Parasites that target host reproductive systems strike an optimal balance of resource consumption in hosts. The parasite gleans a nutrient-rich source of energy for their growth and reproduction, while taxing a host resource that is nonvital for host survival. Parasites can also exploit alterations in host reproductive behavior to further increase parasite fitness. Many alterations of host behavior benefit the parasite, and seem to constitute a parasite strategy for increased survival and reproduction. However, there are systems in which the host alters reproductive efforts in response to parasites, perhaps attempting to mitigate the damaging effects eventually induced by infection. Such struggles between host and parasite for host energetic resources drive the dynamics of host and parasite coevolution.
