The Mediterranean monk seal (Monachus monachus) is a monk seal belonging to the family Phocidae. , 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 long at birth up to an average of as adults, females slightly shorter than males. Males weigh an average of and females weigh , with overall weight ranging from . 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 long and weigh around , 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
The Mediterranean monk seal can be found in the Mediterranean Sea off of Croatia, Cyprus, Greece, Albania, and Turkey, as well as the North Atlantic Ocean off of Madeira, Mauritania and Western Sahara. It may be locally extinct (extirpated) in and around Corsica, Egypt, France, Italy, Libya, Malta, Monaco, Montenegro, southern Spain (and the Balearic Islands), and Tunisia. Its status in Algeria, Israel, Lebanon, Morocco and Syria is unknown.
This earless seal's historical range extended from the northern Atlantic coastline of Western Africa east to the Black Sea, including all offshore islands within the Mediterranean, the Canary Islands, Madeira, Desertas, Porto Santo, and as far west as the Azores. Vagrants could be found as far south as The Gambia and the Cape Verde (Cabo Verde) islands, and as far north as Portugal to Northern Spain and the Bay of Biscay to the coast of Brittany.
Several causes provoked a dramatic population decrease over time: on one hand, commercial hunting (especially during the Roman Empire and Middle Ages) and, during the 20th century, eradication by fishermen, who used to consider it a pest due to the damage the seal causes to fishing nets when it preys on fish caught in them; and, on the other hand, coastal urbanization and pollution.
Some seals have survived in the Sea of Marmara, but the last report of a seal in the Black Sea dates to 1997. Monk seals were present at Snake Island until the 1950s, and several locations such as the and Doğankent were the last known hauling-out sites post-1990.
Nowadays, its entire population is estimated to be less than 700 individuals widely scattered, which qualifies this species as endangered. Its current very sparse population is one more serious threat to the species, as it only has two key sites that can be deemed viable. One is the Aegean Sea (250–300 animals in Greece, with the largest concentration of animals in Gyaros island, and some 100 in Turkey); the other important subpopulation is in the Atlantic Ocean, in the Western Saharan portion of Cabo Blanco (around 270 individuals which may support the small, but growing, nucleus in the Desertas Islands – approximately 30–40 individuals). There may be some individuals using coastal areas among other parts of Western Sahara, such as in Cintra Bay.
These two key sites are virtually in the extreme opposites of the species' distribution range, which makes natural population interchange between them impossible. All the other remaining subpopulations are composed of less than 50 mature individuals, many of them being only loose groups of extremely reduced size – often less than five individuals.
Other remaining populations are in southwestern Turkey and the Ionian Sea (both in the eastern Mediterranean). The species status is virtually moribund in the western Mediterranean, which still holds tiny Moroccan and Algerian populations, associated with rare sightings of vagrants in the Balearic Islands, Sardinia, and other western Mediterranean locations, including Gibraltar.
In Sardinia the Mediterranean monk seal was last sighted in May 2007 and April 2010. The increase of sightings in Sardinia suggests that the seal occasionally inhabits the Central Eastern Sardinian coasts, preserved since 1998 by the National Park of Golfo of Orosei.
Colonies on the Pelagian Islands (Linosa and Lampedusa) were destroyed by fishermen, which likely resulted in local extinction.
Cabo Blanco 1997 die off and recovery
Cabo Blanco, in the Atlantic Ocean, is the largest surviving single population of the species, and the only remaining site that still seems to preserve a colony structure. In the summer of 1997, more than 200 animals or two-thirds of its seal population were wiped out within two months, compromising the species' viable population. While opinions on the precise causes of this epidemic remain divided between a morbillivirus or, more likely, a toxic algae bloom, the mass die-off emphasized the precarious status of a species already regarded as critically endangered throughout its range.
Numbers in this all-important location started a slow-paced recovery ever since. A small but incipient (up to 20 animals by 2009) sub-population in the area had started using open beaches. In 2009, for the first time in centuries, a female delivered her pup on the beach (open beaches are the optimal habitat for the survival of pups, but had been abandoned due to human disturbance and persecution in past centuries).The recovery of the Mediterranean monk seal in the Atlantic: a success history. cbd.int
Only by 2016 the colony had recovered to its previous population (about 300 animals). This was made possible by a recovery plan financed by Spain. Also in 2016, a new record of births was set for the colony (83 pups).
However, the threat of a similar incident, which could severely reduce or wipe out the entire population, remains.
Recent sightings
In June 2009, there was a report of a sighting off the island of Giglio, in Italy. On 7 January 2010, fishermen spotted an injured Mediterranean monk seal off the coasts of Tel Aviv, Israel. When zoo veterinarians arrived to help the seal, it had slipped back into the waters. Members of the Israel Marine Mammal Research and Assistance Center arrived at the scene and tried to locate the injured mammal, but with no success. This was the first sighting of the species in the region since Lebanese authorities claimed to have found a population of 10–20 other seals on their coasts 70 years earlier. In addition, the seal was also sighted a couple of weeks later in the northern kibbutz of Rosh Hanikra.