Bear has you in a tree? Do this:

I'd say it takes a LOT of practise..... If you're a girl

The real impressive part is saying it after you've died.

ipeedonabearonce

honestly, why not.... it might work. A black bear doesn't get that big though... much easier to scare off. A brown bear won't usually climb since it's not worth it... in that case just make yourself as small as you can and still pee on it XD