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The summer solstice, which marks the longest day of the year in the Northern Hemisphere, happens today (June 21) at 6:07 a.m. EDT (1007 GMT). This event happens when Earth's tilt toward the sun is at its maximum and the sun points directly over the Tropic of Cancer.
That extended daylight makes it difficult for people in northern latitudes to know when to go to sleep if they aren't looking at a clock, but the midnight sun is no problem for many other animals.
Animals - Latitudes - Cycles - Conditions - Cory
But many animals in northern latitudes can naturally control their sleep-wake cycles in extreme daylight conditions, said Cory Williams, a biologist at the University of Alaska Fairbanks.
"There are animals that stop having a prolonged period of sleep," and they abandon their usual daily rhythm during this time of year, Williams told Live Science. For example, semipalmated sandpipers (Calidris pusilla) — small, brown-and-white shorebirds that breed above the Arctic Circle — are unfazed by the long periods of daylight. They alternate sleeping and waking hours with their nesting mate throughout the day. "When the male is active, the female is at the nest and vice versa," Williams said. "It's not on a 24-hour schedule."
Sandpiper - Marsh
A semipalmated sandpiper in a marsh.
Reindeer also ignore the absence of a light-dark cycle during the summer months. Instead,...
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