But the footage that came back took them all by surprise when it showed monkeys they had never seen before.
With virtually no photographs of the grizzled langurs in existence, it was a challenge to confirm their suspicions at first, said Brent Loken, a PhD student at Simon Fraser University in Canada, and one of the lead researchers.
The only images they had access to were museum sketches.
"We were all pretty ecstatic, the fact that, wow, this monkey still lives, and also that it's in Wehea," said Mr Loken.
The monkey, which has hooded eyes and a pinkish nose and lips, once roamed the northeastern part of Borneo, as well as the islands of Sumatra and Java.
But concerns were voiced several years ago they may be extinct.
Forests where the monkeys once lived have been destroyed by fires, human encroachment and conversion of land for agriculture and mining and an extensive field survey in 2005 turned up empty.
The next step will be returning to the 90,000 acre (38,000 hectare) forest to try to find out how many grizzly langurs there are, according to the team of local and international scientists, who have published their findings in the American Journal of Primatology.
They appear in more than 4,000 pictures captured over a two-month period, said Mr Loken, but it is possible one or two families kept returning.
"We are trying to find out all we can," he said. "But it really feels like a race against time."


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