The European eel is a surprisingly enigmatic creature. Its breeding behaviour in particular has confounded people for over 2,000 years. To some, its proliferation seemed inexplicable. The great Greek thinker Aristotle, for example, believed that eels spontaneously emerged from mud. A few hundred years later, Pliny the Elder had his own imaginative ideas about eel reproduction – he thought they bred by rubbing their bellies against rocks.
The great salmon run of North America. The famous wildebeest trek across the Serengeti. The mammoth migration of the green sea turtle to lay its eggs. These are just a few examples of epic journeys undertaken by animals. But even these pale in comparison to the migration of a small, slender, white seabird with a forked tail that weighs less than half a pound: the Arctic tern.