TY - JOUR
T1 - Social Cues of Safety Can Override Differences in Threat Level
AU - Ferreira, Clara H.
AU - Heinemans, Mirjam
AU - Farias, Matheus
AU - Gonçalves, Rui
AU - Moita, Marta A.
N1 - Funding Information: This study was supported by Fundação Champalimaud, by Fundação para a Ciência e a Tecnologia (FCT) project UIDB/04443/2020 and ERCCoG819630-A-Fro, as well as by the research infrastructure CONGENTO LISBOA-01-0145-FEDER-022170. MH and MF were supported by fellowships from FCT, respectively, SFRH/BD/143423/2019 and SFRH/BD/130320/2017.
PY - 2022/6/24
Y1 - 2022/6/24
N2 - Animals in groups integrate social with directly gathered information about the environment to guide decisions regarding reproduction, foraging, and defence against predatory threats. In the context of predation, usage of social information has acute fitness benefits, aiding the detection of predators, the mounting of concerted defensive responses, or allowing the inference of safety, permitting other beneficial behaviors, such as foraging for food. We previously showed that Drosophila melanogaster exposed to an inescapable visual threat use freezing by surrounding flies as a cue of danger and movement resumption as a cue of safety. Moreover, group responses were primarily guided by the safety cues, resulting in a net social buffering effect, i.e., a graded decrease in freezing behavior with increasing group sizes, similar to other animals. Whether and how different threat levels affect the use of social cues to guide defense responses remains elusive. Here, we investigated this issue by exposing flies individually and in groups to two threat imminences using looms of different speeds. We showed that freezing responses are stronger to the faster looms regardless of social condition. However, social buffering was stronger for groups exposed to the fast looms, such that the increase in freezing caused by the higher threat was less prominent in flies tested in groups than those tested individually. Through artificial control of movement, we created groups composed of moving and freezing flies and by varying group composition, we titrated the motion cues that surrounding flies produce, which were held constant across threat levels. We found that the same level of safety motion cues had a bigger weight on the flies’ decisions when these were exposed to the higher threat, thus overriding differences in perceived threat levels. These findings shed light on the “safety in numbers” effect, revealing the modulation of the saliency of social safety cues across threat intensities, a possible mechanism to regulate costly defensive responses.
AB - Animals in groups integrate social with directly gathered information about the environment to guide decisions regarding reproduction, foraging, and defence against predatory threats. In the context of predation, usage of social information has acute fitness benefits, aiding the detection of predators, the mounting of concerted defensive responses, or allowing the inference of safety, permitting other beneficial behaviors, such as foraging for food. We previously showed that Drosophila melanogaster exposed to an inescapable visual threat use freezing by surrounding flies as a cue of danger and movement resumption as a cue of safety. Moreover, group responses were primarily guided by the safety cues, resulting in a net social buffering effect, i.e., a graded decrease in freezing behavior with increasing group sizes, similar to other animals. Whether and how different threat levels affect the use of social cues to guide defense responses remains elusive. Here, we investigated this issue by exposing flies individually and in groups to two threat imminences using looms of different speeds. We showed that freezing responses are stronger to the faster looms regardless of social condition. However, social buffering was stronger for groups exposed to the fast looms, such that the increase in freezing caused by the higher threat was less prominent in flies tested in groups than those tested individually. Through artificial control of movement, we created groups composed of moving and freezing flies and by varying group composition, we titrated the motion cues that surrounding flies produce, which were held constant across threat levels. We found that the same level of safety motion cues had a bigger weight on the flies’ decisions when these were exposed to the higher threat, thus overriding differences in perceived threat levels. These findings shed light on the “safety in numbers” effect, revealing the modulation of the saliency of social safety cues across threat intensities, a possible mechanism to regulate costly defensive responses.
KW - defensive behavior
KW - Drosophila melanogaster
KW - fear
KW - freezing
KW - looming stimulus
KW - motion cues
KW - safety in numbers
KW - social buffering
UR - http://www.scopus.com/inward/record.url?scp=85134055202&partnerID=8YFLogxK
U2 - 10.3389/fevo.2022.885795
DO - 10.3389/fevo.2022.885795
M3 - Article
AN - SCOPUS:85134055202
SN - 2296-701X
VL - 10
SP - 1
EP - 13
JO - Frontiers in Ecology and Evolution
JF - Frontiers in Ecology and Evolution
M1 - 885795
ER -