From nought to 100 in no time: how humpback whales (Megaptera novaeangliae) came into the Southern North Sea

The humpback whale (Megaptera novaeangliae) has a cosmopolitan distribution: it occurs in all oceans and in many seas. Remarkably, the species was missing from the southern North Sea until recently. Even strandings of dead animals have always been very rare but from the 1990s onward this started to change. A trickle of dead humpback whales was the first sign that things were about to change, followed by sightings of live whales from 2001 on. Many of the first whales to arrive in the southern North Sea did not survive, and stranded, but this too has changed. Today, humpback whales visit the region every year in small numbers and both adults and juveniles are involved. The whales rarely fluke in the shallow coastal waters where they are mostly seen but a few wellmarked individuals have been seen in different years and some stayed up to several months in the area. It remains unclear what might have triggered this range extension. Numbers of humpback whales in the Atlantic are increasing after the cessation of whaling, but numbers are still short of the pre-whaling population size (when the species was absent from the southern North Sea). Some forage fish species, like herring (Clupea harengus) are also on the increase, but stocks are still depleted compared to the past. Most likely, therefore, something has changed in the whales themselves, causing them to be more inquisitive and to explore new waters. Once they have arrived in the southern North Sea, their behaviour shows that they can find sufficient food here.