Author of the drawing: Alessio Marrucci.
Chinese River Dolphin or Baiji Dolphin
INFORMATION AND CHARACTERISTICS.
The Chinese river dolphin or Baiji is the rarest freshwater cetacean of all. This affirmation has little to do with their physical appearance and their rare sightings, given the great danger that runs in their natural habitat. In fact, since 2006 nobody has seen a specimen alive, so presumably is already extinct.
Its name in Chinese, Baiji, means “white dolphin” and is known by the nickname of “the goddess of the Yangtsé,” regarding the river that inhabited.
HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.
This river dolphin is small, with a body fully adapted to life in freshwater systems.
Weight and size.
There is sexual dimorphism since adult females are slightly longer than males. The male length is on average 2.3 meters, and the female is 2.5 meters. Their weight ranges between 135 and 320 kilograms.
It has a fusiform body like the other species of dolphins, but more robust. It has a small head with a prominent melon. The skull is devoid of maxillary ridges. The eyes are quite small in comparison to those of the oceanic dolphins, and this is because in the muddy water of its habitat they do not need to have good visibility. Their round pectoral flippers are very long, and the dorsal fin is short, triangular and situated in the posterior part of the dorsum.
It exhibits countershading characterized by bluish-gray color in the dorsal region and white in the lower part of the body.
When this dolphin swims just below the surface of the river, its small dorsal fin protrudes and resembles a flag, so the locals call it “white-flag dolphin.” Another way to recognize the Baiji dolphin is by observing its very long and narrow beak which has the tip curved upwards.
WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.
This species is endemic to the Yangtze River in China but also lived in the Poyang and Dongting lakes of the same country some time ago. Its distribution range extends from the mouth of the Yangtze River to the Gezhouba dam. The last sightings occurred in the middle and lower parts of the Yangtze River.
It inhabits only fresh water and has a marked preference for the tributaries of the river and where there are swirling sandbanks.
WHAT DO THEY EAT? DIET AND EATING HABITS.
The Baiji is a carnivore that feeds on a variety of small fish. It uses its long “beak” to explore the muddy riverbed and detect hidden prey since its vision is not very good. However, it has a highly developed sense of echolocation.
It submerges for 10 or 20 seconds, catch its food and comes back to the surface. It probably does not has preferred prey, but prioritize the capture of large animals.
HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.
Evidently, there is not enough information about this dolphin. The mating system of the Baiji is unknown, but there are two mating seasons per year; The first during the spring and the second during the summer. The highest reproduction time occurs during the first half of the year.
These dolphins reach sexual maturity between 4 and six years of age. After mating, the pregnant female has a gestation period of 10 to 11 months although other estimates indicate that it can be 6 and up to 12. Deliveries occur between February and April, and the offspring are born with a length of 1 meter.
The mother provides dedicated care to the newborn calf helping it to reach the surface to breathe, teaching it to catch food and keeping it close to her, even after weaning.
HOW DO THEY BEHAVE? BEHAVIOR
This cetacean is rather timid, and that is why it is so difficult to observe in its natural habitat. This fact gives hope about its possible extinction.
They usually live in small groups of 3 or 4 dolphins or pairs; The largest pod on record was 16 members. Occasionally they are associated with finless porpoises (Neophocaena phocaenoides), cetaceans of fresh water that also undergo a severe decrease of population.
The groups spend most of the day in water swirls looking for food, but they are more active during the nights and until the mornings. They usually rest in areas of slow currents. They communicate by whistles and clicks. They use the latter when they identify prey or other objects in their environment.
Their dives are shallow, boats have seen them on very few occasions. If they come to the surface to breathe, they do it with minimal splashing. Their breathing intervals are short: they last between 10 and 20 seconds; Maximum of 200 seconds.
WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.
Conservation Status: Extinct.
The populations of Chinese river dolphins dramatically began to decrease since China became industrialized. Many cities prospered on the banks of the Yangtze River, and this situation affected the endemic species.
At the beginning of the 1980s, there were approximately 400 specimens. A few years later the number was reduced to 300. By the end of the decade of the 1990s there were 13 individuals, and by 2006, researchers did not find a single Baiji dolphin in the river, so it is possible that it is extinct in the wild. A sighting report in 2007 restored the hope, but unfortunately, the existence of a few individuals is not enough to save the species.
The main threats that Baijis faced and took them to the extinction were:
– Illegal fishing. Using electricity and rolling hooks.
– Overfishing. An activity that reduced the number and diversity of available food.
– Contamination produced by companies and factories near the river.
– Collisions with boats.
– Construction of dams that split populations.
This dolphin is protected in China since 1975 and in 1986 Chinese biologists established protection strategies. They even created a dolphin reserve along the Yangtze (Baiji Xin-Luo National Reserve), but obviously, it was too late to get results. Currently, the patrol boats of the reserve are responsible for supervising the compliance of the protection measures and investigating sightings and deaths of species that inhabit the river, but sadly these dolphins are not there anymore.
William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 71.