Can animals smell fear? Plus: where have all the Levis’ rivets gone?

Dear Cecil: When I was a kid I remember being warned, when in the presence of, say, a large, scary dog, not to act like I was afraid, because “animals can smell fear” and would be more likely to attack. Recently I was out with my five-year-old daughter when a Marmaduke-sized mutt, though leashed, made a lunge at her. My daughter began to cry in fright, at which point the dog began to bark and strain at the leash. I gave the owner a dirty look, scooped up my daughter, and hustled her out of there. Later I began to wonder: can animals in fact smell fear? Though the incident was hardly a scientific test, it sure looked that way to me. Sugar Daddy, Santa Cruz, California

Cecil replies:

We need to examine this concept, pops. Suppose you’re Joe Caveman, facing off against a ferocious saber-toothed tiger. Naturally you’re scared stiff, and due to one of those random mutations that occur as species evolve, your body is equipped with tiny fear glands churning out fear molecules. These waft over to the tiger and tell him, “Yo! Yonder hominid is in the last stages of panic! Attack!” Two seconds later you’re cat food. Just a hunch, but I’d say the eat-me scent is one trait you’ll have a tough time passing along to your descendants. So it seems highly unlikely that predators can literally smell fear.

But you’re not convinced. Isn’t it true, you ask, that some animals, when frightened, emit odors of varying degrees of intensity? For example, species having odoriferous anal sacs, such as skunks, weasels, and cats? And judging from experimental evidence, probably also cows, rats, and mice?

A. Of course.

Q. Isn’t it also true that other animals can detect these scents? That they can, as you put it, “literally smell fear”?

A. Sure. But I was talking about predators.

Q. Exactly. And isn’t it true that many predators, upon detecting signs of fear, will pounce?

A. Right.

Q. So doesn’t this undercut your entire argument?

A. Not at all. We’re talking about two pretty much unrelated phenomena. Research suggests that animals emit fear scents primarily to alert members of their own species and, in the case of animals whose scent is especially pungent, to repel enemies. But the predator isn’t necessarily responding to the fear scent. Many predators — cats, for example — are programmed to respond to sudden movements, such as panicked attempts at flight.

Figuratively speaking, of course, predators smell fear just as lawyers smell money. So the old advice about not showing fear in threatening situations is probably worth heeding. But there’s little evidence that fearful humans give off a characteristic scent that predators can detect.

Then again, who knows? Some anecdotal accounts suggest that people give off “fear sweat” when truly stressed. If there is such a thing, one likely source is the apocrine glands, the odor-producing type of sweat glands found in the crotch and armpits. But there are other sources as well. Bovine fear scent, for example, seems to be carried in the urine. This brings to mind the Jurassic Park scene in which a character confronted by a T. rex feels a sudden urge to visit the facilities and promptly gets clobbered. Not that I believe in fear scent, but if a predator’s ever got you in a tight spot, I’d keep a tight grip.

Dear Cecil:

Whatever happened to those rivets on the back pockets of Levi’s jeans? My wife says that they stopped putting them on the back pockets because school chairs were being scratched up. What’s the Straight Dope?

— HAP Proctor, via the Internet

Cecil replies:

The rivets are still there; they’re just covered up. Levi Strauss & Company says the change was made due to customer demand and that there have been “reports of rivets causing scratches or other property damage.” So yes, quite possibly somebody at Levi Strauss got an earful about dinged-up school chairs.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.