"The largest ever release of captive chimpanzees into the wild has been declared a success. Five of the 37 chimps released in the Republic of the
Congo have bred in the wild, and only five have been confirmed dead. But the scheme was not trouble-free, and has raised questions over whether
reintroduction is the most cost-effective way of conserving chimps.
The chimps were all wild-born animals that had been rescued from markets or from owners who no longer wanted them as pets. They were initially
transported to islands away from poachers and predators by the charity Ecological Habitat and Freedom of Primates, Congo. Then between 1996 and 2001
they were released into the Conkouati-Douli National Park on the border with Gabon.
The charity's founder had always intended to return them to the wild. "She thought they deserved to have their life back," says Joanna Setchell of
the University of Cambridge, who co-led the scheme with Benoît Goossens of Cardiff University, UK. There were fears that political instability in the
region might have prevented researchers from feeding the island-bound animals, which would then have starved.
But the return to the wild held its own hazards, even in an area with only a few wild chimps. While adolescent females integrated most easily into
wild groups, males of all ages and other females were frequently attacked by wild and previously released chimpanzees.
The team documented 47 vicious attacks that left wounds all over the victims' bodies. Eight attacks on females inflicted wounds on their genitalia,
while one male lost a testicle and another two lost parts of their penises in fights. Worse, three males and one female were killed, and without
veterinary care around half of the males would have died, the researchers say.
This fits with the chimps' natural family structure. While males stay within their native group and cooperate in defending a territory, females move
to neighbouring groups when they reach around 11 years old. So chimpanzees are used to accepting new females, but attack unfamiliar males. The
researchers conclude that male chimps should not be released in areas that already have a chimp population.
The animals were fitted with radio collars, which allowed the 23 animals that stayed in the release area to be tracked. Most of the nine that left the
area probably travelled off with groups of wild chimps (see table). The biggest success was that four females bred, producing five offspring in total.
A released male called Mekoutou also bred successfully in the wild with a released female called Choupette (New Scientist print edition, 25 January
Cost per chimp
But looking after the chimps was expensive: the cost of field assistants, the radio collars and veterinary care amounted to $5200 per chimp per year.
While applauding the success, some conservationists say the money could have been better spent. "
This "release" has been declared a success but there are many questions left. What about the possibility that "human" disease was introduced into
this "wild" population? The cost per "chimp" is $5,200 per year. How many "human" children could be fed for that money?
Returning animal to the wild is a romantic gesture, but it is the "wise" thing to do?