From the Vaquita to the Right Whale: The 7 Most Endangered Marine Mammals in the World

Marine mammals include whales, dolphins, and porpoises (Cetacea), but also seals, sea lions, and walruses (Pinnipedia), as well as manatees and dugongs (Sirenia). Sometimes even sea otters and polar bears are counted among them because their lives are so closely tied to the sea, something visible in their dense fur, thick layer of blubber, and in some species even webbing between the toes.

Marine mammals are key species in the oceans. But many species are coming under increasing pressure: bycatch in gillnets, collisions with ships, underwater noise, pollution, and the climate crisis are taking a massive toll on them. Some have already disappeared: Steller’s sea cow, for example, was exterminated as early as 1768, less than 30 years after its discovery. The Japanese sea lion and the Caribbean monk seal also disappeared at almost the same time in the middle of the 20th century.

The rarest marine mammals in the world

Vaquita (California porpoise) – Gulf of California, Mexico – <10 animals

The vaquita (Phocoena sinus) is not only the smallest of all porpoises, but also probably the rarest marine mammal in the world, by far. In 1997, around 567 animals were still alive in the northern Gulf of California. In 2016 there were about 30, in 2023 only ten to 13, and the latest survey in 2024 yielded the perhaps saddest figure: only six to eight individuals could still be detected.

The main reason for this collapse is illegal gillnet fishing. Although it is banned, the nets continue to be used, above all to catch the likewise threatened totoaba (Totoaba macdonaldi). Its swim bladder is traded in China as a luxury good and is known there as the “cocaine of the sea.” For vaquitas, this demand becomes a death trap: they get entangled in the nets, can no longer surface, and suffocate.

Today, the last California porpoises survive only in a tiny area, the so-called Zero Tolerance Area, a protected zone of just 300 square kilometers. Officially, nobody should be fishing there, but reality looks different: despite international pressure, Mexico has so far failed to enforce the ban consistently.

And yet there are tiny glimmers of hope. Some animals bear scars suggesting that they have learned to escape the nets. In 2024, Sea Shepherd even managed to film a mother with her calf, a rare and encouraging sign of reproduction. But soberly speaking, the outlook is bad: with fewer than ten individuals, the vaquita is listed by the IUCN as Critically Endangered. Such a tiny population is hardly enough to survive in the long term.

Rice’s whale – Gulf of Mexico – about 50 animals

Rice’s whale (Balaenoptera ricei) is perhaps the newest whale species in the world: only in 2021 was it confirmed that this is not a local population of Bryde’s whale (B. edeni brydei), but a distinct, clearly separate baleen whale species. It was identified through the examination of a stranded animal in Florida; only genetic analyses and skull comparisons brought certainty. The Gulf of Mexico thus got its very own whale, with the label Critically Endangered (IUCN).

The population is estimated at only about 50 individuals. That makes Rice’s whale one of the rarest great whale species on Earth. It spends the entire year in the northeastern Gulf of Mexico, preferring the edge of the continental shelf at depths of 100 to 400 meters, so its habitat is extremely limited.

The dangers facing the species are many: Rice’s whales rest close below the water surface at night and are therefore easily struck by ships. Underwater noise, for example from shipping or seismic surveys for oil and gas, also impairs the animals’ communication and orientation. The Deepwater Horizon oil spill of 2010 probably wiped out a fifth of the entire population. Other risks include contact with fishing gear and the ingestion of marine debris.

Protecting this species is a real challenge: with so few animals and such a small range, every loss matters. Experts are therefore calling for speed limits for ships in core zones, stricter rules for oil and gas activities, and effective monitoring of the habitat. Whether this “new” whale has a future will likely be decided in the coming decades. Marine biologist Jeremy Kiszka once put it aptly: “Honestly, I would not bet my life that Rice’s whale will still exist in 50 years.”

Māui dolphin (Popoto) – west coast of New Zealand’s North Island – 48–64 animals

The Māui dolphin (Cephalorhynchus hectori maui) is one of the rarest dolphins in the world, and one of the smallest as well. It lives exclusively along a short stretch of the west coast of New Zealand’s North Island, mostly in very shallow water less than 20 meters deep. Taxonomically, it is considered a subspecies of Hector’s dolphin, which occurs around the South Island.

The latest estimates speak of only 48 to 64 individuals older than one year, in other words hardly more than 55 adult animals in total. New Zealand therefore classifies the Māui dolphin as “nationally critical”: at acute risk of extinction.

It is threatened on many fronts: the greatest danger comes from gillnets, in which the animals drown. Added to that are diseases such as toxoplasmosis and brucellosis, which can weaken entire groups. Shipping, tourism, and underwater noise create further disturbance, and climate change worsens the situation, because in its already warm habitat prey fish are becoming increasingly scarce.

