How about this --- any animal that can evaluate it's environment and use this information to make deliberate decisions that enhance it's odds of survival --- is

How about this --- any animal that can evaluate it's environment and use this information to make deliberate decisions that enhance it's odds of survival --- is sentient to some degree. A mosquito that moves to evade a hand trying to swat it is sentient to some extent. Or taken to a grander scale --- the universe is sentient and this is manifested in living creatures both great and small.