"From there, it has either been released or escaped. The population is just exploding at the moment," said Nik Cole, a reptile expert with the Mauritian Wildlife Foundation.

The Malagasy species is a major threat to native reptiles such as the Mauritian day gecko, he told Reuters.

Other recent arrivals include the apple snail and the red-eared terrapin.

On the small Mauritian island of Rodrigues, scientists have noticed the disappearance of native centipedes since the arrival less than 10 years ago of the Indian musk shrew.

"With many exotic introductions, you don't notice an impact until their numbers reach a certain level," Cole said, echoing the warnings of many other local environmentalists.

"You have got species that are found nowhere else in the world, and they are very na ve to certain types of competition or predation, so they can very easily be wiped out," he said.

The exotic imported animals, plants and even germs out-compete or hunt native Mauritian species which evolved in a less competitive environment over millions of years.

Plants are also at risk from aggressive arrivals such as the Chinese guava, the Malagasy traveller's palm and hiptage which often smother the Mauritian trees.

"Most of the plants in Mauritius that are rare, are rare because of invasive species," Vikash Tatayah, Conservation Manager at the Mauritian Wildlife Foundation, said by phone.

His organisation has had notable success in saving endangered birds such as the echo parakeet, the pink pigeon, and the Mauritius kestrel, down to just 4 known birds in 1974, though the local broad-billed and grey parrots are extinct.

In the case of the green-feathered echo parakeet, ravaged by rats, monkeys and the loss of forests, conservationists swap eggs or chicks between mother birds to maximise their chance of survival, wrap plastic round tree trunks to deter climbing rats, and deepen holes in trunks to hide nests from monkeys.

Scientists say the world has suffered five mass extinctions in its history and a sixth is looming, linked to human activity.

Small islands like Mauritius, evolving at a distance from the larger landmasses, often developed a rich and unique biodiversity -- but in modern times find their flora and fauna threatened with extinction as a result of the growth of global travel and trade.