SORRY, Superman. The largest animal capable of soaring across the sky unaided could have weighed no more than a labrador. Or so says some controversial research which claims to cast doubt on the flying ability of the quarter-tonne pterosaur.
Katsufumi Sato of the University of Tokyo, Japan, travelled to the Crozet Islands, halfway between Madagascar and Antarctica. He attached accelerometers, the size of AA batteries, to the wings of 28 birds from five large species, including the world鈥檚 biggest flying bird, the wandering albatross.
Unlike turkeys or bustards, whose short wings are good for quick take-off but not for soaring, these birds fly long distances using dynamic soaring 鈥� they ride changing wind currents without moving their wings. When the wind dies down, or blows at a constant speed, they have to flap or be pulled down by air resistance and gravity.
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Months of data from Sato鈥檚 instruments showed that each species has two flapping speeds: fast for taking off and slow for staying aloft in zero wind. The maximum speed a bird can flap is limited by its muscle strength and decreases for heavier species with longer wings.
Sato says animals heavier than 40 kilograms wouldn鈥檛 be able to flap fast enough to stay aloft. This would explain why the wandering albatross weighs only 22 kg. A bird weighing too close to 40 kg 鈥渨ould not have a safety margin to fly in bad weather,鈥� he says.
Other researchers have tied weights to albatross wings or counted the frequency of their wing beats to measure the power they generate. Sato is the first to study free-flying large birds in the wild in this way.
The results Sato presented at the Third Annual Biologging Science Symposium at Stanford University, California, last month are unlikely to win him friends in the dinosaur community. Palaeobiologists who reconstruct the flight of pterosaurs, winged lizards that lived 200 million years ago, believe that they were dynamic soarers. With wingspans up to 15 metres across, they would have weighed almost a quarter of a tonne.
鈥淗is 40-kilo threshold is problematic,鈥� says Mike Habib of Johns Hopkins Medical School in Baltimore, Maryland, when it comes to predicting the flight of pterosaurs or teratorns. Although they were built like albatrosses only four times heavier, he says, differences in anatomy, physiology and environment must all be taken into account.
Dinosaurs 鈥� Learn more in our comprehensive special report.
