Caribbean Monk Seal
This page is currenty (August 2011) beng updated
Distribution and Numbers
The Caribbean, or West Indian, monk seal is thought to have originally inhabited the beaches, cays and reefs of the Caribbean, including at least the Greater Antilles, the northern Lesser Antilles, the Bahamas, the northeastern coasts of Central America, Mexico's Yucatan Peninsula and the Florida Keys. A reconstruction analysis indicates a probable total historical population up to the early 17th century of at east 13 breeding colonies each separated by ~300km, totalling between 233,000 and 338,000 individuals (McClenaghan and Cooper, 2008). The last remaining group of seals is believed to have been seen in 1952 at Serranilla Bank, halfway between Nicaragua and Jamaica (Rice, 1973; Monachus Guardian).
So, what happened to make an abundant seal species ranging over a wide area go extinct? The seals were a curiosity and a source of food to the early explorers in the region. Christopher Columbus ordered 8 'sea-wolves' to be killed in 1494 and de Leon killed 14 seals in 1512 (King, 1956; McClenaghan and Cooper, 2008). British and Dutch hunters frequented the area in the 17th century. Hans Sloane in 1707 described how fishermen would kill 100 in one night to fuel their oil lamps, and also described - from about 1688 - settlers who had established sugar plantations sending hunters to kill hundreds nightly for oil to grease the machinery of sugar plantations. By 1850 there were no longer enough seals remaining to make hunting a viable business (Gray, 1850; cited by McClenaghan and Cooper, 2008). H.L. Ward killed 40 in one day at the Triangles in 1886 (Ward, 1887a and b, cited by King, 1956). 1922 there were no seals left in the entire northern Caribbean (Neill, 1957; cited by McClenaghan and Cooper, 2008). McClenaghan and Cooper (2008) summarised the decline as the first wave of extinction in the 18th century eliminating colonies at the periphery of the species' range, wth these having a 35% chance of extinction compared with colonies within 1500 km of the centre of the range. In the 2nd wave of extinction the probability for all colonies going extinct was increased, though this was still greater for the colonies at the periphery. The peripheral colonies were less likely to be repopulated when reduced by hunting.
Since 1973 there have been several surveys of the Caribbean area in an effort to spot any remaining live seals, including an extensive aerial survey carried out in 1973 by Kenyon, but no seals have been seen on these surveys (Kenyon, 1973; Sergeant et al., 1980; LeBoeuf et a., 1986). However, the seal has actually rarely been sighted since 1850, and the probablity of seing one during a dedicated survey is extremely low (Solow, 1993; cited by Boyd and Stanfield, 1998). A carefully designed questionnaire study for fishermen carried out in 1997 provided cautious grounds for optimism, since interviewees reported seeing an animal resembling a monk seal about as often as a manatee - also a relatively rare animal in Caribbean waters (Boyd and Stanfield, 1998). Howevever, these authors also reported that the fishermen said they actively hunted seals with spear guns on an oportunistic basis, so it seems very unlikely that seals would continue to survive fishermen's sightings, especially since Kenyon (1977) stated that 'the remotest habitats of the Caribbean monk seal have now been invaded by fishermen'. It has been suggested that seal sightings may possibly have been vagrant seals of other species, most probably hooded seals, since there have been 11 confirmed records of hooded seals in North Carolina, Florida, Georgia, Puerto Rico and the US Virgin Islands between 1910 and 1996 (Mignucci-Giannoni and Odell, 2001). In a faint hope that this monk seal may yet survive, it is listed as an Appendix I species under CITES, but is nevertheless now listed as Extinct on the IUCN Red List (Kovacs, 2008).
Life history and appearance
The adults were greyish-brown with a yellowish tinge to the tips of the hairs. They were a yellowish colour underneath, with the males being paler on the venter than the females. The pups had long black woolly coats (King, 1956). Thius the Caribbean monk seal resembled the closely-related Hawaiian monk seal (Monachus schauinslandi) in appearance. The Caribbean monk seal was about 2-2.4m in length and weighed about 160–200kg, with pregnant and nursing females being heavier than males (King, 1956). The pups were born about the beginning of December, probably a litte less than a metre in length. The animals was heard to be very vocal in air, with adults making a variety of 'grunts, barks and snarls', while the pups emitted a 'long drawn out gutural 'ah' with a series of vocal hitches during its enunciation' (Ward, 1887a and b, cited by King, 1956). These noises were presumably made by the animals as they were being attacked and killed by humans. The seals tended to lie on open beaches, where they reared their young, and had little or no flight response to humans, but otherwise there is no information on the seal's behaviour and ecology. It is assumed that they were, like the Hawaiian and Mediterranean monk seals, shallow water, mainly benthic, feeders on reef fish and benthic invertebrates.
