Animals are liable for their actions. The punishment is usually death by lethal injection or firing squad.
The stronger argument is that animals aren't as aware as humans which actions will have consequences. Animals do have customs about what's okay and what's not, but they often don't align with human society's laws.
It's "ignorance of the law is no excuse" taken to an extreme.
I don't really agree. While humans can and do punish animals, it doesn't follow that the animal itself is liable for its own actions. In pretty much all cases, the owner of the animal is the one liable - and animals without owners are liable to nobody. An animal without an owner might still be killed - for example, if it is a danger to people - but I don't think you can call that just punishment.
For another argument, consider that if you went into the woods and were mauled by a bear, nobody who found your body would feel the need to confront the bear and hold it responsible. The bear would not need to be convicted in order to be acted against.
The stronger argument is that animals aren't as aware as humans which actions will have consequences. Animals do have customs about what's okay and what's not, but they often don't align with human society's laws.
It's "ignorance of the law is no excuse" taken to an extreme.