Mediterranean Monk Seal
Nearly 140 million people live along the Mediterranean Sea’s 28,000 miles (45,000 km) of coastline. An equal number of tourists flood the area from May to October every year to enjoy the white sand beaches and warm waters. This crush of people has left little room for one of the area’s oldest inhabitants, the Mediterranean monk seal (Monachus monachus).
Monk seals are pinnipeds, a term which means “fin foot” and is used to describe seals, sea lions, and walruses. The monk seal has been called a “living fossil,” because fossil records show it was hunting the tropical seas as long as 15 million years ago.
Once abundant in some areas of the Pacific, Caribbean, and Mediterranean seas, the monk seal became extinct in the Caribbean in the 1950s (see Case Study on the Caribbean Monk Seal).
Monk seals survive in low numbers in a few places in the Mediterranean and Hawaii. These populationof monk seals have been separated for so long that scientists consider them separate species, although physically and behaviorally they are very similar.
Description and Natural History
The Mediterranean monk seal was first described by Aristotle in the third century B.C. As recently as the 16th century, there were enough Mediterranean monk seals to fuel a commercial harvest. There are fewer than 500 remaining in the wild today.
The most tropical of seals, the monk seal looks like a big-eyed torpedo. Reaching about 6 feet (1.8 m) in length and 400 pounds (182 kg), it is a speedy swimmer that can outmaneuver a shark. Monk seals feed at night mostly in shallow coastal waters and sleep on beaches during the heat of day, often digging down to lie in cooler, damp sand. They eat spiny lobsters, eels, octopus, and some reef fishes.
Monk seals reproduce slowly, sometimes only every other year, starting at the age of four. Adult females, larger than the males, come ashore to give birth to one pup, then remain on the beach nursing and protecting the pup for up to six weeks. Living off stored fat, the female does not leave the pup even to feed herself during this period. The pup may stay with its mother for as long as three years after weaning.
CAUSES OF ENDANGERMENT
This shore loving, easy to approach seal was slaughtered in droves for food by early seafaring explorers and native peoples alike. It is still sometimes killed by fishers who see it as competition for food fish.
Pollution, particularly human waste, fouls the water and kills the monk seal’s food. Even after an 18 year clean up effort, still only 30 percent of the Mediterranean monk sea’s coastal towns and cities had sewage treatment plants by 1993. In addition, tons of industrial and agricultural pollutants and sediments flow into the Mediterranean from its feeder rivers and streams.
Disturbance by Humans
The shy monk seal is easily disturbed by humans, and most remaining Mediterranean monk seals come ashore only in small, hidden coastal caves and beaches. Continued population growth of Mediterranean countries brings increased beach use, boat traffic, and overfishing of the monk seal’s prey. Long-line and net fisheries also injure and drown monk seals.
With the monk seal already extinct in the Caribbean and the Mediterranean monk seal’s status so precarious, the Hawaiian population represents the best chance for survival. Approximately 1,300 Hawaiian monk seals remained as of 1994. These seals breed almost exclusively on protected islands within the Hawaiian Islands National Wildlife Refuge, where human disturbance is carefully controlled.
However, only a few hundred females remain in the Hawaiian population. This imbalance between males and females is interfering with reproduction. Some females are so isolated that they do not encounter other monk seals during the breeding season.
In other areas, the few females are mobbed by males and may be injured or killed when the males attempt to mate. Biologists are testing a program of relocating females, and darting surplus males with a testosterone-suppressant drug to control aggression. The imbalance of males to females is a serious threat to the survival of the Hawaiian monk seal.
The International Union for the Conservation of Nature (IUCN) first classified the Mediterranean monk seal as endangered in 1966. Because so many different countries occupy the shores of the Mediterranean, coordinated conservation efforts have been difficult.
Efforts to save the species emphasize research (tagging and monitoring wild seals) as well as the creation of protected areas. Campaigns to reduce pollution of the Mediterranean are being driven mostly by concern for human health, but these campaigns will benefit the monk seal also.
There is disagreement among biologists about whether captive breeding can help the monk seal. These unusual seals have never survived well in captivity, let alone been bred successfully. Some biologists believe, however, that the only way to save them is to capture some for captive breeding.
Question for Thought
Monk seals have a low reproduction rate, which has complicated their recovery from over hunting. What other endangered species have low reproduction rates, and why is it a problem in conservation?
When disturbed, a female monk seal may stop producing milk or may abandon her pup. What can be done to protect breeding monk seals?
Activities: [CS1-1, General]
Words in bold italics can be found in the glossary.