Top 10 Most-Endangered Species of Cetaceans

In order, with the most endangered first, and their IUCN status listed:

  1. Vaquita or Gulf of CA harbor porpoise (Phocoena sinus) CR
  2. North Pacific right whale (Eubalaena japonica) EN
  3. North Atlantic right whale (Eubalaena glacialis) EN
  4. South Asian River dolphin (Platanista gangetica) EN
  5. Atlantic humpback dolphin (Sousa teuszii) VU
  6. Hector’s dolphin (Cephalorhynchus hectori) EN
  7. Chilean dolphin (Cephalorhynchus eutropia) NT
  8. Franciscana (Pontoporia blainvillei) VU
  9. Australian snubfin dolphin (Orcaella heinsohni) NT
  10. Indo-Pacific humpback dolphin (Sousa chinensis) NT

Extinct (EX): There is no reasonable doubt that the last individual has died.
Extinct in the Wild (EW): Known only to survive in captivity or as a naturalized population well outside the past range.
Critically Endangered (CR): Facing an extremely high risk of extinction in the wild.
Endangered (EN): Facing a very high risk of extinction in the wild.
Vulnerable (VU): Facing a high risk of extinction in the wild.
Near Threatened (NT): Not in one of the categories above, but is close to qualifying for or is likely to be in a threatened category in the near future.
Least Concern (LC): Not in one of the categories above. Widespread and abundant taxa are included in this category.

*Note: The Baiji or Chinese River dolphin was declared extinct in 2007. The dubious distinction of now being the No. 1 most critically endangered population of a cetacean species is the Vaquita or Gulf of California porpoise.


The Most-Endangered Cetacean Species

Thomas A. Jefferson, Ph.D., Visiting Scientist at the Southwest Fisheries Science Center in La Jolla, CA

Cetaceans have long been highly prized by humans looking for a good source of food, oil and a whole host of other products. Cetaceans are attractive subjects for human exploitation because of their enormous size. Until the last few hundred years, their relatively inaccessible habitats made them difficult to hunt. Although there is evidence that prehistoric humans may have taken advantage of the fortuitous stranding of a fresh whale or dolphin on their shores, most cetacean species were relatively safe from large-scale human exploitation until recently.

The first known large-scale hunting of whales was by the Basques, starting in the first millennium AD. They hunted in the Bay of Biscay bounded on the east by the west coast of France and on the south by the north coast of Spain. They mainly targeted the North Atlantic right whale (Eubalaena glacialis), and were so effective in killing so many of this species that their recovery is in doubt today. Norse and Icelandic whalers also hunted in the North Atlantic, and the Japanese began their culture of whale hunting in the 1600s. In the 1700s, the “Yankee whaling” era began, focusing largely on sperm whales (Physeter macrocephalus). This led to the United States becoming a major player in the commercial whaling game. In the late 1800s, the development of steam-powered vessels and the exploding harpoon ushered in the modern era of commercial whaling. Fast-swimming Balaenoptera species, such as the rorquals (blue, fin, sei, Bryde’s and minke whales) were now within the realm of commercial whalers. It did not take long for whalers to decimate species after species, starting with the largest and working their way down the list, to “commercial extinction” (the point at which it is no longer financially viable to continue the hunt).

However, the public perception that all large whales are endangered is wrong. The truth is that most large whales are no longer commercially hunted and many are recovering from past exploitation—with major exceptions being the North Atlantic and North Pacific right whale (E. japonica) species. The real serious conservation problems now lie with several of the smaller cetacean species. The vaquita (Phocoena sinus), Indus susu (Platanista gangetica minor), North Island Hector’s dolphin (Cephalorhynchus hectori maui) and Atlantic humpback dolphin (Sousa teuszii) are some of the most severely endangered species.

In recent decades, the direct killing of whales and dolphins has become much less important, and the indirect deaths of dolphins and porpoises in particular have increased dramatically. There is now no doubt that more cetaceans die incidentally in fishing nets each year than from any other threat, including whale and dolphin hunting.

