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African elephants use their acute sense of smell as a form of communication, researchers report.
Professor Louw Hoffman from the University of Queensland’s Queensland Alliance of Agriculture and Food Innovation co-led a study of elephants in wildlife parks in Malawi, which found that smell was used to distinguish characteristics including age, health, reproductive status, and family relationships between elephants.
“We tested the DNA, glands, urine, and manure of 113 African elephants to identify family groupings,” Hoffman says.
“We found a number of chemicals were common to group members, but others that were unique to each individual.
“Elephants never mate with a sibling, even if they’ve been separated for years and can tell a strange elephant is close by from the smell of their manure or other excretions.”
Hoffman says social behavior also suggests elephants use odor to monitor other pachyderms, both within and outside their herd.
“We observed elephants greeting each other by squealing and flapping their ears,” he says.
“We believe they’re pushing their pheromones towards the other elephant as a sign of recognition.
“When elephants charge each other flapping their ears, rather than making themselves look bigger, we believe they’re blowing their pheromones as a warning not to mess with them.”
Hoffman says elephants not only identify different smells quickly, but also retain them in their memory.
“Some of the animals in the study were bred in captivity, and one of the tricks they’d been taught was to take a tourist’s hat and smell it,” he says.
“When the tourist came back hours later the elephant would be able to immediately identify who the hat belonged to.”
Hoffman says elephants could be trained to sense many things, including blood and explosives.
“These findings show elephants are complex creatures, and sound is not their only form of communication,” he says.
“We see humans as the apex, but we now know elephants are one of many animals that have senses more finely attuned than ours.
“There is a lot we can learn from the elephant.”
The study was co-led by Katharina von Dürckheim and Alison Leslie from the University of Stellenbosch.
The research appears in Scientific Reports.
Source: University of Queensland
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Researchers are finding new clues to how the olfactory sensory system aids in threat assessment and have found neurons that “learn” if a smell is a threat.
Whether conscious of it or not, when entering a new space, we use our sense of smell to assess whether it is safe or a threat. In fact, for much of the animal kingdom, this ability is necessary for survival and reproduction.
“We are trying to understand how animals interact with smell and how that influences their behavior in threatening social and non-social contexts,” says senior author Julian Meeks, principal investigator of the Chemosensation and Social Learning Laboratory at the Del Monte Institute for Neuroscience at the University of Rochester.
“Our recent research gives us valuable tools to use in our future work and connects specific sets of neurons in our olfactory system to the memory of threatening smells.”
Smell may guide how the brain responds to a social threat. In mice, the researchers identified a specific set of neurons in the accessory olfactory system that can learn the scent of another mouse that is a potential threat. The research appears in the Journal of Neuroscience.
“We knew that territorial aggression increases in a resident male mouse when it is repeatedly introduced to the same male,” says Kelsey Zuk, first author of the research.
“Previous research has shown this behavior is guided by social smells—our research takes what we know one step further. It identifies where in the olfactory system this is happening. We now know plasticity is happening between the neurons, and the aggression between the male mice may be driven by the memory formed by smell.”
The researchers found that “inhibitory” neurons (nerve cells that act by silencing their synaptic partners) in an area of the brain responsible for interpreting social smells become highly active and change their function when males repeatedly meet and increase their territorial aggression.
By disrupting the neurons associated with neuroplasticity—learning—in the accessory olfactory bulb, the researchers revealed that territorial aggression decreased, linking changes to cellular function in the pheromone-sensing circuity of the brain to changes in behavioral responses to social threats.
“It abolished the ramping aggression that is typically exhibited,” says Zuk. “It indicates that this early sensory inhibitory neuron population plays a critical role in regulating the behavioral response to social smells.”
Threat assessment also comes when an animal navigates unknown smells. For example, the smell of a predator it has never encountered. In a second paper in eNeuro, researchers found that a novel predator smell, i.e. the smell of a snake to a mouse, caused the animal to engage in a threat assessment behavior—neither acting “fearful” nor “safe.”
“This offers clues into how chemical odors given off by predators stimulate threat assessment in the brain,” says Jinxin Wang, first author of a paper. “Identifying changes in patterns of animal behavior helps us better understand how threatening smells are processed in the brain.”