There are already various protective measures along the west coast, such as bans on gillnets and trawling, but their impact depends heavily on monitoring and consistent enforcement. At the same time, researchers, NGOs, and citizen science projects are working on monitoring and health checks. The crucial point remains: push nets back further, address disease sources on land (toxoplasmosis inputs), and keep coastal habitats as undisturbed as possible.

Burrunan dolphin – southeastern coast of Australia – <200 animals

The Burrunan dolphin (Tursiops australis) is something like Australia’s “own” dolphin, and at the same time a mystery. Only described in 2011 after having been confused for centuries with the common bottlenose dolphin (Tursiops truncatus), it is now considered critically endangered. About 120 animals live in Port Phillip Bay right on Melbourne’s doorstep, and another 30 in the Gippsland Lakes. Small, poorly studied groups also exist in Tasmania and South Australia. All in all: well under 200 individuals.

Its species status remains disputed to this day: some scientific societies view the Burrunan dolphin more as a special bottlenose population, while others emphasize its genetic and morphological distinctiveness.

Threats are plentiful. Especially dramatic was a mass die-off in 2020, when more than 60% of the dolphins in the Gippsland Lakes died from a novel skin disease. It occurs when, after heavy rainfall, too much freshwater suddenly flows into the lagoons and the salinity balance tips. Pollutants are also a problem: Burrunan dolphins show the highest levels of PFAS chemicals recorded anywhere in the world, and high mercury concentrations also burden the animals. Shipping, algal blooms, climate impacts, and the destruction of coastal habitats further worsen the situation. Also critical is the low genetic diversity: the two main populations are isolated, have different “dialects” and hunting strategies, and there is practically no exchange.

The Project Burrunan of the Marine Mammal Foundation offers hope by bringing together scientists, First Nations communities, and citizen researchers. Together they monitor occurrence, health, and behavior of the animals, analyze threats, and develop conservation strategies. Whether the Burrunan dolphin survives in the long term depends decisively on whether Australia succeeds in consistently securing its last refuges.

North Pacific right whale – western North Atlantic – about 370 animals

The North Pacific right whale (Eubalaena glacialis) is a prime example of a great whale in distress: large, slow, and coastal, and therefore especially vulnerable. According to the NOAA 2025 calving season report, only about 370 animals remain, including just around 70 reproductive females. In winter 2024/25, eleven calves were counted. But since 2017, an Unusual Mortality Event has been underway: more than 20% of the population has since been injured or killed, mostly by entanglement in fishing lines or by ship collisions.

This is especially serious because right whales reproduce very slowly. A female reaches sexual maturity only late, produces only one calf at a time, and actually needs several years of recovery in between. Today, the intervals are six to ten years, further lengthened by additional stress from injuries, ship noise, and shifting food webs. To stop the downward trend, at least 50 calves per season would be needed, but in reality the number is often only around ten to 15.

The whales traditionally calve in the shallow coastal waters from Georgia and Florida up to South Carolina. In 2025, however, several mother-calf pairs were also sighted outside the usual region, an indication that right whales are responding flexibly to changing conditions, but also that they need large-scale protection.

The IUCN lists the species as Critically Endangered. What would help is actually obvious: make ships travel more slowly, maintain minimum distances, use fishing gear without fixed vertical lines, and consistently protect critical habitats. Every single surviving right whale counts.

Saimaa ringed seal – Lake Saimaa, Finland – about 430 animals

The Saimaa ringed seal (Pusa hispida saimensis) is one of the rarest seal taxa in the world, and one of the very few that live exclusively in freshwater. Its only occurrence is Lake Saimaa in southeastern Finland, a huge labyrinthine lake system that was cut off from the sea during the last Ice Age.

Today, only around 430 animals remain (as of 2024). The IUCN classifies the subspecies as Endangered. In the 1980s, the population had even fallen below 200 individuals. Only intensive conservation measures prevented extinction.

The greatest threat to the Saimaa ringed seal is climate change. These seals give birth in snow lairs along the shore in winter, but winters on Lake Saimaa are becoming ever shorter and less snowy. Without protective snow, many pups freeze, starve, or become easy prey for predators. In addition, seals, especially young animals, drown every year as bycatch in gillnets. Construction along the lakeshore and growing tourism further constrain the habitat.

Today the subspecies is strictly protected. Net bans in sensitive areas, artificial snowdrifts as replacements for natural lairs, and local awareness efforts are meant to secure a future for the seals. The population is growing slowly, a success that nevertheless remains fragile. Whether the Saimaa ringed seal can survive in the long term depends on how strongly the climate changes in Finland and whether protective measures are consistently respected.

