For red squirrel moms, it only makes sense to take a chance

about the episode

Let’s say you were told the winning lottery numbers, but you don’t know in which month of the year the jackpot will fall. Playing along every month (with the same combination of numbers) costs money of course, but in this case the prize is big enough to do it anyway.

Female North American red squirrels seem to do something similar when they estimate how much food will be available for their offspring. From an evolutionary standpoint, it is beneficial to have a large nest during a time when there is plenty of food available. Hence the chance of the young surviving and being healthy is logically greatest.

White spruce trees in the Canadian Yukon produce additional seeds once every four to seven years. Think of this as winning the jackpot. A female squirrel lives, on average, only 3.5 years. Suppose she makes the little litters just to be on the safe side, because it is not certain when there will be such a rise in food security, it is likely that she will stay healthier and the few little ones she makes will survive instead of raising huge litters.

But researchers have seen — in more than 30 years of data — that some females take risks. They make one big nest at a time, so that when the jackpot hits, their genes are passed on to a large number of young. It’s a gamble, but when they succeed, they win big.

Well, some squirrels seem to have a better sense of when they’ll hit the jackpot. It is assumed that they receive signals from trees, but that has not been well studied yet. The researchers warn that these signals are becoming less reliable due to climate change and that this is likely bad news for red squirrels in the Yukon.

Read more about research here: Squirrels that gamble gain a lot when it comes to evolutionary fitness.