Roosters May Recognize Their Reflections in Mirrors, Study Suggests

The findings demonstrate self-recognition could be more common among animals than previously thought

A side view of a rooster on a black background
In the new experiment, roosters made fewer alarm calls, meant to warn peers of predators, when placed in front a mirror versus when standing near another rooster. Stefano Spaziani / picture alliance via Getty Images

In a variation of a classic experiment, scientists showed that roosters may recognize their own reflections in a mirror.

This ability is considered a sign of self-awareness in animals. The traditional experiment, which involves placing a mark on an animal and seeing whether they touch it when put in front of a mirror, had only detected self-recognition in a limited number of species. But the new findings suggest more species may be able to discern their reflections than previously thought, per a new paper published Wednesday in the journal PLOS One.

“This is exciting, as it moves away from the rigid dogma that the mark test is the only valid test for self-recognition in animals,” Nathan Emery, who researches animal intelligence at Queen Mary University of London and did not contribute to the findings, tells New Scientist’s Jake Buehler.

For the classic mirror test, the mark is placed on a part of an animal’s face or body that it can only see when in front of a mirror. If the animal then investigates or touches the mark, that’s considered an indication that it recognizes the reflection as its own, a sign of self-awareness.

Only a few non-human animals have passed the mirror test, including great apes, bottlenose dolphins, elephants, magpies and crows. But the test could have some limitations—in previous experiments, only some individuals of a species have passed, which could mean the test has a high rate of false negatives, according to the new study. Additionally, training animals with mirrors can improve their test results.

The mirror test also might be less accurate for animals that have different abilities from apes, writes the New York Times’ Darren Incorvaia. To test other animals, the researchers thought they should incorporate behaviors connected to the creatures’ day-to-day activities, as they might not all be motivated to touch marks on their bodies, Sonja Hillemacher, a co-author of the study and animal behavior researcher at the University of Bonn in Germany, tells New Scientist.

To adapt the mirror test for roosters, the team decided to measure their alarm calls. When predators are nearby, roosters typically make calls to warn others, but they’ll remain silent if they’re alone. The researchers placed one of the birds in front of a mirror and projected a silhouette of a hawk flying above it. If the rooster remained silent, that could indicate it recognized itself and didn’t feel the need to vocalize a warning, whereas a call might mean the rooster confused its reflection for a companion.

For comparison’s sake, the hawk silhouette was also projected above roosters under some different conditions: when they were alone with no mirror, accompanied by another rooster visible to them in an adjacent compartment and accompanied by another rooster in an adjacent compartment that was blocked from sight by a mirror. They tested 68 roosters in total, and all the birds were tested in multiple setups.

4 diagrams: A) rooster alone with hawk flying above, making no sound; B) rooster with mirror and hawk above, no sound; C) rooster with another rooster and no mirror, a hawk above, makes call; D) rooster with another it can't see behind a mirror, no sound
Four diagrams depict the different experimental conditions and outcomes—roosters made the most alarm calls when they were placed with another rooster they could see, as opposed to when alone or with a mirror. Hillemacher et al., PLOS One 2023, under CC BY 4.0

In the experiments, the roosters made significantly fewer warning calls when placed next to a mirror versus next to a rooster they could see, suggesting they recognized the reflection was not another bird. They also made a similar number of calls in the mirror setup as they did when they were alone. In tests with another rooster hidden behind a mirror, the animals also made a low number of calls, suggesting they recognize the presence of other roosters visually, not by their smells or sounds.

The roosters also failed the classic “mark” version of the mirror test.

“Potentially, this study shows strong evidence for self-awareness,” Masanori Kohda, a biologist at Osaka Metropolitan University in Japan who did not contribute to the findings, tells the New York Times. “However, these results will not be enough to persuade all scientists.”

Despite observing the roosters’ actions, scientists don’t know exactly what went through the animals’ heads. “It’s equally feasible that they regarded their reflection as an odd [member of their species] mimicking their every move, leading them not to emit an alarm call out of irritation,” Hillemacher says to the Guardian’s Nicola Davis.

Still, the findings suggest self-recognition might not be as exclusive as previously thought.

“If ecologically relevant behavior like the alarm call in chicken will be used in the studies on self-awareness in animals, the animals’ self-awareness will be more correctly judged,” Kohda tells the New York Times.

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