Time sharing between host searching and food searching in parasitoids: state-dependent optimal strategies

By varying the time spent searching for food, parasitoids modifytheir expected lifespan, and therefore their total lifetimereproductive success. Using a stochastic dynamic approach, wedefine the best choice between searching for food and searchingfor hosts as a function of the state of the parasitoid and theavailability of food when hosts and food are found in differentparts of the environment A first model deals with the influenceof food availability and survivorship conditions on the behaviorof a single parasitoid. Our results suggest that under conditionsof very low food availability, parasitoids should never searchfor food. When food availability is moderate, parasitoids shouldnot wait until their reserves are low before searching for food.When food is abundant and survivorship is independent of foodconsumption, parasitoids should search for food only when theirreserves are almost exhausted. They should not wait so longif survivorship depends on the energy reserves. By finding thestate-dependent ideal free distribution for a population ofparasitoids, we are able to predict their distribution betweenthe feeding area and the host living area at equilibrium. Theproportion of parasitoids in each area is altered by the numberof competitors and interference. Finally, the model predictsthat optimal time sharing between food searching and host searchingmay promote the stability of the host-parasitoid system.