The first thing you notice about a rabbit is its oversized ears which, as one might guess, enhance its ability to hear. The two ears can move independently of each other and can be rotated 270 degrees.
In addition to being designed to catch sound from any direction, rabbit ears regulate a rabbit’s body temperature. There is a very extensive network of blood vessels in a rabbit’s ears that provide a large surface area for heat exchange. These vessels swell (vasodilation) when the rabbit is hot, and contract (vasoconstriction) when it is cool, so much so that they are barely visible in cold weather. In the summer, the increased circulation of warm blood from the body’s core to the rabbit’s ears, where heat is lost to the cooler surrounding air, provides internal air-conditioning for the rabbit. (Photo: Eastern Cottontail)
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An owl’s range of audible sounds is not unlike that of humans, but an owl’s hearing is much more acute at certain frequencies, enabling it to hear even the slightest movement of their prey under two feet of snow. When a noise is heard, the owl is able to tell its direction because of the minute time difference in which the sound is perceived in the left and right ear. If the sound is to the left of the owl, the left ear hears it before the right ear. The owl turns its head so the sound arrives at both ears simultaneously, at which point it knows its prey is right in front of it. Owls can detect a left/right time difference of about 0.00003 seconds.
Once an owl has determined the direction of its next victim, it flies towards it, keeping its head in line with the direction of the last sound the prey made. If the prey moves, the owl makes corrections mid-flight. When about two feet from the prey, the owl brings its feet forward and spread its talons, and just before striking, thrusts its legs out in front of its face and often close its eyes before the kill. (Photo: barred owl wings and feet imprints; inset: barred owl ear opening.)