Maphead_ Charting the Wide, Weird World of Geography Wonks - Ken Jennings [10]
Not all feats of spatial memory are long-distance migrations straight out of Walt Disney movies. The frillfin goby is a small tropical fish that’s usually found in rocky pools along the Atlantic shore. When threatened in a tide pool, either by a predator or by falling water levels, it has a remarkable defense mechanism: it escapes by shooting itself up into the air, like James Bond from an Aston Martin ejector seat. If you ever had a suicidal goldfish as a child, you know that accurate jumping isn’t always a fish specialty, but the goby always jumps straight into another (safer) pool. Sometimes it makes up to six consecutive pool hops until it arrives in open water. Obviously the fish can’t see out of its own pool, so how does it make these leaps of faith? It plans ahead. It takes advantage of every high tide to explore its surroundings so it knows—and remembers—where the safest spots are likely to be once the tide goes out.
But just because an animal can perform an impressive bit of way-finding doesn’t mean it’s relying on a sophisticated cognitive map. The clarinetist’s shearwater, for example, was crossing territory it had never seen before, the North Atlantic. It was obviously flying on instinct, not a mental map from past experience. We now know that many migrating birds rely on the position of the sun as a compass, as well as the sights and even smells of habitats along the way. Baby turtles are sensitive to tiny variations in the earth’s magnetic field; you can get a loggerhead turtle to change directions in a swimming pool by placing powerful magnets nearby.*
We humans use many of the same tools to orient ourselves that animals do; we’re just not as good at them. We don’t have magnetite in our beaks like homing pigeons do, but otherwise the principles are the same. Take my family’s recent trip to Washington, D.C.
• On our first day there, we walked from the Metro to the Air and Space Museum and then to the Natural History Museum. To get back to the Metro, we didn’t retrace our steps through both museums. We mentally gauged the distances and directions we’d traveled and set out to walk directly toward the Metro. Animal species from fiddler crabs to ground squirrels can do something analogous, only with much greater accuracy. An ant, for example, can wander around aimlessly for two hundred meters (at human scale, the equivalent of running a marathon) and then, from any point, return in a straight line to exactly where it started. This is called “path integration,” and it’s a crucial ability for foraging animals, which wander over a vast territory looking for food but need to be able to return directly to the nest as soon as they find enough to eat.
• Every time we double-checked our location by looking to see where we were relative to the Tidal Basin or the Washington Monument, we were mimicking another common animal trick: the use of landmarks. Many species of jays and nutcrackers, for example, are “scatter hoarders,” meaning that they store little food caches in as many as eighty thousand locations over a single winter. These birds rely heavily on landmarks to recover their hidden goodies; if nearby visual cues are tampered with, the food will be lost forever.
• We even used some rudimentary celestial navigation on our trip, as the Manx shearwater does. In which direction is the late-afternoon sun? All right, then, the White House is that way.
By the end of the day, we had the lay of the land down pretty well; even Mindy could find her way between any two monuments we’d visited without resorting to landmarks or a sun compass. It’s hard to be sure which animals can do the same. We can’t exactly ask them. The current consensus is that mammals, and possibly even some insects, like honeybees, can think in terms of maplike models. In one experiment that’s been repeated with both dogs and chimpanzees,