Catherine Brahic, New Scientist 27 Apr 09;
Swooping down in a last-ditch effort to thwart extinction, conservationists have airlifted 50 "mountain chickens" – frogs to us – from the Caribbean island of Montserrat.
While conservation biologists prefer to help a species survive in its natural environment, extreme cases like that of the chicken frog call for extreme rescue measures. Here we present eight of our favourite attempts at species' saving.
1. California condor
In 1987, the last remaining 22 California condors were brought into captivity and bred at the San Diego Wild Animal Park and the Los Angeles Zoo. The scientists removed the first-laid clutches to encourage females to produce more eggs, but this meant that roughly half the young had to be reared by humans. To make them as "wild" as possible, they were fed and reared using condor-shaped hand puppets.
The human effort didn't end there. When young condors released into the wild electrocuted themselves on power lines, the scientists installed mock pylons in their cages, delivering mild electric shocks to any bird that perched on them.
Even still, the released birds did not behave "properly" – they congregated in urbanised zones and played with garbage. One researcher said it was like "putting teenagers together without adult supervision. They were behaving like a bunch of hooligans". The researchers used the remaining captive wild birds to discipline the youngsters.
The scientists' work to help the species paid off, with 322 condors known to be living with 172 in the wild as of April 2009. Read about the plight of the condor here.
2. Whooping crane
Less than 20 of the enormous North American whooping crane were alive in 1940, and the bird was declared endangered in 1967. A captive breeding programme was implemented, which required scientists to dress in white sheets and wear arm puppets shaped like an adult whooping crane's neck and head when feeding them.
To further prevent extinction, the birds were taught to migrate along a safer route between Wisconsin and Florida. No problem – the scientists set up Operation Migration, whereby cranes followed an ultralight aircraft on the outward migration to Florida, spent the winter there and returned un-aided the following spring. This programme has been successfully building up the wild population since 2001.
3. Gaur
Captive breeding is one thing, but cloning an endangered species is an entirely different matter. Born on 8 January 2001, Noah was the first successful birth of a cloned animal from an endangered species. He died of dysentery after 48 hours, although the illness is thought to be unrelated to his cloning.
Noah was created by fusing skin cells from a gaur – a rare species of wild ox that lives mostly in India – that had died in 1993 with cow eggs stripped of their nuclei. The technique was the same as was used to create Dolly the sheep. Noah's foster mother was a cow called Bessie.
4. Przewalski's horse
In June 2008, veterinarians at the Smithsonian National Zoological Park in Washington, DC, performed the first successful reverse vasectomy on an endangered horse.
The lucky fellow, Minnesota, is a Przewalski's horse, a species native to China and Mongolia that was declared extinct in the wild in 1970. Before his transfer for the National Zoo, Minnesota's previous institution made the near-calamitous decision to vasectomise him in 1999 so that he could be kept with female horses without reproducing. Scientists later determined that he was far too genetically valuable to be kept out of the breeding programme and decided to reverse the vasectomy.
With the aid of specialists in horse anaesthesiology and Sherman Silber, a urologist who pioneered microsurgery for reverse vasectomy, the operation was a success. Minnesota's genes will increase the genetic diversity of the Przewalski's horse population, which is founded on only 14 animals.
5. Kakapo
The kakapo (Strigops habroptila) is a very unusual parrot. It can't fly, has the fat and puffy shape of a barn owl, and has a strong, sweet musky smell. It apparently evolved without any predators; accordingly, it is virtually defenceless. When European settlers introduced cats, stoats and rodents to its native New Zealand, the ground-dwelling Kakapo all but vanished.
When only 18 males were found in their native home in 1977 and populations around New Zealand were facing similar threats, a rescue plan was launched. In the late 1980s, the entire remaining population of the parrot was relocated on numerous occasions to various small islands that had to be re-vegetated and made free of feral cats and other predators.
Ralph Powlesland, a kakapo scientist, baited the birds to platforms on which he laid out grains, nuts, dried vegetables and commercial parrot feed to figure out what fatty foods they preferred. Using his results, the team have enriched the birds' diet. They also watch all nests and place electric blankets on the eggs to keep them warm when females leave the nest for food.
The population has stabilised and by 2000, was growing slowly.
6. Pyrenean Ibex
The notion of saving endangered species through cloning was taken one step further earlier this year. For the first time, a subspecies that had already been declared extinct was cloned from preserved frozen cells.
The Pyrenean Ibex (Capra pyrenaica pyrenaica) is a subspecies of mountain goat that became extinct in 2000 when the last surviving individual, a 13-year old female named Celia, was found dead. Before Celia's death, Jose Folch of the Centre for Agricultural and Technological Research in Aragon, Spain, collected and froze a sample of her skin cells.
In a process similar to the one that produced Dolly, the researchers combined Celia's nuclear DNA with domestic goat cells. This produced over 1000 embryos, 30 of which were implanted into the uterus of five domestic goats. One embryo came to term, was born and survived for a few minutes. Its lungs were malformed, which is a common problem in cloned animals.
Encouraged by this relative success, Folch and his colleagues are pursuing their attempts.
7. African Wild Dog
The African Wild Dog (Lycaon pictus) was declared endangered by the International Union for Conservation of Nature in 1990. The BioBoundary project has the pungent task of studying wild dog urine to identify the scents that demarcate territory and send a "no trespassing" message.
The hope is that these can be used to create invisible "bio-boundaries" that will keep the wild dogs away from areas where they are likely to clash with humans.
8. Black robin
Every one of the over 250 New Zealand black robins that are alive today descends from a single female, nicknamed "Old Blue" after the colour of the tag she was given by ornithologists (see The robin's return).
Old Blue was one of just seven black robins (Petroica traversi) that remained in the late 1970s. A team of conservationists led by Don Merton, then with New Zealand's Wildlife Service, were given permission to interfere in ways no one had ever dared.
Females usually lay only two eggs, but in 1979, Merton found that if it loses a clutch, it will try again, so the birds have the potential to produce many more offspring than they actually do. The team coaxed Old Blue into laying more eggs than she would normally by removing her first clutch and placing it under the foster care of another species of bird called Tomtit (Petroica macrocephala).
The method is now known as cross-fostering and has since been used to boost populations of other bird species.
