Tactics: Nik'too bite aggressively, fleeing only when in fear for their lives.
A giant turtle-like creature with a visciously sharp beak.
I didn't say "viscous," actually. There's an "i" in there.
And, while I won't quibble with "large," nik'too are Large, just like a horse.
The rest is fine, although there are some misplaced commas and run-ons. Editing:
Shouldn't actually be a comma before "but can weigh more" in that last bit of red text. There's no new subject. But the rest looks good to me.