Author of the picture: Whymper and P. Smit Lydekker, Richard. This work is in the public domain.
Ganges River Dolphin
(Platanista gangetica gangetica)
INFORMATION AND CHARACTERISTICS.
It is one of two subspecies of the South Asian river dolphin (Platanista gangetica), and it has the title of the national aquatic animal of India, where is also called Ganges susu or shushuk.
HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.
The Ganges River dolphin and its closely related subspecies, the Indus River dolphin, have an appearance quite different from that of oceanic dolphins. Specifically, this species has the following characteristics:
Morphology.
It has a robust body with an asymmetrical skull, a protruded front, and a very flexible neck. Its long snout measures almost 20 percent of its body length and in adult females is even longer than that of the males. It has a small crest on the melon.
The dorsal fin is a little triangle with a broad base, and the longer pectoral flippers are flat. Its eyes are tiny.
Order: Cetacea
Family: Platanistidae
Genus: Platanista
Species: Platanista gangetica
Weight and size.
An adult has a length between 2 and 2.2 meters, and it has an approximate weight of 51-89 kilograms.
Skin Coloration.
The body has a dark gray or brown color, with a lighter color in the ventral area.
Distinctive characteristics.
It’s hard to differentiate a Ganges River dolphin from an Indus River dolphin, but the former species has a slightly longer tail than that of its relative.
WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.
The Ganges River dolphin distribution is limited to the east of India. It inhabits the freshwater system Ganges-Brahmaputra-Megna (GBM) and the Karnaphuli-Sango river systems, and their tributaries, which run through Nepal, Bhutan, and Bangladesh.
It Inhabits large sections of these rivers or their tributaries from the tidal zone to the foothills of the Himalayas, the Cachar Hills (District of India) and the Garo Hills of Meghalaya (Indian state). During the flooding season, this dolphin leaves the main canals and reach the temporary tributaries and flooded lowlands.
It is most frequently found in bodies of countercurrent water located between the convergence of channels and meanders (pronounced curves) and occasionally go to channels and reservoirs. Their habitat has a depth of 3 to 9 meters, and water temperatures between 8 and 33 Celsius degrees.
WHAT DO THEY EAT? DIET AND EATING HABITS.
The Ganges River dolphin has a carnivorous diet which includes a large variety of fish and invertebrate animals; perhaps it is also capable of consuming birds and turtles. These are some of their usual prey:
– Common carp.
– Gobio.
– Prawn.
– Freshwater sharks.
– Mahseer fish (Family Cyprinidae).
– Shrimp.
Although it has visible teeth in the jaws, it does not use them to chew but to hold their prey firmly. Its eyes are not useful to find food because in the muddy waters of its habitat they are not required, that is, it is an animal functionally blind, so it uses echolocation to detect prey.
This dolphin usually swims with a fin touching the riverbed to feel the sediments since animals hide there. Its snout is very useful for this. Once it finds a suitable prey, it holds the victim with the jaws and begins to swallow it whole starting from the head so that the scales (if the prey has them) do not hurt its throat.
It does not always look for food at the riverbed. Its most common practice is finding a school of fish near the surface and drag them to the bottom to eat them.
HOW DO THEY BEHAVE? BEHAVIOR.
The maximum speed that this dolphin reaches when swimming in its natural habitat is 27 kilometers per hour.
This dolphin has a shy, quiet and rather passive behavior. It swims alone or with 1 or 2 more individuals (pods may have 2-10 members) and rarely gather in large groups although some people report sightings of groups with up to 30 members. It is probably a semi-gregarious and territorial animal since sometimes it chases other dolphins aggressively. Their leaps out of the water are related to reactions to aggressions or external disturbances.
The primary function of the sense of echolocation in this species is searching for food rather than communicating. An unusual behavior observed in this species is the habit of swimming sideways, especially to the right. The reason is unknown. The maximum speed that reaches when swimming in its natural habitat is 27 kilometers per hour.
During the rainy season, this dolphin ventures into the tributaries of the river and returns to the main canals in the winter.
HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.
The Ganges River dolphin mates throughout the year and not in any specific season. The first breeding occurs between six and ten years of age and females give birth once every 2 or 3 years. It is a relatively large interval that, together with the late maturation, produce a low natality rate that does not contribute to increasing the number of individuals in the wild.
It is not known the process of courtship and mating, and a calf is born 8 to 12 months after the intercourse more frequently between December and January and between March and May. Maternal care is presumed to be similar to that of other dolphin species, but in this case, after weaning (1 year after birth), the offspring do not maintain ties with its mother.
WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.
Conservation status: “Endangered.”
As is frequently the case in the world of dolphins, the greatest threat to this species are humans who, looking for their meat and oil, have hunted them for many years putting them close to extinction.
According to the Red List Of the International Union for the Conservation of Nature (IUCN), this subspecies has a conservation status of endangered.
These dolphins do not have many predators in their habitat, so most of their threats are anthropogenic like:
– Dam construction.
These structures separate different populations of the same species which reduces the genetic diversity and the amount of mature individual available to mate.
– Bycatch.
They are sometimes trapped or entangled in fishing nets and other devices which are not intended to hunt these cetaceans.
– Pollution.
The contamination of the Ganges river comes from chemicals, garbage, residual waters and industry spills.
There are less than 2,000 Ganges dolphins left in the wild and a few time to help them survive in this challenging context. But the cause is not entirely lost, as the Indian Wildlife Protection Act looks for the protection of this species as a priority. Also, international organizations such as the WWF (World Wide Fund for Nature) have established programs to move from theory to practice and reduce the degradation of this dolphin’s habitat.
References
http://www.iucnredlist.org/details/41758/0
Rashmi Sanghi. Our National River Ganga: Lifeline of Millions. Springer Science & Business Media, 2013.
http://s3.amazonaws.com/academia.edu.documents/46348097/Sources_and_Accumulation_of_Butyltin_Com20160608-24155-1njpezf.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1489183099&Signature=0jehfoy3PH4ix9VZ15G6QKFQMVU%3D&response-content-disposition=inline%3B%20filename%3DSources_and_accumulation_of_butyltin_com.pdf
Mammals in the Seas: Small cetaceans, seals, sirenians and otters. Food & Agriculture Org., 1978.
http://animaldiversity.org/accounts/Platanista_gangetica/