Why did the Caribbean monk seal go extinct?
The Caribbean monk seal is the only pinniped species which has become extinct in modern times. The reason for the extinction would seem to be quite obvious: they were mindlessly slaughtered in large numbers by European hunters, by plantation settlers and even by so-called scientists from the 17th to the 19th centuries. They were also persecuted and deliberately klled by native fishermen as they also expanded their range of activity to all parts of the seals' distribution range. The monk seals were a shallow-water species, hauling out in large aggregations on open beaches, where each mother would nurse her pup for about 30-50 days (assuming the nursing period was similar to that of the Hawaiian monk seal). During the nursing period they were particularly vulnerable to hunters, and apparently showed little or no flight response to humans. Right up until the point of inevitable extinction in the mid to late 20th century the human environment has remained hostile to them, with apparently no attempt at conservation measures or protected areas. A small number of Mediterranean monk seals were able to survive in retreated from human habitat intrusion into secluded caves, but probably there was no such shelter available to the Caribbean seals. Coupled with the seal slaughter was historical overfishing of the reef fish. Estimates of the historical fish biomass suggest that the historical reefs were several times more productive than they are today, with modern reefs hosting less than 25% of the fishes on historical reefs. This could mean that the once abundant monk seal could not survive with the fish resources that remain in the depleted Caribeean reefs, i.e. the Caribbean ecosystem did not provide the seal with sufficient resources for population recovery (McClenaghan & Cooper, 2008). There is some evidence that intensive overfishing has reduced the prey base for Hawaiian monk seals as well, and that this is most evident in the poor condition of juveniles (Craig and Ragen, 1999). Successful recovery plans for both the Mediterranean and Hawaiian monk seals must include, in addition to protecting the seals themselves, efforts to allow recovery of fish stocks. Even if we cannot bring the Caribbean monk seal back to life, perhaps at least we can learn lessons which may help to save its sister species from a similar fate of extinction.
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Kenyon, K.W. (1977). Caribbean monk seal extinct. J. Mammal. 58(1): 97–98.
King, J.E. (1956). The monk seals genus Monachus. Bull. Br. Mus. nat. Hist. (Zool.) 3(5): 203–256. Available on internet
King, J.E. (1983). Seals of the World (2nd ed.). British Museum (Natural History). Cornell University Press, Ithaca, N.Y. 240pp.
Kovacs, K. 2008. Monachus tropicalis. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.1. <www.iucnredlist.org>.
LeBoeuf, B.J. Kenyon, K.W. and Villa-Ramirez, B. (1986). The Caribbean monk seal is extinct. Mar. Mamm. Sci. 2(1): 70–72.
McClenachan, L. and Cooper, A. (2008). Extinction rate, historical population structure and ecological role of the Caribbean monk seal. Proc. Roy. Soc. B. doi.1098/rspb.2007.1757. Published online.
Mignucci-Giannoni, A.A. and Odell, D.K. (2001). Tropical and subtropical records of hooded seals (Cystophora cristata) dispel the myth of extant Caribbean monk seals (Monachus tropicalis). Bull. Mar. Sci. 68(1): 47–58.
Rice, D.W. (1973). Caribbean monk seal (Monachus tropicalis). In Seals. Proceedings of working meeting of seal specialists on threatened and depleted seals of the world, held under the auspices of the Survival Service Commission of the IUCN, 18–19 August, Univ. Guelph, Ontario, Canada. IUCN Publ. New Ser, Suppl. paper, Morges, Switzerland
Ward, H.A. (1887a). The West Indian seal (Monachus tropicalis). Nature 35: 392.
Ward, H.A. (1887b). Notes on the life history of Monachus tropicalis, the West Indian seal. Amer. Nat., 21: 257-264.