Sumatran rhinoceros could once be found through India, China and Southeast Asia. Today, the range of the critically endangered species is constantly shrinking.

Recently, researchers announced the extant species can no longer be found in the wilds of Malaysia. Now, only three wild populations remain, all on the island of Sumatra.

According to a new report by researchers at the University of Copenhagen, no Sumatran rhinos have been spotted on the Malay Peninsula since 2007 -- aside from two females, which were captured and transported to a captive breeding program.

There are now fewer than 100 wild Sumatran rhinos in Indonesia, researchers report.

"It is vital for the survival of the species that all remaining Sumatran rhinos are viewed as a metapopulation, meaning that all are managed in a single program across national and international borders in order to maximize overall birth rate," Rasmus Gren Havmoller, a researcher at Copenhagen's Center for Macroecology, Evolution and Climate, explained in a press release. "This includes the individuals currently held in captivity."

Havmoller is the lead author of a new report on the health of the Sumatran rhino, published in Oryx, the International Journal of Conservation.

The study's authors say more intense management and protection of the rhinos' breeding grounds are necessary to save the species from extinction.

"Serious effort by the government of Indonesia should be put to strengthen rhino protection by creating Intensive Protection Zone (IPZ), intensive survey of the current known habitats, habitat management, captive breeding, and mobilizing national resources and support from related local governments and other stakeholders," researchers write in the new report.

The Sumatran rhino, also known as the hairy rhinoceros or Asian two-horned rhinoceros, lost much of its habitat during the 1980s to logging. Poaching further exacerbated their decline. Today, the main problem is isolation, as males and females have trouble finding each other to breed as deforestation and development continue to carve up the wilderness.