A male Northern Yellow Cheeked Crested Gibbons (nomascus annamensis) in Veun Sai-Siem Pang National Park in Cambodia’s Ratanakiri province. Photo: Peter Williams

A male Northern Yellow Cheeked Crested Gibbons (nomascus annamensis) in Veun Sai-Siem Pang National Park in Cambodia’s Ratanakiri province. Photo: Peter Williams

No ape jape

Jane Faure-Brac reports on why gibbons need protection from COVID too.

Jessica Williams’ home for months at a time was a wooden shack by a river with no running water or toilet, in as remote a place as it’s possible to find.

Cut off from any form of civilisation in the vast wilderness of Cambodia’s Veun Sai-Siem Pang National Park, Ms Williams, was observing wild gibbons for her PhD.

The park is one of the few remaining places on Earth where gibbons live in the wild. She’s trying to find out how these small apes are affected by the presence of tourists. No one anywhere in the world has studied this before. Ms Williams made some startling discoveries.

Rising in pitch dark before 4.30am, she would prepare for a full day in the forest.

“My guides and I would walk about 40 minutes out from the shack to this big open grass plain and we’d sit on the edge of the forest and wait for the gibbons to start calling,” Ms Williams says.

“This was my favourite part of the day. The sun would be rising, and you’d start hearing the gibbon groups singing. They’re really doing this to establish their territory.

“Gibbons are monogamous like humans; they mate for life. So, a mated pair will sing a duet together signalling that they are a strong couple, and this is their patch.

“The song doesn’t sound like anything you’d imagine; it’s more like an ambulance siren going off and it tells other groups if they try to come in, they’ll be fought off. They’re essentially saying, ‘don’t even bother to waste your energy and time encroaching into our territory’.”

When Ms Williams and her co-researchers heard a group calling, they sprinted through the forest to reach them.

“Once we found them, we’d spend all day observing them, following them and noting down their behaviour,” Ms Williams says.

“We did this just on our own and then repeated the exercise when groups of tourists were taken into the forest to visit the gibbons.”

She found the gibbons significantly alter their behaviour, to their own detriment, when tourists are present.

Instead of resting and socialising, gibbons spend more time on the lookout for danger and displaying stress and anxiety behaviours when tourist groups followed them.

“Animals monitor their environment and detect danger by scanning the landscape,” Ms Williams says. “When tourists were present, we found they spent much more time scanning.

“This was coupled with a decrease in time spent resting, which is essential for maintaining normal brain function and immune responses.

“If the gibbons’ immune system is affected it can have negative side-effects. It can shorten their life or make them more susceptible to catching diseases – and because we’re all primates, they may be able to catch something from us.”