Birds Can Smell, and One Scientist is Leading the Charge to Prove It
For more than a century nearly everyone believed birds sense of smell was poorly developed or nonexistent. They were wrong.
Gabrielle Nevitt's supply list for her first Antarctic research cruise in 1991 contained some decidedly odd items. The huge kites and vats of fishy smelling liquid wouldn't be a problem, the macho National Science Foundation contractor told her. Then she asked for hundreds of boxes of super-absorbent tampons. "He just kind of stammered," recalls Nevitt a petite brunette who was then a 31-year-old zoology post-doc at Cornell University. "Then he said, 'Uh, I don't think I can get those for you, ma'am.' " So Nevitt lugged them onboard herself and set to work. She was hoping to lure albatrosses and petrels from the open sea with the scent of dinner, like a street-food vendor might entice passersby with a hot pretzel. She dipped the tampons in pungent compounds found in marine fish and small crustaceans called krill, and painstakingly attached the briny bait to parachute-like kites that she let fly off the rear deck. Then she waited.
It was an outlandish experiment, and not just because of the tampons. For more than a century nearly everyone believed that the sense of smell was poorly developed or nonexistent in most birds. So no one had ever fully investigated to what extent tube-nosed procellariiformes--petrels, albatrosses, and shearwaters--use their olfactory anatomy to pinpoint prey in the vast, featureless ocean. The long-lived birds spend nearly their entire existence at sea, soaring for hundreds to thousands of miles in search of ever-shifting schools of krill, fish, and squid. On the day Nevitt ran her experiment, dozens of them swooped in so close that she feared they would tangle in the line and drown. So she grounded the kites and improvised, releasing vegetable oil into the water, some of it laced with the fishy compounds. Albatrosses and petrels flocked to the stinky slicks. She was ecstatic. But she still had no idea how they used olfactory cues to home in on their ephemeral quarry. "I was really passionate about figuring this out, so I wasn't giving up," says Nevitt. "I knew I'd be back again soon on another cruise."
Nevitt is 53 now and a professor at the University of California-Davis. She is a woman obsessed with smell. As head of a sensory ecology lab, she's spent the past two decades picking apart how seabirds' ability to detect scents is key to their survival. Nevitt had the good fortune to arrive in the field on the heels of a handful of pioneering bird olfaction studies. Yet changing long-held beliefs takes time, and the scientific community is no exception. Dozens of Nevitt's grant proposals have been rejected because of the birds-can't-smell fallacy. A program officer once called to say her application was the worst he'd ever seen. "Your idea that birds can smell is ridiculous,"he said. "This will never be funded, so stop wasting your time." She ignored him, and her perseverance and inventive methods have inspired others who share her fascination.
"Gaby's been very influential," says Julie Hagelin, a wildlife biologist with the Alaska Department of Fish and Game who has conducted several studies on the role of odor in bird behavior. "Her work propelled me forward and helped me develop several ideas." Nevitt, Hagelin, and other avian olfaction trailblazers have pushed past criticism, failure, and even bodily injury in their quest to disprove one of biology's most pervasive myths. "In science," says Nevitt, "we rediscover the obvious sometimes."
Nevitt could blame John James Audubon, of all people, for the incredulity she's endured. In the 1820s the famous naturalist set out to prove that turkey vultures use their superior eyesight, rather than their nostrils, to find carrion. He stuffed a deerskin with grass and added clay eyes, sewed up the imposter, and placed it in a meadow with its legs in the air. He watched as a vulture swooped down on it. The duped bird ripped out the eyes and tore apart stitches, flying after failing to find any meat. Audubon later placed a dead hog, its carcass reeking of decay in the July heat, in a ravine and covered it with brush. This time vultures circled but didn't descend. The results were "fully conclusive," he wrote. Vultures did not scavenge by smell.
Audubon's ego would've taken a hit had he lived to see Kenneth Stager put his findings to the test. In 1960 Stager, an ornithologist at the Los Angeles County Natural History Museum, showed that turkey vultures prefer fresher carcasses--typically no more than four days old--to putrid ones like Audubon hid. Stager also identified the specific scent that drew vultures to carrion, with the help of natural gas engineers who told him they followed the birds to ruptured pipelines. Decomposing carcasses, it turns out, give off ethyl mercaptan, the same sulfurous compound added to natural gas so humans can sniff out a leak (and which gives asparagus eaters' urine that distinctive rotten-egg odor). Stager had shattered Audubon's theory. Hardly anyone noticed.