Influence of food shortage during the summer on body composition and reproductive hormones in the red fox, Vulpes vulpes

Some mammalian carnivores compensate for prey shortage during the summer by increasing their consumption of wild berries. We tested whether such prey shortage affected all body components (e.g., fat, protein, water) equally, and whether it could affect reproduction. Two groups of wild red foxes (Vulpes vulpes) were kept in captivity: the first group was fed a control diet of dog food, and the second group was fed a diet of dog food and fresh apples for 8 weeks during midsummer. The experimental diet contained 95% of the energy content of the control diet but only 55% of the protein and 46% of the fat content. Foxes fed the experimental diet simultaneously lost body fat and protein on the apple diet, but body reserves were quickly restored upon return to the control diet. We found no evidence that protein and energy deficiency during summer impaired reproduction the following spring.