Chickadees have extraordinary memories.A new study explains why

Lost your key? Can’t remember where you parked your car? If only you had the memory of tits.

These half-ounce birds, with brains slightly larger than a pea, hide tens of thousands of food items, such as seeds, in tree bark, under dead leaves and in pine cones on mountains. When winter arrives, they can recall the exact location of their stash, a skill that helps them survive freezing temperatures and deep snow.

A new study published April 17 in the journal modern biologyResearchers at the University of Colorado Boulder and the University of Nevada, Reno have discovered nearly a hundred genes associated with birds’ spatial memory, or the ability to recall the location of objects. The paper also suggests there may be a potential trade-off between having reliable long-term memories and being able to quickly discard old memories to form new ones.

These findings could help biologists better understand the evolution of spatial memory in animals, including humans.

“Chickadees are impressive birds,” said Scott Taylor, director of the Mountain Research Station and associate professor in the Department of Ecology and Evolutionary Biology at the University of Colorado, Boulder. “They can remember tens of thousands of locations where food was stored throughout the winter and remember a new set of locations the next winter. Their spatial memory is more developed than many other birds, which don’t need this strategy to survive survive the cold winter.

To assess spatial memory in wild chickadees, Taylor’s collaborators, Vladimir Pravosudov, a biologist professor at the University of Nevada, Reno, devised an ingenious test. They hung multiple feeder arrays, each containing eight seed-filled bird feeders, in California’s Sierra Nevada Mountains. Each feeder has a door with a radio-frequency reader that detects tags the researchers have placed on the chickadees. The team then programmed each gate to be open only to certain birds, so that the chickadees had to remember the location of feeders open to them.

Pravosudov and his team then counted the number of times each chickadee landed on the wrong feeder before recalling the correct feeder. The theory is that birds with better spatial memory will have lower error rates.

The University of Colorado Boulder team also used blood samples to sequence the entire genomes of 162 tagged chickadees, creating the largest data set ever collected to assess the genetic basis of cognitive abilities in chickadees. By comparing the birds’ genomes to their performance in feeding tests, the team identified 97 genes related to spatial learning and memory in chickadees. Birds with specific genetic variations in these genes make fewer false attempts before landing on a given feeder.

Much of the variation is related to the formation of neurons in the hippocampus, the part of the brain responsible for learning and memory, said co-author Sara Padula, a doctoral student. student in the Department of Ecology and Evolutionary Biology.

“Understanding the genetic basis of this trait will allow us to understand how this trait evolved,” Taylor said.

Taylor points out that the common ancestor of all North American chickadees stored food. But two of the seven species of chickadees now found here are not.

“They live in a milder environment, where food is usually available year-round. Now that we know the genetic region behind spatial memory, we can see what variation looks like in these species that have lost their cache,” he said.

“This study significantly advances our understanding of the genetics of spatial memory and broader behavioral genetics in birds,” said Georgy Semenov, a co-author of the paper and a researcher in the Department of Ecology and Evolutionary Biology. Semenov) said.

a trade-off

Chickadees with special spatial memories can live up to nine years, which is a long time for a small bird, Taylor said. But research shows that having good long-term memory may come at a cost.

After a few days of initial mission, Pravosudov’s team assigned the birds new feeders.

To the team’s surprise, the chickadees that performed better in the initial tests often had difficulty adapting to the new feeders. They seem to have difficulty letting go of their original memories and creating new ones.

“In more variable environments, our collaborators found that chickadees with good long-term memories may be at a disadvantage. For example, if an unexpected snowstorm occurs, the birds may continue to try to access caches buried in the snow rather than forgetting They look for other caches,” Padula said.

climate change

Birds that can form new memories quickly may fare better in the face of a rapidly changing climate.

“As a result of climate change, we might expect these selective pressures that have shaped chickadees’ specialized memories to change significantly over thousands of years,” Taylor said.

This winter, Taylor and his team built the same type of feeder array at the University’s Mountain Research Station west of Boulder.

Over the past million years, chickadees in the Rocky Mountains evolved independently of those in the Sierra Nevada. The research team wanted to investigate whether two groups of birds evolved spatial memory in the same way in different geographical areas.

The team is also interested in learning whether black-capped chickadees, which coexist with chickadees in the Rockies, display different spatial memory abilities. During the coming winter, they will continue their feeder experiments at the mountain research station to collect more data.

“We don’t have to go to remote parts of the world like Antarctica to study how animals are responding to climate change. We can do it with these birds that most North Americans are familiar with. I think that’s what’s special about chickadees,” Taylor said .