Jains, buddhists, many South Indians....all vegetarians, all happily thriving.....living good active healthy lives and breeding successfully. Most are however lacto vegetarians.
Robson Valley said it; the body uses what it gets.
It's fine to say 'kill something' and eat it, but the reality is that it's not that easy to catch something.
Passive snares ? fine, find your prey first, make your snare, sit hungry while you hope you've set it up in the right place.
I know folks who 'take for the pot'. They all, without exception, try to have stuff stored in the freezer because even those who do it often, often don't catch.
So, survival situation ? I'd say keep your options open and don't focus just on catching something.