A remotely controlled camera set up in a forest in Sabah state on Borneo captured a still picture of the rhino on Feb. 25, said Raymond Alfred of the World Wildlife Fund.
It is the first such image in the wild of a female thought to be pregnant, providing cheer to conservationists after the initial failure of a breeding-in-captivity program for the Borneo Sumatran rhino, whose numbers are believed to have dwindled to less than 30.
"The size (of the rhino) is quite extraordinary," Alfred told The Associated Press. "Based on the shape and the size of the body and stomach," it would appear that the rhino is pregnant.
But it is difficult to be conclusive on the basis of the picture alone, he said.
Another 50 cameras have been set up in the area to gather more evidence about the female, which appears to be 20 years old, he said, adding that researchers were also trying to find its dung for analysis.
Government officials and WWF experts had set up the first camera in January and retrieved it last week, Alfred said.
The picture shows the Borneo Sumatran rhino - a subspecies of the bristly, snub-nosed rhino native to Indonesia's Sumatra island - wallowing in the soil to cool off and protect her body.
"The most important thing now is to ensure that this area is protected from logging activity," he said, declining to disclose the rhino's exact whereabouts.
Malaysia's Borneo Sumatran rhino population has declined from some 200 about a half-century ago as they are hunted for Chinese medicine and crowded out through deforestation and palm oil plantations. Conservationists have warned the rhinos could face extinction in the next 10 years.
Alfred said conservationists have tried but so far failed to rescue isolated rhinos that have been cut off from the rest by deforestation and make them breed.
Only one male rhino named Tam was rescued in the last two years. It was hoped Tam would mate with a female in captivity, but she turned out to be too old to reproduce, Alfred said.