- Dolphin in Bangladesh Sundarbans Photo
- WCS marine biologists have identified Bangladesh's estuarine, coastal, and oceanic waters as a "hot spot" for cetaceans, marine mammals that include whales, dolphins, and porpoises.
- Looking at Dolphins Photo
- In 2009, WCS scientists discovered that about 6,000 of the rare Irrawaddy dolphin inhabit the Sundarbans mangrove forest and the adjacent waters of the Bay of Bengal.
- ©Brian Smith
- Surveying in Coastal Waters Photo
- WCS researchers surveying Irrawaddy dolphins in order to scientifically estimate their population numbers.
The recent discovery of a huge population of rare dolphins in the Indian Ocean was the kind of news conservationists live for. WCS researchers reported in early 2009 that nearly 6,000 Irrawaddy dolphins—marine mammals that are related to orcas, or killer whales—were living in freshwater regions of Bangladesh’s Sundarbans mangrove forests and the adjacent waters of the Bay of Bengal.
The dolphins, which are threatened by climate change, habitat changes, and other factors, have been the focus of limited research, and it is unknown how many remain worldwide. Prior to the discovery, the largest known populations numbered in the low hundreds.The discovery reaffirms that Bangladesh is an important sanctuary for the species, and emphasizes the need for conservation in the country’s marine ecosystems.
- Irrawaddy dolphins were placed on the IUCN Red List of endangered species in 2008, based on documented declines in known dolphin populations.
- The dolphins grow to about 6.5 to 8 feet in length and frequent large rivers, estuaries, and freshwater lagoons in South and Southeast Asia.
Despite the discovery of the extraordinarily large Irrawaddy population in the waters of Bangladesh, WCS researchers warn that the species is increasingly threatened by accidental entanglement in fishing nets. Researchers reported finding two dolphins that had become entangled and subsequently drowned in fishing nets—a common occurrence, according to local fishermen. Another study concluded that the dolphins are threatened by declining freshwater supplies caused by upstream water diversion in India, coupled with sea-level rise due to climate change. The same circumstances also threaten Ganges River dolphins, an endangered species with a range that overlaps that of the Irrawaddy dolphins in the Sundarbans mangrove forest. The Yangtze River dolphin, or baiji, a type of freshwater dolphin, is thought to be extinct due to the impact of humans.
In 2006, WCS helped establish a protected area along Myanmar's Irrawaddy River to conserve this critically endangered marine mammal population. In Bangladesh, WCS is working on establishing a similar protected area network for both Irrawaddy and Ganges River dolphins in the Sundarbans mangrove forest.
WCS is tracking shifts in the distribution of freshwater and coastal dolphins. Ultimately, these studies will alert scientists to environmental changes in the Sundarbans and its offshore waters. For the local communities that depend on the same resources—fish and fresh water—this early-warning system could provide them with time to adapt.
Beyond the Sundarbans and adjacent coastal waters, WCS recently discovered a rich variety of deep water cetaceans in a submarine canyon called the Swatch-of-No-Ground, located just 25 miles from the mangrove forest. Recent studies examining the impacts of climate change on these species indicate that the canyon’s highly productivity, cool waters could serve as a vitally important refuge for them. WCS is now working to include the Swatch as part of the protected area network.
From the Newsroom
WCS’s Bangladesh Cetacean Diversity Project promotes public awareness of two threatened dolphin species in the Sundarbans.