I've seen enough Nature shows to determine that a lot of the time its
because something is about to eat them.
I've said this before (a long time ago) but: at least some gliding animals
glide simply as a way of getting around. I have watched gliding lizards
(Draco) in Borneo; they tend to simply sit on a vertical tree trunk, then
dart across to an adjacent tree (for no apparent reason, but I presume to
change stalking perches); the glide is almost horizontal - you can easily
mistake them for butterflies at first glance.
Also in Borneo, I watched a giant flying squirrel (Petaurista) at Danum
Valley, Sabah, in what I gathered was a nightly ritual - emerging from its
roost tree at dusk and, after a few minutes, casually launching into a
glide of 100 feet or so across the river into the forest. I assume that
gliding enabled it to use the forest but roost in a tree well separated
from it, perhaps for safety.
Anyway, gliders may glide without having either a predator on their tail or
a prey item in their sights. For a highly-adapted glider, it's simply a
low-cost way to commute.
--
Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2 mailto:ornstn@home.com