Africa's primates in danger

2003-04-08 14:33

Gabon - The Ebola virus and hunting have plunged gorilla and chimpanzee populations in the forests of west Africa by about half in the past 20 years, leaving the species more threatened than previously thought.

A report released by journal Nature, quoted ecologist Peter Walsh of Princeton University, New Jersey as saying "the finding that apes that live near people are in decline because of hunting confirms the long-standing suspicions of conservation workers".

"But the extent of Ebola's reach in the ape populations has taken experts by surprise. In one remote area where there is little or no hunting, it has cut the population by more than 90 percent since 1991."

Nature said Walsh reported the "populations of both species have plunged by about half over the past 20 years", and he called for the conservation status of each species to be shifted from "endangered" to "critically endangered".

The latter category covers species whose population risks declining by 80 percent in 10 years, or three generations. With an annual decline rate of 4.7 percent, "ape populations would decline by an additional 80 percent within 33 years ? a generation and one-half for chimpanzees and perhaps two generations for gorillas", the study said.

Accelerating

"Given that...decline rates have probably been accelerating during recent years, the 80 percent threshold will probably be reached much sooner."

Walsh's survey was carried out in the west African state of Gabon. But gorilla populations in neighbouring Congo ? the other remaining population stronghold of these apes in west Africa ? are thought to be experiencing similarly high mortality, Nature said.

The epidemic of the incurable haemorrhagic-fever Ebola among the animals may be a consequence of high ape population density, Nature quoted Alexander Harcourt, a primatologist at the University of California, Davis, as saying. "The normal density of gorillas is about one every two square-kilometres," he said, "but in some of these regions there are 10 in every square-kilometre."

Wildlife-disease expert Andrew Cunningham of the Institute of Zoology in London, said another possibility is that environmental changes, such as human encroachment on the forest, have brought apes and the virus into more contact, Nature said. "The mortality suggests that there has been some trigger leading to the emergence of Ebola as an important cause of ape mortality," he says. The Ebola virus is thought to reside in an unidentified reservoir species, possibly a fruit bat or other small mammal.

Nature said an Ebola outbreak in Gabon killed 50 people between December 2001 and March 2002, mostly in the remote areas where the ape disease is worst. A current outbreak in Congo has killed 120, according to the World Health Organisation. - Sapa-AFP

- SAPA