In the last few decades, we have also seen the development of other major threats to these animals in the form of habitat degradation, environmental contamination, noise pollution (including naval sonars), and even live captures for captive display and research. Despite a number of populations of cetaceans in specific regions being annihilated by humans (e.g., the Atlantic gray whale by commercial whaling), it is only recently that an entire cetacean species has gone extinct at the hands of humans. However, several other species, such as the vaquita in Mexico and Northern Hemisphere right whales, are now on the verge of that same fate.

The baiji, found only in the Yangtze River and some connected lakes in China, was declared to be probably extinct in 2007, after an extensive survey of nearly their entire known range turned up no sightings or acoustic detections. Besides incidental deaths in fishing gear and problems of severe pollution, the baiji suffered from general habitat loss and degradation. Their environment was severely degraded from rapid modification of the river for human use, with little or no concern for its original inhabitants. The Chinese Government had been warned of this for decades and ignored the pleas of the outside world.

Closer to home for those of us in the U.S., the vaquita seeks out a precarious existence in the northern Gulf of California, Mexico. This small porpoise species has serious problems with incidental catches in gillnets (and much less, so trawls). There are other potential threats as well, but they probably pale in comparison to the fishery entanglement problems.

The vaquita population numbers no more than a few hundred (the current best estimate is about 150). The Mexican government appears to be taking the situation very seriously, and is making an attempt to remove gillnets from the vaquita’s range. Although the species is still in serious trouble, there is some reason for cautious optimism about the vaquita’s future, but we must move fast to avoid a repeat of the baiji tragedy.

One thing that is important to remember about endangered species is that some “Endangered Species Lists” include species mainly for political reasons, and their legal status listing may not be accurate. Thus, there is a difference between Endangered (the official status listing, with a capital E) and endangered (the true status of a species, with a lower-case e). For example, the sperm whale is listed as Vulnerable by the International Union for the Conservation of Nature (IUCN) and Endangered by the US Government, yet it is globally distributed, numbers in the hundreds of thousands and many populations are quite healthy. Thus, the sperm whale is not really endangered.

Nonetheless, several cetacean species, and many other populations, are genuinely in danger of extinction in the next decade or two. This is a sad statement on the depths of human greed and carelessness for the natural environment. It is my hope that this article will help people appreciate the diversity and fragility of the world’s marine mammals, and will inspire them to work towards their long-term protection.

IUCN Classifications of Degrees of Threat:
By classifying species into categories of threat, conservation recommendations can be made based on the status of the species, its abundance, and distribution.

Extinct (EX): There is no reasonable doubt that the last individual has died.

Extinct in the Wild (EW): Known only to survive in captivity or as a naturalized population well outside the past range.

Critically Endangered (CR): Facing an extremely high risk of extinction in the wild.

Endangered (EN): Facing a very high risk of extinction in the wild.

Vulnerable (VU): Facing a high risk of extinction in the wild.

Near Threatened (NT): Not in one of the categories above, but is close to qualifying for or is likely to be in a threatened category in the near future.

Least Concern (LC): Not in one of the categories above. Widespread and abundant taxa are included in this category.

Clarifying endangered isolated populations vs. entire species, a quote from Dr. Jefferson:

“The gray, sei, blue, and fin whale species are not endangered on a global scale, but isolated populations of these species have been severely depleted and face some danger of extinction. Sadly, there have probably been several cetacean populations that have been exterminated by humans before they were even documented by scientists. In fact, even today for most species of cetaceans, global population structure is very poorly known.”

For additional reading about Endangered Species of Cetaceans:

JEFFERSON, T. A., M. A. WEBBER and R. L. PITMAN. 2008. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press/Elsevier, 573 pp.

REEVES, R. R., B. D. SMITH, E. A. CRESPO and G. NOTARBARTOLO DI SCIARA. 2003. Dolphins, Whales and Porpoises: 2002-2010 Conservation Action Plan for the World’s Cetaceans. IUCN – The World Conservation Union, 139 pp.

REEVES, R. R. 2009. Conservation efforts. Pp. 275-289 in Encyclopedia of Marine Mammals (Second Edition) (W. F. Perrin, B. Würsig and J. G. M. Thewissen). Academic Press.

SCHIPPER, J., and many, many others. 2008. The status of the World’s land and marine mammals: Diversity, threat, and knowledge. Science 322:225-230.

