Other names include Cochito, Gulf of California Harbor Porpoise, Gulf of California Porpoise, Gulf Porpoise, Hafenschweinswal, and Marsouin du Golfe de Californie
The Vaquita has a classic porpoise shape (stocky and curved into a star shape when viewed from the side). It is the smallest of the porpoises, a group of marine mammals that differ from dolphins in their stockier, robust body, lack of an elongated beak, and their distinctively shaped teeth. Individuals may reach a mature size of 1.2-1.5 m (4-5 ft) and may weigh 40-55 kg (90-120 lb). They have large black eye rings and lip patches. The upper side of the body is medium to dark grey. The underside is off-white to light grey but the demarcation between the sides is indistinct. The flippers are proportionately larger than in other porpoises and the fin is taller and more falcate. The skull is smaller and the rostrum is shorter and broader than in other members of the genus.
The habitat of the vaquita is thought to be restricted to the northern area of the Gulf of California. The vaquita lives in shallow, murky lagoons along the shoreline and is rarely seen in water much deeper than 30 meters; indeed, it can survive in lagoons so shallow that its back protrudes above the surface. The vaquita is most often sighted in water 11 to 50 metres deep, 11 to 25 kilometres from the coast, over silt and clay bottoms. Its habitat is characterised by turbid water with a high nutrient content. Other characteristics of its habitat are strong tidal mixing, convection processes and high primary and secondary productivity.
There are very few records of the Vaquita in the wild. It appears to swim and feed in a leisurely manner, but is elusive and will avoid boats of any kind. It rises to breathe with a slow, forward-rolling movement that barely disturbs the surface of the water, and then disappears quickly, often for a long time. It has an indistinct blow, but makes a loud, sharp, puffing sound reminiscent of the Harbour Porpoise.
Like other phocoenids, the vaquita occurs singly or in small groups, usually from 1 - 3 individuals but as many as 8 - 10.
All of the 17 fish species found in vaquita stomachs can be classified as demersal and or benthic species inhabiting relatively shallow water in the upper Gulf of California, and it appears that the vaquita is a rather non-selective feeder on small fishes and squids in this zone. Like other cetaceans, the vaquita produces high-frequency clicks which are used in echolocation. This may be used to locate their prey, but several of the fish species it feeds on are known to produce sound and so it is possible that the vaquita locates them by following their sound, rather than by echolocating.
Most calving apparently occurs in the spring. Gestation is probably 10–11 months. Maximum observed life span was 21 years.
Vaquita have never been hunted directly. Indeed their continued existence was only confirmed by a dedicated survey in 1985. However, it is known that the vaquita population is declining. Estimates have placed the vaquita population at 567 in 1997 and 150 in 2007. The decline in the vaquita population is believed to be due to the animals becoming trapped in gillnets intended for capturing another species endemic to the Gulf, the totoaba. CIRVA, the Committee for the Recovery of the Vaquita, concluded in 2000 that between 39 and 84 individuals are killed each year by such gillnets. The Vaquita is listed by the IUCN and the Convention on International Trade in the Endangered Species of Wild Fauna and Flora in the most critical category at risk of extinction. In order to try to prevent extinction, the Mexican government has created a nature reserve covering the upper part of the Gulf of California and the Colorado River delta. CIRVA is recommending that this reserve be extended southwards to cover the full known area of the Vaquita's range and that trawlers be completely banned from the reserve area. Even if the number of Vaquita killed by fisheries is reduced to zero, concerns remain amongst conservationists. Use of chlorinated pesticides, reduced flow of freshwater from the Colorado River due to irrigation, and depression due to inbreeding may also have a detrimental effect.
The Vaquita is one of the top 100 EDGE Species, meaning "Evolutionarily Distinct, Globally Endangered". Evolutionarily distinct animals have no close relatives and represent proportionally more of the tree of life than other species, meaning they are top priority for conservation campaigns.
On October 28, 2008, Canada, Mexico, and the United States, under the jurisdiction of the NAFTA environmental organization, the Commission for Environmental Cooperation, launched the North American Conservation Action Plan (NACAP) for the Vaquita. The NACAP is a strategy to support Mexico’s efforts to recover the Vaquita, which is considered the world’s most-endangered marine mammal. The U.S. government has listed the vaquita as endangered under the Endangered Species Act.