Monk Seals: Monachus monachus, M. tropicalis, and M. schauinslandi

Abstract

The genus Monachus includes two endangered species that live in the world's tropical and subtropical seas of the Northern Hemisphere. Mediterranean monk seals are uniformly black at birth with a conspicuous white ventral patch unique to each individual and distinct in shape by sex. Hawaiian monk seals are also black at birth, with some showing small white patches at various sites. Both extant monk seal species consume a highly diverse diet of diurnally and nocturnally active fish, octopus, squid, and lobster. Proportions of these prey species in the diet vary by location, season, and age of the seals. Hawaiian monk seals have a broad prey base of at least 40 species. Mediterranean monk seals are mostly benthic feeders, regularly reaching bottom depths in areas of wide continental shelf like the Western Sahara. Caribbean monk seals probably preyed upon fish and crustaceans. Killer whales and sharks are probably the only predators of monk seals. A mating tactic of some nondominant male Hawaiian monk seals is an attack by a group of these males, a few to over 20, on an adult female or an immature seal on some occasions. The attention of the dominant male in consort with the female becomes distracted by one or more of the challengers in the group, allowing the others to then breed with the female during bouts that may last over 3 h in the water. Pup mortality increases sharply for Mediterranean and Hawaiian monk seals when human use of a preferred beach habitat forces females to give birth at unsuitable pup-rearing sites. Hawaiian monk seal numbers have also been reduced because of human activities.