Parasite removal increases reproductive success in a social African ground squirrel

Parasites can be detrimental to the health, longevity, and reproduction of their hosts, but these costs are rarely quantified in nature. We removed ectoparasites and endoparasites from Cape ground squirrels (Xerus inauris), a highly social sciurid in southern Africa. Parasites were removed for 3 months during the dry winter season, when fewer resources are available and the impact of parasites may be greatest. We examined changes in female body mass, reproduction, grooming, and burrow use. Female body mass did not increase with parasite removal, but reproductive success (number of offspring raised to emergence) was nearly 4 times higher for treated females. Rates of allogrooming were lower for treated females, but we were unable to detect a significant change in burrow movements, perhaps because factors other than parasites (e.g., predator avoidance) affect such movements. Gestation and lactation are the most physiologically stressful processes that females undergo, and the dramatic increase in reproductive success in treated females suggests that parasites drain resources that would otherwise be allocated to reproduction. Our results suggest that nonparasitized females put the extra energy into reproduction rather than into their own body weight, which appears to enhance juvenile survival.