 Some non-venomous snakes, such as American hognose snakes or European grass snake, play dead when in danger; some, including the grass snake, exude a foul-smelling liquid to deter attackers.When a crocodilian is concerned about its safety, it will gape to expose the teeth and yellow tongue.If this doesn't work, the crocodilian gets a little more agitated and typically begins to make hissing sounds.