The idea of a chicken running around with its head cut off, inspired by a real-life story, may make it seem like the bird doesn’t have much going on upstairs. But Sonja Hillemacher, an animal behavior researcher at the University of Bonn in Germany, always knew that chickens were more than mindless sources of wings and nuggets.
“They are way smarter than you think,” Ms. Hillemacher said.
Now, in a study published in the journal PLOS One on Wednesday, Ms. Hillemacher and her colleagues say they have found evidence that roosters can recognize themselves in mirrors. In addition to shedding new light on chicken intellect, the researchers hope that their experiment can prompt re-evaluations of the smarts of other animals.
The mirror test is a common, but contested, test of self-awareness. It was introduced by the psychologist Gordon Gallup in 1970. He housed chimpanzees with mirrors and then marked their faces with red dye. The chimps didn’t seem to notice until they could see their reflections, and then they began inspecting and touching the marked spot on their faces, suggesting that they recognized themselves in the mirror. The mirror test has since been used to assess self-recognition in many other species. But only a few — such as dolphins and elephants — have passed.
After being piloted on primates, the mirror test was “somehow sealed in a nearly magical way as sacred,” said Onur Güntürkün, a neuroscientist at Ruhr University Bochum in Germany and an author of the study who worked with Ms. Hillemacher and Inga Tiemann, also at the University of Bonn. But different cognitive processes are active in different situations, and there’s no reason to think that the mirror test is accurate for animals with vastly different sensory abilities and social systems than what chimps have.
The roosters failed the classic mirror test. When the team marked them with pink powder, the birds showed no inclination to inspect or touch the smudge in front of the mirror the way that Dr. Gallup’s chimps did.
As an alternative, the team tested rooster self-awareness in a more fowl friendly way.
Roosters don’t just crow in the morning to wake farmers. They are known to cry out to warn each other when a hawk is circling overhead. But when they’re alone and a predator is near, they stay silent to avoid attracting attention.
Ms. Hillemacher wrangled roosters and gave them time in an enclosure with a mirror, so they could get used to the experimental set-up. Because roosters warn others more reliably than hens do, the team chose to focus on them, but they believe the results of the test apply to all chickens. She then projected a hawk silhouette over the roosters to see how they’d react.
When another rooster was visible through a partition, the rooster that was the subject of an experiment cried out to warn the other of danger. When alone without a mirror, the bird stayed quiet. When another rooster was present, but blocked from view by a mirror, the test subject still tended to stay silent.
The researchers interpreted this behavior to mean that the rooster didn’t perceive its reflection to be another rooster, and felt it also showed that the birds were sensing each other with sight — not hearing or smell.
“Potentially, this study shows strong evidence for self-awareness,” said Masanori Kohda, a biologist at Osaka Metropolitan University in Japan who wasn’t involved in the research. “However, these results will not be enough to persuade all scientists.”
Dr. Kohda emphasized the need for more control experiments to rule out other possibilities. Dr. Kohda knows well how tough persuading scientists can be, after his own extensive efforts to demonstrate self-awareness in the bluestreak cleaner wrasse fish.
Dr. Tiemann hopes to next explore differences between roosters in how much they alarm call, which she said has implications for protecting flocks from predators. “We’re trying to identify those roosters who like to warn,” she said, “who take their job seriously.”
The authors also hope that other researchers will use their approach to test other animals that warn each other about danger, or to test self-awareness in ways that are relevant to the animals in the experiment. It’s possible that many animals that failed the original mirror test may pass a trial more geared to the way they live.
“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,” Dr. Kohda said. “The original mark test exactly delays the progress of understanding animal-mind.”