Translations:AY Honors/Cetaceans/Answer Key/47/en
- Family Lipotidae: baiji
Lipotes vexillifer
Baiji (Lipotes vexillifer)
Where found: Yangtze River in China until extinction
Description: The Baiji (Chinese: 白鱀豚) was a freshwater dolphin found only in the Yangtze River in China. Lipotes meaning "left behind", vexillifer "flag bearer". The baiji population declined drastically in decades as China industrialized and made heavy use of the river for fishing, transportation, and hydroelectricity. Efforts were made to conserve the species, but a late 2006 expedition failed to find any baiji in the river. Organizers declared the baiji functionally extinct, which would make it the first known aquatic mammal species to become extinct since the demise of the Japanese sea lion and the Caribbean monk seal in the 1950s. It would also be the first recorded extinction of a well-studied cetacean species to be directly attributable to human influence. In August 2007, a Chinese man reportedly videotaped a large white animal swimming in the Yangtze. Although it was tentatively confirmed that the animal on the video is probably a baiji, the presence of only one or a few animals, particularly of advanced age, is not enough to save a functionally extinct species from true extinction. The last known living baiji was Qiqi (淇淇), who died in 2002.
- Family Platanistidae: South Asian river dolphin
Platanista gangetica
South Asian river dolphin (Platanista gangetica)
Where found: The South Asian river dolphins are native to the freshwater river systems located in Nepal, India, Bangladesh, and Pakistan. They can be most commonly found in water with high abundance of prey and reduced flow. The Ganges subspecies (P. g. gangetica) can be found along the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Bangladesh and India, although its range formerly extended to Nepal. A small subpopulation can be still found on the Ghaghara River and possibly the Sapta Kosi River. The majority of the Indus subspecies (P. g. minor) is located between the Sukkur and Guddu barrage in the Sind Province of Pakistan. Two smaller subpopulations have also been recorded in the Punjab and Khyber Pakhtunkhwa Provinces. Since the two river systems are not connected in any way, it is a mystery how these sub-species ended up in the two rivers. It is improbable that the river dolphins made it from one river to another through the sea route since the two estuaries are very far apart. Makes you think God put them there.
Description: The South Asian river dolphin has the long, pointed nose characteristic of all river dolphins. Its teeth are visible in both the upper and lower jaws even when the mouth is closed. The teeth of young animals are almost an inch long, thin and curved; however, as animals age, the teeth undergo considerable changes and in mature adults become square, bony, flat disks. The snout thickens towards its end. The species is effectively blind, although it may still be able to detect the intensity and direction of light. Navigation and hunting are carried out using echolocation. They are unique among cetaceans in that they swim on their sides. The body is a brownish color and stocky at the middle. The species has only a small, triangular lump in the place of a dorsal fin. The flippers and tail are thin and large in relation to the body size, which is about 2-2.2 meters in males and 2.4-2.6 m in females. The oldest recorded animal was a 28-year-old male, 199 cm in length. Mature adult females are larger than males. Entanglement in fishing nets can cause significant damage to local population numbers. Some individuals are still taken each year and their oil and meat used as a liniment, as an aphrodisiac, and as bait for catfish. Irrigation has lowered water levels. Poisoning of the water supply from industrial and agricultural chemicals may have also contributed to population decline. Perhaps the most significant issue is the building of more than 50 dams along many rivers, causing the segregation of populations and a narrowed gene pool in which dolphins can breed. Currently, three subpopulations of Indus dolphins are considered capable of long-term survival if protected.
