For Beavers, Days Get Longer in Winter
Beavers become near shut-ins during winter, living off of previously stored food or the deposits of fat in their distinctive tails. They conserve energy by avoiding the cold outdoors, opting instead to remain in dark lodgings inside their pile of wood and mud. As a result these rodents, which normally emerge at sunset and turn in at sunrise, have no light cues to entrain their sleep cycle. The beaver's biological sense of timeshifts, and she develops a "free running circadian rhythm" of 29-hour days.
Birds Use Landmarks to Navigate Long Journeys
Can you imagine a road trip
vacation without missed exits, stubborn drivers or map-folding disasters? Of course not�you're not a bird. Pigeons can fly thousands of miles to find the same roosting spot with no navigational difficulties. Some species of birds, like the Arctic tern, make a 25,000 mile round-trip journey every year. Many species use built-in ferromagnets to detect their orientation with respect to the Earth's magnetic field. A November 2006 study published in Animal Behaviour suggests that pigeons also use familiar landmarks on the ground below to help find their way home.
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