Third-party Social Evaluation of Humans by Bystander Ravens and Crows

Popular Abstract

Can Crows and Ravens Tell Selfish and Generous Humans Apart?

Imagine that you observe two people at the store reaching for the two last packages of their favourite cookies. The person that arrived last at the spot asks the first one for a package. In the first scenario, the human that arrived first acts generously and gives one package, while in the alternative scenario, the human acts selfishly and walks away with both packages. Who would you choose to take a cookie from when asked to? Would you trust the selfish person?

The evaluation of someone as cooperative or uncooperative could be a useful tool for social animals forming groups in nature. Social evaluation is considered to increase survival through the avoidance of harmful individuals, and to improve reproductive success through the choice of an appropriate mating partner. Researchers have investigated whether animals, mainly primates and dogs, under laboratory conditions are able to discriminate between two humans after observing them behaving cooperatively or uncooperatively in a food-sharing or problem-solving situation. The goal was to assess whether the animals could understand what they have seen during the demonstration as observers and whether they would show bias for or against one of the humans.

Birds belonging to the corvid family are known for their highly developed cognitive skills. Common ravens and carrion crows are renowned for both their complex behaviour and their use of anthropogenic food resources, exposing them to a variety of individuals of the same or different animal species. In my study, I tested whether crows and ravens could discriminate between two humans after observing a demonstration of food being transferred from a human donor, acting either selfishly or generously, to a neutral human recipient.

Crows and ravens avoid selfish humans, but do not prefer cooperative ones
The crows and ravens of my study showed aversion to the selfish human and preferred the neutral recipient after observing the selfish scenario but did not discriminate between the humans in the generous scenario. This result shows that crows and ravens seem to understand third party interactions as observers, but they are also sensitive to inequity. The fact that the birds did not show preference for the generous donor shows that negativity bias towards the uncooperative individual might be more widespread in animals. Six weeks after the demonstration, when the birds were tested again, they did not show any biases towards the humans, which implies that they did not remember the demonstration or that they thought that the humans’ behaviour was only temporary.

The similarities in behavioural responses of corvids in my study with primates from other social evaluation experiments, further support the theory that the socio-cognitive skills that birds and mammals share may have evolved independently in these animal groups.

Master’s Degree Project in Biology 45 credits 2022
Department of Biology, Lund University

Internal supervisor: Prof. Anders Brodin
External supervisor: Prof. Thomas Bugnyar
Internal supervisor’s Department: Department of Biology, Lund University
External supervisor’s Department: Department of Behavioural and Cognitive Biology, University of Vienna

• author: Kragkaris, Efthymios
• supervisor: Anders Brodin; Thomas Bugnyar
• organization: Degree Projects in Biology
• course: BION02 20212
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9079333
• date added to LUP: 2022-05-13 15:32:42
• date last changed: 2022-05-13 15:32:42