Even pests have a purpose
by Marian Lyman Kirst
It’s a remarkable achievement: According to a census in April, the number of California condors, one of the largest and most endangered birds in the world, has reached 405, including both wild and captive birds. That's the most condors to exist on the planet since recovery of the species began in the 1980s, when only 23 remained.
The birds, which can live to the venerable age of 60, continue to be threatened by lead poisoning, which happens when the condors eat carrion peppered with the shards of exploded lead bullets. The condors' alarming die-off prompted the U.S. Fish and Wildlife Service to capture the remaining birds in 1987, and place them in a handful of captive breeding programs around the West.
As the April census indicates, the recovery programs have been a great success, pulling the magnificent, bald-headed birds, whose wingspans are nearly 10 feet across, back from extinction. But in the process, another certainly less charismatic creature, has been wiped out: Colpocephalum californici, an avian chewing louse that lived only on the California condor.
“As far as scientists can tell, based on very limited knowledge, C. californici caused its condor hosts no harm. The bird was simply a mobile home, providing shelter and the occasional feather meal,” reports the San Diego Union-Tribune.
The louse was one of an estimated 6,300 known “affiliate species” -- pollinators, parasites and mutualists (organisms that carry on a mutually beneficial relationship with another species) -- that are uniquely adapted to the creatures on which they depend. Because of the intimate relationships affiliate species have with their hosts, they can tell us a great deal about the biology of the hosts themselves, which can prove especially handy when the host species is rare or endangered.
But when the U. S. Fish and Wildlife Service rounded up the world’s last remaining condors in the late ‘80s, and sent them to recovery and breeding centers, they were treated for parasites and, as SEED Magazine eloquently describes, “the last C. californici vanished from the Earth in a puff of carbaryl-powder fumigation.”
The lice’s disappearance -- the result of negligence rather than deliberate extermination -- is a fine example of “coextinction,” a term coined in the early 2000s to describe what happens when a particular species goes extinct because the creatures on which it relies become very rare or vanish entirely. A 2004 study found that, in the last 200 years, at least 100 species of butterflies, beetles and lice have disappeared as a result of coextinction.
Indeed, in a 2005 article in Conservation Biology about modern insect extinctions, zoologist Rob Dunn warns that hundreds of affiliates could be lost, given the number of species recommended for captive breeding programs -- which, through fumigation or disinfection, can inadvertently wipe out mutualists or parasites, such as the condor louse.
“The potential magnitude of coextinctions should make them a key focus of conservation biology, yet the process of coextinction has been little studied,” Dunn says.
And while the annihilation of tiny, blood-sucking parasites and itty-bitty invertebrates may seem like a trifling problem (or even a plus), studies suggest that the extinction of such species is a blow, not a boon, to science. Pestiferous critters like ticks, mites and lice are “great repositories of history, living chronicles of how organisms evolve over time,” says the Union-Tribune. Because parasites reproduce faster, evolve more quickly, are much more abundant, and have greater genetic diversity than their imperiled hosts, they can often teach us more about those hosts than can the hosts themselves.
The feline immunodeficiency virus (a pathogen, not a parasite) helped reveal the movements and demographics of isolated cougar populations in the Northern Rocky Mountains. And scientists studying the Galapagos hawk, an endangered raptor endemic to the Galapagos Islands, looked to the bird’s feather lice to figure out how and when the birds colonized the archipelago and how each population is related to its neighbors.
So when California condor populations finally top 450 birds, the number required before the species can officially be considered for downlisting under the Endangered Species Act, we should by all means celebrate. But let’s not forget to raise a glass as well to the little lice that once lived on the great bird but which is now lost forever, as well as to all the parasites, pathogens and symbionts threatened by coextinction. They may not look as charming on a wildlife calendar, but they are as worthy of conservation as their more endearing hosts.