Advertisement They are very strong for there size, a wolf spider gets crushed by a T the same size . Threat display is a warning too anything that they will fight to survive. often there colors confuse predators and they think it isn't a spider.
because predators are looking only for spiders and see a tarantula with it's confusing colors and think.. hhmm.. I'm hungry but nope nope.. that's not a spider!! moving along.. LOL
Is it odd that while I have pretty much every "bad reputation" T out there, I have had only two full threat postures? I occasionally get a a "front leg lift" where they lift their front pair then put them back down, I don't consider that a threat posture. I've housed all of them (obviously) and rehoused some of them, even have a couple that I was specifically warned about by the dealer who sold them to me - no problems. They're all healthy, eating and molting with no problems. If it sounds like I'm bragging, well maybe I am a little, but I keep reading all the "horror stories" and wondering why I don't have these problems? Here, I'll brag a little more, I have a lot the "hair kickers" too, they are all walking around with their completely fur covered butts. I typed this with my fingers crossed (makes it really hard to type).
Generally because they aren't hungry. This is a pretty standard pre-molt response to live prey. If they aren't gonna eat it, they want it to go away...threat posing and striking are how they make things go away.