Irrawaddy Dolphin

Irrawaddy Dolphin
Irrawaddy Dolphin” by Stefan Brending (2eight) is licensed under CC BY-SA 3.0 de

 

Irrawaddy_INFOG.jpg

Introduction

  • Scientific name: Orcaella brevirostris
  • Only dolphin species with no beak and a flexible neck which means that they can look up, down, left, and right without having to turn their entire body
  • They use echolocation to navigate and hunt for food such as small fish
  • The entire population is considered to be vulnerable by the International Union for Conservation of Nature (IUCN) Distribution, however there are critically endangered subpopulations in different countries such as the Philippines and Malaysia

Distribution

Irrawaddy dolphins are rare and they primarily live in the waters of Southeast Asia. They can also be found between eastern India all the way to Indonesia and the Philippines. They prefer to live close to the shore and in rivers and can live in both freshwater and saltwater environments.

Surveys have shown that different subpopulations number less than 100 in numerous areas. Within the Coral Triangle, subpopulations in the Malampaya Sound region (Palawan, Philippines) and the Mahakam River (West Kalimantan, Indonesia) are considered to be critically endangered. For instance, a recent survey conducted by the World Wildlife Fund (WWF) in 2001 in Malampaya Sound showed only 77 dolphins.

Why they are important

If you see a lot of dolphins in an area, then it generally means that the local ecosystem is healthy enough to support them. They are apex predators that make sure that the populations of their prey remain healthy and do not grow too big, which can disrupt the food chain. They help maintain their ecosystem by having a diet of fish, mollusks, and aquatic crustaceans such as crab and shrimp.

Irrawaddy dolphins provide income for coastal communities through ecotourism. They are well recognized for their “smiling” faces and are known for their ability to spit water which is thought to be used as a way to herd fish.

Biology

The Irrawaddy dolphin is unique when it comes to dolphin species as it has a flexible neck and unlike the traditional image that dolphins have, Irrawaddy dolphins do not have a beak but have a stubby rounded face instead. Their dorsal fin is also short, blunt, and triangular. More images of irrawaddy dolphins here.

Not much is known about the Irrawaddy’s mating habits. Initial research from some Irrawaddy populations in India has found that they have a slow rate of reproduction. They reach sexual maturity between the ages of 4 to 9 and they produce only a single calf in every 2 to 3 years. This makes them vulnerable to threats such as pollution and accidental drowning in fishing nets because their populations are small and they reproduce very slowly.

Irrawaddy dolphins have excellent hearing, their habitats are often murky and unclear which makes it hard to navigate using their eyes so they use echolocation to navigate through the waters. They make sounds which bounce off objects enabling to avoid obstacles and locate prey.

Threats

Irrawaddy dolphins are sensitive to coastal development because they prefer to stay close to the shore or in rivers. Developments such as residential areas or resorts can increase their vulnerability to pollution, being accidentally caught as by-catch in fishing nets and being hit by boats.

Their highly sensitive hearing can be injured by fishermen who use dynamite fishing, a destructive fishing practice. Dolphin strandings have been known to occur in areas where fishermen practice dynamite fishing, without their sense of hearing Irrawaddy dolphins will have a hard time navigating the waters, catching prey, or interacting with members of their pod. In the Philippines, one of the reported strandings in 2014 was suspected to be caused by dynamite fishing due to the dolphin having acoustic trauma from the loud blasts.

What you can do

Report any instance of dynamite fishing to the authorities.
Fishermen often recycle bottles for use in dynamite fishing, they can be visually identified because they often have a fuse sticking out of the top. When you are on the coast, dynamite fishing can be heard by faint or distant booms.

Do not support improperly built coastal developments.
You can conduct research on coastal developments such as residential areas or resorts before deciding to stay there, try reading reviews or any news about whether or not the developments are environmentally friendly. Improperly managed coastal developments can increase the amount of pollution and boat impacts for the dolphins and other marine life.

Laws that protect Irrawaddy Dolphin in the CT3

 

Quiz

Echolocation is very important to the Irrawaddy dolphin. What is an example of how they can use echolocation to navigate? How do they know the distance of each obstacle?