Environmentalists said they are worried about the emergence of Facebook as an online marketplace for trade in endangered species.
Wildlife monitoring network Traffic found hundreds of protected animals for sale on Facebook groups in Malaysia, including sun bears, gibbons, and binturongs, also known as bearcats.
It says this type of illegal trading is a growing threat around the world.
Facebook said it "will not hesitate" to remove content promoting such trade.
The researchers monitored 14 Facebook groups for 30 minutes daily over a period of five months. They found more than 300 wild, live animals for sale as pets.

"You often find that in trading there's a small percentage of people involved in illegal activity," said Sarah Stoner from Traffic, one of the report's authors.
"But we identified 236 posts where there was perceived illegal activity, there were 106 different sellers, that's quite a lot of different people and it shows how prevalent it is."
The researchers say the development of an online trade is surprising in Malaysia because open wildlife markets are not found in the country, unlike in other parts of Asia.
"The demand for these animals has always existed in Malaysia but it's never really had an outlet to flourish whereas the internet and Facebook seems to be providing that platform to enable the trade to happen in this manner," said Sarah Stoner.
Almost half of the species recorded were protected and illegal to sell under Malaysian law. Some 25 of the 69 non-native animals protected under the Convention on Trade in Endangered Species of Wild Fauna and Flora (Cites).
Traffic say they have shared the details of their investigation with Facebook who are looking to develop practical solutions to combat the trade.
"We are committed to working with Traffic to help tackle the illegal online trade of wildlife in Malaysia," Facebook said in a statement.
"Facebook does not allow the sale and trade of endangered animals and we will not hesitate to remove any content that violates our terms of service."
The investigators also passed on their information to the Malaysian authorities.
"We have carried out 43 successful seizures, arrested at least 54 illegal traders and saved over 67 wildlife species from being traded illegally on Facebook,'' said Hasnan Yusop, from the Department of Wildlife and National Parks, who pointed out that his colleagues have been Facebook groups selling wildlife since 2013.
''More importantly, we also want to send out a stern warning - if anyone is caught violating our law, they will face harsh penalties," he added.
Investigators are concerned that the use of social media and smartphones means that anyone interested in selling wildlife can rapidly access huge numbers of potential buyers.
They are worried that technology is opening lucrative new markets, all over the world.
"Although the findings are about illegal wildlife trade in Malaysia, we believe it reflects a worldwide problem," said Traffic's Sarah Stoner.
"Social media's ability to put traffickers in touch with many potential buyers quickly, cheaply and anonymously is of concern for threatened wildlife and enforcement agencies which demands nothing short of a concerted global response.''