For decades, scientists thought that flying squirrels could do little more than glide, controlling their descent from a high point to a low point. After all, that's what the squirrels did when observed. But most detailed observations took place in laboratory settings.
The laboratory is not where Alexander Badyaev prefers to be. Badyaev is a University of Arizona professor of evolutionary biology. He was born in Russia, so, when pronouncing the word "squirrel," he endearingly calls to mind Boris Badenov.
He regularly conducts northern flying squirrel research in the forests of Montana. A few years ago, Badyaev spent night after night staking out a corner of the Bob Marshall Wilderness. He came to learn the habits of a particular female - when she was active, which trees she launched herself from. And he knew that in mating season, male squirrels would compete to get her attention.
It was there, on a freezing February night, that Badyaev saw the object of his attention leap up from a tree branch, unfurl her patagia - the winglike material that stretches from front legs to back legs - and soar away in level flight.
It was the start of an aerial demonstration that Badyaev captured with his camera. A pair of squabbling male squirrels glided more than 60 feet with little observable loss in altitude. Other flying squirrels made 180-degree midair turns to escape the clutches of hungry owls.
Badyaev's images showed that they were capable of complex aerobatics. But how?
More than 15 years ago, after studying hundreds of specimens, Dick Thorington, the Smithsonian's resident squirrel expert, had noted an odd bit of cartilage at the end of the wrists of flying squirrels.
"What Dick postulated at the time was that these were used for maneuverability in flight," said Badyaev, who was recently in Washington for a National Science Foundation meeting.
The cartilage is similar to the upturned vertical tips you see at the end of wings on passenger jets.
"By adjusting the angle of the wing tip, the squirrel can generate a substantial lift, modifying the speed, distance and trajectory of its glides midflight," Badyaev later wrote.