Smart birds think smart and economical

Birds need significantly less energy for their brains than mammals.
Credit: RUB, Marquard

Bird brain cells only need about a third of the energy mammals have to use to supply their brains. "This partly explains how birds manage to be so smart, even though their brains are so much smaller than that of mammals," says Prof. Dr. Onur Güntürkun, head of the biopsychology unit at the Ruhr University Bochum. Together with colleagues from Cologne, Jülich and Düsseldorf, his research team examined the energy consumption of the brains of pigeons using imaging methods. The researchers report in the Current Biology journal dated 8. September 2022.

Why it can take in a crow with a chimpanzee

Our brain only makes up about two percent of our body weight, but consumes about 20 to 25 percent of body energy. "The brain is by far the most energetically expensive organ in our body, and we could only afford it in the course of evolution by successfully learning to supply a lot of energy," explains Güntürkun. The brains of birds are much smaller in comparison. Nevertheless, birds are just as smart as many mammals: crows and parrots, for example, whose brains only weigh about 10 to 20 grams, can cognitively absorb a chimpanzee whose brain weighs 400 grams.

How can that be? A study in 2016 brought light into the dark: It showed that birds per volume of brain mass have two to three times as many nerve cells as mammals. So, your brains are packed much denser. In addition, their cranial nerve cells are smaller. “But the question still arises: How can such a small animal afford so many nerve cells??“Says Onur Güntürkun.

The extent of the difference in energy consumption was surprising

To investigate this question, he and his team took a closer look at the brains of pigeons. For this they used the method of positron emission tomography, PET for short. Thanks to a special contrast medium, they were able to use the images obtained to estimate how much glucose the nerve cells in the pigeon's brain were awake and consumed in the anesthetized state. The energy consumption was therefore only a third of what a mammalian brain consumes.

"What surprised us the most is not that the nerve cells consume less glucose at all - this was to be expected due to their smaller size," said Güntürkun. “But the difference is so big it means that birds have additional mechanisms that reduce nerve cell energy consumption. This could partly be related to the higher body temperature of birds, but probably also to additional factors that are currently completely unknown,” explains the researcher. “Our study fits into a growing number of studies that show that birds have developed their own and very successful way of creating intelligent brains in evolution."

The study included researchers from the RUB, the Faculty of Medicine and the University Hospital Cologne, the Research Center Jülich, the German Center for Neurodegenerative Diseases, the Max Planck Institute for Metabolism Research and the Cecile and Oskar Vogt Institute for Brain Research of the University Hospital Düsseldorf, Heinrich Heine University Düsseldorf.

The work was funded by the German Research Foundation, funding codes Gu 227 / 16-1 and Gu 227 / 21-1.

Source/Credit: Ruhr University Bochum

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