As human populations grow and spread, clearing patches of forest along the way, the habitat of one of mankind's closest living relatives is shrinking.

New research suggests the bonobo, a chimpanzee-like ape, avoids areas of high human activity and forest fragmentation and that as little as 28 percent of the bonobo's range remains suitable for living.

"This assessment is a major step towards addressing the substantial information gap regarding the conservation status of bonobos across their entire range," said lead author Jena Hickey of both Cornell University and the University of Georgia. "The results of the study demonstrate that human activities reduce the amount of effective bonobo habitat and will help us identify where to propose future protected areas for this great ape."

Hickey and her colleagues reported their findings in the journal Biodiversity and Conservation.

Ashley Vosper of the Wildlife Conservation Society said that for the bonobo to survivie for the next century or longer, "it is extremely important that we understand the extent of their range, their distribution, and drivers of that distribution so that conservation actions can be targeted in the most effective way and achieve the desired results.

"Bonobos are probably the least understood great ape in Africa, so this paper is pivotal in increasing our knowledge and understanding of this beautiful and charismatic animal."

The bonobo, once referred to as the pygmy chimpanzee, is smaller in size and more slender in build than the common chimpanzee. Bonobo's live in complex, matriarchal societies and, unlike common chimpanzees, they establish social bonds and diffuse tension with sexual behaviors.

The bonobo's range falls in the lowland forests of the Democratic Republic of Congo, a land currently beset with warfare and insecurity.

In mapping the bonobo's territory, the researchers found that proximity to human agricultural areas was the most important predictor of bonobo presence.

"Bonobos that live in closer proximity to human activity and to points of human access are more vulnerable to poaching, one of their main threats," said Janet Nackoney, of the University of Maryland and second author of the study. "Our results point to the need for more places where bonobos can be safe from hunters, which is an enormous challenge in the DRC."

The researchers also found that only 27.8 percent of suitable bonobo habitat lies within protected forest areas.

"The fact that only a quarter of the bonobo range that is currently suitable for bonobos is located within protected areas is a finding that decision-makers can use to improve management of existing protected areas, and expand the country's parks and reserves in order to save vital habitat for this great ape," said Innocent Liengola, WCS's Project Director for the Bonobo Conservation Project and co-author on the study.