It's hard to believe there are still places on Earth that haven't been fully explored. And yet this week brings news that conservation teams working in jungles in Bangladesh and Borneo have discovered previously unknown populations of two critically endangered species, the Irrawaddy dolphin and the Bornean orangutan.

In Bangladesh, the news is especially good, as the Wildlife Conservation Society (WCS) reports finding nearly 6,000 Irrawaddy dolphins (Orcaella brevirostris) in the fresh waters surrounding the Sundarbans mangrove forest and in the nearby Bay of Bengal, areas where the WCS says little marine mammal research has previously been conducted. This discovery nearly doubles the estimates of the worldwide population for the rare dolphins, and represents the largest single population of the species. According to the WCS, known populations of Irrawaddy dolphins prior to this study numbered in the low hundreds or fewer. The species is listed as critically endangered on the IUCN Red List of Threatened Species.

The WCS, headquartered in Bronx, N.Y., says it is currently working closely with Bangladesh's Ministry of Environment and Forests to establish a protected area for Irrawaddy dolphins in the mangrove forest. The group helped to establish a similar conservation area along the Ayeyarwady River in 2006.

But WCS says more funding will need to be raised from private and government sources to establish this protected area and to keep studying the dolphin and its habitat. It warns that the dolphins are threatened by fishing – they tend to get entangled in nets – and by declining freshwater supplies brought about by dams and climate change.

The news was announced yesterday at the First International Conference on Marine Mammal Protected Areas in Maui, Hawaii; the study is set to be published in the Journal of Cetacean Research and Management. A companion paper about declining freshwater supplies and the effect that will have on dolphins and similar cetacean species appears in the March/April issue of Aquatic Conservation: Marine and Freshwater Ecosystem.

Meanwhile, an expedition funded by The Nature Conservancy, headquartered in Arlington, Va., has reported finding a new population of orangutans (Pongo pygmaeus) deep in the heart of a two-million-acre forest in Borneo's East Kalimantan Province. The team found 219 orangutan nests in an area where orangutans were not previously believed to live. "It is quite likely that this area has a population of several hundred orangutans, possibly more than a thousand," Erik Meijaard, senior ecologist for The Nature Conservancy in Indonesia, writes in the organization's blog, Cool Green Science.

Orangutan populations on Borneo are currently estimated at fewer than 50,000 by the IUCN Red List. The Bornean orangutan's cousin, the even rarer Sumatran Orangutan (P. abelii), has an estimated population of just 7,300 animals.

If this new population proves to be as large as Meijaard believes, it would be a big boost for the critically endangered ape. The population's isolated location could also be of help, since orangutan habitats throughout Indonesia are being lost to the timber industry or palm-oil plantations.

Image courtesy of Wikimedia Commons/Miraceti