Pink dolphins have long lived in the urban waters around the islands and in the harbor of Hong Kong, where they have earned a symbolic place in the city’s history and culture. However, there is rising concern among scientists that these rare dolphins will disappear from the bustling waters unless more is done to preserve them.

Increasing habitat loss, noise pollution, and other threats have had a severe impact on the numbers of these pink dolphins, also known as Chinese white dolphins, in the last decade.

The ongoing construction of the Hong Kong-Zhuhai-Macau Bridge through the dolphins’ territory may put additional stress on them, conservationists warn.

Chinese white dolphins are born gray but become pink as they grow older. (See dolphin talk decoded.)

These highly social creatures are often known as Indo-Pacific humpback dolphins (Sousa chinensis) in scientific circles. The species is believed to exist from the east coast of India through the Malay Archipelago and toward Australia. Because of their fragmented range, it is difficult to pinpoint their exact population, though reports suggest that the number is in decline.

We talked to dolphin biologist Samuel Hung Ka-yiu, chairman of the Hong Kong Dolphin Conservation Society, who has worked with pink dolphins in the city for nearly 20 years.

What is significant about the history of pink dolphins in the region?

Presumably, the dolphins have been here in Hong Kong and the Pearl River Estuary for a long time, probably before our ancestors started to populate this region. Awareness of them grew in the 1990s, when the government started planning for the new international airport to the north of Lantau, which impacted their habitat. The dolphins became very famous when they were chosen as the official mascot for the city’s handover ceremony [from the U.K. to China] in 1997.

How are the dolphins faring?

The local dolphin population is quite unstable ... a significant decline in dolphin number has been detected in the last decade. We went from 158 dolphins in 2003 to only 61 dolphins in 2014. The figure is even lower for 2015, but we are not able to release the exact data to the public yet.

Why have the animals been in such decline?

There are multiple threats to the dolphins, including overfishing (which leads to lack of prey and increased risks of net entanglement), pollution (we found high concentrations of contaminants in their bodies, even in calves, which can suppress their immune systems and impair their reproductive ability), and vessel traffic (which can disrupt them with loud sounds or kill them in collisions).

Coastal development is probably the biggest problem in the long run, as there are quite a lot of infrastructure projects under construction and being proposed. We are campaigning against the construction of a third runway for the airport, which would involve massive reclamation of 650 hectares of sea areas that are identified as important habitat for the dolphins.

What is the dolphins’ behavior like and what conditions do they need?

The dolphins are quite curious and acrobatic. Once in a while they come close to check us out, and they often breach when foraging for food. They live in a fission-fusion society so their social structure is quite fluid. At times they can be alone, but they often can be found in groups up to 20.

The conditions that they prefer to live in include natural coastlines with abundant food resources and less human disturbance. They particularly like to forage along the edge of deep water channels. (Learn more about dolphin intelligence.)

What is the prognosis for their survival?

Their reproduction rate is very poor and we found high calf mortality, which means at least half of the young don’t survive after birth. Also, the calving interval is longer than most dolphins, about four to six years, so they only have a small number of offspring during their lives.

We have been conducting a long-term monitoring study to better understand their status.

Is the city of Hong Kong doing enough to protect the dolphins?

The government has been sponsoring the monitoring study, to their credit, and they have a conservation program in place. But we need more marine protected areas and regulations on vessel traffic and fishing.

The government is also still proposing more development within the dolphin habitat that could further degrade their habitat, so we are constantly asking for more conservation efforts.