It is endemic to the northern part of the Gulf of California.
The vaquita (Phocoena sinus) is a rare species of porpoise. The estimated number of individuals dropped below 100 in 2014, putting it in imminent danger of extinction. Since the baiji(Lipotes vexillifer) is believed to have gone extinct by 2006, the vaquita has taken on the title of the most endangered cetacean in the world.
Vaquitas are the smallest and most endangered species of the cetacean order and are endemic to the northern end of the Gulf of California. The vaquita is stocky and has a classic porpoise shape. The species is distinguishable by the dark rings surrounding their eyes, patches on their lips, and a line that extends from their dorsal fins to their mouth. Their back is a dark grey that fades to a white underside. As vaquitas mature, the shades of grey lighten.
Female vaquitas tend to grow to be a bit larger than the male. Females usually end up at a length of 140.6 cm (55.4 in), compared to the males 134.9 cm (53.1 in). The lifespan, pattern of growth, seasonal reproduction, and testis size of the vaquita are all similar to that of the harbour porpoise. The flippers are proportionately larger than 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 females are discernible from the males due to their larger size.
Vaquitas tend to forage near lagoons. 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. Vaquitas appear to be rather nonselective feeders on small fish and squid in this area. Some of the most common prey are teleosts (fish with bony skeletons) such as grunts, croakers, and sea trout. Like other cetaceans, vaquitas may use echolocation to locate prey. It also is possible they locate their prey by following the sounds of prey movement.
Little is known about the life cycle of vaquitas. Researchers are still determining things such as their age at sexual maturity, longevity, reproductive cycle and population dynamics. It is believed that vaquitas live approximately 20 years in ideal conditions. Vaquitas sexually mature at 1.3 meters, as early as 3 years but more likely at 6 years old. Reproduction occurs during late spring or early summer. Their gestation period is between 10 and 11 months. They have seasonal reproduction, and usually have one calf in March. The interbirth period, or elapsed time between offspring birth, is between 1 and 2 years. The young are then nursed for about 6 to 8 months until they are capable of fending for themselves.
Vaquitas use high-pitched sounds to communicate with one another and for echolocation to navigate through their habitats. They generally seem to feed and swim at a leisurely pace. Vaquitas avoid all boats and are very evasive. They rise to breathe with a slow forward motion and then disappear quickly. This lack of activity at the surface makes them difficult to observe. Vaquitas are usually alone unless they are accompanied by a calf, meaning that they are less social than other dolphin species. They may also be more competitive during mating season. They are the only species belonging to the porpoise family that live in warm waters. Vaquitas are nonselective predators.