Sheena Hynd had planned to spend only a few weeks at an orangutan rehab centre in North Borneo but ended up staying for four years. The 27-year-old from Balmullo, near Leuchars in Fife, had spent years studying primates but leapt at the chance of being able to observe them up close in their natural habitat. Her research was to prove invaluable for the centre, which is fighting to save the primate from extinction.

She heard about the centre while working for a charity called the Sepilok Orangutan Appeal UK. "I got an opportunity to go out with them about a year later so I jumped at the chance," says Hynd, who is still in Borneo. "It was originally meant to be for six weeks. I thoroughly enjoyed myself out there and the opportunities kept coming up to go back."

Within a short time of arriving at the Sepilok Centre in the Malaysian Sabah district of North Borneo, she was enchanted with both the animals and the people. "I've been very content out here. I've never really felt homesick. The people are so friendly from the moment you arrive - they are very interested in you and the country you come from. It's a wonderful community and I instantly felt at home here. Time went very quickly because I really enjoyed the work."

Borneo, which is divided between Malaysia and Indonesia, and Sumatra, part of Indonesia, are the only two places in the world where these so-called red men of the forest can be found in the wild. According to the WWF (World Wide Fund for Nature) the Bornean Orangutan is listed as an endangered species, with as few as 40,000 remaining in the wild.

The organisation says that the dwindling numbers are due to habitat fragmentation, illegal logging, forest conversion, illegal trade and forest fires.

In a bid to save the orangutans from extinction, the government-run Sepilok centre was established in 1964, making it the longest-running orangutan rehabilitation centre. It cares for orphans aged from a few months old to a few years.

"Rehab centres were set up for orangutans out here in Asia because the wildlife departments in Malaysia and Indonesia were getting these orphans which had come through because of land clearance - forests being cut down for cash crops - and a lot of them were coming into contact with humans and becoming known as a pest species," explains Hynd.

"Mothers were often injured, killed or scared off, leaving behind orphans. It got to the point where nobody really knew what to do with them, so that's why the rehab centres were set up, to try and return confiscated animals to the wild."

Today there are around 80 orangutans living in the reserve around the centre. It also cares for sun bears, gibbons, sumatran rhinos and elephants. When they arrive, the animals are quarantined for three months to ensure they are healthy and free from disease. In the nursery, there is a lot of cleaning and taking the animals out into the forest to practise climbing. A subsequent socialisation phase allows them to learn and develop the skills they will need when they are released.

If the centre wasn't there and able to put the animals back into the forest, they would either have died or have spent much of their lives caged. "Some of them come in very sick or injured, and if they were not given the appropriate veterinary treatment they wouldn't survive. The ones which come in healthy would otherwise have spent the rest of their life in some form of captivity, so it's an essential part of the conservation of a species."

Hynd worked with older animals, aged from five years and upwards, who had already been released from the centre. Before her arrival, there had been no research into the fate of the animals after being released from the centre. "There haven't really been any long-term detailed studies of exactly what happens to them," she says. "It's a case of releasing them into the forest. There are feeding platforms located in the reserve to allow them a gentle introduction to life on their own, but after that it's a matter of hoping they do well. The aim was to discover any problems and address them as to benefit the animals coming through the centre at the moment.

"After release, some stay close to the centre for a few days and then go off and are never seen again. Others are more cautious and stay in the area for a long time."

During her time at the centre, she came particularly close to several animals including Nini, an adolescent female. "She came in when she was around a year old and, because she had already had that time with her mother in the forest, she was always strong. While I was following her she had a little baby, her first infant. She has grown into a very big and strong animal and so has he - he is finding food for himself. It's really nice to see the orphans go on and have their own young, especially because some don't survive."

Not all the animals have such an easy time. Another female, Analisa, was less robust and spent six years at the centre, a longer time than most. "She didn't do too well in the second stage of rehab where the animals are encouraged to socialise with each other. She was getting bullied a lot and when the animals were feeding she would get picked on and wasn't getting her quota of food. She was often sickly and was treated several times for diarrhoea. Even when she was released, she came back a few times because she was underweight. She was finally released last year and is doing well, even looking after some of the younger orangutans."

Hynd believes her initial interest in wild animals was sparked by watching nature programmes as a child. "From when I was younger I'd always wanted to work with animals, but I wasn't too sure which area. From the age of 15, I realised that it was primate conservation that I wanted to be involved in." She went on to complete a degree in animal behaviour and welfare at Chester University before undertaking an MA in primate studies at Oxford Brookes College. Through her research she heard about the Sepilok Orangutan Appeal, which was set up in 2000. The charity's aim is to provide additional funding for the centre and has funded a refurbishment of the clinic and the purchase of a Land Rover to take the animals to locations further away.

After her unexpected four-year stint, Hynd is now looking for another project in the area. "I am still passionate about the work," she says. "I want to stay in conservation and I want to work with orangutans."