The researchers used video tracking to observe the movement and posture of mice exploring familiar environments with different odors—like other mice and snakes. Wang and colleagues developed a hybrid machine learning approach that helped them to uncover that mice respond to novel predator odors in ways that were unique and distinguishable from how mice reacted to non-predator odors. These behaviors were neither fearful nor safe but rather a state of assessment.
“These findings offer new clues into how smells impact social behavior and what it may mean for survival, but this study also offers new tools that will propel this science forward,” says Meeks.
“We combined methods that had known limitations to improve the accuracy, information depth, and human-interpretability of the collected data. We think this approach will be valuable for future research into how the blends of chemical odorants given off by predators stimulate threat assessment in the brain.”
Additional coauthors of the Journal of Neuroscience research are from the University of Rochester and the University of Florida. Support for the research came from the National Institutes of Health.
Additional coauthors of the eNeuro research are from the University of Texas Southwestern Medical Center. Support for the research came from the National Institute on Deafness and Other Communication Disorders.
Source: University of Rochester
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Neanderthal noses were less sensitive to urine and sweat than ours are, research finds.
The noses of hunting-and-gathering Denisovans on the Asian steppes were particularly sensitive to energy-rich honey, according to the findings.
Though we can’t really know what these two extinct human species perceived or preferred to eat, the new study reveals a bit more about what they might have been able to smell.
Using a technique that lets researchers test smell sensitivity on odor receptors grown in a lab dish, researchers Claire de March of CNRS Paris Saclay University and Hiroaki Matsunami of Duke University were able to compare the scents-abilities of three kinds of humans. Their work appears in the journal iScience.
Drawing from published databases of genomes, including ancient DNA collections amassed by 2022 Nobel Prize winner Svante Pääbo, the researchers were able to characterize the receptors of each of the three human species by looking at the relevant genes.
“It is very difficult to predict a behavior just from the genomic sequence,” says de March, who did the work as a postdoctoral research associate at Duke. “We had the odorant receptor genomes from Neanderthal and Denisovan individuals and we could compare them with today’s humans and determine if they resulted in a different protein.”
So then they tested the responses of 30 lab-grown olfactory receptors from each hominin against a battery of smells to measure how sensitive each kind of receptor was to a particular fragrance.
The laboratory tests showed the modern and ancient human receptors were essentially detecting the same odors, but their sensitivities differed.
The Denisovans, who lived 30,000 to 50,000 years ago, were shown to be less sensitive to the odors that present-day humans perceive as floral, but four times better at sensing sulfur and three times better at balsamic. And they were very attuned to honey.
“We don’t know what Denisovans ate, but there some reasons why this receptor has to be sensitive,” says Matsunami, who is a professor of molecular genetics and microbiology in the Duke School of Medicine. Contemporary hunter-gatherers such as the Hadza of Tanzania are famous for their love of honey, an essential high-calorie fuel.
Neanderthals, who were still around up to 40,000 years ago and who apparently swapped a few genes with modern humans, were three times less responsive to green, floral, and spicy scents, using pretty much the same receptors we have today. “They may exhibit different sensitivity, but the selectivity remains the same,” Matsunami says.
“The Neanderthal odorant receptors are mostly the same as contemporary humans, and the few that were different were no more responsive,” de March adds.
Odor receptors have been linked to ecological and dietary needs in many species and presumably evolve as a species changes ranges and diets.
“Each species must evolve olfactory receptors to maximize their fitness for finding food,” Matsunami says. “In humans, it’s more complicated because we eat a lot of things. We’re not really specialized.”
The lab has also used their cell-based scent tester for seeing genetic variation among modern humans. “Some people can smell certain chemicals, but others can’t,” Matsunami says. “That can be explained by functional changes.”
Funding for this research came from the National Institutes of Health and the US National Science Foundation.
Source: Duke University
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KFC Thailand has launched a line of incense that smells like fried chicken. The incense sticks are also meant to resemble the fast food chain's chicken. For now, the incense can't be purchased but must be won as part of a Lunar New Year contest. — Read the rest
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