TURVEY, S. T., R. L. PITMAN, B. L. TAYLOR, J. BARLOW, T. AKAMATSU, L. A. BARRETT, X. ZHAO, R. R. REEVES, B. S. STEWART, K. WANG, Z. WEI, Z. ZHANG, L. T. PUSSER, M. RICHLEN, J. R. BANDON and D. WANG. 2007. First human-caused extinction of a cetacean species. Biology Letters 3:537-540.

ISAAC, N. J. B., S. T. TURVEY, B. COLLEN, C. WATERMAN and J. E. M. BAILLIE. 2007. Mammals on the EDGE: Conservation priorities based on threat and phylogeny. PLoS ONE 2:published online (doi:10.1371/journal.pone0000296).

TURVEY, S. 2008. Witness to Extinction: How We Failed to Save the Yangtze River Dolphin. Oxford University Press, 234 pp.

To learn more about Endangered Cetaceans through the Internet visit:


Irrawaddy Dolphins Disappearing from the Mekong River

Isabel L. Beasley, Ph.D.

As a result of intense competition with humans for freshwater resources, freshwater Irrawaddy dolphin populations are some of the most endangered of all cetacean species. Irrawaddy dolphins, Orcaella brevirostris are found in localized coastal/estuarine regions around Southeast Asia, with riverine populations in the Mahakam (Indonesia), Ayeyarwady (Myanmar) and Mekong (southern Laos, Cambodia and Vietnam) River systems. The Irrawaddy dolphin subpopulation in the Mekong River (hereafter referred to as the “Mekong dolphin population”) was classified as “Critically Endangered” by the World Conservation Union (IUCN) in 2004, and is thought to be declining rapidly.

The Mekong dolphin population is now restricted to the upper 190km (190km = 118.06 miles) of the Cambodian Mekong River, from Kratie north to the Laos/Cambodian border. Photo-identification studies have shown that the total population was an estimated 127 individuals in 2005, as may now be as few as 86 individuals. The main problems facing the population are unsustainable newborn mortalities; accidental gillnet entanglement; and dolphin-watching tourism.

During dedicated studies conducted from 2001-2005, only two calves were known to survive past the first few weeks of life (these two calves were born in January 2004 and were still alive as of April 2005); all other newborns observed in the river were found dead within weeks of being sighted. These unsustainable newborn mortalities have continued in recent years, with 16 newborns found dead in 2006 and nine in 2007. WWF-Cambodia now have a dedicated Mekong dolphin veterinary program in an attempt to determine cause of death, however no definitive answers have yet been found.

As with many cetacean populations gillnet entanglement is a known problem, and has contributed to at least half the known adult mortalities. In 2005, the Cambodian Government decreed that the Kratie to Lao/Cambodian border river stretch would be a gill-net free area, in a well-intentioned attempt to conserve the remaining dolphin population from a major source of anthropogenic mortality. Unfortunately, there was no prior consultation with the local communities along the river, who commonly use gillnets for subsistence fishing. Additionally, no alternative livelihoods were provided (except independently by a local Cambodian NGO in only two villages), or gear modification trials conducted, before this legislation came into effect. These well-enforced initiatives have inevitably alienated the local people, despite the communities’ positive perceptions towards dolphins and demonstrated willingness to participate in small-scale management efforts previously initiated by dolphin conservationists.

Dolphin-watching tourism occurs in two areas of the river, and based on results of other dolphin-watching studies around the world are no doubt having significant impacts on targeted populations. Irrawaddy dolphins inhabit the same small deep-water pools for most of their lives (some pools no larger than 2km x 2km, 2km = 1.24 miles). The noise and harassment from daily dolphin-watching tourism in small motorised boats affects all dolphins inhabiting the small, confined pools, and may be one of the factors responsible for the high newborn mortality. As an example, In Kampi Pool near Kratie Township, there are at least 20 small boats operating in the 1 km x 1 km (1km = 0.62 miles) pool during the dry season. There is minimal management of this tourism; no educational/awareness information provided to tourists; no benefit to the targeted dolphin groups; and despite outside appearances, very little revenue goes back to the local community. An international awareness campaign is therefore planned to encourage international and national tourists to view the dolphins from land (easily viewed during the dry season), rather than hiring boats to view them.

