What kind of animal is a dolphin that belongs to the river dolphin family? We will explain its long length, body, characteristics, distribution, ecology, habitat, and types. These include the Ganges river dolphin and the Indus river dolphin, both of which are designated as endangered species, so they are in a very critical situation. Therefore, I will explain in detail.
What is the dolphin family? About basic status
The dolphin family is classified as an artiodactyla (some say it is a cetacean artiodactyla) among dolphins. It is also called the Ganges river dolphin family. The scientific name is Platanistidae. It has a long body, measuring 2-2.2m in length. It is a chordate that appears in encyclopedias, and data shows that it lives in estuaries. Males are larger than females.
| Japanese（和名） | カワイルカ |
| English（英名） | river dolphin |
| scientific name(学名) | Platanistidae |
| classification（分類） | Mammalia、 Cetartiodactyla、Platanistidae 哺乳綱、鯨偶蹄目、カワイルカ科 |
| IUCN Status(保全状況) | ENDANGERED |
| Length（体長） | 2-2.2m |
| Weight（体重） | ? |
About classification
The river dolphin family was thought to consist of the Amazon river dolphin family, the La Plata river dolphin family, and the European river dolphin family, but all of these river dolphin families were considered to be common dolphins. Currently, the classification is as follows.
| Name (名前) | Scientific Name (学名) |
| ganges river dolphin ガンジスカワイルカ | Platanista gangetica |
| Indus river dolphin インダスカワイルカ | Platanista minor |
Platanista gangetica
The Ganges river dolphin is a species of toothed whale that belongs to the Cetacean artiodactyla family. It has a large body that can reach up to 2.6 meters and is blind. We are active on the Ganges River in India, Bangladesh, Nepal, etc. Unfortunately, it is listed as an endangered species.
Platanista minor
The Indus River Dolphin lives in the Indus River. Cannot see up to 2.6m. It is rarely seen because it prefers the deepest parts of rivers. This species is also listed as endangered. It is able to quickly catch fish using its elongated snout.
Where is its habitat?
The river dolphin family lives in waters around India and Bangladesh in Asia.
- Geographic Distribution
Living primarily in coastal areas of Asia
Around Japan, they are found in the following areas:
Sea of Japan coast (coasts of Honshu and Hokkaido)
East China Sea coast
Seto Inland Sea
Some inhabit inland bays such as Tokyo Bay and Osaka Bay
Also found in Southeast Asia, the coast of China, Indonesia, and Vietnam
- Habitat
Prefers coastal and estuary areas
Inland bays and estuaries with shallow waters and relatively calm waves
Living in schools
Moves in small schools (approximately 10-30 individuals)
Sensitive to water temperature and salinity
Can also live in estuaries where freshwater and seawater mix
- Habitat Characteristics
Feeds on fish and crustaceans in shallow coastal waters
May prefer muddy or sandy seabeds
Vulnerable to environmental changes (estuary reclamation and water quality deterioration)
feature is? What kind of creature is it?
River dolphins typically swim alone or in pairs. They have a very social personality and tend to live in groups.
- Body Size and Shape
Body Length: Approximately 1.4-2.0m
Weight: Approximately 40-60kg
Body Type: Small, stocky, and rounded
Dorsal fin: Low, triangular, and inconspicuous
- Body Color
Body color: Gray to pale blue-gray
Dark back, slightly whitish underbelly
Unlike other dolphins, they lack large markings and are relatively plain
- Face, Mouth, and Teeth
Rounded head, short snout
Fine teeth, adapted to preying on fish and small crustaceans
- Behavior and Personality
School Life
Forms small schools (approximately 10-30 individuals)
Relatively cautious
Shy of boats and humans, they often move away when approached
Moderate Swimming Speed
Able to move quickly in shallow waters and estuaries
- Ecological Characteristics
They are primarily coastal and bay-dwelling, preferring shallow waters and estuaries.
They feed on fish and crustaceans.
They breathe near the surface and search for food.
What is the ecology like?
River dolphins mainly feed on fish and crustaceans. The lifespan of river dolphins is not well known, but it is said that they live for about 10 to 20 years in captivity.
