Why do rats smell

The smell of togetherness - rats smell helpfulness

Mutual aid is more widespread in the animal kingdom than you think. According to the principle “like you me, so me you”, animals take turns taking turns in grooming each other, but also in procuring food, on guard and in brood care. The animals take care not to be exploited by selfish social partners.

Brown rats help each other to get food and do social grooming. They even exchange different amenities with each other, for example according to the motto "If you get me a treat, I'll clean your neck fur". Rats are nocturnal and see comparatively poorly. They communicate in the ultrasound range and, like rodents in general, they have a highly developed sense of smell. So how do they perceive how generous certain conspecifics are? Because they only want to be generous to helpful partners.

Helpfulness smells

In a series of experiments, researchers at the Hasli Ethological Station at the University of Bern have now shown that rats make their decision as to whether to help others based on the smell that their conspecifics produce when they are giving help. The first author of the study, Nina Gerber, who carried out these tests at the University of Bern, combined her four-legged test subjects with social partners in such a way that she experimentally decoupled their assistance and the smell they give off. "Regardless of whether the partner rat in the neighboring compartment was helpful or not - as soon as the test animal was blown into the cage by the smell of another rat that was helping someone, the rat agreed to be cooperative," says Gerber, who is now at the Georg-August University of Göttingen is working. The study is the first evidence of olfactory cooperation signals in the animal kingdom and was published in the "Proceedings of the Royal Society B" in London.

"Surprisingly, the smell, and only the smell alone, was responsible for the willingness of the test animals to help, even if the help action took place in another room - that is, only the air extracted there was transferred into the test cage," adds Manon Schweinfurth, who at was involved in the study and is currently doing research at the University of St Andrews. In this way, any alternative stimuli could be excluded as possible triggers for the willingness of the test animals to help, since only the air flow was transferred from room to room, i.e. neither visual nor acoustic signals were available.

Are rats honest too?

So it seems as if rats convey their assistance to social partners by smell. The question that remains unanswered is whether they could not 'trick' them into being generous in this way, but without really giving help. What is stopping them from giving off a 'scent of cooperation' in order to receive help themselves in return, but without actually giving help? "We have no evidence of this," says Michael Taborsky, head of the study from the Behavioral Ecology Department at the Institute for Ecology and Evolution at the University of Bern. “In this case, the smell of non-cooperating animals should have triggered the volunteers' willingness to help, but this was not the case. Perhaps in a natural community of rats there are additional means of verifying the honesty of signals of cooperative behavior. "

Publication information:

Gerber N, Schweinfurth MK, Taborsky M. 2020 The smell of cooperation: rats increase helpful behavior when receiving odor cues of a conspecific performing a cooperative task. Proc. R. Soc. B 287: 20202327. http://dx.doi.org/10.1098/rspb.2020.2327