As it turns out, humans aren't the only ones who appreciate the aroma of a fresh batch of beer. According to researchers at the Oregon Hatchery Research Center in Alsea, Oregon, the scent of ale is tempting to fish, too, and could successfully lure salmon back to their home hatcheries.
Wild salmon are famous for their arduous migrations between the ocean and the rivers of their origins, where they return as adults after several years of ocean wandering to spawn. Relying on their finely tuned senses of smell, they swim their way back to the rivers where they were born, all for the purposes of reproduction.
But some salmon released into the wild from hatcheries do not use their sense of smell in the same way, wreaking havoc in the wild whenever they fail to return to their home hatcheries. After trialing a host of scents, however, researchers are finding that the leftovers of beer production could be used to attract these released fish back to their hatchery homes.
Of course, salmon are far from the only species with a keen sense of smell for the odd and curious. All sorts of animals are interested in strange scents, which they use for all manner of purposes, such as attracting mates and finding meals. Here are six more animals with strange senses for surprising smells.
1. What Smells Attract Flies and Mosquitos?
The odor of ammonia is noxious and urine-like to humans but endlessly enticing to insects like flies. That's because it lays out a stinky pathway, guiding them to their food. The attraction doesn’t come from their noses, however, but thanks to the hairs, or sensilla, on their antenna. In 2021, researchers at the University of Connecticut found that each sensilla contains tiny neurons specifically adapted for sensing the odor of ammonia.
Given that insects such as mosquitoes use the smell of ammonia in human sweat to hone in on their human victims, researchers hope to find ways to block molecules known as ammonia transporters, which allow the scent of ammonia in and out of our cells. Blocking these molecules would impede the bug's smell-based sensibilities, protecting humans from swollen, scratchy, and bug-bitten skin.
2. What Sense of Smell Does A Lemur Have?
In the world of animal mating, meanwhile, a keen sense of smell does wonders for those seeking a potential partner. Ring-tailed lemurs are masters at producing their own pongy perfume. When mating season comes around, males secrete a "fruity and floral aroma," engaging in what some scientists have dubbed "stink flirting."
"During the yearly breeding season, male lemurs rub the glands on their wrists against their fluffy tails and then wave them at females," said Kazushige Touhara, a biochemist at the University of Tokyo who studied this behavior, in a statement from 2017. "Since only ring-tailed lemurs have these wrist glands and exhibit 'stink flirting' behavior, we reasoned that specific odorants for sexual communication must be involved."
3. What Smells Are Frogs Attracted To?
But not all animals produce such fresh-smelling scents as a form of attraction, however. In Brazil, scientists say, foul-smelling frogs use the stores of stinky bacteria on their backs to attract mates and to differentiate themselves from other frogs. It's a strange example of smelly symbiosis, according to a 2019 study about the aroma, since the bacteria emit an odor that helps the frogs find mates, all in exchange for a home on a frog's back.
According to the study, patches of pungent bacteria probably adorn the skin of other amphibians, too, including salamanders.
Read More: Meet 10 of the World's Most Adorable Frogs
4. What Smells Attract Ants?
For some species, scent-driven attraction is even more distasteful. There are plenty of ants and other insects that are attracted to the smell of death and decay, with the pungent odor promising tasty, decomposed treats. But the smell of rot isn't always associated with rotting.
The titan arum is a flower found only on the island of Sumatra in Indonesia. Known as one of the smelliest plants on Earth, its scent is one of death, specifically that of decomposing flesh. When in bloom, it attracts all sorts of scavenging insects. But instead of feasting, these bugs act as unwitting pollinators for the death-scented blossom.
Another plant in the same family follows a similar strategy; the aptly named dead-horse arum emits a smell similar to that of a rotting corpse, tricking potential pollinators to come closer for a taste.
Read More: How Smell Holds Ant Societies Together
5. What Smells Are Dogs Attracted To?
Our best friends — domesticated dogs — are also renowned for their sharp sense of smell, which is far superior to our own. The well-tuned canine nose can be trained to help us sniff out bombs, drugs, and even diseases such as cancer and Parkinson’s disease. But owners are perhaps more accustomed to their pets' penchant for rolling in foul-smelling feces or rotting carcasses on walks.
It's thought that this behavior is either a method for marking territory or an "evolutionary throwback" to the domesticated dog's wild ancestor, the wolf, as these strong scents can help an animal camouflage itself from potential prey.
Curiously, researchers investigating the scent of dogs found that they also have a fondness, or at least an interest, in sweeter smells such as lavender, rose, blueberry, blackberry, and mint, suggesting that the smell preferences of some animals are even more diverse and sophisticated than we ever believed.
Read More: Dogs May Be Smelling Our Stress
6. What Are Mice Attracted To?
Rather horrifically, the parasite Toxoplasma gondii can cause a fatal attraction to certain odors in mice and rats. Though T. gondii is capable of infecting all kinds of organisms, it reduces the anxiety of mice and rats when it infects them, making the critters much more adventurous. In reducing rodent anxiety, the parasite's ultimate mission is for the mouse or rat that it infects to be consumed by a cat, the only animal in which T. gondii reproduces.
One study from 2011 suggests that infected rats approach the smell of cat urine, with the parasite creating a form of sexual attraction to an odor that would normally cause the animals to flee. Another study from 2013 found that this cat attraction is permanent, even without the continued presence of the parasite.
Read More: How Animals Follow Their Nose