for National Geographic News
Arctic foxes create "nest eggs" each year to prepare for leaner times, according to a new study.
Like squirrels gathering nuts for the winter, the small foxes hoard bird eggs in case there's not enough of their favorite prey—the collard lemming—to go around in the spring.
The stored eggs can last for up to a year after being buried, thanks to the Arctic permafrost and natural preservatives inside the eggs.
"It appears as if cached eggs are used as a backup for unpredictable changes in lemming numbers," lead study author Gustaf Samelius of Grimsö Wildlife Research Station in Riddarhyttan, Sweden, said in an email.
"This is a neat adaptation in an environment where food abundance changes dramatically both among seasons and years."
(Related news: "No Nuts, No Problem: Squirrels Harvest Maple Syrup" [February 18, 2005].)
Samelius added that the study is the first to show the extent to which the carnivores can depend on stored rations.
Other carnivores are known to store food, the researcher noted, but they generally cache for only a few days and base their diets more on fresh kills.
"Our results of about 50 percent of the [arctic fox's] diet coming from cached foods might be on the extreme end" compared with other meat-eaters, Samelius said.
Samelius's team based its findings on the behavior of arctic foxes living near Karrak Lake in the Queen Maud Gulf Bird Sanctuary in the territory of Nunavut, Canada, between 2000 and 2004 (see a map of Nunavut).
Karrak Lake is the summer breeding ground for up to a million snow geese and Ross's geese. The birds' nests supply ample pickings for the region's foxes, which store between 2,000 and 3,000 eggs a year.
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