FrizzText: Before Otto Lilienthal and others risked their lives by flight tests, some other creatures already knew how it works!
Grey-headed flying fox, a photo by Chi Liu, kindly sent to my group BLOG IT!, click on the picture to enter his galleries on Flickr.com
P.S.: When I visited the Alps, I curiously watched some sporty flying foxes:
photo by frizztext, click on the picture to enter my photo pool on Flickr.com