Lemur in pet captivity in Madagascar. Kim Reuter/Temple University

Illegal pet trade could hasten the extinction of some species of the Earth's most endangered group of mammals, lemurs.

An estimated 28,000 lemurs have been illegally kept as pets in urban areas of Madagascar over the past three years, threatening conservation efforts and hastening the extinction of the endangered primates, says a study by Temple University researchers.

Led by Temple biology doctoral student Kim Reuter, the researchers spent three months in Madagascar surveying over 1,000 households in 17 cities and villages to arrive at the figures.

Reuter, who is one of the creators of the Lemur Conservation Network, said that although pet lemur ownership is illegal, enforcement of the law was weak.

"You see it everywhere; even government officials and the people who are supposed to be enforcing the ban on pet lemurs own them."

With at least 14 lemur species having populations of less than 10 thousand, lemur pet ownership could even cause some populations to go extinct altogether, she says.

The research findings, 'Live capture and ownership of lemurs in Madagascar: extent and conservation implications,' was published online in the international conservation journal, Oryx.

At present over 90% of lemur species are threatened with extinction, with driving factors including habitats destruction, poaching and the lack of conservation programmes.

Twenty-two of the 101 lemur species are now classified as critically endangered, with a further 48 on the endangered list and 20 classed as vulnerable.

Lemurs have been studied for insight into human sleep, as they are the closest genetic relative to humans that are known to hibernate. Fat-tailed dwarf lemurs, from Madagascar, hibernate for up to seven months of the year during winter.