City squirrels can't think straight when humans are nearby

Cities are filled with everyday encounters between humans and animals. Squirrels, with their darting movements and sharp minds, are among the most visible. They are quick to adapt, yet the true cost of sharing space with humans remains an open question.

Scientists in Finland decided to test whether the daily activities of people – walking, cycling, dog walking, or playing – can reshape the minds of Eurasian red squirrels.

Problem-solving matters for squirrels

Problem-solving is not just a sign of intelligence but a key survival tool. For squirrels, it can mean the difference between thriving in a park or struggling to find food. It involves using memory, making decisions, and adjusting behavior to novel challenges.

Squirrels are celebrated for hiding nuts in clever spots and returning months later to retrieve them. But beyond these feats, researchers wanted to know how constant exposure to humans might hinder or enhance such abilities.

Testing the minds of city squirrels

The team, from the University of Chester and the University of Oulu, designed an experiment that was both natural and demanding. They placed puzzle boxes filled with hazelnuts across 15 urban green spaces in Oulu.

The puzzles required squirrels to push or pull levers, forcing them to shift from their instinctive tree-foraging behavior to ground-based problem-solving in unfamiliar conditions.

Hazelnuts were chosen because they are a familiar and highly valued food source, ensuring strong motivation. Success required persistence, creativity, and innovation, qualities squirrels often display when adapting to city life and overcoming unexpected environmental challenges.

Human activity as stressor

The researchers measured three things: overall solving success, individual solving success, and the speed at which squirrels accessed the hazelnuts. The results revealed a striking pattern.

Sites with higher levels of human presence showed fewer problem-solvers. Walking through parks significantly reduced a squirrel’s chance of solving the task, while playground activity had the strongest negative effect of all.

Noise and movement may play critical roles here. Playground activity likely masks important environmental cues, such as the sounds of approaching predators. Even simple walking signals potential danger to squirrels, influencing their decision to invest time and energy in solving puzzles.

“Our field experiment demonstrates that human intensity and activities, most notably walking, dog walking and playground activity, significantly affect Eurasian red squirrels’ performance in solving a novel food-extraction task,” said Dr. Pizza Ka Yee Chow, lead researcher at the University of Chester.

Surprising effect of dogs

There was one unexpected finding. For squirrels that succeeded early, the presence of dogs actually sped up their problem-solving. This could reflect an adaptive response, where squirrels work faster to secure food before a perceived threat approaches.

According to Dr. Olli Loukola, the team’s motion-triggered cameras revealed that nearly two-thirds of dog walkers ignored the leash law in public parks in Oulu.

“While Finns are usually great at following rules, it seems many simply don’t realize that letting dogs roam freely can stress out urban wildlife. This study helps raise awareness of how small everyday choices can affect animal behavior,” said Dr. Loukola.

Human pressure on wildlife

The findings extend beyond squirrels. They suggest that human activity reshapes how urban wildlife thinks and acts.

“The research has identified specific features of human activity that likely exert pressure and shape urban wildlife cognition, which can help us understand the traits and mechanisms that enable urban wildlife to adapt to or thrive in urban environments,” said Dr. Chow.

She also noted the practical implications. “Importantly, our results may be useful for evaluating or tightening existing urban management and policy, such as leash laws or pet-free zones around key foraging sites, which could alleviate stress on urban squirrels and other wild animals,” added Dr. Chow.

Squirrels navigating city life

Urban parks are shared spaces, yet they are also complex habitats where animals must adapt quickly to survive.

This study shows how even routine human activities like walking, cycling, dog walking, or children playing can alter animal cognition and decision-making in unexpected ways.

For wildlife, these seemingly harmless actions create stress, forcing them to balance vigilance with foraging. By considering wildlife in city planning, daily habits, and personal choices, humans can help reduce unnecessary pressures for species like squirrels.

Such research reveals not just the resilience and adaptability of urban animals but also the profound, lasting influence people hold over their survival, well-being, and evolutionary future.

The study is published in the journal Behavioral Ecology.

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