Baiji (Chinese river dolphin) – Yangtze, China – 0–5 animals?

Whether the baiji (Lipotes vexillifer) is still alive is highly doubtful. There have been no confirmed records for more than 20 years, and even large-scale search efforts have failed. In 2007, after a six-week expedition without results, zoologist Samuel T. Turvey proposed classifying the species as “functionally extinct”, meaning that even if individual animals still exist, they are no longer enough for a reproducing population. Because of alleged sightings, the IUCN remains cautious and continues to list the baiji as Critically Endangered (Possibly Extinct).

Why did it disappear? The Yangtze became uninhabitable for the baiji. Large dams and river engineering fragmented its habitat, while pollution and overfishing caused prey fish to disappear. Added to that were gillnets, illegal fishing methods, ship collisions, and the constant noise of shipping, which disrupted echolocation. The species also reproduced slowly and suffered from low genetic diversity; conservation measures came too late and were too weak.

Today, the habitat remains under massive pressure, and the chances that the baiji has survived are vanishingly small. Other inhabitants of the Yangtze are also on the brink: the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) and the Chinese alligator (Alligator sinensis) are Critically Endangered, the Yangtze sturgeon (Acipenser dabryanus) is considered Extinct in the Wild, of the Yangtze giant softshell turtle (Rafetus swinhoei) only two males remain, and the Chinese paddlefish (Psephurus gladius) disappeared entirely between 2005 and 2010.

Why are marine mammals so often threatened?

Whether whales, dolphins, porpoises, or sea cows, marine mammals often seem large, powerful, and adaptable. But in reality, many of them are among the most vulnerable species of all. Their habitat, the oceans and coasts, has been altered so heavily by humans that many populations scarcely stand a chance anymore. A 2023 analysis shows that around a quarter of all whale, dolphin, and porpoise species are considered threatened, and the situation is especially severe for species living in coastal waters or rivers.

Not only whales and dolphins suffer from human impacts, the peaceful sea cows, manatees (Trichechus) and dugongs (Dugong dugon), are also under pressure. They are pure herbivores and graze seagrass meadows, yet precisely these habitats are disappearing due to coastal construction, pollution, and the climate crisis. Added to this are injuries from boat propellers and bycatch in nets. The situation in the South China Sea is particularly alarming: there, the dugong has been considered functionally extinct since 2022. All four still-living sea cow species are now listed as Vulnerable on the IUCN Red List. Their future depends on whether their last refuges are protected consistently.

The causes are varied, but they often interact:

• Bycatch in nets: Gillnets and drift nets are deadly traps, as in the case of the vaquita in Mexico or river dolphins worldwide.
• Shipping and collisions: Slow-swimming species such as the North Pacific right whale or Rice’s whale are especially easily struck.
• Underwater noise: Constant sound from shipping, oil and gas exploration, or construction work disrupts communication, orientation, and feeding.
• Pollution and habitat loss: Plastic waste, chemicals, and coastal development destroy seagrass meadows and kelp forests, important habitats for many marine mammals.
• Climate crisis: Warming, marine heat waves, algal blooms, and shifting food webs further aggravate the situation.

How can marine mammals be saved?

Marine mammals have seen both sad losses and impressive successes in recent decades. Some species, such as the vaquita or Rice’s whale, have been pushed to the brink of extinction. Others, such as the Mediterranean monk seal (Monachus monachus) or humpback whales (Megaptera novaeangliae), have been able to recover at least partly thanks to consistent conservation measures. These experiences make one thing clear: protective measures are effective only when they are implemented consistently and over the long term.

Important measures include:

• Net-free zones & effective enforcement: bans on gillnets in sensitive habitats, alternative fishing gear (“ropeless gear”), and consistent monitoring.
• Safer shipping: speed limits, altered routes in collision hotspots, and distance rules around whales and dolphins.
• Noise reduction: quieter propellers, reduced speeds, and restrictions on especially loud industries such as oil and gas exploration.
• Protecting and restoring habitats: conservation and restoration of seagrass meadows, kelp forests, and undisturbed resting sites.
• Involving communities: cooperation with fishers through compensation payments, alternative livelihoods, and participatory monitoring.
• Improving the data basis: acoustic monitoring, photo-identification, environmental DNA, and the systematic investigation of stranded dead animals.

Marine mammals are resilient “engineers” of their ecosystems, they help maintain the balance of the seas. But their future depends directly on our actions. The examples show: where protection exists only on paper, extinction looms. Where it is implemented consistently, there is hope for recovery.

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