Irrawaddy Dolphin

Irrawaddy Dolphin

Irrawaddy Dolphin

Orcaella brevirostris

 

Introduction to Irrawaddy Dolphin

One of the notable things about the Irrawaddy Dolphin is that it has an appearance different from most species. They are noted for their flexible neck and the appearance of creases that are found at the back of the head. The Orca is closely related to them.

Class Mammalia
Order Cetacea
Family Delphinidae
Genus Orcaella
Conservation status  Vulnerable

Irrawaddy Dolphin Description

The Irrawaddy Dolphin features a round head and they don’t have a beak. They have a forehead that extends beyond the rest of the facial features. The color is dark – either blue or gray – and then they feature light gray on the belly. The dorsal fin is triangular with a round end, and it is small. They have flippers that are both wide and long. They can be from 70 to 108 inches long and they can weigh from 215 to 350 pounds.

Females tend to be smaller than the males. The males also have a larger dorsal fin than females so such features can help to distinguish the gender. The teeth are pointed and narrow like pegs. They have teeth found in the upper and lower jaws. They don’t have two stomachs but instead they have one with three compartments. They don’t have a cardiac sphincter.

Irrawaddy Dolphin Distribution

There is a wide distribution for the Irrawaddy Dolphin. They are found in India around the Northeast and around the Philippines. They have been identified in the waters of the Indo-Pacific as well. These dolphins live in the shallow waters closer to the coastline. They are one of the few species that are known to be able to live in freshwater habitats.

Irrawaddy Dolphin Behavior

The Irrawaddy Dolphin has to get air every minute to 2 ½ minutes so they are seen at the surface often. However, it is usually only the head that is seen. Rarely will they have their entire body out of the water. It is going to be a very rare occasion that you see one with the fluke out of the water. Since they don’t come out of the water and into the air as other dolphins, they are deemed as being less active.

This species of dolphin lives in smaller pods than most of the species. They may have up to 6 members and some pods only have 2. They are still very social though and they create a very deep bond with the members of their pod. They are curious and they will look around at their surroundings when they come to the surface for air.

Irrawaddy dolphin - Orcaella brevirostris

Irrawaddy dolphin – Author: C. Berjeau

Irrawaddy Dolphin Feeding

Cephalopods, fish, and crustaceans are the food sources for the Irrawaddy Dolphins. They take part in the process of spitting water and this could be a way for them to round up schools of fish since they have fewer members to gather food. There is still plenty of mystery though that surrounds this particular action. They also work with humans sometimes to gather food in the wild and that is really interesting to observe.

Some fishermen are known to tape on the side of the boat to get the attention of the dolphins. Then they will swim in circles to gather up the schools of fish into one location. Once they do so there is enough turbulence for the fishermen to place their nets and to capture them. There are some fish that will be on the outer edges of the nets which the Irrawaddy Dolphins feed upon.

Irrawaddy Dolphin Reproduction

Very little information is known about the mating rituals of these dolphins. Since their pods are so small, it is believed they mix with other pods in order for breeding to occur. Mating may occur from December through June. The males are highly competitive with each other for mating rites. They will go to great efforts to be able to mate with as many females as they can.

The time it takes for the calf to be born ranges from 9 to 14 months depending on the location where the mother lives. The females will typically have a new calf every 3 year. The young remain with their mother until they are about 2 years of age and then they will be weaned and care for themselves. The young are introduced to food other than milk when they are about 6 months old. The average lifespan in the wild for the Irrawaddy Dolphin is 28 years.

Irrawaddy dolphin Facts and Information

Irrawaddy dolphin – Author: C. Berjeau

Irrawaddy Dolphin Conservation Status and Threats

They are considered to be a vulnerable dolphin species, with about 6,000 of them remaining in the wild today. There are conservation efforts in place to help them. The largest decline of them has been found in Thailand due to commercial fishing efforts. In some locations, fishing is off limits and in others the fishermen are asked to use safer equipment. They are also asked to carefully watch for dolphins so that they can be freed if they do get captured by accident.

One of the problems for the Irrawaddy Dolphin though as to do with the loss of habitat. The areas where they live have been widely used for mining, dams, and more. This has made it harder for them to move around to find food and to find mates. It has also increased stress levels for the dolphins. In some locations it is illegal to hunt them such as Laos, Vietnam, and Cambodia.

 

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