BIOLOGY
The Mediterranean monk seal, Monachus monachus, is the rarest of the 33 extant seal species on Earth. It is also the most endangered marine mammal in Europe and one of the most critically endangered animals known. Of the 700 individuals estimated to survive in and around the Mediterranean, almost half of the population lives in Greek territorial waters.
MORPHOLOGY
The Mediterranean monk seal is one of the largest “true” seals (or earless seals) species on Earth. Adult monk seals can reach a length of 2.8 m and weigh as much as 300 kg. Their body is torpedo-like, which, in combination with their flippers, makes moving in the aquatic environment much easier.
Mediterranean monk seals do not have external ears, but small acoustic holes and long, smooth vibrissae (whiskers), which function as sensory organs.
The Mediterranean monk seal is characterized by slight sexual dimorphism (i.e., differences in the appearances between females and males). Adult male Mediterranean monk seals are slightly larger and heavier than adult females.
Newborn pups are approximately 1m long when born and weigh 15-18 kg. The new born pups possess a soft and wooly pelt or “lanugo”, which is approximately 1-1.5 cm long.
Older monk seal pups have a black coat with a distinctive white or yellowish patch on the belly. The shape of this patch characterized each individual as a fingerprint; however, its general pattern differs between male and females and can be used by scientists for individual identification.
Juvenile and sub-adult Mediterranean monk seals have a close-cropped pelt, gray on the back and withish at the belly. However, according to the molting stage, it could appear darker or brownish.
Scars, resulting from interactions with other animals, are used by scientists to help identify individual animals, and are accumulated with age on the animals’ bodies. Adult females, reaching sexual maturity maintain the gray back, withish belly as the previous stages while males when reaching adulthood turn black on the back and it reappears completely the white patch on the belly.
Monk seals can live up to 30-40 years in the wild.
REPRODUCTION
Sexual maturity is attained at 3-4 years of age for females and 5-6 years for males. Monk seals mate in the water and gestation lasts approximately 8 months, after which a single pup is born on land. The pupping season appears to have peaks from June to November, however births are recorded all the year around. Lactation and nursing can last up to 4 months and is the longest known for “true” seals. During lactation, mothers do not fast and often leave their pups unattended in the maternal cave in search of food. Mediterranean monk seals are polygynous, i.e. an adult male will mate with more than one female.
MARINE & TERRESTRIAL HABITAT
Mediterranean monk seals are marine mammals and spend most of their lives at sea, however pinnipeds have preserved a link to dry land, as a place where to haul out to rest, and give birth.
Monk seals once used beaches and marine caves as terrestrial habitat, while today is mainly limited to the latter ones.
Suitable caves have one or more above-surface or underwater entrances that lead to a main resting area with a beach or a flat, rocky surface.
Monk seals can travel significant distances at sea in a short time period (i.e., 150 nautical miles in 3 months). Average known depths that the species is able to reach is down to 200 m starting at a very young age, although recent research showed the species ability to reach deeper depths (around 400 m).
Mediterranean monk seals feed on a variety of sea organisms, including fishes, crustacean and mollusks, sparids and octopus seem to represent a huge portion of their preferred diet.
As with all other seals, monk seals also haul out on land in order to rest, but most importantly to give birth to, and care for, their young. The preferred terrestrial habitat used by monk seals are well-protected marine caves found along remote and inaccessible stretches of coastline. Suitable caves have one or more above-surface or underwater entrances that lead to a main resting area with a beach or a flat, rocky surface. According to the information currently available, monk seals in Greece use the caves mainly at night, and cave usage increases significantly during the pupping season and in the winter. During the first months of their lives, young monk seal pups spend a lot of time on the beach or in the water inside the cave. Monk seal survival seems to be very dependent on the existence of suitable pupping caves.