Additional large-scale conservation concerns for the Mekong dolphin population result from various sources of habitat degradation (e.g., large scale dam construction; contaminants from industry and agriculture; and conversion of natural habitat to farmland), disease, reduced prey, and loss of genetic diversity. Even with the most comprehensive management plan accepted by all stakeholders, dolphins will not survive in the river if adequate habitat is not available. Dolphins rely on deep-water areas during the dry season and annual fish migrations to replenish fish stocks. The construction of dams along the mainstream lower Mekong River (particularly southern Laos or Cambodia), will no doubt substantially increase the risk of the Mekong dolphin population’s extinction.

On a more positive note, dedicated efforts to conserve the remaining population are continuing by WWF-Cambodia, with recent assistance and advice from the IUCN Cetacean Specialist Group and associated researchers. If it is not already too late to conserve the remaining dolphin population, with effective in-situ conservation and management, Irrawaddy dolphins could serve as a flagship species for conservation of the Cambodian Mekong River stretch from Kratie to the Lao/Cambodia border, which is a biologically diverse, highly important ecosystem for a number of endangered flora and fauna species.


Threats to Whales

A century ago parts of the sea were teaming with whales. But human intervention changed this. The commercial whaling era killed millions of whales and made them into lamp oil, lubricants, cosmetics, and meal. Today, some whales are barely recovering from the whaling industry, while others have increasing numbers. But they face so many dangers other than whaling: pollution, loss of food sources, loss of habitat, climate change, toxic substances, being entangled in or ingesting plastic, sonar testing, net entanglement, trapped as incidental by-catch of the fishing industry, and ship strikes are some of the dangers maiming and killing whales.

Learn about the 10 Most-Endangered Species of Cetaceans on this same website.

No marine species remains unaffected by human activities. A viable population depends on the health of the ecosystem in which it exists, and the many forms of pollution extend to all the world’s oceans threatening all species. Low-level contamination of the smaller prey species becomes concentrated in the tissue of larger marine predators and marine mammals.Planktonic organisms are carried great distances by winds and sea currents and larger nektonic creatures travel large expanses of oceans on their own accord. Both carry pesticides, heavy metals, and disease causing organisms to all sea areas. Contamination levels in toothed whales and dolphins are high. How this affects their individual fitness or their ability to reproduce is still largely unknown.

The beluga whale population of the St. Lawrence in Canada has been declining since protection in 1979. Through autopsies, researchers have discovered high concentrations of PCB and DDT, which are stored in the fatty tissues of mammals. Dead belugas have revealed bladder and liver cancer which has never been seen before in marine mammals. Other diseases found in belugas are hepatitis, splenic tumors, pneumonia, herpes, skin diseases, ulcers and blood poisoning, all of which suggest suppression of the immune system.

Toxicologists based in New York have completed research on elephant seals off Northern California coasts. They have found high levels of coplanar PCBs and skin diseases in this species. Along the west coast of the United States, autopsies of bottlenose dolphins show high PCB and DDT levels.

In addition to chemical pollution, oil slicks are commonplace in the oceans. Some whales and dolphins in the Western North Atlantic have been surfacing repeatedly through oil-slicked areas. In contrast, gray whales studies off of the Southern California coast changed their migratory path and their swimming and diving behavior when coming into contact with oil patches from seepage. Gill nets and fish traps kill thousands of marine mammals annually. Whaling hunting is practiced today by Norway, the Faroe Islands and Japan.

Noise pollution also threatens the existence of cetaceans. Large ships and boats make a tremendous amount of noise that falls into the same frequency range of many whales. This could be a contributing factor to the noticeable shift in the migration route of some California gray whales. Some are making a detour around the west side of the Channel Islands, possibly to avoid the noise pollution of Southern California sea traffic. Recent studies done in Newfoundland reveal that humpback whales entangled in gill nets have damaged ears. Since sound plays a vital role in the life of whales, dolphins and porpoises, noise pollution must be considered a significant cause of death as increasing numbers of whales are stranding where sonar testing is being conducted. This is one of the most prevalent dangers facing whales, large and small, today.