Exploitative Interactions

***The following notes are taken directly from –Exploitative Interactions, Chapter 14 of  Ecology:  Concepts and Applications, 5th edition, by Manuel C. Molles Jr.***


*In nature, the consumer eventually becomes the consumed.

*Predators are animals that feed on other animals.

*Parasites live on the tissues of their host, often reducing the fitness of the host, but not generally killing it.

*Parasitoids are insects whose larva consume its host and kills it in the process.

*Pathogens induce desease in their hosts.

*Predators, parasites, and pathogens influence the distribution, abundance, and structure of prey aand host populations.

* Exploitative Interactions are interactions between species that enhance the fitness of one individual at the expense of another.

*To persist in the face of exploitation, hosts and prey need refuge.

*Refuges are situations (not always places) in which members of an exploited population have some protection from predators and parasites. *One example is the Detroit RiverInternational Wildlife Refuge: http://www.fws.gov/refuges/profiles/index.cfm?id=31521

*Spatial refuges include:  burrows, trees, air, water (if faced with terrestrial predators), and land (if faced with aquatic predators).

*Predator satiation is a defensive tactic in which prey reduce their individual probablitity of being eaten by occurring at very high densities.

*Many organisms select their prey by size, and averge prey size shows a significant correlatoin with predator size across taxa.

*The leading parasitic disease in humans is malaria, which is transmitted to humans by mosquitoes and infects an estimated 250 million people.

*Schistosomiasis–caused by blood flukes–is the second most prevalent parasitic disease, affecting approximately 200 million people. Although Schistosomiasis can now be treated with drugs, many patients are reinfected.

*Introduction of  snails that competitively displace the snail species that serve as intermediate hosts for the Schistosomia parasite is proving effective in controling infection rates of Schistosomiasis among humans.

*Predators and parasites have been used to control populations of insects that attack crops or to control invasive weeds..


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