Bearded seal bones recovered from dig in Aleutians
Remains of bearded seal (Erignathus barbatus) of all ages
have been recovered from the Amaknak Bridge site on
the Island of Unalaska in the eastern Aleutians. Shown
here are mandibles from a fully mature prehistoric
adult and a pup several weeks old (top). Bearded seals
give birth on sea ice in early April and nurse their young
for about three weeks.

Winter ice once clogged the Bering Strait until late summer and surrounded the rugged shores of the Pribilof Islands most of the year, according to a new study of ancient animal bones at an Aleutian archeaological site.

This frigid climate, occurring during a mysterious 2,000-year-long cold snap that ended about 2,500 years ago, was powerful enough to trigger decisive shifts in the migrations of whales and the breeding habits of Northern fur seals, ultimately creating a thriving ecology very different than the one observed during the past few hundred yeaers.

Two Canadian archaeozoologists — Susan Crockford and Gay Frederick of Pacific Identifications Inc — say the findings suggest a startling conclusion: that marine mammals like seals may be far more adaptable that people realize.

“Sea ice not only extended further south than it does today but persisted longer into the summer,” they added. “No other type of evidence has documented an expansion of sea ice in the Bering Sea during this time period, which appears to explain the prehistoric distribution of at least one North Pacific marine mammal.”

Among other things, the two scientists found remains of a newborn bearded seal pup, an ice seal, suggesting that floes existed near Unalaska Island as late as April.

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