User:HallieOberg/Yangtze finless porpoise

Lead
The Yangtze finless porpoise (Neophocaena asiaeorientalis) is one of eight species of toothed whale in the family Phocoenidae. It is endemic to the Yangtze River in China, making it the country's only known freshwater cetacean following the possible extinction of the baiji (Lipotes vexillifer). The Yangtze finless porpoise is considered critically endangered and it is estimated that only about 1,000 remain. This small toothed whale faces many of the same threats that caused the baiji dolphin to possibly be extinct. The Yangtze River has a high traffic rate of human activity causing population declines due to illegal fishing, pollution, vessel traffic, and dam construction. Due to the rapidly declining population the Chinese Government and other conservation charities are working to help save them from extinction.

Article body
Taxonomy:

The Yangtze finless porpoise is considered a freshwater cetacean (whales, dolphins, and porpoises that live in a variety of aquatic habitats). The finless porpoise originally inhabited salt water niches along the coast of the Indo-Pacific Ocean. However, a population dispersed into the fresh water environment of the Yangtze River. Recent studies have found that the East Asian finless porpoise (N. sunameri) and the Yangtze finless porpoise (N. asiaeorientalis) have had separate reproduction and gene flow for thousands of years. The East Asian finless porpoise and the Yangtze finless porpoise were formerly considered one species going by the scientific name of N. phocaenoides, but genetic studies support the Yangtze finless porpoise being a distinct species, or at least an incipient one, due to the lack of gene flow.

Names:

In Mandarin Chinese, it is known as jiangtun (Chinese: 江豚, p jiāngtún, lit.  "river piglet").

Description:

A finless porpoise can grow up to 2.27 m (7 ft 5 in) in length and weigh up to 71.8 kg (158.3 Ibs), however, most are smaller than this. The average adult is usually between 5 ft - 6ft and weighs around 100 Ibs. Females are normally smaller than males. Flippers are curved and pointed at the end and relatively large, about 20% of the total body length. As denoted by the name, they have flat backs and are completely finless. Instead of a dorsal fin, these porpoises have a dorsal ridge or "groove" that is covered in varying rows of tubercles. These tubercles are round in shape and raised. They are said to have some kind of biological and mechanical function. The amount of rows of tubercles and dorsal ridge sizes vary depending on the species and location of the porpoise. The East Asian finless porpoise and the Yangtze finless porpoise usually have a higher and narrower ridge with only 1 - 10 rows of tubercles, as for the Indo-Pacific finless porpoise (''Neophocaena phocaenoides) tends to have a lower and wider ridge with 10 - 25 rows of tubercles. In addition to this, body color also varies depending on habitat location and age. Newborn Yangtze finless porpoise's and East Asian finless porpoise's tend to be a dark gray or black color, that lightens within a few months to a lighter gray. However, the Indo-Pacific species has a reverse trend, in which newborns are light in color and get darker with age. After death Yangtze finless porpoise's usually become black in color. It is also very common for there to be lighter patches of color around the mouth and genitals, however this is more noticeable at a young age. These cetacean's have unique foreheads because they have a very steep forehead and no beak.'' In addition to this they also have an unfused neck vertebrae that allows free head movement. They are stocky in the middle body which then tappers towards the tail, but in general they are more slender in shape than most other Phocoenidae. They are considered a cetacean because they possess teeth, they have 15 - 22 pairs of teeth on the upper and lower jaw.

Habitat:

The Yangtze finless porpoise is found in the main body of the Yangtze River and in connecting lakes. They are exclusive to fresh water, making them different from other finless porpoises. They tend to be found in shallow bay areas, swamps, and estuaries year round, as they are not a migratory species. However, there has been distribution changes seasonally, in the winter the highest distribution was found in the middle and lower regions of the Yangtze River. Their preferred climate is tropical or warm temperatures.

Diet:

The diet of the Yangtze finless porpoise may vary according to the season and the dominant prey of the season. This variation in their diet suggest that the Yangtze finless porpoise may be opportunistic feeders. Among the fishes in their diet, the most common are Coilia brachygnathus, Pseudobrama simoni, Pelteobagrus nitidus, and Hemiculter bleekeri.

behavior:

They tend to be shy and do not come to the surface often when there is human activity nearby. They are usually most active when eating and usually spend most of their time near river banks or at the merging of two waterways. Yangtze finless porpoises travel in small groups of about 3 - 6, however groups of 20 have been reported. A radio-tracking study confirmed that the average diving behavior consisted of one long dive followed by two shorter dives. These longer dives were more common during the day time. At night the Yangtze finless porpoise's tended to go into sleep cycles. Although, it is not heavily confirmed, there has been multiple mentions of mothers carrying calves on their backs.

References