Vaquita – Last Chance for the Desert Porpoise

The Yangtze River Dolphin (Baiji)
Family – Lipotidae
Genus – Lipotes
Species – vexillifer

Although baiji had been known to be the most critically endangered cetacean species in the world for the last 2-3 decades, it wasn’t until last year that a full scale, range wide survey was organized to try to estimate the number of remaining baiji. The survey was meant to be a prelude to capturing several baiji and starting a captive breeding program.

Description

In Chinese folklore, the baiji was dubbed ‘Goddess of the Yangtze’, a beneficent animal once revered by the fishing people of the river. The species was declared a National Treasure of China and has been a protected species since 1975.
The baiji was a very shy and graceful freshwater dolphin, with a rather stocky body, roughly the size of an adult human. It was bluish-grey in color becoming whitish on the underside. Like all river dolphins, it had a very long, narrow beak with a slightly upturned tip, and small eyes placed high up on the face. The dorsal fin was positioned low on the body and was triangular in shape and the flippers were wide and rounded. Females were larger than males; they grew over 7.5′ long and could weigh over 500lbs. The baiji’s Latin name Lipotes, derives from the Greek for ‘left behind’.

Life History

There are no historical estimates of baiji abundance. By the 1970’s, when the first surveys occurred, the population had already started declining, and that decline continued through the 1980s and 1990s. The list of factors that contributed to the decline included a tremendous increase in shipping traffic, but the main threat, as is the case for all small cetaceans in coastal areas was undoubtedly incidental mortality due to fishing gear.

Social Structure and Behavior

We know very little about the biology of baiji. Because the baiji was so rare and extremely shy, observation of them in the wild was difficult. In fact, you can read all that was ever been written about it in a couple of hours. It traveled in small groups of four to five animals, fed on fish, preferred the deeper, slower water in the river and foraged among eddies downstream of islands and tributaries. A recent study found that they often swam with finless porpoises (Neophocaena phocaenoides), the only other cetacean in the Yangtze River, which is also threatened (classified as Endangered on the IUCN Red List). They were most active through the night from early evening to early morning. When surfacing to breath, baiji broke the surface of the water without creating a splash.

Distribution and Migration

Historically, baiji was confined entirely to the Yangtze River drainage, from Yichang just below the Three Gorges Dam, down river to the Shanghai estuary near the Pacific Ocean – a distance of about 800 miles. Above Three Gorges and the Dam, the current was apparently too swift for baiji.

The Cause of Extinction

Humans have inhabited the Yangtze River for thousands of years. Over the millennia, their habitat was greatly modified for agriculture and flood control. In recent decades, the Yangtze River has become one of the world’s busiest waterways and is subject to a great range of human pressures that had a devastating effect on the baiji. Currently 10% of the world’s population inhabits the Yangtze River Valley- this means the tremendous amount of economic activity along the river including shipping traffic, construction, pollution, and illegal fishing is truly astonishing.
In the midst of all this industrial activity the artisanal fishing goes on as it has for hundreds of years, with dolphins being caught in nets and on ‘rolling hooks.’ This is probably what ultimately caused the demise of the baiji – fishermen feeding their families.

River Dolphins

• Yangtze River Dolphin (Baiji) – Lipotes vexillifer
• Ganges and Indus River Dolphins – Platanista gangetica
• Amazon River Dolphin – Inia geoffrensis
• Franciscana – Pontoporia blainvillei

River Dolphin Distribution

River dolphins are a disparate group of four species of cetacean. You will notice from the Latin names in italics that each of these dolphins belong to different genera, in fact they each belong to separate families, – there is a lot of mammalian evolution represented among this group.
This leads to further intrigue, as not all river dolphins are found in rivers, and not all dolphins that live in rivers are river dolphins. Only three of the four species actually live in rivers.

River dolphins have very long beaks, are slow swimmers so they have rather floppy appendages, usually have a reduced dorsal fin, nondescript color patterning, and a vestigial eye with reduced ability to see. All of these features are considered adaptations to living in a riverine environment where the water is typically shallow and very turbid.

Until recently there were 4 species of river dolphins that lived in 3 major river systems. In December 2006, the Yangtze River Dolphin, called the baiji (pronounced ‘bye gee’) was declared functionally extinct, the first cetacean species to go extinct in modern times as a result of human activity.