User:CoeA/sandbox

=Host Behavior=

Animals also have behavioral defenses that allow them to eliminate parasites or reduce their overall risk. One type of behavioral defense is the increased grouping of individuals to reduce individual risk, also known as the dilution effect. An example of this has been well-documented in wild horse populations in France. In colder periods, when levels of parasitic flies were low, horses were more likely to be found in smaller groups. When fly levels went up during warmer periods, the horses merged into larger groups. While this behavior attracted more parasitic flies, the greater number of horses effectively lowered each individual’s risk of parasitization. This behavior of forming larger groups to dilute the effect of parasites has been observed in other mammals, birds, reptiles, fish, and insects.

Animals may also avoid locations or food sources that increase their risk of parasitization. In sheep populations, individuals tended to avoid feeding in pastures where roundworm eggs had accumulated in feces over the previous year. When compared to non-immunized individuals, sheep immunized against infection were more likely to eat in these patches after other food resources had been exhausted, indicating that the sheep actively avoided areas that increased their chance of being parasitized. Similarly, it has been suggested that baboons rotate sleeping groves every few days in order to avoid extended contact with fecal deposits that act as a reservoir for parasites. Alternatively, animals may actively take steps to remove parasites. This is seen in the preening behaviors of various mammals and in the ingestion of alcohol by infected fruit flies as self-medication against blood-borne parasites.