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Can Birds Smell?

Legendary birdman John James Audubon would tell you decisively that, no, birds can't smell. In the 1820s, Audubon designed two experiments to prove that turkey vultures followed their eyes, not their noses, to carrion. First, the naturalist left a stuffed deer in a meadow with its legs in the air. Before long, the deer attracted the attention of a vulture, who dropped out of the sky to investigate. Finding nothing but grass inside the fake deer, the vulture took off.

The second experiment took place in the sweltering heat of July. Audubon dragged a decaying pig carcass into a ravine and covered the body with brush. The vultures spotted it, but they weren’t interested. That was that, said Audubon. No smell.

For more than a century, scientists took him at his word. Then, in the 1960s, an ornithologist at the Los Angeles County Natural History Museum named Kenneth Stager realized why vultures ignored Audubon’s carcass in the woods: it was just too gross. Like any discriminating diner, a turkey vulture prefers a fresh carcass [PDF], no more than four days old.

Through rather odd means, Stager learned that vultures actually do use smell. A gas company worker mentioned to him that turkey vultures would congregate around leaks in the pipeline, showing up so reliably that they began to use the birds as leak detectors.

This behavior occurred because the company had added a smelly chemical called ethyl mercaptan to the gas. You know what else gives off ethyl mercaptan? Carrion. Stager was able to tie the two together to suggest that vultures do in fact sniff their way to supper.

Stager wasn’t the only scientist interested in bird olfaction. In 1965, physiologist Bernice Wenzel of UCLA hooked pigeons up to heart monitors and exposed them to strong smells. The pigeons’ heart rates spiked each time a scent wafted their way. Then she attached electrodes to the pigeons’ olfactory bulbs (the smell centers of the brain) and started again. The results were just as dramatic.

In the half-century since, scientists have tested more than a hundred bird species, and all of them have had at least some sense of smell.

At times, their experiments have swerved into the realm of the bizarre. Sensory ecologist Gabrielle Nevitt once soaked super-absorbent tampons in fish-scented oil and tied the tampons to kites, launching them over the sea. The experiment worked a little too well: after a short while, the swarming seabirds were so intense that Nevitt had to bring the kites down in order to keep them from getting tangled in the strings.

Just how much a bird can smell depends on its species. The humble kiwi has one of the strongest senses of smell in the bird family, and it’s the only bird with nostrils at the end of its beak. At night, the kiwis sweep their beak tips along the ground like metal detectors, sniffing out earthworms and grubs.

Eurasian rollers, on the other hand, use scent in self-defense. When threatened, roller chicks vomit up an awful-smelling orange liquid. The stink not only deters potential predators, but it also acts as a warning. When the adult birds return to the nest, the scent tells them that a predator has been, and may still be, near.

Other birds use scent as an instrument of seduction. Crested auklets produce a tangerine-scented oil, which they dab all over their feathers like perfume. The better a bird smells, the better its chances of mating.

The same goes for the pudgy, flightless parrot known as the kakapo, which is said to emit a smell like lavender and honey. The kakapo is extremely endangered—there are only 124 left in the wild—so mating is of dire importance. One researcher even considered creating a synthetic kakapo perfume and applying it to unattractive males in the hopes of boosting their chances.

As for Toucan Sam, the jury's still out.

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Listen to the Impossibly Adorable Sounds of a Baby Sloth
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RODRIGO ARANGUA/AFP/GettyImages

Sometimes baby sloths seem almost too adorable to be real. But the little muppet-faced treasures don't just look cute—turns out they sound cute, too. We know what you're thinking: How could you have gone your whole life without knowing what these precious creatures sound like? Well, fear not: Just in time for International Sloth Day (today), we have some footage of how the tiny mammals express themselves—and it's a lot of squeaking. (Or maybe that's you squealing?)

The sloths featured in the heart-obliterating video below come from the Sloth Sanctuary of Costa Rica. The institution rescues orphaned sloths, rehabilitates them, and gets them ready to be released back into the wild.

[h/t The Kid Should See This]

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