15 March 2012 Last updated at 02:47

Silky sifakas fight for survival in Madagascar

Silky sifaka in the trees of Marojejy National Park (c) Tuppence Stone

Silky sifakas, which live in the rainforests of Madagascar, are critically endangered, with as few as 300 individuals remaining. A team of biologists is undertaking an emergency effort to protect and study the primates.

Female silky sifakas give birth to only one baby every two years, and are fertile for just one day a year.

Erik Patel holding a silky sifaka (c) Tuppence Stone

Dr Erik Patel from Duke University in North Carolina, US, studies these troubled primates in Madagascar. In the UK, his work features in the BBC Two's Natural World: Madagascar, Lemurs and Spies on Thursday 15 March at 20:00 GMT.

Researchers give a silky sifaka a medical check (c) Tuppence Stone

Dr Patel's team have been studying a troop found living in a disturbed part of the rainforest. This animal was darted to allow the researchers to take blood samples before it was fitted with a radio collar.

Silky sifaka receiving shots (c) Tuppence Stone

The radio collars allow researchers to follow the the silky sifaka troop and find out how they cope in parts of the forest affected by illegal logging.

Silky sifakas have a very complex diet - feeding mainly on leaves and seeds, but also fruit and flowers. This is one of the reasons they are especially vulnerable in the face of habitat loss.

Erik Patel heading upriver in Marojejy National Park on a boat (c) Tuppence Stone

Dr Erik Patel is involved in trying to protect the rainforest from the illegal logging of ebony and rosewood trees: "The only way to save silky sifakas is to save the few remaining patches of forest where they are found."

Illegal loggers set up camp in the Marojejy National Park (c) Toby Smith

Illegal logging reached crisis point in 2009 after a political coup. In the chaos, there was no longer any protection for Madagascar's remote national parks. As a result, organised gangs took to the forests and cut down valuable ebony and rosewood trees, worth up to US$4,000 (£2,550).

Logger illegally chopping rosewood in Marojejy National Park (c) Toby Smith

The US Environmental Investigation Agency started to track where illegally cut wood was being exported. US guitar maker Gibson was raided, with federal agents seizing a shipment of Madagascan ebony. The firm is now facing legal action.