Bornean Orangutans are now spending a lot of time walking on the forest floor, a new study has found. Researchers believe that their new behavior shows that they are trying to adapt to loss of trees in the region.

Bornean orangutans once roamed large areas of Kalimantan (Indonesia) and Sarawak and Sabah (Malaysia) on the island of Borneo, according to WWF. However, the species are now under threat as their population has dropped by 50 percent in about 60 years along with a habitat loss of 55 percent in the past two decades.

The study was conducted at the Wehea Forest in East Kalimantan region of Borneo. The region is known for the presence of many types of primates including Pongo pygmaeus morio, which is an elusive Bornean orangutan.

The expedition was led by Brent Loken from Simon Fraser University and Dr. Stephanie Spehar from the University of Wisconsin Oshkosh. The scientists installed cameras in parts of forests where these orangutans were previously spotted. This helped them capture evidence of the apes walking.

"Orangutans are elusive and one reason why recorded evidence of orangutans on the ground is so rare is that the presence of observers inhibits this behaviour," said Loken. "However, with camera traps we are offered a behind the scenes glimpse at orangutan behaviour."

Results showed that, time spent by the orangutans walking was comparable to that of a native pig, macaque, Macaca nemestrina. Over a period of eight months, pigs were photographed 113 times while the number was 110 for the orangutans.

Researchers aren't sure why the orangutans have started spending more time on ground; one reason could be the absence of large predators in the region while another could be that the apes are losing their habitats rapidly and are being forced to start walking to look for food.

"Borneo is a network of timber plantations, agro-forestry areas and mines, with patches of natural forest," said Loken. "The transformation of the landscape could be forcing orangutans to change their habitat and their behaviour."

The study is published in the American Journal of Primatology. 

According to WWF, the apes in Bornea are disappearing mainly due to loss of habitat, hunting and pet trade.