Trade-offs in parasitology, evolution and behavior

Most animal pare,~ts find caring for offspring to be costly, whether in terms of increased vigilance against predators or higher grocery bills. Most parasitologists know that defense against pathogens is costly as well, requiring elaborate physiological and biochemical mechanisms to recognize and destroy the invader. In both cases, the parent or host can be seen as making a trade-off, allocating energy to one task, such as protection of the young or production of macrophages, at the expense of another, such as feeding oneself or devoting energy to growth rather than ~mmune defense. Trade-offs in life history traits are much studied in evolutionary biology and ecology: examples include the choice between early maturation and growth ~2, the production of a few large offspring vs many smaller ones ~.2, or the investment in reproducing this year rather than saving some resour,:es for a later season ~,2. Only recently, however, has the notion of a life history trade-off been linl