The Mediterranean monk seal (Monachus monachus) is a monk seal belonging to the family Phocidae. As of 2026, it is estimated that between 800 and 1000 individuals survive in isolated subpopulations in the Mediterranean, (especially) in the Aegean Sea, the archipelago of Madeira, and the Cabo Blanco area in the northeastern Atlantic Ocean spanning the border of Mauritania and Western Sahara. It is believed to be the world's rarest pinniped species. It is the only extant species in the genus Monachus, the other two monk seal species being in Neomonachus.
Description
This species of seal grows from approximately 80 centimetres (2.6 ft) long at birth up to an average of 2.4 metres (7.9 ft) as adults, females slightly shorter than males. Males weigh an average of 320 kilograms (710 lb) and females weigh 300 kilograms (660 lb), with overall weight ranging from 240–400 kilograms (530–880 lb). They are thought to live up to 45 years old; the average life span is thought to be 20 to 25 years old and reproductive maturity is reached at around age four. The monk seals' pups are about 1 metre (3.3 ft) long and weigh around 15–18 kilograms (33–40 lb), their skin being covered by 1–1.5 centimeter-long, dark brown to black hair. On their bellies, there is a white stripe, which differs in color and shape between the two sexes. In females the stripe is usually rectangular in shape whereas in males it is usually butterfly shaped. This hair is replaced after six to eight weeks by the usual short hair adults carry. Adults will continue to molt annually, causing their color vibrancy to change throughout the year. Pregnant Mediterranean monk seals typically use inaccessible undersea caves while giving birth, though historical descriptions show they used open beaches until the 18th century. There are eight pairs of teeth in both jaws. Believed to have the shortest hair of any pinniped, the Mediterranean monk seal fur is black (males) or brown to dark grey (females), with a paler belly, which is close to white in males. The snout is short broad and flat, with very pronounced, long nostrils that face upward, unlike their Hawaiian relative, which tend to have more forward nostrils. The flippers are relatively short, with small slender claws. Monk seals have two pairs of retractable abdominal teats, unlike most other pinnipeds.
Behaviour and ecology
Reproduction
Very little is known of this seal's reproduction. As of 2020, it is thought that there are roughly 500 pairs of monk seals remaining in the world. Scientists have suggested that they are polygynous, with males being very territorial where they mate with females. Although there is no breeding season since births take place year-round, there is a peak in September, October, and November. Although mating will take place in the water, females will give birth and care for the pups on beaches or underwater caves. The use of underwater caves may have begun in order to make predatory actions almost impossible as these caves are difficult to access. Because they will stay with the pups to nurse and protect, they use their stored fat reserves to nurse. Data analysis indicates that only 29% of pups born between September and January survive. One cause of this low survival rate is the timing of high surf around the areas of breeding, creating a threat to young pups. As well, if a female is in an unsafe environment, she may have an abortion, indirectly lowering the population. Because of smaller populations there is an increase in genetic events such as inbreeding and lack of genetic variation. During other months of the year, pups have an estimated survival rate of 71%. In 2008, lactation was reported in an open beach, the first such record since 1945, which could suggest the seal could begin feeling increasingly safe to return to open beaches for breeding purposes in Cabo Blanco. Pups make first contact with the water two weeks after their birth and are weaned at around 18 weeks of age; females caring for pups will go off to feed for an average of nine hours. Most female individuals are believed to reach maturity at four years of age, at which point they will begin to breed. Males begin to breed at age six. The gestation period lasts close to a year. However, it is believed to be common among monk seals of the Cabo Blanco colony to have a gestation period lasting slightly longer than a year.
Diet Mediterranean monk seals are diurnal and feed on a variety of fish, crustaceans, and mollusks, primarily octopus, squid, lobsters, mullets, flatfish, tuna, sardines, and eels, up to 3 kg per day. Although they commonly feed in shallow coastal waters, they are also known to forage at depths up to 250 meters, with an average depth varying between specimens. Monk seals prefer hunting in wide-open spaces, enabling them to use their speed more effectively. They are successful bottom-feeding hunters; some have even been observed lifting slabs of rock in search of prey.
Habitat
The habitat of this pinniped has changed over the years. In ancient times, and up until the 20th century, Mediterranean monk seals had been known to congregate, give birth, and seek refuge on open beaches. In more recent times, they have left their former habitat and now only use sea caves for these activities. Often these caves are inaccessible to humans. Frequently their caves have underwater entries, and many caves are positioned along remote or rugged coastlines. Scientists have confirmed this is a recent adaptation, most likely due to the rapid increase in human population, tourism, and industry, which have caused increased disturbance by humans and the destruction of the species' natural habitat. Because of these seals' shy nature and sensitivity to human disturbance, they have slowly adapted to try to avoid contact with humans completely within the last century, and, perhaps, even earlier. The coastal caves are, however, dangerous for newborns, and are causes of major mortality among pups when sea storms hit the caves.
Distribution and status
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