cellio | daf bit: Bava Kama 16

The talmud describes two categories of damages, mu'ad and tam. The first, mu'ad, means cases where an outcome could reasonably be expected -- an animal will eat anything palatable and available, animals don't walk gently so if they step on something delicate you expect damage, and the ox that gores is known to gore. The other, tam, means cases where there is no such expectation.

If damages are done through mu'ad -- for example, a man doesn't restrict his goats and they go eat somebody else's crops -- then the responsible person owes full payment out of the best of his estate. If damages are done through tam, on the other hand, the responsible person and the victim share the damages (which are further limited) -- this is a case of "accidents happen". (The torah covers full versus half payments explicitly in Exodus 21 in talking about the ox that gores.)

The mishna says that a wolf, lion, bear, leopard, panther, and snake are all mu'ad. R' Eleazer says they are not mu'ad if they have been tamed, except that the snake is always mu'ad. (15b-16b)

In Jewish law, mu'ad applies to the custodian, not to the victim. "You should have known that would happen" is something we say to the owner of an animal as an explanation for why he must make full restitution -- not something we say to the victim to absolve the other of any responsibility. Your animals (or children or own behaviors) are your obligation to manage, not others' to dodge. (I suspect this doesn't apply to provocation or trespass, though; the talmud talks about things like not keeping your animals in, not about people climbing your fences and getting themselves hurt by your animals. There is probably also halacha on attractive nuisances, but I don't know what it is.)