Mediterranean Monk Seal

The Mediterranean monk seal is one of the rarest marine mammals in the world and one of only a few pinniped species to reside in tropical and subtropical waters. Currently, only 600 to 700 individuals remain. Major threats to the Mediterranean monk seal include displacement and habitat deterioration, deliberate killing by humans, and fisheries bycatch and entanglement. The Mediterranean monk seal is found in the Mediterranean Sea and the eastern Atlantic Ocean along the coast of Northwest Africa. The Mediterranean monk seal is listed as endangered under the Endangered Species Act and depleted under the Marine Mammal Protection Act.

 Newborn pups have a black or dark brown woolly coat called “lanugo” with a white, sometimes spotted, patch on the belly side of the seal. The shape, size, spot-pattern, and position of the patch varies between seals and can be used to identify individual seals and their gender prior to the first molting. When the pup is approximately four to eight weeks old, the first molt occurs, and short, glossy, grey hair replaces the long, black lanugo. At the adult and juvenile stages, the seal’s coat becomes short and bristly. Adult males have a black fur coat and usually retain the white ventral patch. In contrast, adult females typically exhibit a brown or gray coat with a lighter belly.

Historically, monk seals hauled out on open beaches for resting and pupping, but due to centuries of human persecution and disturbance, they have been extirpated from much of their original habitat. Now in response to anthropogenic pressures, females tend to give birth in remote, marine caves. Pupping females prefer caves where they and their pups cannot be seen. These caves also tend to have some light, multiple entrances/escape routes, a low risk of pup washout, interior beaches with soft substrate, and are not easily accessible to humans. Generally, Mediterranean monk seals are thought to dive and feed in shallow, nearshore waters. Mediterranean monk seals are considered opportunistic predators and feed on a variety of prey including, bony fishes, cephalopods (mainly the common octopus Octopus vulgaris), and crustaceans.

The current distribution of the Mediterranean monk seal encompasses the eastern Mediterranean and the Northeast Atlantic (i.e., the peninsula of Cabo Blanco on the coasts of Western Sahara and Mauritania and the archipelago of Madeira). Each location supports an isolated subpopulation of seals. Historically, the species was present throughout the Mediterranean and Black seas and throughout North Atlantic waters from Cabo Blanco to Spain.

Female Mediterranean monk seals typically reach sexual maturity between 5 and 6 years of age, while the earliest age males have been observed mating is 7. Over the last 30 years, however, female monk seals have been observed mating earlier. Mating of Mediterranean monk seals takes place in the water. Gestation lasts 9-11 months and females give birth to one pup. Female monk seals can give birth in consecutive years and often give birth within the same few days each year. Although pups may be born year-round, most pupping takes place in autumn.

Habitat destruction and degradation

The curtailment of the Mediterranean monk seal’s range is largely due to habitat deterioration and human encroachment. Anthropogenic pressures have forced the species to shift from hauling out on open beaches to inaccessible marine caves, which had devastating effects on pup survival. The construction of hotels, roads, houses, and thermal and nuclear power plants has been linked to substantial decreases in pup survival. Some hotels have even been constructed directly atop marine caves used by the seals for breeding.

While construction represents a substantial threat to the seals, tourism (and the construction it prompts) is arguably the largest threat monk seals now face. Disturbance by high-intensity tourism may be responsible for somewhat recent extirpations of small surviving populations in the Mediterranean. In Turkey, diving tourists frequent monk seal habitat and pupping activity has ceased at many of these sites. Increased boat activity (for pleasure boating, recreational fishing, diving, etc.) has also led to a number of boat strikes and has allowed tourists to reach even the most isolated areas. Tourism continues to threaten this species in Morocco, Greece, and Turkey. 

Harassment and Entanglement

The frequency of fishery-related deaths (i.e., deliberate killings and entanglements) are considered one of the main threats prohibiting the recovery of the Mediterranean monk seal. Deliberate killings are usually committed by fishermen in response to damage to fishing gear or lost catch. Although the deliberate killing of a monk seal is illegal, fishermen have been observed shooting seals and using explosives in occupied caves. Deliberate killing is primarily a threat to this species in the areas of Greece, Turkey, and Cabo Blanco. 

Accidental entanglement in fishing gear and drowning as a result of entanglement (especially in static nets) is also a major source of mortality, particularly for sub-adult monk seals in the eastern Mediterranean. Tempted by an easy meal, younger seals tend to be less cautious and experienced than adults when approaching nets and often are not strong enough to disentangle themselves. Monk seals can become entangled in a wide variety of fishing gear, including set-nets, trawl nets, and long lines.