Raccoons have long been credited with outwitting latches, and a study has tested that reputation. University of British Columbia researchers Hannah Griebling and Dr Sarah Benson-Amram gave captive raccoons a custom puzzle box with nine entry points, grouped as easy, medium and hard. Each 20-minute trial held a single marshmallow; the raccoons often kept opening new mechanisms after eating it. Sixteen adult raccoons were tested in Colorado, and fourteen completed all three difficulty levels. The authors call the behaviour information foraging, and the paper reports that all but one raccoon solved multiple solutions within single trials.
How did scientists test raccoons with a nine-way puzzle
According to the University of British Columbia news release, the researchers used a custom multi-access puzzle box with mechanisms such as latches, sliding doors and knobs. The box had nine entry points, grouped as easy, medium and hard. The paper states that the box was a Plexiglas cube measuring 25.4 centimetres on each side, with removable panels. One panel was plain Plexiglas, and the other three held solutions that gave access to the food in the centre, so each raccoon faced three solutions at a time.The easy ones were a door, a slide latch and a pull-down window. The medium ones were a hook-and-eye latch, a hasp latch and a push-up window. The hard ones were a draw-catch latch, a turn knob and an unlocked padlock placed in the hasp. According to the paper, sixteen adult raccoons were tested at the United States Department of Agriculture’s National Wildlife Research Centre in Fort Collins, Colorado. Eight were captive-reared males, six were captive-reared females, and two were wild-caught males. Fourteen completed all three difficulty levels.
Why did raccoons keep solving the puzzle after eating the marshmallow
According to the study published in ScienceDirect, titled ‘Raccoons optimally forage for information: exploration–exploitation trade-offs in innovation’, each raccoon had five trials a night for 10 nights, giving 50 trials in total. Trials lasted 15 to 20 minutes, and most ran for the full 20. The raccoons were not deprived of food, although their second daily ration was held back until testing finished each night. Before the puzzle trials, a food preference test showed that the raccoons were more likely to choose a marshmallow than a dried prune dipped in sardine juice or a sardine. Each raccoon met the easy solutions first. It moved on to the next level only after opening one solution 15 cumulative times.The box held a single marshmallow in each 20-minute trial, yet raccoons often continued opening new mechanisms after eating it. “They kept problem-solving even when there was no marshmallow at the end,” Griebling said. The paper reports that all but one raccoon solved multiple solutions within single trials at all three difficulty levels. The raccoons could see and feel with their forepaws that no further food was inside the box.
How did raccoons change their puzzle-solving strategies
The raccoons took longer to solve their first hard solution than their first easy or medium one. The mean number of solutions solved per trial was 1.79 for easy, 1.63 for medium and 1.44 for hard. The paper also scored how varied the raccoons’ solving order was, on a scale from 0 to 1. The mean scores were 0.57 for easy, 0.52 for medium and 0.35 for hard. The authors say this shows the raccoons explored more on easier problems and relied on known solutions more on harder ones.UBC states that raccoons tried multiple openings and varied their order when solutions were easy. As difficulty rose, they favoured a dependable solution, but they still explored several solutions at the hardest level. Griebling compared the pattern to ordering at a restaurant, choosing a favourite dish or trying something new. In her words, as reported by UBC, raccoons explore when the cost is low and play it safe when the stakes are higher. The paper adds that the more time raccoons spent exploring the box, the more solutions they solved. That exploration also slowed how quickly they opened the first solution and reached the food. The authors report that this effect diminished as trials continued.
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How do raccoons’ problem-solving skills help them thrive in cities
The findings help explain why raccoons thrive in urban centres such as Vancouver. The release says their forepaws are rich in sensory nerves for foraging in streams, which suits them to handling latches and handles as humans do. Raccoons recorded the highest average occupancy of mammals across 20 North American cities, citing Magle and colleagues (2021). Griebling said that understanding the traits that help raccoons thrive can guide the management of species that struggle. She added that it can also inform strategies for species such as bears, which use problem-solving to reach human-made resources.The experiment involved captive animals. Previous research suggests wild raccoons show similar problem-solving abilities, but UBC says the researchers caution that the behaviours may not be identical. Raccoons were searching for another reward. In their conclusion, they say this behaviour may lead raccoons into conflict with humans if their problem-solving defeats raccoon exclusion measures.
