Background
Effects of captivity on species
Changes in the food web structure caused by species loss
During the time a species spend in captivity it is not only its traits that change, the ecosystem in which it once lived may also undergo significant changes that can affect the reintroduction success. When a species goes extinct, the ecosystem does not just stay the way it was, it can react differently depending on what place and function the extinct species had in the community. In worst case scenarios there is a risk for the whole ecosystem to collapse, due to trophic cascade effects caused by the extinction of one species whereas in other cases there is a few secondary extinctions or none at al.
The strength of the link between species is essential when it comes to how other parts of an ecosystem react to extinctions. The link-strength is not the only vital parameter if species are removed from an ecosystem, for example species richness and connectance is vital when it comes to the robustness of a food-web. For example, if there are few connections between species in a food-web, the chances of secondary extinctions are much higher compared with ecosystems with many connections.
Christanou & Ebenman (2006) list four possible different outcomes when a species is reintroduced into a food-web;

Effects of a reintroduction
Not only can the loss of a species affect the food-web, but also the reintroduction can cause further damage and secondary extinctions, especially if there were secondary extinctions when the species initially disappeared. Laikre et. al. (2010, p. 520) lists four additional risks with reintroducing a captive bred species back into the wild: (I) loss of genetic variation, (II) loss of adaptations, (III) change of population composition and (IV) change of population structure. They further state that these risks are largely neglected today, especially in the commercial markets such as the hunting, foresting or fishing industry where enormous amounts of animals are released and plants set out each year.
The effects on food-webs when a captive bred species is reintroduced have not yet been studied to any further extent. Studies have been conducted on the success-rate of reintroduction, reintroduced species born in captivity and their chances of success. Since we know that the invasion of alien species can alter the whole structure of a food-web it is also important to see how the food-web reacts to a reintroduction of a species with changed attributes due to the time spent in captivity.
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Director of undergraduate studies Biology
Last updated:
05/26/11