Current releases of captive California condors into the wild will probably fail unless changes in the program are made soon, according to a study that will be reported in the August issue of the journal Conservation Biology.
Captive rearing techniques are producing excessively tame condors that pose threats to humans, and the released birds are at constant risk of death by lead poisoning from eating carcasses contaminated with bullet fragments, which was a main cause of the extinction of wild condors in the 1980s.
"Many condors are reared in captivity by humans using condor-shaped puppets, and this has created birds that readily approach people, cars and buildings," said Vicky Meretsky, assistant professor in the School of Public and Environmental Affairs at Indiana University and lead author of the journal article. In the past year there have been repeated instances of condors prying shingles off buildings, destroying camping equipment, and approaching people for food handouts, Meretsky said.
"Behavioral problems have been common in released young condors that were taken from their parents and reared by puppets in isolation, but not in young condors that were raised by their parents. Unfortunately, despite this important difference, program managers have continued to release puppet-reared birds to the wild instead of limiting releases to parent-reared birds," she said.
The other authors of the article are Noel Snyder of Wildlife Preservation Trust International; Associate Professor Steven Beissinger of the Department of Environmental Policy and Management, University of California, Berkeley; David Clendenen of Wind Wolves Preserve; and James Wiley of the Grambling Cooperative Wildlife Project, Grambling State University.
Lead poisoning was a major factor responsible for the extinction of the wild condor population in the mid-1980s, and it is again killing condors because releases have been conducted without attempting to solve the problem. In the last few months, five released birds have died of lead poisoning, and others are contaminated, Meretsky said.
"Until sources of lead contamination are effectively countered, releases of captive condors cannot be expected to result in viable wild populations," she said.
"To re-establish any wild species, the main causes of its extinction must be identified and eliminated before releases of captive animals are attempted. This basic tenet is being neglected in the current condor release program, even though alternative ammunitions are now available," said Snyder, senior author of the recent book The California Condor: A Saga of Natural History and Conservation (Academic Press).
"The California condor program is the flagship of endangered species conservation programs," Beissinger said. "Large amounts of money have been spent and many individuals have worked hard to breed condors in captivity and to develop techniques for reintroducing them to the wild. Success is definitely achievable, but only if basic changes are made in the current condor release program. If not, it may become a perpetual and very expensive black hole."
California condors once could be found along the Pacific coast from Canada to Mexico. By the late 1970s, only about 30 birds remained. A captive flock was started in 1982, and free-flying birds were captured when it became clear that the wild population was beyond rescue. The last wild condor was captured in 1987. Breeding in captivity was successful, and releases of captive-born young condors to the wild began in 1992. But the death rate of released birds has been too great to sustain a wild population.
Part of the problem is that birds raised using puppet condors have been excessively tame, despite efforts to train these birds to avoid humans and human structures. One group of eight birds wound up in a resident1s bedroom after tearing through a screen door to enter the house. In Grand Canyon a condor ripped through the side of a camper1s tent as he lay sleeping within.
Only one release site, near Big Sur, Calif., has had a purely parent-reared group of condors, and it has been essentially free of tameness problems, Meretsky said. Unfortunately, these birds recently expanded their range and joined one of the groups containing puppet-reared birds, and now they are beginning to follow the puppet-reared birds into developed areas.
"Mixing the two stocks in the wild has resulted in the transfer of bad habits from the puppet-reared to the parent-reared birds," Meretsky said. "All misbehaving birds in the wild should be re-trapped and returned to captivity, since they pose a risk of passing on their bad behaviors to birds released in the future."
The study strongly urges that future releases be limited to parent-reared birds, especially ones that are raised free of all contact with humans in field enclosures that do not resemble human structures.
Short-term measures to reduce lead poisoning were suggested as far back as the 1980s, when condor releases were first discussed. The proposal was to use only one or two feeding locations to provide condors with uncontaminated food until lead in their environment was no longer a problem. But release programs have instead emphasized more natural foraging patterns, using supplied food to tempt the birds to fly more widely, and then reducing and even eliminating the provision of safe food. First encouraged to feed on their own and then forced to do so, condors are now dying of lead poisoning.
"If lead contamination persists in the environment and increased feeding on natural carcasses continues, the mortality rate of released condors will equal the disastrously high mortality that once drove condors to the brink of extinction," Beissinger warned.
The most promising solution is to require hunters in areas where wild condors live to use a new non-toxic ammunition made from a composite of tungsten, tin and bismuth (TTB), which has hunting characteristics equal to lead ammunition, according to the study.
Government agencies have made no move to require non-toxic ammunition in areas where condors forage. However, the U.S. Army has begun to substitute TTB for lead in ammunition, and commercial production may begin soon.
"The technology for a practical solution to the lead-poisoning problem is already in hand. Government agencies need to be involved in encouraging production of TTB ammunition and restricting ammunition in release areas," Snyder said.
CONTACT: Hal Kibbey
812-855-0074
hkibbey@indiana.edu
Meretsky can be reached at 812-855-5971 or 435-644-3738 or meretsky@indiana.edu
Beissinger can be reached at 510-643-3038 or beis@nature.berkeley.edu
Snyder can be reached at 520-558-2413 or noelsnyder@vtc.net
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Journal
Conservation Biology