Abstract

The period following the withdrawal of parental care has been highlighted as a key developmental period
for juveniles. One reason for this is that juveniles cannot forage as competently as adults, potentially placing
them at greater risk from environmentally-induced changes in food availability. However, no study has
examined this topic. Using a long-term dataset on red foxes (Vulpes vulpes), we examined (i) dietary
changes that occurred in the one-month period following the attainment of nutritional independence,
(ii) diet composition in relation to climatic variation, and (iii) the effect of climatic variation on subsequent
full-grown mass. Diet at nutritional independence contained increased quantities of easy-to-catch
food items (earthworms and insects) when compared with pre-independence. Interannual variation in
the volume of rainfall at nutritional independence was positively correlated to the proportion of
earthworms in cub diet. Pre-independence cub mass and rainfall immediately following nutritional
independence explained a significant proportion of variance in full-grown mass, with environmental
variation affecting full-grown mass of the entire cohorts. Thus, weather-mediated availability of easyto-
catch food items at a key developmental stage has lifelong implications for the development of juvenile
foxes by affecting full-grown mass, which in turn appears to be an important component of individual
reproductive potential.