Raising pups of urban San Joaquin kit fox: relative roles of adult group members

Abstract

Maternal care of young is the norm in mammals because of internal gestation and lactation by females. Care by adults other than the mother is rare in most mammals but is common in primates, rodents, and carnivores. We studied parental care in an urban population of the San Joaquin kit fox (Vulpes macrotis mutica), a small canid endemic to the San Joaquin Desert in California. Kit fox family groups typically consist of a mated pair, the young-of-the-year, and occasionally older offspring from previous years known as helpers. The relative contributions of the parents and helpers to the rearing of young are unknown in San Joaquin kit foxes. We determined the relative time investment (den attendance), the tasks performed (e.g., provisioning and guarding), and the chronology of participation and tasks performed by adult group members in pup rearing. We classified group members into 3 categories (mother, father, and helper) and monitored them for 3 periods of the reproductive season (preparturition, nursing, and weaned). There was no difference in den attendance between periods, but there was a significant difference in den attendance by role. Mothers spent significantly more time at the den than either fathers or helpers. There was no significant difference between average provisioning events per hour per individual by role, but provisioning rates were significantly lower during the nursing period compared to the weaned period. Mothers provided the most direct care to young, while the role of fathers was primarily to guard the family and maintain the territory. Assistance provided by helpers supplemented the efforts of the mother and father and consisted primarily of guarding and some social interaction, especially play. Pups in groups with helpers were left unattended significantly less than pups in the group with no helpers, which may result in lower predation levels on pups. Helpers were likely tolerated because of a superabundance of food in the urban environment, but their presence may reduce pup-rearing costs for parents and enhance the successful rearing of the current litter. Future research should compare parental care in urban and nonurban kit foxes and determine whether helpers increase pup survival rates.