From schools of fish, to herds of antelope and even human societies, one of the group’s many advantages is its inherent safety. Surrounded by their peers, individuals can lower their vigilance and calmly engage in other activities, such as foraging, or watching youtube videos.
But the Safety in Numbers rule has more to it than just being together. In many cases, communication also plays a big role. Social cues of danger are fairly well known. Just think about the different ways animals use to convey the presence of a threat. Shrieks, yelps and barks immediately come to mind.
Now, how about naming a few examples of social cues of safety? After all, knowing that the danger has passed is important for lowering one’s defences and resuming other activities. The reason this task is more challenging is because it’s actually a trick question – no social safety cues have been identified until now.
Remarkably, the discovery of the first social safety cue was made thanks to a tiny insect: the fruit fly. These results, published (August 21st) in the scientific journal Nature Communications, mark a new phase in our understanding of how social communication works.
A silent sign of danger
“When people think about social communication of danger, they normally think about alarm calls”, says Marta Moita, a principal investigator at the Champalimaud Centre for the Unknown in Portugal. “But we are interested in a different type of threat cue, the expression of the defensive behaviours themselves.”
Freezing is one of the three universal defence responses, together with fight and flight. This response is the best course of action in situations where escape is either impossible or less advantageous than just staying still with the hope of remaining unnoticed.
“Freezing may actually be a safer way of conveying the existence of danger to others”, Moita points out. “This manner of social communication does not require the active production of a signal that may result in drawing unwelcome attention. Also, freezing may constitute a public cue that can be used by any surrounding animal regardless of species”, she explains.
Moita’s team has recently demonstrated that individual fruit flies freeze in response to an inescapable threat. This finding triggered their curiosity, would this behaviour change if there other flies were around?
Safety in (exactly how many) numbers
To answer this question, Clara Ferreira, the lead author of the study, proceeded with a systematic set of experiments, beginning with one fly, then two, three, and so forth, up to groups of ten.
“We placed the flies in a transparent closed chamber and repeatedly exposed them to an expanding dark disc, which mimics an object on a collision course. Just imagine the visual effect of an approaching open palm”, Ferreira explains. “Many visual animals that are exposed to such a stimulus respond defensively, including humans. If they freeze, they often stay motionless for quite some time, even after the threat is gone.”
Their results revealed that group size matters. “All groups – from two to ten – froze less than individual flies. However, we were surprised to find a complex effect of group size on the flies’ behaviour”, says Ferreira.
In groups of six and more, the flies froze transiently when the threat appeared and then resumed movement once it was gone. On the other hand, the flies’ response pattern in groups of five or less was more similar to that of individual flies.
“Flies in those groups still froze less than single flies. However, their freezing time increased as the experiment progressed. The more repetitions of the threatening stimulus they experienced, the longer they would remain motionless when it reappeared”, Ferreira explains. “These results were very intriguing”, she adds. “This was the first time the effect of group size on freezing was systematically characterised in any species and it revealed a fascinating and intricate relation.”
Should I stay or should I go?
These findings clearly demonstrated that flies change their defensive responses when others are present. This novel observation raised a pressing question – what social cues were the flies responding to? To find the answer, Ferreira and Moita meticulously analysed their previous results and conducted additional experiments using blind flies and controllable magnetic “dummy flies”.
The results revealed a two-part answer. “The first part describes the flies’ response to the appearance of the threat”, Ferreira recounts. “We learned that an individual fly was more likely to enter freezing if its peers (magnetic or otherwise) froze in response to the threat. We were somewhat expecting to see this. Previous studies in the lab showed that in specific situations, freezing is a social cue of danger in rats. Here, we witnessed a similar behaviour in flies.”
The second part of the answer, however, caught the researchers by surprise: flies were more likely to exit freezing if others began to move. “This means that flies were using the resumption of movement as a social cue of safety!”, Ferreira points out.
“This is a completely novel phenomenon”, Moita adds. “There are many types of recorded social alarm cues, but this is the first social safety cue to be identified in any animal species. It also pins down movement as the social cue we were searching for. In a sense, this cue ‘kills two birds with one stone’: the sudden cessation of movement signifies danger, whereas its resumption signifies safety.”
Next stop – the brain
Moita and Ferreira’s series of striking discoveries opens a unique opportunity to learn how the brain perceives and responds to social cues. “The fruit fly is one of the most powerful animal models used in scientific research nowadays”, says Ferreira. “It offers specialised tools to study neurobiology in a very specific and targeted manner.”
Indeed, the authors have already begun unraveling the neural basis of this behaviour. “In this project, we identified a set of visual neurons that are crucial for perceiving the movement of others as a safety cue”, Ferreira explains. “And we are planning to continue investigating the neural circuits involved.”
As Moita points out, even though flies and humans are different, there are parallels across these and other species that may make findings in the fly relevant for revealing general principles. “Since we are studying a fundamental behaviour spanning almost all of animal life – the tendency to seek safety in numbers – we believe that our work paves the way for understanding conserved mechanisms in other animals”, she concludes. Reference:
Ferreira et al. Behavioral and neuronal underpinnings of safety in numbers in fruit flies, Nature Communications (2020). DOI: 10.1038/s41467-020-17856-4
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NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
