Mediterranean monk seal
Mediterranean monk seal.
The Mediterranean monk seal (Monachus monachus), also known as the Pied monk seal, is one of nineteen species of marine mammals in the family of true seals. Together with the families of Eared seals and Walruses, True seals form the group of marine mammals known as pinnipeds.
The Mediterranean monk seal is one of the most critically endangered mammals in the world. Over the last several centuries this species has been persecuted and killed in significant numbers by fishermen, who have perceived this seal as a competitor in commercial fisheries. In addition, boat traffic, human use of haul out beaches and water pollution are ongoing threats to this animal, who is on the brink of extinction. The description of this species by Aristotle was the first known written account of a pinniped, and the head of a monk seal appeared on one of the early coins, around 500 BC.
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Physical Description
 Mediterranean monk seal. Source: Giovanni Dall'Orto |
Conservation Status  |
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Scientific Classification Kingdom: Animalia (Animals) |
Adult Mediterranean monk seals can be any color from dark brown or black to light grey. They are typically light gray along the belly. Older males are darker in colour and often become black, but retain the ventral white patch.
Pups have a black woolly coat and a white or yellow patch on the belly, the shape of which can sometimes be used to determine the sex of an individual. They molt at about four to six weeks and their black woolly coat is replaced by a silvery gray coat that can darken over time.
Adult males are on average about 2.4 metres in length, with females being of slightly less stature. Males weigh about 315 kilograms (kg), and females weigh about 300 kg.
Reproduction/lifespan
Mediterranean monk seals mate during the months of September to November, with mating chiefly taking place in the water. They reproduction rate is slow, eith sexual maturity not commencing until age of four or six. The time interval between births is 13 months, and the gestation period is 11 months. Pups are born about 80-100 centimetres long and weigh 17-24 kg.
Prior to females giving birth, they haul out onto a beach or seek refuge in caves. A female will usually remain on the beach or in the cave nursing and protecting the pup for up to six weeks. During this time, the female must live off of stored fat because she never leaves the pup, not even to feed herself. The pup may remain with its mother for as long as three years after weaning.
The social organisation of the Mediterranean monk seal is not known, but groups tend to form in the breeding caves.This seal species may realise a life span of up to 30 years.
Behavior
The Mediterranean monk seal spends most of its time in a limited range, and never migrate long distances. There can be up to 20 individuals in a colony of Mediterranean monk seals. On land, the seal is a solitary species. In the water, they more gregarious and are excellent divers and swimmers. They swim so well that they can outmaneuver a shark. When communicating with each other they make very high pitched sounds. This vocalisation is accomplished mainly while in the water, to let each other know if something is wrong or if danger is approaching.
Distribution
Coastal distribution of the Mediterranean monk seal; the Libyan population is now regarded as extirpated. Once widespread throughout the Mediterranean (Mediterranean Sea), the Black Sea and the northwestern coast of Africa, this monk seal has suffered a devastating population decline. It is now restricted to a handful of small and scattered colonies in the Ionian and Aegean Seas and the southern coast of Turkey in the Mediterranean, as well as scattered populations on the coasts of the western Sahara and Mauritania, and the Portuguese Desertas Islands, Madeira. It is thought that just two of these populations are viable, in Greece and northwest Africa. Mediterranean monk seals are thought to have been extirpated along the Libyan coast, due to water pollution and lack of protection in that locale. The species has not been seen in the Black Sea for over five years. Although no reliable estimates of total population size exist, it is thought to number between just 400 to 500 individuals, and is declining.
Habitat
Mediterranean monk seals are usually found along coastal waters, especially on the coastlines of islands. They are sometimes found in sea caves with submarine entrances, when the female is giving birth or to seek refuge fom other disturbances, such as boating activity.
Food Habits
Mediterranean monk seals are diurnal. They feed in shallow coastal waters on a large variety of fish. Specific prey include eels, sardines, tuna, lobsters, flatfish and mullets. They also feed on cephalopods such as octopuses.
Conservation Status
The Mediterranean monk seal is critically endangered, with a total worldwide population probably in the range of 350-450. It is estimated that there were twice this number 20 years ago. The number of sexually mature Mediterranean monk seals in thought to be less than 250. With such a small genetic pool, this species has probably already reached a population bottleneck, such that risk of extinction is magnified by loss of genetic diversity and hence reduced immunity to disease and other threats where genetic variety can assist in defending the species from extinction.
This taxon is classified as Critically Endangered (CR) by the IUCN Red List 2008. Listed on Appendix I of CITES and Appendices I and II of the Convention on Migratory Species (CMS, or Bonn Convention). The IUCN Species Survival Commission Seal Specialist Group has devised an Action Plan for the conservation of the species, the aims of which include the involvement of local fishermen, research into the status of the species and the development of a captive breeding programme. A Greek National Programme for the Protection of the Monk Seal has been established, aiming to prevent human-induced mortalities of the species and to restore and maintain a viable self-supporting population. Some experts believe that the removal of pups from a population, to supply a captive programme, could severely affect breeding within the wild population, and injure the pups concerned. Captive breeding is usually recommended for mammal species of such low numbers as this and with threats continuing in the wild, but concerns that removing young seals from the wild will not severely affect breeding in the wild and will not injure or negatively affect survival of the captured young must be adequately addressed. It is clear that determined action is urgently required if this reclusive, beleaguered species is to escape total extinction.
Mediterranean monk seals are highly sensitive to disturbance and humans have extensively used both the sea and beaches of their habitat for centuries, causing the population to collapse. The main threats facing this species are deliberate killing by fishermen who perceive the species as a competitor for fish, entanglement in fishing gear, disturbance and habitat loss through development and tourism, disease, and the effects of toxic algal blooms. These shy creatures have taken to hauling out in caves to give birth, rather than on developed beaches, and the collapse of such caves is a further threat to the survival of the species.
In 1996-7 timeframe, over half of the seals in the largest population, located at Cabo Blanco, Mauritania, were lost, their number dropping from an estimated 317 to less than 130. It is believed that the most likely cause of this die off was the accumulation of toxins in fish following an algal bloom.
Economic Importance for Humans
In the past the Mediterranean monk seal was killed for its skin and body parts, which were reputed to provide protection against a variety of medical problems. The seal has also been killed for food. The only way that Mediterranean monk seals affect humans negatively is minor competition with fishermen.
Further Reading
- Monachus monachus (Hermann, 1779) Encyclopedia of Life (accessed May 13, 2010)
- Monachus monachus, Benton, M., 2000, Animal Diversity Web (accessed May 13, 2010)
- [1]Monachus monachus, IUCN Red List of Threatened Species (accessed May 13, 2010)
- The Pinnipeds: Seals, Sea Lions, and Walruses, Marianne Riedman, University of California Press, 1991 ISBN: 0520064984
- Encyclopedia of Marine Mammals, Bernd Wursig, Academic Press, 2002 ISBN: 0125513402
- Marine Mammal Research: Conservation beyond Crisis, edited by John E. Reynolds III, William F. Perrin, Randall R. Reeves, Suzanne Montgomery and Timothy J. Ragen, Johns Hopkins University Press, 2005 ISBN: 0801882559
- Walker's Mammals of the World, Ronald M. Nowak, Johns Hopkins University Press, 1999 ISBN: 0801857899
- Mediterranean monk seal, MarineBio.org (accessed May 13, 2010)
