COSTS OF BOT FLY INFECTION IN WHITE-FOOTED MICE - ENERGY AND MASS-FLOW

We quantified the impact of bot fly larvae (Cuterebra fontinella) on t he energy budget of their small-mammal hosts (white-footed mice, Perom yscus leucopus). We estimated the fluxes of water from the host to the parasite and from the parasite to the host by injecting infected host s (or bot fly larvae) with tritiated water and measuring the uptake by the parasite (or the host). Using these fluxes, we then constructed a fluid flux budget for the host-parasite system, and estimated that a bot fly larva receives ca. 1% of the host's nutrient budget. We also f ound a 5% increase in the metabolic rate of infected hosts in the labo ratory, but no such effect in the field. No effect of bot fly larvae o n digestive efficiency or food consumption was detected; however, infe cted mice lost body mass during a field trial. We conclude that bot fl y larvae have a relatively modest effect, although energetically stres sed individuals, such as lactating females, could suffer substantially .