And which is a torn beast for which he does not pay? A beast torn by a wolf, a lion, a bear, a tiger, a leopard, or a snake. Since the Torah writes (9) "and it die, just as he is not liable to pay in an instance of (natural) death, so, in all instances where he cannot rescue the beast, he is not liable to pay. Thus, "For the torn beast he shall not pay."
Which Is a Torn Beast for Which He Does Not Pay
Mekhilta Tractate Nezikin 16:20