Last modified: Thursday September 24th, 1999

Monk seals


Mediterranean monk seal

Monachus monachus (Hermann, 1779)>

Appearance

Males are on average 214 cm long and weigh 172 kg. Females are larger: 234 cm long and a weight of 270 kg. Pups are 100 cm at birth and weigh 16-18 kg. The monk seal is dark brown to black in colour and lighter ventrally.

Distribution

These seals used to live on sandy beaches, but can only be found in caves and on small islands. The monk seal can be found in countries around the Mediterranean Sea, on islands in the Adriatic Sea, on the Madeira Islands, the Canary Islands and the Atlantic ridge islands.

Feeding

The monk seal lives on local fish and octopus. The diet includes fish species, such as eel, carp, whiting, sardine and bonito.

Population dynamics and life history

There is little information about this seal. They probably become mature at the age of 4 and gestation lasts probably 11 months. Other parameters are unknown.

Trophic relations

There is probably no competition and there are no natural predators.

Interactions

Because the monk seal feeds on fish species that are commercially exploited, there are interactions with fisheries. Monk seals get entangled in fishing nets and are shot by fishermen, trying to protect their nets. Over-exploitation of fish stocks severely depletes the monk seal's food supply. These seal are very sensitive for disturbance.

Population size:

The total population size is probably no larger than 500-600 seals and is declining. There have been some estimates made for parts of the monk seal's range: Morocco and Algeria: 100; Greece: 150; Port Etienne: 50; Black Sea: 50; Cyprus and Lebanon: 50; Desertas: 50; small groups of 20 seals or less on Madeira, Canary Islands and in Turkey.

Exploitation

The monk seal is protected throughout its range. Despite the protection monk seal are still killed by fishermen.

Threats to the population

This small population of secretive animals, that is spread out over a large area is very vulnerable. These seals are very sensitive to disturbance, which explains why they retreat further all the time. Additional threats are net entanglement and incidental kill by fishermen, food supply depletion and pollution. There have been a number of conferences on the conservation of this species. Some of the conclusions of these meetings have been summarized by Johnson and Lavigne (1995).

In May 1997, a sudden mass mortality struck the North-west African population. In a month, about 150 animals died. The estimated population size before the die-off was about 300 animals. A bloom of dinoflagellates (algae) producing saxitoxins have been implicated in this mass mortality (Lavigne, 1997).

References

Boulva, J. (1979)
Mediterranean Monk Seal. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 95-100
Johnson, W.M. and Lavigne, D.M. (1995)
The Mediterranean Monk Seal - Conservation Guidelines. 52pp. International Marine Mammal Association Inc.
Kenyon, K.W. (1981)
Monk Seals, Monachus Fleming, 1822. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 195-220, Academic Press Inc., Ltd, London
King, J.E. (1983)
Seals of the world, 2nd edition. British Museum (Natural History), London and Oxford University Press, Oxford, 240pp.
Lavigne, D. (1997)
Red tide is suspect killer. BBC Wildlife 15(7):21
Ronald, K., Healey, P.J. (1982)
The Monk Seal (Monachus monachus). in: Mammals in the Seas, Volume IV: small cetaceans, seals, sirenians and otters. FAO Fisheries Series, No. 5, vol. IV, pp. 243-252
See also: Phil Gibbs' Mediterranean Monk Seal page

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West Indian monk seal

Monachus tropicalis (Gray, 1850)

Nomenclature

The West Indian monk seal is also referred to as the Caribbean monk seal.

Appearance

This seal is 200-220 cm long and weighs 160 kg. Pups are 85 cm long. Pup weights are unknown. This seal is greyish brown with a yellowish ventral. Females have a slightly darker ventral.

Distribution

The range of this species was from the Bahamas through the Florida keys and the Yucatan peninsula into the Caribbean Sea, including Cuba and Jamaica.

Feeding

unknown

Population dynamics

no data available.

Trophic relations

Its main predators are sharks.

Interactions

Very sensitive to disturbance.

Population size

The West Indian monk seal is believed to be extinct. Repeated surveys of its former habitat have gien no indications of the presence of living seals. This believe was confirmed by a 1984 census (LeBoeuf et al, 1987).

Exploitation

This species has been severely over-exploited in the past. Since it is believed to be extinct, no protective measures are taken.

References

Boulva, J. (1979)
Caribbean Monk Seal. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 101-103
Kenyon, K.W. (1981)
Monk Seals, Monachus Fleming, 1822. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 195-220, Academic Press Inc., Ltd, London
King, J.E. (1983)
Seals of the world, 2nd edition. British Museum (Natural History), London and Oxford University Press, Oxford, 240pp.
LeBoeuf, B.J., Kenyon, K.W., Villa-Ramirez, B. (1987)
The Caribbean monk seal is extinct. Mar. Mamm. Sci. 2(1): 70-72

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Hawaiian monk seal

Monachus schauinslandi (Matschie, 1905)

Appearance

Males grow upto 210 cm and can weigh 173 kg. Females can be as long as 230 cm and weigh upto 273 kg. Pups are 100cm at birth and weigh 16-17 kg. This seal has a slate-grey dorsal side and a light silvery grey ventral.

Distribution

This seal is found on sandy beaches in the Leeward Chain of the Hawaiian Islands: Pearl and Hermes Reef, Lisianski Island, Laysan Island, Frenah Frigates Shoal. They used to breed on Midway and Kure Atoll, but they left there, because of increased disturbance.

Feeding

There is little known about the diet, but it includes cephalopods, eel and reef and bottom fish.

Population dynamics and life history

Female become sexually mature by the age of 5 years (Iwasa and Atkinson, 1996). In the Northwest Hawaiian islands (Laysan Island and Lisianksi Island), birth rates for all adult-sized females is 0.544 (Johanos et al, 1994). Pupping occurs in late March and early April. Weaning occurs in May. Mating appears to occur in late May and June. Molting occurs in July. The pupping interval for females giving birth in consecutive years was 381 days: females that pupped in consecutive years gave birth later each season. This seal has an aberrant mating system, in which groups of males "mob" the females, often injuring them. The injuries are occassionally fatal.

Trophic relations

There is no competition. The main predators are sharks.

Interactions

There is no interaction with fisheries. This seal species is very sensitive for human disturbance. There is some competition for space with humans.

Population size

In 1956-1958 the total population was estimated at 1,200 seals. In 1980 there were only 700 left.

Exploitation

There is no exploitation of this seal. The breeding area is in the Hawaiian Islands National Wildlife Refuge (HINWR). Access to this refuge by tourists is discouraged or even prohibited. A few rehabilitated animals are on display at Sea Life Park, Hawaii (where the pictures on this page were taken).

Threats to the population

This small population is very sensitive for disturbance. In addition, the "mobbing" behavior of the males causes increased mortalities among females.

References

Brenton, C. (1979)
Hawaiian Monk Seal. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 104-105
Iwasa, M. and Atkinson, S. (1996)
Analysis of corpora lutea to estimate reproductive cycles of wild Hawaiian monk seals (Monachus schauinslandi). Marine Mammal Science 12(2):182-198
Johanos, T.C, Becker, B.L. and Ragen, T.J. (1994)
Annual reproductive cycle of the female Hawaiian monk seal (Monachus schauinslandi). Marine Mammal Science 10(1): 13-30
Kenyon, K.W. (1981)
Monk Seals, Monachus Fleming, 1822. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 195-220, Academic Press Inc., Ltd, London
King, J.E. (1983)
Seals of the world, 2nd edition. British Museum (Natural History), London and Oxford University Press, Oxford, 240pp.

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