Prodigal son is back and he’s on a promise

Richard Collins looks at the role zoos play in saving the orang-utans.

SIBU, Dublin Zoo’s senior male orang-utan, has returned to town, having spent the last seven years at Rhenen Zoo in the Netherlands. He was expected to become a daddy to several babies but he managed to sire only one youngster. Still, it’s better than nothing and he has other abilities. According to zoo director, Leo Oosterweghel, Sibu is an excellent vocalist; he gives a fine rendering of the ‘long call’ which male orang-utans use to defend their patch. The prodigal son will be in quarantine for about six weeks after which he will join the zoo’s three females for a happy reunion.

Orang-utans live to about the age of 40. Thirty-year-old Sibu is getting on a bit but the zoo has a younger male, away in Britain at present. These primates are in big trouble; one species may be extinct within 10 years. It’s of crucial importance, therefore, that healthy zoo populations be developed and the stud-book holders want the Dublin males to contribute their genes to the pool. Orang-utan childhoods are long and it takes time to build up numbers. It’s recommended that females in zoos should breed every seven years or so.

Orang-utan means ‘person of the woods’ in the Indonesian language; these great apes are forest dwellers. There are two species, one found in Borneo, the other in Sumatra. Sibu, who was born in Los Angeles is a Bornean. Males are much bigger than females, a mature daddy might tip the scales at 90kg. His great size is dictated by competition; males fight each other for access to females. The biggest male gets to mate with every available female in his area. Evolutionary pressure, therefore, has favoured a large body size.

Orang-utans live mainly on fruit which is fairly widely distributed. To get enough food, an orang-utan must forage alone over a wide area. Those other great apes, the gorillas and chimpanzees, live in groups where they pool their mental resources, learning tricks and skills from each other. Such opportunities are fewer for the solitary orang-utans.

Tool-use by chimpanzees was documented in the 1960s but it was not observed in orang-utans until the 1990s. The chimps are usually considered to be the Einsteins of the animal kingdom but studies by the primatologist, Carel van Schaik, have shown that orang-utans are capable of feats beyond those of chimps. Architecture is a particular skill. Orang-utans build nests in which to sleep and will construct roofs of leaves during wet weather. Mothers teach their youngsters how to construct tools and zoologists have trained orang-utans to recognise up to 40 signs.

An orang-utan born in San Diego Zoo in 1971, became famous for absconding repeatedly from an enclosure thought to be escape-proof. He would stroll around the zoo looking at the other animals but he was never aggressive to anybody.

Zoo keepers could not figure out how this Houdini managed his escapes. Surveillance was mounted, with undercover keepers posing as tourists in the hope of catching him in the act, but he seemed to know that he was being watched.

It was only when other, less careful, orang-utans began to copy him that his secret was revealed. Rock-climbers were employed to find the tiny toe and finger points which he used to scale a wall. It cost $40,000 to solve the problem.

All is not well in the forests where orang-utans live. According to the IUCN Red List, the Sumatran species is critically endangered; there are thought to be only 7,000 individuals left. About 60,000 Bornean orang-utans remain, less than 14% of the original population. The forests on which they depend are being destroyed by loggers or burned so that oil palms can be planted. The oil is sold for cooking, cosmetics and biofuels. Baby orang-utans are being captured for the pet trade.

With such a dismal outlook for orang-utans, zoos have an increasing role to play in saving these extraordinary animals from extinction. The next phase of Dublin Zoo’s development programme will include new facilities for the orang-utans and their cousins, the gorillas. The orang-utan installation will be three times larger than the present one and incorporate an island on the zoo’s lake.