Indo-Pacific humpback dolphin

The Indo-Pacific humpback dolphin (Sousa chinensis) is a special kind of dolphin that lives in the coastal waters of the eastern Indian and western Pacific Oceans. These dolphins are sometimes called the Chinese white dolphin in places like mainland China, Macau, Hong Kong, Singapore, and Taiwan.

Scientists have studied these dolphins and found that they are different from another type called the Indian Ocean humpback dolphin. Even though some people thought they might be the same, DNA testing showed they are really separate species. In 2014, scientists also discovered another type called the Australian humpback dolphin, which is now known to be its own unique species too.

There are still some questions about how exactly these dolphins are related, but they are all important animals that help keep the oceans healthy.

Taxonomy

There are two subspecies of the Indo-Pacific humpback dolphin. One is called the Chinese humpback dolphin, and the other is called the Taiwanese humpback dolphin.

Description

The Indo-Pacific humpback dolphin can be grey, white, or pink, and sometimes looks like an albino dolphin. In areas like China and Thailand, these dolphins are often seen with pink skin. This pink color isn't from pigment but comes from extra blood vessels that help them stay warm.

These dolphins grow to be 2 to 3.5 meters long as adults and weigh between 150 to 230 kilograms. Babies are born dark grey or black and are about 1 meter long. As they grow older, their color changes to a lighter, mottled grey. These dolphins can live up to 40 years.

Behaviour

Indo-Pacific humpback dolphins live in small groups, usually with fewer than ten dolphins together. They work together to hunt using a special sense called echolocation.

Adult dolphins come up to breathe for about 20 to 30 seconds before diving deep for two to eight minutes. Young dolphins need to come up more often, about twice as often as adults, and they stay underwater for only one to three minutes. These dolphins sometimes jump completely out of the water and can also rise up straight, showing the top half of their bodies. Their eyes are made in a way that lets them see well both in air and water.

Reproduction

Female Indo-Pacific humpback dolphins reach maturity around ten years old, while males mature around 13 years old. Mating typically happens from late summer into autumn, and after a gestation period of eleven months, calves are born. Mothers stay close to their calves until they are ready to find food on their own, usually when the calves are about 3 to 4 years old.

Main article: Dolphin § Reproduction and sexuality

Threats

The Indo-Pacific humpback dolphin faces many dangers. Its home near coastlines is often damaged by human activities like building and fishing. There is also more boat traffic, which can hurt the dolphins.

Water pollution is a big problem. In Hong Kong, the number of these dolphins dropped sharply because of toxins in the water. Plastic pollution is also very harmful. Dolphins often live in shallow waters close to shore, where plastics and other harmful substances collect. Eating plastic or absorbing toxins from it can make dolphins very sick. Even if they don’t eat plastic directly, they can still get sick from pollutants that build up in their bodies over time.

Plastic can also confuse dolphins. They use sounds to find their way and locate food, but plastic in the water can block these sounds, making it hard for dolphins to navigate. This can cause a lot of stress and health problems for them.

Distributions and watching

In Hong Kong, people have been taking boat trips to see the Indo-Pacific humpback dolphins since the 1990s. These dolphins mostly live in the waters of Lantau North, Southeast Lantau, the Soko Islands, and Peng Chau. There are rules to help protect the dolphins during these trips.

Some reports have shown that not all dolphin-watching tours follow these rules, especially small private tours in places like Sanniang Bay near Qinzhou and off Xiamen. In Nan'ao County, there is a special area called Nánpēng Islands Marine Sanctuary where local groups of dolphins live. There is also a large group of nearly 1,000 dolphins in Leizhou Bay on the Leizhou Peninsula, which might be used for tourism in the future. Dolphins can also be found near Sanya Bay and other areas around Hainan Island, as well as in Weizhou and Xieyang Islands. In Vietnam's Gulf of Tonkin, there may be more dolphins that have not been studied yet, possibly appearing near Xuân Thủy National Park and Hòn Dáu Island in Hải Phòng.

In Cambodia, in December 2023, the Marine Conservation Cambodia estimated that between 100 and 200 Indo-Pacific humpback dolphins live around Kampot and Koh Kong. In May 2024, they saw a group of these dolphins together with an Irrawady dolphin mother and her calf on the Prek Tnaot River in Kampot.

Taiwanese humpback dolphin

The Taiwanese humpback dolphin is a special group of dolphins found in the waters near the west coast of Taiwan. These dolphins were first seen there in 2002. They usually live in very shallow water, less than 5 meters deep, and never go into water deeper than 15 meters.

There are not many of these dolphins left. In 2012, only about 62 were left, down from fewer than 100 just a few years earlier. Scientists say this group is in big trouble and could disappear if we do not help them.

There are several reasons why these dolphins are disappearing. Human activities, like building things along the shore and digging up sand, change their homes and make it hard for them to live. Fishing nets and boats can hurt or kill dolphins. There is also less fresh water reaching the areas where they live, which makes their homes less suitable. Too much noise from construction and boats can also bother the dolphins, since they rely on sound to find food and talk to each other.

Conservation

The Indo-Pacific humpback dolphin is protected under an international agreement called the Convention on the Conservation of Migratory Species of Wild Animals. Its numbers have dropped sharply, especially around Hong Kong, where the population fell by 60% over ten years. Threats to these dolphins include pollution, collisions with boats, overfishing, and noise underwater.

These dolphins face many challenges because they grow slowly, have fewer babies, and take a long time between having each calf. To help protect them, Taiwan created a large sanctuary along its coast, and there are also agreements to conserve cetaceans in the Pacific Islands region.

Timeline of main events

• 1637: The Indo-Pacific humpback dolphin was first written about in English by an adventurer named Peter Mundy in Hong Kong near the Pearl River. These dolphins like the area because of its mix of fresh and salty water.
• 1765: A scientist named Pehr Osbeck gave the first detailed scientific description of the species.
• Late 1980s: People who care about nature started to focus more on the Indo-Pacific humpback dolphin population.
• Early 1990: People in Hong Kong began to notice these dolphins more because of the building of the Chek Lap Kok Airport. This was a very big project that took away part of the sea near Northern Lantau, an area where many dolphins lived.
• Early 1993: There was a new look at how the airport building was affecting the environment. This brought more attention from nature groups and the media, and the Hong Kong Government started funding research on these dolphins.
• Late 1993: A new department was created to look after farming, fishing, and protecting nature.
• 1996: A scientist named Dr. Thomas Jefferson started studying these dolphins to learn more about them.
• 1997: The Indo-Pacific humpback dolphin was chosen as a symbol for important ceremonies in Hong Kong.
• 1998: Dr. Jefferson’s research findings were published in a scientific book.
• 1998: A group called Hong Kong Dolphinwatch started tours for people to see the dolphins and learn about them.
• 2000: The government department began watching the dolphins over a long time.
• 2000: The number of Indo-Pacific humpback dolphins in the Pearl River area was about 80 to 140.
• 2014: Scientists updated the classification of humpback dolphins and described a new species, the Australian humpback dolphin, and set the common name for the Indo-Pacific humpback dolphin.