Ectoparasite load increase in reproductively active sand lizards

Abstract. Sexual reproduction imposes risks on participating adults through increased probability of injury, predation pressure, or parasite exposure. Evolutionary theory predicts that animals will tolerate parasite infection during reproduction at the expense of increased parasite load, resulting in individual trade-offs between the temporary costs of current reproduction against the long-term evolutionary benefits in the form of life-long production of viable offspring. We tested this hypothesis, predicting that participation in sexual reproduction increases parasite exposure by investigating ectoparasite load on sand lizards (Lacerta agilis). Using generalized additive models to correct for bimodal seasonal dynamics of ectoparasite activity, site and year, we found that ectoparasite load is higher in adults (animals that overwintered at least twice) than in subadults that overwintered once only. Between sexes of adult sand lizards, males had a higher number of blood-sucking ectoparasites than females. Our results indicate that both sexually-motivated extensive locomotion associated with territory defence and mate search in males, and increased energy uptake during gestation in females, contribute to elevated ectoparasite exposure. Increased host mobility associated with increased ectoparasite exposure leads to collateral burden of reproduction on sand lizard populations.