MONK SEALS IN THE INDIAN OCEAN?
François Moutou
French Mammal Society
125 avenue de Versailles, 75016 Paris, France
e-mail: fmoutou@noos.fr
As discussed in some detail by Johnson and Lavigne (1999), the possible former presence of an unknown species of Pinniped in the Western Indian Ocean and Red Sea remains an open question.
While I have no definitive answer to offer, the aforementioned publication brought to mind documentation I collected some years ago during a two-year stay on Ile de la Réunion, a French island in the Mascarene archipelago. Due to the scarcity of information available on the subject, this historical evidence may prove useful to the discussion.
Historical reports of a seal species inhabiting the tropical waters of the Western Indian Ocean and Red Sea has raised the theoretical possibility of a former monk seal (Monachus sp.) presence, as they are the only seals known today to occur at such latitudes.
An alternative explanation is that observers confused seals with the dugong or sea cow (Dugong dugon, Sirenian) which are, or were, also present in the area. Dugongs continue to survive in the Red Sea and in the Persian Gulf, as well as along some East African shores, the Madagascar lagoon and around the Comoros islands. Older records of dugongs originate from around Mauritius and Rodriguez islands (Mascarene archipelago), from where they were extirpated during past centuries. The review of this topic by Stoddart (1972) is reasonably comprehensive.
Two fragments of historical information may now be added to the discussion.
On dugongs:
An authentic Holocene dugong butchery site was discovered some years ago in Umm al Qiwain, United Arab Emirates (Faure et al. 1993). The site is 4000 years old, and half of the mammal bones identified originate from dugongs. Another site is located on Akab island, adjacent to the city of Umm al Qiwain, dated between 4700 and 3000 BP. Nearly all the bones unearthed originate from dugongs (Faure et al. 1993). This might offer additional context to historical records of the "fish-eating tribes" discussed by Johnson and Lavigne (1999).
On seals:
A description of a visit to the Seychelles islands by a Marion-Dufresne expedition in 1768 appears to have been overlooked by some researchers (Lionet 1981). The expedition was mounted from Mauritius (then "île de France") and was composed of two ships, "La Digue" and "La Curieuse". In the logbook of "La Digue" it is recorded that on the morning of 4th of October 1768:
"…about 20 'sea cows' were found, deeply asleep [on a beach on Mamelles islet]. They were killed. The largest was 7 feet 9 thumb long and up to 18 thumb in girth. The others were a third smaller. They were carried on board, and I boiled their fat, which gave me 38 pots of good oil to burn. This oil could have some other properties that I don't know of."
Conceivably, the larger specimen may have been a bull and the others its harem females. According to the logbook, this was the only location in the archipelago where these animals were found during the expedition and yet, apparently undeterred by that fact, the writer already speaks of the possibility of larger-scale exploitation.
That the animals were observed sleeping on a beach appears to indicate that they were Pinnipeds, not Sirenians. As with similar historical records from the region, this again raises the possibility that the sightings were of a now extinct Pinniped species, or of the southern elephant seal (Mirounga leonina). The latter hypothesis is bolstered by more recent historical sightings of the species in the area, as well as the logbook's description of the marked size differences between males and females (if correctly interpreted).
What remains surprising is that this species is, at least today, normally linked to sub-Antarctic waters and weather. It is partly for this reason, in fact, that the Monachus hypothesis has been raised – even though it relies on no hard data. In analysing the historical records available, it appears far more plausible that a local (possibly breeding) population of southern elephant seals may have been present in the area, even if only vagrant animals are known today. Indeed, the 1768 sighting in the Seychelles took place in early October – precisely the season that adult southern elephant seals haul out for breeding (Le Boeuf and Laws 1994). Significantly, perhaps, Johnson (1990) also reports the sighting of a southern elephant seal as far north as Oman.
The depletion of the population through historical exploitation by sealers, coupled with massive overfishing pressures in modern times, makes it questionable whether we will ever see a recovery of the species at these tropical latitudes (Le Boeuf and Laws 1994).
Sources
Faure, M., C. Guerin & M. Raimbault. 1993. L'exploitation des Siréniens à travers le temps. In: J. Desse & F. Audoin-Rouzeau. Exploitation des animaux sauvages à travers le temps, APDCA, Juan-les-Pins, France: 307-317.
Johnson, D.W. 1990. A southern elephant seal (Mirounga leonina Linn.) in the northern hemisphere (Sultanate of Oman). Marine Mammal Science 6 (3): 242-243.
Johnson, W. M. & D. M. Lavigne. 1999. Monk seals in antiquity. The Mediterranean monk seal (Monachus monachus) in ancient history and literature. Mededelingen 35: 1-101. The Netherlands Commission for International Nature Protection. [Online abstract].
Le Boeuf, B.J. & R. M. Laws. 1994. Elephant Seals. University of California Press, Berkeley: 1-414.
Lionet, G. 1981. Vaches marines ou phoque? Info-Nature Ile de la Réunion. N°18: 43-46.
Stoddart, D.R. 1972. Pinnipeds or sirenians at western Indian Ocean Islands? J. Zool., Lond. 167: 207-217.
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