(adapted from an article appeared in Italian on La Rivista della Natura)
A huge back breaks the calm surface of the Mediterranean in front of Jaffa, attracting the attention of Aviad Scheinin, of the Israel Marine Mammal Research & Assistance Centre. It is the morning of 8 May 2010, and Aviad is surveying the Israeli coastal waters during one of his regular dolphin monitoring campaigns. Whales are not rare in the Mediterranean Sea, but their presence in the Levantine Sea is unusual. This one, however, is a very special whale. Back in his lab, Aviad consults with colleagues over the net to identify the species, and when he sends the photos taken that morning all doubts vanish. The Leviathan’s grey mottled colouration and the shape of its back and tail are unmistakeably those of a California grey whale.
To try to give an idea of the extravagance of this event, we could compare it to the sight of a kangaroo hopping across an olive grove in Tuscany, or to the appearance of a penguin in the Venice Lagoon. Kangaroo and penguin, however, would have been likely runaways from some passing circus. The grey whale instead had obviously reached the Mediterranean on its own, after a swim lap at least 15,000 km long.
Less than a month later, on 30 May, the same whale reappears 3,000 km to the west of the Israeli coast, this time in front of Barcelona. Unique patterns of dark and light grey give away its identity just like fingerprints: it is the same guy (or girl) that had been spotted off Israel. Three thousand km covered in three weeks may seem no mean feat for most animals, but not for a whale. These mammals are like ships that never dock; even when they swim slowly, semi-dozing, they may be able to inch forward by 5-7 km in one hour. It is when they want to stay in one place – for example, when they have located a dense patch of prey – that they have to concentrate on their whereabouts, swimming back and forth to avoid losing their dinner. But as soon as whales start swimming with a constant bearing, like when they migrate, they eat up mileage with no special effort, finding themselves, a few weeks later, on the other side of an ocean.
None of this, however, is sufficient to account for what business might have had in the Mediterranean a grey whale, a species which is typical of the Pacific Ocean. True, once upon a time there were grey whales in the North Atlantic, some even venturing into the Baltic Sea; this tribe, however, became extinct towards the mid-1600s, for reasons unknown. Today two extant populations exist, both roaming the North Pacific. The western population, made up of a scanty 120 animals, lives off the Russian shores and is the most critically endangered of all whales. By contrast, the eastern group – a hefty population in excess of 20,000 animals – shuttles seasonally between Mexico and Alaska along the North American coast.
The wandering whale that ended up inside the Mediterranean almost certainly came from this eastern group. Why did a whale endeavour to swim halfway across the planet is open to the wildest, albeit fascinating conjectures. One thing we know is that grey whales are powerful migrants. After spending their winter in their breeding lagoons in Baja California, whales manage to reach their summer feeding grounds in the Bering and Beaufort seas around Alaska. In recent years, thanks to the progressive thawing of the polar icecap due to global warming, grey whales have been seen venturing farther and farther to the east. Therefore it may not seem so unlikely that our whale, when the time came of turning south on its winter migration, unwittingly found itself into the Atlantic instead than in the Pacific.
We will perhaps never find out what happened with certainty. But should something like this occur again, we would find it somewhat ironic if climate change were to allow grey whales to re-colonise the Atlantic, thereby resulting, against all expectations, in an increase of this ocean’s biodiversity.