ZOO Animals <> Wildlife!
certainly fill flash is important, although i don't use Tory Lepps device anymore because it's heavy and loosens your flash over time.... i've been using the lighter version made by Art Morris.
With wild animals and birds some are not frightened of flashes (the thought is that it looks like lightining which they are used to????), but others take a while to get used to it. If you have been camping out for several hours waiting for your shot, having a reflective surface be your give away ain't fun! been there, done that!
YMMV.
Sam
