Like people, rats cooperate with one another and give food to those in need, but how can they be sure that other rats are being truthful about how hungry they are?
The answer may lie in smell-based cues that signal a rat’s appetite more reliably than its begging gestures and squeaks, a study said Tuesday.
The paper’s lead author Karin Schneeberger of the University of Potsdam in Germany told AFP she was interested in learning more about how social animals identify “cheaters” and freeloaders.
She and her colleagues studied Norway rats (Rattus norvegicus), publishing their findings in the journal PLOS Biology.
Previous work has shown the rats share their food reciprocally, with the donation of what they deem high value food items, like bananas, more likely to elicit a gift in return than low value items, like carrots.
But the scientists believed the calls and gestures used by rats to solicit food might not always reflect their actual needs, allowing dishonest rodents to trick givers out of their hard earned gains.
To test out the idea, they took rats that were either hungry from fasting overnight, or well-fed, and placed them in a separate room from the “focal” rat whose generosity they wanted to test.
Air from the rooms of the hungry or well-fed rats was pumped into the chamber of the focal rat.
They found that the focal rats were much quicker to provide help — by pulling a food tray within reaching distance of another rat — when the air was pumped from a hungry rat’s room.
It took 16 focal rats an average of 29 seconds to provide help for hungry rats, compared to an average of 85 seconds to give help to the well-fed.
The authors then analyzed the air around the rats and found seven different organic compounds that differed significantly in their abundance between hungry and satiated rats.
– Good rat citizens –
These might result from recently ingested food sources, the metabolic processes involved in digestion, or possibly even a pheromone that indicates hunger.
Taken together, these signals form a “smell of hunger” for rats that serves as a reliable cue of need, said Schneeberger.
Apart from identifying freeloaders, the rats may be acting to reduce the suffering of others, she added.
“It could be that they do that out of an emotional state — I don’t really want to call it empathy because that’s something that is very anthropomorphic,” said Schneeberger.
“But having somebody in distress next to yourself can cause stress in yourself too.”
Rats could also be investing in a better rodent society that ultimately serves their own interests, just like humans do, she added.
“Maybe when we are old and we need help crossing the street, then we are also very happy to live in a society where it generally is the rule that you help elderly people to cross the street.
“So we try to keep the society as social as possible.”
© 2020 AFP
WATCH: John Oliver exposes Trump’s lies about vote-by-mail — and the Fox News ‘cult’ claiming the election is already ‘rigged’
"Last Week Tonight" host John Oliver's main story Sunday refuted President Donald Trump's latest crusade against vote-by-mail. Trump announced on Twitter that the more people who vote in an election, the more Republicans tend to lose. So, he wants fewer people to have access to the ballot in November, even if people are too scared to go out during the coronavirus crisis.
Oliver called out Missouri Gov. Mike Parson (R-MO), who outright told people not to vote if they were too afraid to vote in the local elections next week.
"Well, hold on there," Oliver interjected. "Voting is a right. It has to be easy to understand and accessible to anyone."
John Oliver rips Fox News’ Tucker Carlson for urging ‘order’ from people of color — but never demanding it of police
John Oliver opened his Sunday show, shredding Fox News host Tucker Carlson for uring "order" among protesters, but refusing to urge "order" to police and "wannabe police" who can't stop killing people.
It's a lot, Oliver explained. "How these protests are a response to a legacy of police misconduct, both in Minneapolis and the nation at large and how that misconduct is, itself, built on a legacy of white supremacy that prioritizes the comfort of white Americans over the safety of people of color."
While some of it is complicated, Oliver conceded, most of it is "all too clear."
Cars set on fire blocks from White House as DC protests turn violent
The Washington, D.C. protests turned violent as the city approached the 11 p.m. curfew the mayor instituted Sunday afternoon.
The policy of D.C. police is that when they are attacked, they advance forward. So, when fireworks were fired, the line of officers began pushing the protesters back further from the White House. Behind the line of police officers also stand a line of National Guard troops that President Donald Trump has demanded stand watch in the city.
Lights that normally shine on the White House have also been turned off, reporters revealed.