A special mirror test has so far determined whether an animal is self-aware. Roosters usually don't pass this test, but they may still have ego perception, as an alternative test adapted to their natural behavior suggests. When the roosters see themselves in the mirror while a bird of prey silhouette is projected on the ceiling, they do not try to alert their reflection as they would a member of their species. Biologists speculate that this may be because they recognize themselves in the mirror.
In order to check which animals have a human-like ego consciousness, special mirror tests are used in behavioral research. The ultimate criterion is the so-called marking test. A colored dot is painted on the animal's face or another part of the body that cannot be seen. If it begins to look for and explore this marking on itself with the help of its reflection, this is considered evidence that the animal recognizes itself in the mirror and probably has ego consciousness. So far, chimpanzees, elephants, dolphins, magpies and cleaner fish have passed this test.
Warning calls as an alternative test
Chickens, on the other hand, typically fail the marking test and show little interest in painted dots. But does that really mean that they have no ego perception? Not necessarily, says Sonja Hillemacher from the University of Bonn. Together with her colleagues, she has now developed an alternative test for roosters that is intended to provide more nuanced insights into their self-perception. “Our goal was to carry out the mirror test in an environment that is better adapted to the ecologically relevant behavior of the chickens,” explains co-author Inga Tiemann, also from the University of Bonn.
Roosters are known to warn their peers with special calls when a predator such as a bird of prey or fox appears. However, if there are no other birds nearby, the birds usually remain silent in order to remain undetected. Hillemacher and her team were also able to observe this behavior on 58 roosters in the laboratory. When they separated two roosters with a grid and then projected the silhouette of a bird of prey onto the ceiling above one of them, it often emitted a warning call to its companion next door. However, when he was alone with the bird of prey, he usually stayed quiet. But how would the roosters react if the grid was replaced by a mirror? Would they give a warning call because they thought they recognized a member of their own species in the reflection? Or would they remain silent because they realize they are alone with the bird of prey?
Roosters may recognize themselves
The result: In 174 mirror runs, the researchers recorded a total of only 25 warning calls from their roosters. “This proves that the roosters did not identify a member of their species in their reflection,” says Hillemacher. Otherwise they would have tried much more often to warn them about the bird of prey. However, what exactly the birds think instead when they look in the mirror is not known. On the one hand, the test result could be an indication that the roosters recognized themselves in their reflection. On the other hand, it would also be theoretically possible that the roosters simply saw their image as a strange animal that imitated their movements and therefore refrained from making a warning call, as the biologists explain. “Further investigations are needed here,” says Tiemann.
Either way, the results of the alternative test for ego perception suggest that the classic mirror-marking test would be more reliable if it were adapted more closely to the natural behavior of the animal species being tested. “In the classic situation, a rooster may not show self-awareness,” says co-author Onur Güntürkün from the University of Bochum. “But when a predator threatens him, it becomes clear that his reflection is not another rooster, but himself.” Against this background, it would be entirely possible that many animal species have already been denied the ability to self-knowledge, although this only became apparent under different experimental conditions would have shown.
Source: Rheinische Friedrich-Wilhelms-Universität Bonn; Specialist article: PLOS ONE, doi: 10.1371/journal.pone.0291416