Credit: John Kascht
From the AUG/SEP issue of Seed:
When the last surviving California condors were taken into captivity by the US Fish and Wildlife Service in the mid-1980s, they were transported to the San Diego Zoo's Wild Animal Park and Los Angeles Zoo where, among other things, they were treated for parasites. Living within the feathers of the birds were Colpocephalum californici—an avian chewing louse that looks pretty much like all other lice: a bulbous head, stubby thorax, six hooked legs and a stout, hairy, segmented abdomen. But these lice lived only on California condors and were also facing extinction. More overlooked than willfully extinguished, the last C. californici vanished from the Earth in a puff of carbaryl-powder fumigation.
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Its disappearance is an example of "coextinction," or the extinction of one species because of the extinction or extreme rarity of a species on which it depends. Including the species at risk of coextinction would mean severe upward revisions to our estimates of endangered species. "They would absolutely skyrocket," said Piotr Naskrecki, director of the Invertebrate Diversity Initiative at Conservation International. A 2004 study in Science estimated that 6,300 "affiliate" species—parasites, pollinators and mutualists—might be "coendangered" because their hosts are threatened. Rob Dunn, a zoologist at North Carolina State University and a coauthor of the study, said the figure is likely much higher. "It's quite clear that we're going to be losing species before they're even described," said Nigel Stork, an entomologist and CEO of the Rainforest Cooperative Research Center in northern Australia, who likely coined the term "coextinction" in a letter in Nature in 1993.
"Charismatic animals hog conservation dollars; the only ethic that makes the condor more important than its louse is its aesthetic value."
It can be hard to see how the demise of a louse matters much. Though there is a general feeling that the extinction of anything—save a few lethal viruses, perhaps—is to be avoided, parasites are third-class citizens in the conservation world. Call it the "ick" factor. "It took long enough for people to care about wolves and things like that, so the idea that we would care about parasites is pretty far-fetched," said Dunn. "On a daily basis we confront the issue that we can't save everything," said Oliver A. Ryder, a geneticist at Conservation and Research of Endangered Species at the Zoological Society of San Diego.
Nonetheless, there are many rationales for keeping a species from extinction. The most commonly cited are its intrinsic right to exist, its functional roles in ecosystems and the potential to provide some value to humans. By these criteria, the tiny, repulsive and multi-legged creatures are just as important as, if not more so than, tigers, condors or whales. But charismatic animals hog conservation dollars; the only ethic that makes the condor more important than its louse is its aesthetic value. "That's a potentially justifiable reason to do conservation," said Dunn, who belongs more to the intrinsic-value school, "but if that's what we're doing, we need to fess up to it."
Noah Whiteman, a postdoc at the University of Missouri, St. Louis, has made the argument for parasite conservation based on their rich natural histories. In an article last year in the journal Animal Conservation, he wrote that if we don't want to save parasites for their own sakes, we should save them for what they can teach us about their hosts.