In nature, all animals have a collection of various species of commensals, parasites, and other associated species from viruses to fleas, lice, and flukes. All of these modify their hosts' behaviour, reproductive fitness, and as a result have a cascade of effects through the entire ecosystem. When a captive population is established, almost all of these are destroyed for the sake of the health of the primary species being conserved. When a captive-bred animal is returned to the wild, all of these links are disrupted, so my question is, what measures do readers think could be taken to restore as far as possible the status quo?
Very interesting topic! Imho in captivity only the associated species with negative impacts are eliminated. Can anyone enlighten me with some other examples? I am not aware of any positive or important functions of any parasite/disease in any ecosystem. They might have an impact but are dispensable for the system. Again examples to the contrary are welcome. If I remember correctly, the reintroduction of the Przewalski's horse run into trouble in the beginning because the animals were naive to some of the present parasites/pathogens. I believe there is no need to conserve parasites/pathogens and there is no space to do so either, we struggle to find enough space/money to conserve the primary species. But if possible one should carefully document what is around to have an idea what to face at time of reintroduction.
Examples of parasite interactions I was thinking of are those where a parasite modifies a host's behaviour in order to improve the chances of its host falling victim to a predator. For example, the Toxoplasmosis parasite alters the behaviour of the rodent it is infecting by making it less cautious, meaning it gets eaten by a cat where the parasite can complete its life cycle. Without Toxoplasmosis in the ecosystem, would cats be able to hunt successfully enough to raise their young? I suspect many parasitic organisms with multiple hosts have a similar effect on their primary hosts. My point is that these parasitic organisms have a major feed through in ecological interactions and these are not currently being captured by conservation strategies aimed mainly at vertebrates. I am not sure what the answer is, but I am sure that an animal returned to the wild from zoo-bred stock would leave a lot of these interactions behind, with unpredictable effects on the ecosystem it is reintroduced to.
Great question @Zoovolunteer! I don't know of any research into what you're thinking about, but some recent papers may be of interest: Moir, M. L., Vesk, P. A., Brennan, K. E., Poulin, R., Hughes, L., Keith, D. A., ... & Coates, D. J. (2012). Considering extinction of dependent species during translocation, ex situ conservation, and assisted migration of threatened hosts. Conservation Biology, 26(2), 199-207. http://s3.amazonaws.com/academia.edu.documents/44364009/Considering_Extinction_of_Dependent_Spec20160403-15792-xogn9p.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1488285504&Signature=rfLF7f1BC09G4Bdx+sVL8VTqdAY=&response-content-disposition=inline; filename=Considering_Extinction_of_Dependent_Spec.pdf Gómez, A., & Nichols, E. (2013). Neglected wild life: parasitic biodiversity as a conservation target. International Journal for Parasitology: Parasites and Wildlife, 2, 222-227. http://www.sciencedirect.com/science/article/pii/S2213224413000230 Jørgensen, D. (2015). Conservation implications of parasite co-reintroduction. Conservation Biology, 29(2), 602-604. http://dolly.jorgensenweb.net/wp-content/uploads/2014/11/Jorgensen-conservation-implications-of-coreintroduction-final.pdf @Daniel Parasites structure ecosystems in innumerable ways, both directly and through indirect effects. Toxoplasmosis is a behavioural example mediated by a parasite, but indirect effects are usually observed as demographic impacts. For example, increasing the population of one species can decrease the population of another species through increasing the abundance of shared parasites. Any system where ≥3 species interact will have indirect effects, mostly undocumented. And a pedantic point: Not the commensals; surely?!
@Giant Panda Thx for the links to scientific literature! The topic seems to be broader than I will be able to understand quickly. Quick conlusion: if you can, safe the parasites too But they and there influences seem very much understudied.
