Squirrels are Amazing Gamblers, University of Michigan Research Discovers

Posted on: January 23, 2023, 08:16h. 

Last updated on: January 26, 2023, 04:22h.

North American red squirrels, new research finds, are quite skilled at gambling.

North American red squirrels gamblers gambling reproduction
A North American red squirrel enjoys a conifer cone loaded with rodent-friendly seeds. Researchers at the University of Michigan have found that red squirrels are rather competent gamblers when it comes to reproduction. (Image: Getty)

University of Michigan biopsychology research fellow Dr. Lauren Petrullo recently discovered that North American red squirrels living in highly variable environments, such as the Canadian Yukon, regularly make big bets on the game of reproduction. Petrullo and her team discovered that North American red squirrels are rather competent in making seasonal wagers on whether the environmental conditions will be ripe for large litters.

A mast year — a boom in seeds from white spruce tree cones — occurs once every four to seven years. A mast denotes a season in which the trees synchronize their reproduction and drop large amounts of the fruit-bearing cones, the primary food source for the red squirrels.

The Michigan researchers observed that red squirrels regularly outperform their counterparts in the game of reproduction by betting big — and often — that the upcoming spring will be ripe for offspring.

Betting Big and Often

Petrullo said the North American red squirrels tend to produce large numbers of offspring even when other animals that rely on the spruce cones hedge their bets and produce fewer babies.

Animals in the Yukon, Petrullo said, play their own version of the lottery by trying to predict how much food will be available in the spring. Animals use an array of clues to make reproductive decisions.

The university collects data on how many squirrels are birthed and how many spruce cones are consumed each year.

“There is a constant tug-of-war between the trees and the squirrels, with each player trying to deceive the other for its own fitness gain,” Petrullo said.

We were surprised to find that some females have large litters in years when there won’t be enough food for their babies to survive the winter,” Petrullo continued. “Because it’s biologically expensive to produce offspring, we wanted to know why these females make what appears to be an error in their reproductive strategy.”

Petrullo found that by making big bets annually with large litters, the red squirrels have benefited from improved genes and overall fitness by always profiting off of the mast year. Other squirrels in the region that tried to more closely predict when the mast would come often missed the feast. And that has resulted in poorer genetics and health for those animals.

Jackpot Coming

The Chinese have a saying: “If you don’t gamble, you don’t know how lucky you are.” It’s a motto the North American red squirrels seem to follow.

Petrullo says by regularly betting big, the squirrels are almost guaranteeing a payout at some point. But unlike being told that six specific numbers would eventually win the Powerball jackpot and a lottery player continuing to play the numbers until they hit, squirrels do face substantial risk in betting big each year.

“In some ways, this strategy of gambling with litter sizes is like playing with fire,” Petrullo said. “Because the average squirrel lifespan is 3.5 years and masts only happen every four to seven, a female could potentially be sabotaging her fitness by having too many babies in low-food years, hoping for a mast when she may die before she ever gets to experience a mast at all. This could be pretty costly.”

However, Petrullo says it appears the red squirrels’ gambling strategy is currently the best bet in the Yukon.

“It’s essentially impossible for a female to recuperate the fitness costs of not ramping up reproduction in a mast year, so the stakes are extremely high,” she concluded.