The vaquita is the rarest marine mammal in the world, and critically endangered, according to the International Union for the Conservation of Nature (IUCN). In 2016, it was estimated that there were only 30 of these porpoises left in existence. But new research suggests that the number has been cut down by more than a third—with less than 20 vaquitas left on Earth. Which is likely too small a population for the vaquita to successfully reproduce and replenish its population. Here are 11 things to know about the species before it disappears forever.

1. Scientists first identified the vaquita in 1958.

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In 1950, University of California scientist Kenneth Norris found a bleached skull on a beach north of Punta San Felipe in Baja, California. A year later, Norris's colleagues found two more. When a colleague compared the skulls to those of another porpoise at the Museum of Vertebrate Zoology at Berkeley, California, they noticed differences striking enough to consider the finds a new species. Norris first described Phocoena sinus (gulf porpoise) in the Journal of Mammalogy in 1958.

2. Vaquita means "little cow" in Spanish.

The vaquita measures about 5 feet long (the females are slightly larger than the males) and weighs no more than 100 pounds. They're the smallest of all porpoises, with chunky bodies and rounded heads. Dark rings surround their eyes and mouths, which may account for their common name (vaquita means “little cow” in Spanish). Living in relatively shallow, cloudy water, they feed on a variety of fish, squid, and crustaceans.

3. Scientists can identify individual vaquitas based on a single feature.

Some vaquitas have individually distinctive nicks and notches on their dorsal fins, which makes it possible to identify specific individuals from high-quality photographs. Beginning in 2008, scientists created a catalog of these photos, adding new individuals and recording sightings of previously identified animals. Photo ID catalogs serve as a tool to help track an individual, revealing its life history, social organization, movements, and habitat use. Researchers use them with many marine animals that have distinctive markings. Individual manta rays, for example, can be identified by the spot patterns on their undersides.

4. The vaquita is found in only one place in the world.


Vaquitas live only in the northern Gulf of California, the body of water between Baja. California and mainland Mexico. They're homebodies, staying within the northernmost part of the Gulf, and have the smallest range of any cetacean (the taxonomic order including whales, dolphins, and porpoises). Vaquitas reproduce only once every two years, while most porpoises have a calf every year. They're most closely related to porpoises in South America, but the species diverged from these relatives at least 2.5 million years ago.

5. Up to 15 percent of vaquitas died in fishing nets every year.

For decades, fishermen after shrimp and finfish such as corvina and sierra unintentionally entangled and drowned vaquitas in their gillnets; these long, curtain-like nets float in the water, snagging the gills of fish and shrimp that swim into them. A study showed that boats from a single fishing port in the upper Gulf accounted for the fatal bycatch of 39 to 84 vaquitas each year—an annual death sentence for 7 to 15 percent of the total population.

By the 1980s, the problem had become so bad that the vaquita was listed as endangered under the U.S. Endangered Species Act in 1985 and a year later as vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Some good news came when UNESCO declared the upper Gulf of California a Biosphere Preserve in 1995, but it didn't do much good—just a year later, the IUCN changed the vaquita's status to critically endangered.

6. Fishing nets meant to be vaquita-proof couldn't compete with illegal fishing ...

In 2006, scientists and conservationists began developing gear that could catch fish and shrimp without harming vaquitas, including smaller nets dragged behind boats that the porpoises could avoid. Some fishermen in the Gulf agreed to test the gear. The initial results looked promising, and those efforts may well have eventually succeeded, but a bigger threat loomed: illegal fishing for totoaba, a large fish that had also been critically endangered for two decades. A single dried swim bladder of a totoaba can fetch as much as $50,000 in China, where they are given as gifts, eaten, or used in traditional medicine. People fishing illegally for totoaba continue to use gillnets, outweighing any benefit the safer, vaquita-proof nets might have had.

7. ... So the first official population estimate, in 1997, was bad news.

Scientists have a hard time making precise estimates of the number of rare and cryptic (hard to find) species such as the vaquita. These porpoises prove particularly challenging, as they tend to avoid motorized boats, travel alone or in pairs, and are barely noticeable when they surface to take slow breaths. They're so shy that some locals say they've never seen one.

