The raccoons introduced to Europe are successful cultural followers. They rob even locked garbage cans and find shelter under our roof. There could be a special ability of the cute marten relatives behind this: they naturally enjoy exploring and puzzling, as an experiment shows. In this, the guard bears continued to tinker with different ways to open a box, even though they had long since received their reward.
Raccoons (Procyon lotor) were originally only native to North America, but were brought to Europe at the beginning of the 20th century – originally as fur animals and for wildlife parks. A growing population also developed from escaped and abandoned animals. There are now more than 100,000 raccoons living in Germany – not always to the delight of local residents. The adaptable and intelligent relatives of martens often cause unhappiness through looting garbage cans, roof collapses and noise at night. Even bars don’t seem to be a problem for some raccoons.
A puzzle box for raccoons
But what makes raccoons such successful bioinvasors and cultural followers? One key to this could be their adaptability: the animals quickly learned to find food in cities and also to use man-made objects. In an experiment, Hannah Griebling from the University of British Columbia and her colleagues have now examined in more detail how persistent raccoons are when solving problems. To do this, they presented 14 raccoons with a transparent box containing a marshmallow – a sweet that is also coveted by raccoons.
But in order to get to the marshmallow, the animals had to overcome at least one of nine different opening options. The range ranged from simple sliding doors and flaps to eyelets and latches to rotary knobs and padlocks. Unlike most tests of this type, the test did not end with the successful opening of the box and the food reward: “The raccoons were then allowed to continue playing around with the puzzle box,” report the biologists. They wanted to find out whether raccoons enjoy exploring and trying out new things even without a food reward.
Tinkering even without reward
It turned out that the raccoons not only managed to open the box and take out their snack. Even after eating the marshmallow, they continued to puzzle over it – even though they saw that the box was empty. “All but one raccoon solved several opening tasks per trial,” report Griebling and her colleagues. “They just kept trying, even though there was no marshmallow waiting for them.” According to the researchers, this reveals that raccoons are naturally curious: the animals have an intrinsic motivation to explore their surroundings, even if this doesn’t immediately bring them food.
This ability could bring advantages to the cute bioinvasors, especially in the city: “In urban habitats, resources are very changeable, so it is advantageous to explore your environment often,” explains the team. However, the raccoons adapt their curiosity and desire to explore to the circumstances: If the animals in the experiment were given a puzzle box with several rather simple tasks, they tried it out for longer. On the other hand, if the opening mechanisms were more complicated and required more time, the raccoons puzzled less persistently and were more likely to rely on the opening method that was solved first.
Weighing costs and benefits
“This is a pattern that we know from ourselves,” says Griebling: “When you sit in an expensive restaurant, you are usually less willing to experiment when ordering and are more likely to rely on the safe option.” On the other hand, if the costs are manageable, you are more willing to try new things and take a risk that may not pay off in the end. In a similar way, guard bears also weigh costs and benefits: they explore more if it involves little risk and effort.
“Raccoons have long been considered intelligent, but so far there has been little scientific research on this,” says Griebling’s colleague Sarah Benson-Amram. “Experiments like ours now provide the empirical evidence for this call.”
Source: Hannah Griebling (University of British-Columbia, Vancouver) et al., Animal Behavior, doi: 10.1016/j.anbehav.2026.123491