The Taiwanese white dolphin, also known as the Taiwanese Indo-Pacific humpback dolphin (Sousa chinensis taiwanensis)—first described after a 2002 exploratory survey—is found exclusively in the shallow waters of the western coast of Taiwan. These dolphins are eight or nine feet long with a relatively small dorsal fin, but their most distinctive characteristic is their pink coloration. Their skin pigment is actually white, with gray spots, but when they are active, they “flush” and turn bright pink. They are born dark gray with no spots, but get lighter and more spotted as they age. With a current population estimate of fewer than 751 individuals, it is overwhelmingly clear that they are at risk of extinction.
The Taiwanese white dolphin was formerly considered a subpopulation of the more broadly distributed Indo-Pacific humpback dolphin, Sousa chinensis. Through research into the degree of variation of pink and grey pigmentation between Taiwanese white dolphins and Indo-Pacific humpback dolphins, it was determined that the pigmentation is significantly different between the two populations to distinguish the Taiwanese population as a distinct subspecies.2
Based on survey data collected between 2002 and 2006, the population was initially estimated to be 99 individuals.3 Due to this small number and the predicted decline in the population, the IUCN considered the Taiwanese white dolphin to be at an extremely high risk of extinction, and therefore categorized the subspecies on the Red List of Threatened Species as “Critically Endangered.” An analysis of this population found that it can suffer no more than one human-caused dolphin death every 7 to 7.6 years to remain stable. Therefore, even one human-caused mortality per year would almost certainly lead to extinction.4
In addition to being listed as critically endangered by the IUCN, the Taiwanese white dolphin is currently protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The dolphin is listed on Appendix I of the treaty, which means that commercial trade in the animal is prohibited. However, the population is not targeted for trade. While the population is at high risk of extinction due to several local and regional threats, commercial harvest is not among these. Bycatch, entanglement, habitat destruction and degradation, pollution of coastal and riverine waters, and vessel traffic are among the most significant threats to the subspecies. Of all the human-caused threats to the survival of the Taiwanese white dolphin, fisheries bycatch and entanglement are believed to be the most significant.5 Although there are various types of fishing equipment used through their habitat, the most likely to cause entanglements and death are gillnets and trammel nets. The subspecies is most commonly injured or killed due to the fishery for grey mullet. Fishermen are unlikely to report these incidental catches or entanglements due to their fear that responsive management action will restrict their fishing activity.
Workshops were conducted in 2004, 2007, 2011, 2014, and 2017 to identify and define the dolphin’s conservation status, threats, and potential protection measures. The workshops—where scientists, policymakers, and international partners came together to discuss conservation options—promoted and fostered increased research on the population. Although data continue to be collected by researchers on the population and the threats it faces, there is little evidence of effective management steps being taken based on this information. The Taiwanese government has yet to take significant action to reduce the threats to the Taiwanese white dolphin.
In March 2016, the Animal Welfare Institute, Center for Biological Diversity, and WildEarth Guardians submitted a petition to list the Taiwanese white dolphin under the Endangered Species Act. The National Marine Fisheries Service, after due consideration of the petition, has proposed listing the subspecies as endangered. Protection under the law would include restrictions on trade in the animal; the ultimate goal, however, is to encourage research and increase international pressure on the government of Taiwan to take action. In addition, the United States and concerned nongovernmental organizations can provide technical expertise and resources to support Taiwan’s conservation efforts.
Dungan, S. Z., J. Y. Wang, C. C. Araújo, S.-C. Yang, and B. N. White. 2015. Social structure in a critically endangered Indo-Pacific humpback dolphin (Sousa chinensis) population. Aquatic Conservation: Marine and Freshwater Ecosystems: n/a–n/a.
Slooten, E., J. Wang, S. Dungan, K. Forney, S. Hung, T. Jefferson, K. Riehl, L. Rojas-Bracho, P. Ross, A. Wee, R. Winkler, S. Yang, and C. Chen. 2013. Impacts of fisheries on the Critically Endangered humpback dolphin Sousa chinensis population in the eastern Taiwan Strait. Endangered Species Research 22:99–114.
Wang, J. Y., S. Chu Yang, S. K. Hung, and T. A. Jefferson. 2007b. Distribution, abundance and conservation status of the eastern Taiwan Strait population of Indo-Pacific humpback dolphins, Sousa chinensis. Mammalia 71:157–165.
Wang, J. Y., K. N. Riehl, M. N. Klein, S. Javdan, J. M. Hoffman, S. Z. Dungan, L. E. Dares, and C. Araújo-Wang. 2015b. Biology and Conservation of the Taiwanese Humpback Dolphin, Sousa chinensis taiwanensis. Advances in Marine Biology.
Wang, J. Y., S. C. Yang, P. F. Fruet, F. G. Daura-Jorge, and E. R. Secchi. 2012. MarkRecapture Analysis of the Critically Endangered Eastern Taiwan Strait Population of Indo-Pacific Humpback Dolphins (Sousa Chinensis): Implications for Conservation. Bulletin of Marine Science 88:885–902.
Wang, J. Y., S. C. Yang, and R. R. Reeves. 2007c. Report of the second international workshop on conservation and research needs of the eastern Taiwan Strait population of indopacific humpback dolphins, Sousa chinensis. Page 65. National Museum of Marine Biology and Aquarium, Changhua City, Taiwan.