Rupert the gorilla is a survivor, 21-years-old and an imposing 250 kilos, he lives in a Congolese sanctuary with other orphans of his species, far from the reach of poachers.

Known as the Lesio-Louna reserve, about 170 kilometres north of the Republic of Congo's capital Brazzaville, it was developed to reintroduce baby gorillas, abandoned by poachers or people living near the forests, to their natural habitat.

Twice a day - at mid-morning and again at sunset - eco-guides allow curious tourists to get a peak at the gorillas, taking them on a tour of the reserve via a small boat on the Louna river.

"The reserve is bounded by three rivers," says guide Florent Ikoli, which prevent the gorillas from leaving the sanctuary.

As boat glides along the river, Ikoli points out to the eco-tourists three gorillas taking refuge on an island.

The gorillas have all been named. "We call them by their names. They know them very well," he tells the enthralled visitors.

The massive Rupert is part of the trio on the island, along with Titi and Side, who had suffered from polio around the age of six.

'They have to be fed with milk'

All three were first raised by people and abandoned. "They became orphans between the ages of six and eight. We had to rescue them and reintroduce them (to their environment) in this reserve," Ikoli says.

They owe their survival to the Gorilla Protection Project, launched in 1994 by the Brazzaville government and Britain's John Aspinall Foundation, which also sponsors a similar sanctuary in the Bateke plateau of neighbouring Gabon.

In the two countries, a third of about 60 gorillas have survived being reintroduced to their natural habitat, according to officials.

The Lesio-Louna reserve is currently home to four baby gorillas, brought to the sanctuary over the past two years, says Luc Mathot, coordinator of the primate reintroduction project.

"The little gorillas are between two to four years old and still sleep in cages.... They have to be fed with milk until the age of six and then they are released into the forest," he explains.

Not all of the gorillas, however, make it to Rupert's ripe maturity.

"There are some baby gorillas which cannot handle their reintroduction and unfortunately die," says Mathot.

"While they are aggressive, gorillas are basically vegetarian, unlike chimpanzees" - animals that are omnivores and can "even devour small antelopes," he says.

The gorilla diet, he says, generally consists of forest fruits, papaya, pineapples, avocados, mangoes, cucumbers and the shafts of banana trees. c, especially in comparison with the neighbouring Democratic Republic of Congo facing a rebellion in the east of the country.

Still the gorilla population of Congo and Gabon, which numbered at least 100 000 in early 2000, has suffered from disease like the Ebola virus.