West African Dolphin Now Listed As Critically Endangered On IUCN’s Red List of Threatened Species

Entanglement in fishing gear is one of the many threats faced by the Atlantic humpback dolphin along its coastal range in western Africa. Photo by Tim Collins, WCS

A little-known dolphin that only lives along the Atlantic coasts of Western Africa is now believed to be among the continent’s most endangered mammals, according to Wildlife Conservation Society (WCS) and the International Union for Conservation of Nature (IUCN) Cetacean Specialist Group.

As per WCS, the obscure and poorly studied Atlantic humpback dolphin (Sousa teuszii) has been uplisted from “Vulnerable” to “Critically Endangered” on IUCN’s Red List of Threatened Species. The growing list tragically already includes such widely-known animals as gorillas and black rhinos.

Growing up to more than eight feet in length, the Atlantic humpback dolphin is gray and has a characteristic hump just below its dorsal fin.

These dolphins are shy, occur in small groups, and rarely venture more than a few kilometers from shore. They are highly susceptible to human activities in coastal waters, and threats include entanglement in fishing gear, being trapped near offshore construction like port development, and they are hunted for human consumption.

“Our recent assessment suggests that the global population of the Atlantic humpback dolphin likely numbers fewer than 1,500 breeding adults distributed among several isolated sub-populations, most of which appear to be very small,” said Tim Collins, of WCS’s Ocean Giants Program and the Africa Coordinator of the IUCN’s Cetacean Specialist Group.

The range of the Atlantic humpback dolphin is estimated to stretch more than 7,000 kilometers along the coastal areas of Western Sahara to central Angola.

The previous “Vulnerable” listing was based largely on the belief that dolphins were more abundant in areas where the species was known to occur. The presumption of occurrence in many areas had not been surveyed.

For the new Red List assessment, researchers conducted a thorough review of the available data, which strongly suggest that the dolphins occur in very low and apparently declining numbers throughout most or all of their range.

Most populations are extremely small and several appear to be isolated. Sadly, the species is expected to continue to decline due to the ongoing expansion of identified threats throughout the species’ known range.

Bycatch in fisheries, the principal cause of the declines, has been identified or suspected everywhere the species has been studied. Hunting is known from several areas, and the threat of coastal development in remaining habitats is increasingly prevalent.

Unfortunately, appropriate management interventions that curb habitat loss, bycatch and hunting, are limited or entirely lacking across most of the range.

According to researchers, several marine protected areas provide Atlantic humpback dolphins and other marine wildlife with important refuges that can provide marine managers with a foundation for complementary conservation efforts. This includes the recent creation of a marine protected area network in Gabon.

“The new Critically Endangered listing will hopefully provide greater attention and resources to mitigate primary and cumulative threats faced by the Atlantic humpback dolphin, as well as proactive strategies for protecting the species and its vital habitats in key parts of the range,” noted Howard Rosenbaum, Director of WCS’s Ocean Giants Program and a member of the IUCN Species Survival Commission’s Cetacean Specialist Group.

“Particularly in view of the impending extinction of the vaquita due entirely to overkill in fishing nets, we need to do a better job of not just assessing the present condition of riverine and coastal small cetaceans, but also of looking ahead and anticipating what is likely to happen to species like the Atlantic humpback dolphin unless current trends are reversed, and soon,” concluded Randall Reeves, Chairman of the IUCN Species Survival Commission’s Cetacean Specialist Group.

In addition to long-term field studies on Atlantic humpback dolphins, WCS scientists have also produced important findings on humpback dolphins living in the Atlantic, Indian and Pacific Ocean basins, specifically to resolve confusing taxonomic questions about which populations should be considered full-fledged species or related subspecies.

These investigations determined that four species exist: the Atlantic humpback dolphin; the Indian Ocean humpback dolphin (Sousa plumbea); the Indo-Pacific humpback dolphin (Sousa chinensis); and a newly described species–the Australian humpback dolphin (Sousa sahulensis).

All four species live in coastal habitats and face the same threats; entanglement in fishing nets, coastal development, ship strikes, and increased hunting.

The Indian Ocean humpback dolphin is listed as “Endangered,” whereas the Indo-Pacific and Australian humpback dolphins are both listed as “Vulnerable.”

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