Population Status of the Hawaiian Monk Seal (Monachus schauinslandi), 1978

• Published in: Journal of mammalogy 1982-01, Vol.63 (3), p.415-421
• Main Authors: Johnson, A. M., Delong, Robert L., Fiscus, Clifford H., Kenyon, Karl W.
• Format: Article
• Language: English
• Subjects: Atolls; Censuses; Coral reefs; Depopulation; Frigates; Marine; Monachus schauinslandi; Mortality; Seals; Sharks; Shoals; Young animals
• ISSN: 0022-2372; 1545-1542; 1545-1542; 0022-2372
• DOI: 10.2307/1380438

Hawaiian monk seals, found in the northwestern Hawaiian Islands, regularly haul out and give birth on the beaches of six atolls, regularly haul out but rarely give birth on three additional islands, and are seldom sighted elsewhere. Since 1958, counts of monk seals have indicated a decline in population of about 50%. The population of the westernmost atolls, Kure, Midway, Pearl and Hermes Reef, and Laysan and Lisianski islands, have all declined; the population at the only other major pupping atoll, French Frigate Shoals, increased dramatically from 1957 to 1975 and now appears to be stable. The primary cause of the decline, at least at some atolls, has been increased mortality in early life; however, only some of the factors causing the increase in mortality are known. Predation by sharks has been identified as a cause of mortality, and increased human activity was followed by a decline in seal population on two atolls. In 1978, high mortality, which may have resulted from ciguatera or gastrointestinal parasitism, occurred primarily at Laysan Island. Ciguatera is a disease caused by ciguatoxin produced by a dinoflagellate; this toxin accumulates in prey species of monk seals, such as eels and other fishes. Even though it has been 15 or more years since the monk seal populations declined at Kure Atoll, Midway Island, and Pearl and Hermes Reef, there is no evidence of their recovery.