Flying without Fractals
A new study raises doubts about fractal patterns in animal behavior

Julie J. Rehmeyer

Scientific fashions can rise and fall, like the hems of each year’s skirts. Unlike haute couture, however, scientific fads can shed light on the world.

Fractals have been in fashion for a couple of decades or so, and researchers have been finding fractal-based patterns in the ways that many animals search for food. Albatrosses, deer, and bumblebees are among the growing array of animals with fractal-based search patterns. But a new study has found flaws in the methodology used in all such animal studies, raising questions about whether fractal search patterns really do occur in animal behavior.

Albatrosses don’t use fractal search patterns after all, a new study shows.

Wandering albatrosses were the first animal studied that seemed to use fractal search techniques. In 1996, Gandhimohan M. Viswanathan of Boston University and his colleagues clipped recording devices to the legs of albatrosses to track when the birds were in the water and when they were not. The researchers figured that the birds were resting or feeding when wet and flying when dry.

Most of the time, the albatrosses flew short distances, as the researchers had expected. But sometimes, they flew very far indeed. On rare occasions, the data showed, the birds would fly for as long as 96 hours. The pattern formed by frequent short journeys, less frequent longer journeys and rare very long journeys is known as a “Lévy flight.”

These very long journeys are the critical element that distinguishes Lévy flights from other, more common statistical patterns. By contrast, a speck of dust would never leap to the other side of a room in its random jostlings, so its motion wouldn’t form a Lévy flight.