Matthew Hutson writes:

A while ago, I searched for a beard trimmer in my bedroom. I spent probably forty-five minutes looking in every likely location at least twice, and every unlikely location at least once. I swore up a storm; the trimmer never turned up. I’ve played similar games with pants. There’s a reason for the burgeoning market in electronic tags that track your belongings.

Our poor memories can seem mystifying, especially when you consider animals. This time of year, many species collect and cache food to stave off winter starvation, sometimes from pilfering competitors. So-called larder hoarders typically keep their troves in a single location: last year, a California exterminator found seven hundred pounds of acorns in a client’s wall deposited there by woodpeckers. In contrast, scatter hoarders—including some chickadees, jays, tits, titmice, nuthatches, and nutcrackers—distribute what they gather over a wide area. Grey squirrels use smell to help them find their buried acorns. But many scatter hoarders rely largely on spatial memory.

People first noticed scatter hoarding by 1720 or even earlier. It’s come under serious investigation, however, only in the past century. Scientists now know that birds’ brains can contain elephantine powers of recollection. Some birds can store, or cache, tens or even hundreds of thousands of morsels in trees, or in or on the ground, and retrieve a good portion of them. In 1951, a Swedish ornithologist named P. O. Swanberg reported on Eurasian nutcrackers: over the course of a single autumn, he saw each bird make some eight thousand caches. That winter, the birds dug through the snow to retrieve their stored food. Swanberg examined the excavation holes the birds had left behind and found nutshells in nearly ninety per cent of them—an indication that there had been few fruitless efforts.

In the late nineteen-seventies, researchers at Oxford buried sunflower seeds just ten centimetres from where marsh tits had buried their own morsels. Over the following days, the bird-buried seeds disappeared significantly faster than those the scientists had buried, suggesting that the birds had precise memories of their cache locations. In 1992, other scientists reported that birds known as Clark’s nutcrackers could recall, with better-than-chance accuracy, where they’d buried seeds more than nine months earlier.

Vladimir Pravosudov began studying food caching as an undergraduate at Leningrad (now St. Petersburg) State University. “I’m a big believer in just watching animals,” he told me. Above the Arctic Circle, he’d spend hours a day with binoculars and a stopwatch, observing willow and Siberian tits; he found that they could cache food as frequently as twice a minute. Extrapolating, he estimated that they could store as many as half a million bits of food each year. He grew fascinated with the question of how and why birds had evolved to be “caching machines.” [Continue reading…]