- Lifestyle
Live in coastal and estuary areas
Prefer shallow bays, estuaries, and areas with slow currents
School Life
Live in small schools (approximately 10-30 individuals)
They often cooperate within the school, coordinating foraging and migration
- Diet
Mainly feed on fish and crustaceans
Prey on small fish, shrimp, and crabs
Uses fine teeth to firmly crush small prey
How They Find Food
Search for prey by sound and vision while swimming on the surface or in shallow waters
- Reproduction
Gestation Period
Approximately 10-11 months
Birth
Usually gives birth alone
Baby calves grow up near their mother and are watched over by the entire school
Raising
Nursing for 6-12 months
Baby calves become independent around the age of one
- Behavior/Movement
They are active in shallow waters during the day, breathing and searching for food.
Their range of movement is often limited to coastal areas.
They move in response to environmental conditions (food and water quality).
- Schooling and Defense
They swim close together in schools to protect themselves from predators.
They are highly wary of predators (killer whales and sharks) and human influence.
About Baby River Dolphins
This article summarizes baby river dolphins (finless porpoises, genus Neophocaena). As coastal dolphins, cooperation with their mothers and pods is important for their survival, even from the early stages.
- Birth and Early Characteristics
Birthing Period
Varies depending on region and water temperature, but births are usually in spring and summer.
Number of Pups
Usually one pup is born at a time.
Body Length and Weight
Body Length at Birth: Approximately 70-90cm
Weight: Approximately 7-10kg
Appearance
Same gray body color as their mother, but their backs may appear slightly paler.
Their bodies are soft and have adapted shapes for easy swimming.
- Growth and Behavior
Nursing Period
Grows while drinking breast milk for approximately 6 months.
Learning to Swim
Immediately after birth, they swim alongside their mother, learning to breathe and change direction.
Learning to Feed
Around 2-4 months of age, they observe their mother’s feeding behavior and begin practicing catching fish and small crustaceans.
- Protection within the pack
Chubby animals stay close to their mothers and are watched over by the entire pack.
When faced with predators or other external threats, the pack will take collective action to escape.
The sociality of the pack is directly linked to the survival of young animals.
- Independence and Maturity
Independence: They separate from their mothers between 6 months and 1 year of age and learn how to forage.
Sexual Maturity: Both males and females are capable of breeding at approximately 3-4 years.
Are river dolphins an endangered species?
Both the Ganges river dolphin and the Indus river dolphin are in decline in population and are designated as endangered species. I will explain the reasons for each. It has been listed in CITES Appendix I since 1975, when CITES came into force.
ganges river dolphin
Since 1981, the genus Ganges River Dolphin has been listed in Appendix I of CITES. Their population is drastically decreasing due to habitat fragmentation, water pollution, and even capture.
Indus river dolphin
They are hunted for food and fishing bait, and their population is declining dramatically. Currently, it is legally protected in Pakistan.
🌊 International Assessment (IUCN Red List)
*The coastal finless porpoise (Neophocaena asiaeorientalis) is listed as Endangered (EN). This population, which lives in the shallow waters of Japan and coastal Asia, is experiencing population declines due to human activities and requires protection.
This assessment is based on the IUCN (International Union for Conservation of Nature) Red List.
🌏 Regional Population Status
The freshwater-adapted finless porpoise population of the Yangtze River is listed as Critically Endangered, with very low numbers.
Finally, finless porpoises around Japan are also declining in number due to human impacts (fishing net bycatch, coastal development, deteriorating water quality, etc.), and are considered rare in some areas.
Can river dolphins be kept?
As mentioned above, international trade is strictly restricted by the Washington Convention, and as it is an endangered species, it is extremely difficult to keep it in captivity.
- Current Status of Captivity
They are sometimes kept in captivity in some aquariums around the world and in Japan.
Japan: Kamogawa Sea World, Marine World Uminonakamichi, etc.
Wild capture is prohibited in principle, and captive individuals are kept for conservation and breeding purposes.
- Difficulties of Captivity
Aquarium Size and Water Quality Management
This coastal dolphin is adapted to shallow waters and estuaries, but requires ample swimming space.
Maintaining salinity, water temperature, and clean water quality is essential.
Dietary Management
They are strictly carnivorous, eating mainly fish and crustaceans.
Food freshness, quantity, and nutritional balance must be monitored daily.
Sociality
They have a strong tendency to live in groups, and keeping them alone causes stress.
They must be kept in a reconstructed group.
Health Management
Respiratory and digestive health management is important.
Regular veterinary care is required.
- Laws and Regulations
Listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), international trade requires a permit.
In Japan, compliance with the Animal Welfare Act and the Specified Animal Regulations is required.
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