In 1997, scientists from the U.S. and Mexico spent days aboard a 170-foot ship motoring in a grid pattern over water up to 165 feet deep, trying to spot and count vaquitas. They estimated the total population was 567, which probably already reflected a significant decline due to intense fishing activity and less water emptying into the Gulf from the Colorado River, which was siphoned upstream by farms and towns. The IUCN ran models using fisheries data, the 1997 population number, and other counts, and estimated that, in the early 20th century, the vaquita population may have been 5000.

8. In 2005, the Mexican government banned gillnets to protect vaquitas.

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The alarming 1997 count spurred scientists to form the International Committee for the Recovery of the Vaquita (CIRVA in Spanish), operating with an environmental division of the Mexican government. Mexico established a Vaquita Refuge in 2005 and, after many years of urging by the members of CIRVA to permanently ban gillnets, recently prohibited all gillnet fishing in the porpoise's range—but just for two years. Mexico also provided compensation equivalent to millions of dollars to local people in the fishing industry left high and dry by the ban.

Conservation groups such as Greenpeace, the World Wildlife Fund, and Sea Shepherd Conservation Society patrol the Gulf for illegal fishing, but the totoaba trade continues. The black market money is just too good, says Andy Read, a marine biologist at Duke University and member of CIRVA. "From the perspective of the fishermen, what they could make legally fishing versus illegally fishing for totoaba, there is enormous incentive," Read tells Mental Floss. And, as a recent CIRVA report notes, "laws and enforcement are simply too weak to deter or prevent illegal fishing."

9. Despite these efforts, the vaquita population continued to plummet.

In 2008, CIRVA scientists conducted another ship-based visual survey, scanning the water for vaquitas with high-powered binoculars that could see as far as 3 miles. (Vaquitas tend to stay at least a half-mile away from boats.) They estimated the vaquita population at 245. In 2011, they tried another count, this time relying not on sightings of vaquitas, but a more accurate measure: passive acoustic monitoring devices in the water that detect sounds made by the animals. Vaquitas and other porpoises navigate by echolocation, producing distinctive clicks and whistles. "The devices look for a particular frequency," Read explains. "Nothing else makes sound in the same range, and vaquitas are acoustically very active."

For the next four years, they acoustically monitored Gulf waters—and were dismayed to see the vaquita population drop by 34 percent per year. Another CIRVA survey in 2015 combined visual and passive acoustic data collected simultaneously and made a dismal finding: Only 59 vaquita remained. The population had plummeted by 92 percent since 1997.

10. In 2017, scientists attempted to keep vaquitas in a sea pen.


In 2017, CIRVA scientists desperate to find a solution recommended a controversial plan: Capture vaquitas, keep them in net pens in the Gulf, and hope they would reproduce.

They had no idea whether it would work. No vaquita had ever been kept in captivity, no one knew how the animals would respond, and the effort would only pay off in the unlikely event that gillnet fishing in the Gulf completely stopped. Still, they formed an international team called VaquitaCPR to give it a try. The group subsequently built a high-tech "floating sea enclosure," which they anchored in the Gulf not too far from the beach where the first vaquita skulls were discovered.

In October 2017, VaquitaCPR scientists managed to capture two of the animals. The first, a young female, showed signs of stress—including increased heart rate and respiration rate—so they immediately released her. The second, a mature female, was transported in a stretcher placed inside a box partially filled with sea water to one of the pens and initially seemed to handle the experience well. Then she began swimming frantically and crashing into the sides of the net before finally going limp. The team released her, but she panicked, swimming at the net again. Veterinarians on the team jumped into the water, realized she wasn't breathing, and attempted to resuscitate her. Three hours later, they declared the animal dead, likely due to cardiac arrest.

After that, Read and many other scientists say they were heartbroken, but still felt that the risk of extinction outweighed those of capture. Others disagreed.

"Porpoises generally, like most cetaceans, do not fare well in captivity," Will McCallum of Greenpeace tells Mental Floss. "The population was already drastically depleted, and any capture or rounding up adds extra stress to the remaining animals. The likelihood of vaquita surviving, breeding, and being released was slim."

Efforts continue to enforce the gillnet ban and remove gillnets in the reserve, but they may be too little, too late. "We should have been perfectly able to save the vaquita,” McCallum says. "We know where they are and what needed to happen to save them in the wild."

11. Scientists have sampled and preserved vaquita cells.

Some hope remains, though; cell samples taken by the VaquitaCPR team from the two captured vaquitas have been successfully cultured in the lab and frozen for use in future research. Scientists also plan to use the cells to sequence the vaquita genome.

This story has been updated for 2019.