摘要Reproduction,including lactation,is the most costly activity in terms of energy expenditure in female mammals.Consequently,the energy requirements of the reproducing female may not be met at this time,especially if other energy demanding activities are occurring concomitantly.Such activities could be the activation and maintenance of an immune system in response to parasitic infestation.These protective processes are energetically demanding and require trade-off decisions among competing energy demands.In the case of a reproducing mammal,the trade-offs occur mainly between defence against parasites and reproductive costs of the host.In this paper,I discuss the effects of macroparasites on the energy allocation of reproducing small mammals.