Wandering albatross defies rational explanation

Click to follow
The Independent Online

The wandering albatross does just what its name suggests: wandering at random in its long search for food in the southern oceans of the world, a study of the bird has found.

Experts used to think that there was a hidden method to the apparent madness of the albatross's long-distance flights, which can take the bird from one corner of the world to another, and back again, in search of a meal. However, scientists have found that the wandering albatross has no apparent strategy when it comes to where it decides to land on the ocean and forage for squid and fish.

More than a decade ago, scientists were astounded to find that when they tracked the movements of the wandering albatross, the bird seemed to carry out a search pattern that followed a Lévy flight, a pattern named after the French mathematician Paul Pierre Lévy.

A Lévy flight occurs when a search is conducted in a semi-orderly manner, with clusters of short searches over a relatively small area interweaved between long-distance flights from one region to another. Mathematicians showed this was an optimal strategy for foraging for sparse food.

But scientists have collected fresh data on the feeding habits and movements of wandering albatrosses living on the sub-Antarctic island of South Georgia. They used logging instruments that monitor when they land on water and for how long they stay there between flights.

The results, published in the journal Nature, reveal that the birds do not follow a Lévy flight pattern. When the scientists reanalysed the earlier albatross data, they found that it too did not conform to the mathematical pattern, as previously reported. They also analysed earlier studies of foraging patterns of bumblebees and deer, which were also thought to forage using the Lévy flight pattern, and discovered that they too failed to conform to the expected pattern of movements.

"It now seems that the albatrosses come across food at simple random intervals. Our work also questions whether other animals thought to exhibit Lévy flights do all forage in the same way," said Andrew Edwards, who carried out the work at the British Antarctic Survey in Cambridge. "The idea of albatrosses following a Lévy flight pattern was quite appealing. They can travel up to 10,000 kilometres on one foraging trip. But at the moment these results question that they adopt this kind of foraging strategy."

The wandering albatross was immortalised in The Rime of the Ancient Mariner by Samuel Taylor Coleridge, who warned of the evil fate awaiting anyone who killed the bird.

Expert foragers

* Bumblebees: They need to collect nectar and pollen in the most cost-effective way during daylight hours.

* Deer: Foraging can be costly if too much time is spent walking from one patch of ground to another.

* Grey seals: Have to find shoals of fish in a vast ocean so using a search pattern would pay dividends.

* San people: The "bushmen" of southern Africa appear to follow the Lévy flight pattern in their search for food.

* Urban shoppers: The way some city landscapes are planned conforms to the Lévy flight principle of foraging.