Sunday 10 April 2016

The Last Seals of the Mediterranean

There are eighteen recognised species of "true" seal (that is, as opposed to fur seals, which are actually more closely related to sea lions). Three of these species are currently listed as endangered under the most widely recognised international standard for such things, the IUCN Red List. Compared with some other groups of animals - rhinos being a particularly obvious example - this isn't really all that bad. But it could, of course, be rather better.

One of the endangered seal species is the Caspian seal, found only in the isolated and land-locked sea of the same name. The other two are monk seals, with one species each in the Mediterranean and off the coast of Hawaii. Quite how two such closely related species ended up on opposite sides of the globe is something I've discussed in an earlier post, but for today, the key point is that there used to be three species of monk seal, and that the other one went extinct around 1952.

Given this, the threat to the two remaining species is surely far from hypothetical. There are thought to be a little over a thousand Hawaiian monk seals alive today, but, as confirmed in a recent species review, the most endangered seal species of all is the Mediterranean monk seal (Monachus monachus) - the only seal species to live in the sea for which it is named.

These animals have, of course, been known to we Europeans for rather a long time. In fact, there is actually evidence that Neanderthals living in Gibraltar over 28,000 years ago were already hunting monk seals. Considering the relatively small population of Neanderthals across Europe, and that most of them presumably weren't near the coast anyway, it's unlikely that this had any noticeable effect on the seals' population at the time, though it's certainly quite early to get started.

The first written record we have of their existence is probably that of Aristotle in the 4th century BC, but large scale hunting doesn't seem to have started until the Roman era. Indeed, Roman hunting of fur seals seems to have been particularly extensive, and led to a significant decline of the species in the Mediterranean. While things got rather better for the seals after the fall of the Empire, it's at least possible that the apparent decline in hunting in the post-Roman era was due to the fact that there weren't quite so many left by that time.

However, despite their common (modern) name, Mediterranean monk seals are not restricted to the Mediterranean Sea; even leaving aside the Black Sea, they were also quite common in the eastern Atlantic, from the Spanish coast in the north to what is now the southern border of Western Sahara in the south and the Azores in the west. While the local Arabic population had hunted the animals in these locations during the Middle Ages, they were still said to be very numerous by the 15th century, when Europeans conquering the Canary Islands and Madeira commented on their great numbers.

Their reaction to this discovery seems largely to have been to start hunting them for their hide and oil, and, from this point on, the Atlantic population also began to drop. (The Romans, apparently, also used to eat them, although by all accounts, their meat tastes dreadful, so it may have been a "last resort of impoverished fishermen" sort of thing). And so it continued for the next few centuries.

Monk seals seem to have escaped the attention of Linnaeus when he first devised scientific naming in 1758 - possibly he hadn't realised that they were any different from harbour seals. However, it was not too much later that French naturalist Johann Hermann gave the first formal scientific description of the animals in 1779. As it happens, he had only seen the one, and that at a travelling show that had been visiting his home city of Strasbourg. He described it as a "beautiful and rare animal", and likely wasn't far wrong - the individual in question had come from somewhere in the Adriatic, where local accounts of the time indicate that they were already noted for their rarity.

The decline continued through the 19th century. In 1887, Otto Keller said of the population in the Aegean "one sees them only rarely, and in calm weather or in daylight, probably never," while Croatian zoologist Spiridon Brusina said in 1889 that he had "seen live ones from the Algerian coast, and stuffed ones in various museums, but not one in [the Adriatic]." The species had disappeared from the Balearic Islands by 1914, and from the coast of mainland France by 1935, although they survived off Corsica until the 1970s. The last monk seal in the Black Sea died some time around 1997, although a few may survive in the Sea of Marmara.

Today, the worldwide population of Mediterranean monk seals is thought to number around 700, of which around 450 are adults. At least a half of these live in the Aegean Sea, with smaller numbers on the Ionian coast of Greece, around Cyprus and the southern coasts of Turkey, and (possibly) across the north coast of Africa in Libya, Tunisia, and Morocco. Outside the Mediterranean, two colonies survive, one on Madeira, and the other, larger, one at Ras Nouadhibou on the Western Sahara/Mauritania border. The latter suffered a sudden drop-off in numbers in 1997, leaving less than a third of the seals alive. The cause remains unknown, with an outbreak of distemper and toxic algal blooms both having been blamed, but either way, there does now seem to be a slow recovery in progress.

Hunting Mediterranean monk seals is no longer legal in any of the areas where they survive. This has not, however, prevented them from being killed. There is, for one thing, the inevitable risk of accidental death, where the seals get caught in fishing nets, but there is a significant risk from deliberate, illegal, killing, largely by fishermen concerned that the seals will eat their stocks. Indeed, when the population becomes small enough, sheer bad luck, such as rockslides in areas used for birthing, can do significant harm, even if it doesn't really threaten the survival of the species as a whole.

The decline in population has had significant effects on the seals and their lifestyle. We know, for instance, that their genetic diversity is compromised, something that could potentially lead to them becoming more susceptible to disease outbreaks. More visible to our eyes, however, is the change to the way that they care for their pups.

In the past, Mediterranean monk seals did what most seals do, and hauled themselves out onto beaches, where they gave birth, and looked after their young. On occasion, they still do this, especially where humans are absent, but, for the most part, it has simply become too dangerous. Today, the vast majority of monk seals seek out caves at the base of cliffs, where they can remain hidden from prying eyes.

While this has evidently proved better for them than remaining in plain sight, it is far from ideal. For one thing, caves aren't all that common, which further restricts the areas in which populations can survive. But it's also just not a great environment for raising pups. Caves can get cut off during storms, or even flood temporarily with water - which the mother might not be too bothered by, but could prove lethal for a pup too young to swim. As far back as the 1970s, it has been suggested that finding some way to get the seals back to birthing on beaches, as they used to, might be a key element in saving the species.

In broader terms, protecting their habitat seems the best strategy for preserving the monk seals. A number of reserves now exist, with at least some limitation on legal fishing - helping to reduce the risk that seals and fishermen will need to compete with one another. Other conservation efforts have included changing the way that fishing nets are used, promotion of public awareness, and even the occasional rescue of lost or orphaned pups and their eventual return to the wild.

As a result, there are signs that, over the last thirty or so years, the steady decline in monk seal numbers has halted, and may even have begun to reverse. Last year, the animals were removed from the "Critically Endangered" list, a sign that things were not as bad as we had previously thought. But, nonetheless, they do remain an endangered species, and there is still more work to be done if we wish to preserve the only species of seal that lives in the Mediterranean Sea.

[Photo by Thérèse Gaigé, from Wikimedia Commons.]

1 comment:

  1. Re: "The first written record we have of their existence is probably that of Aristotle in the 4th century BC"
    There is a reference to seals in Book 4 of the "Odyssey." Given the geography, I would assume that the seals herded by Proteus, the Old Man of the Sea, were supposed to be Mediterranean Monk.
    (Thanks for posting the many interesting mammalian stories: yours is one of my favorite websites!)