If humans can indeed smell fear they wouldn’t be unusual in the animal kingdom. Sea anemones, earthworms, minnows, fruit flies, rats, mice, and deer, among others, have all been shown to signal unease through odor. Some responses are even more overt. For example, the offspring of one bird species vomits up a pungent, orange liquid when frightened by a predator; if a parent catches a whiff, it becomes warier in the nest.