Everyone knows that squirrels bury nuts to eat later. However, researchers have discovered that squirrels often play tricks. They'll dig a hole, then NOT bury a nut in the hole. When a squirrel knows that something or someone is watching, and digging up nuts a moment later, he may dig a "fake" hole. This way he could discourage the watcher and get him to give up (maybe a BlueJay or even another squirrel). A squirrel may even re-bury a nut, in the same or another place, to make it harder to pilfer.
Some common birds sing at a higher pitch when living near a highway, or a similar noise-producer. This way, they can be heard above the low-frequency noise of traffic. If the same bird travels to a quieter, more natural setting, he or she switches back to the customary, low-frequency song.
