Thanks in part to advocacy, activism and protective measures around the world, the humpback whale population has been steadily increasing since the 1980s. For example, over the past four decades the number of North Pacific humpbacks has flourished from about 1,000 animals to over 23,000 – with as many as 14,000 humpback whales migrating to Hawaii every winter1. Despite numerous human-made and environmental pressures that continue to pose serious threats, “Save The Whales” is a call to action that has made a real difference.
Sadly, the same success story is not the case for all marine animals struggling to survive in their natural ocean habitat. Pacific Whale Foundation is currently studying five endangered cetaceans on the brink of extinction: the Hawaiian False Killer Whale, the Chilean Blue Whale, the Maui Dolphin, the Arabian Sea Humpback Whale, and the Vaquita.
False killer whales are a type of dolphin that lives in tropical and temperate waters around the world. They get their namesake from the resemblance of their skulls to that of killer whales (orcas). In Hawaii there are three distinct populations of false killer whales, and the Main Hawaiian Islands insular population is listed as endangered under the Endangered Species Act. Their numbers have declined in numbers dramatically over the past 20 years and it is estimated that less than 150 individual animals remain in this population. They are slow to recover from human impacts, including interactions with fisheries, reduced food supply, and exposure to pollutants. When they were listed as endangered in 2012, the National Marine Fisheries Service noted “a probability of greather-than-90-percent likelihood of the DPS [designated population segment] declining to fewer than 20 individuals within 75 years, which would result in functional extinction beyond the point where recovery is possible.”
The blue whale is the largest animal to ever exist and was almost exterminated by commercial whaling. The blue whale is distributed globally but is one of the rarest species of whale. Only one population off the coast of California in the eastern North Pacific Ocean is showing signs of recovery. Recently it was discovered that blue whales found off the southern coast of Chile may represent a unique population or a subspecies of blue whale. Based on differences in the Chilean blue whale and the other known populations, the International Whaling Commission determined that blue whales off Isla de Chiloe need to be managed as a separate population. Little is known about this population, but it appears that Chilean blue whales are the smallest population of blue whales in the Southern Hemisphere. Like other large whales, blue whales are threatened by pollution, habitat loss, overfishing, fishing gear entanglements, vessel collisions, and climate change.
The Maui dolphin is the world’s smallest known dolphin. It is a subspecies of the Hector’s dolphin and is found only off the west coast of New Zealand’s North Island. The Maui dolphin is threatened primarily by certain fishing methods such as set-netting and trawling, although disease, pollution, mining, and natural predation are also factors impacting their survival. Estimates from 2012 indicate that only 55 individual animals remain in this population. In 2014, despite calls for greater protection efforts for the Maui dolphin, the New Zealand government opened up the West Coast North Island Marine Mammal Sanctuary for oil drilling. This area is the main habitat of the Maui dolphin, and in 2015 the population was estimated to be as low as 43 individuals, of which only 10 were reproductively mature females.
Arabian Sea humpback whales are a discrete population of whales that lives in the Arabian Sea year-round and does not migrate. High productivity and upwelling (cold water rising from the deep toward the surface) create conditions suitable for feeding as well as breeding. This is the most isolated and endangered population of humpback whales in the world, thought to contain less than 100 individual animals. Today, it is one of only four humpback whale populations still listed by the Endangered Species Act, and is at a high risk of extinction without conservation efforts. The Arabian Sea humpback whales face unique threats, given that they do not migrate, but instead feed and breed in the same, relatively constrained geographic location. Energy exploration, fishing gear entanglements, disease, vessel collisions, and climate change are likely to reduce the size and/or growth rate of this population.
The vaquita is a tiny porpoise found only off the coast of Mexico in the northern Gulf of California. The greatest threat to this species is entanglement in gillnets (vertical panels of fishing nets typically set in a straight line). It was estimated in 2012 that there were 200 vaquitas remaining, a number which dropped to half that by 2014 and to 60 vaquitas in 2016. The latest estimates published in 2017 indicate that only 30 vaquitas remain. The government of Mexico has taken a number of steps to protect this species, including establishing a refuge to protect their core habitat and banning gillnets within range of vaquitas. Unfortunately, illegal fishing using gillnets is still rampant and it is predicted that the vaquita could go extinct as early as 2018.
1Gregory D. Kaufman and Paul H. Forestell, Hawaii’s Humpback Whales: The Ultimate Guide, Island Heritage Publishing, 2014.