been shown to depend on food availability during winter and spring. To examine cub survival d uring the summer and how it relates to food availability, we conducted a feeding experiment in northern Sweden during 1990, a year of low ro dent density, involving six occupied arctic fox dens. Feeding at dens lowered cub mortality rates. However, condition and growth rates of ju veniles were not influenced by supplementary feeding at dens, nor were they related to the probability of survival for an individual. Thus a rctic foxes seem to minimize risks rather than maximize growth. The ju venile mortality from weaning and over the next 6 wk was 21%, mostly d ue to starvation. Only 8.2% survived from weaning to the first breedin g season. Of the one-year-old foxes, 50% survived their second year. S upplementary feeding of juveniles had no effect on the final survival rates over these two years. However, the immediate, positive effect on cub survival could be used in a long-term, extensive management progr amme if combined with winter feeding.