Woolly Mammoth and Large Mammals Went Extinct as Sea Levels Rose

What caused the extinction of the woolly mammoth, and what were they like when they lived? Scientists are taking a closer look at the life and extinctions among woolly mammoths to learn a bit more about how Arctic mammal species survive environmental changes.

Short periods of warm climate in the midst of the last ice age triggered boom-and-bust cycles in the populations of large mammals in the Arctic. In fact, many large mammals became extinct when these cycles and the ice age ended and spreading peatlands and rising sea levels restricted animals' ability to move between continents.

In this latest study, the researchers radiocarbon dated mammoth fossils and compared their ages and abundances to climate records spanning the past 40,000 years. This allowed them to reconstruct what happened to woolly mammoths, steppe bison and other mammals.

"We wanted to know how these large animals responded to the rapid climatic changes that characterized that period of Earth's history," said Daniel Mann, lead author of the new study, in a news release. "To do this, we tested a hypothesis suggested by (retired) UAF paleontologist Dale Guthrie that megafaunal populations experienced boom-and-bust cycles during the ice age as the vegetation tracked climate change."

The last ice age, which occurred about 80,000 to 12,000 years ago, was a time of diverse climates. The results of the latest study show that animal and plant communities were much more changeable during the ice age than they have been during the last 12,000 years of interglacial climate in which we live today.

The researchers found that a lowered sea level drained the Bering Strait, which is the narrow seaway separating Alaska and Asia. Being able to move across the area is probably what kept large, Artic mammals thriving for so long. This travel corridor allowed animals to come to Alaska where their favored food thrived during warm periods. It also allowed the animals to leave Alaska for greener pastures when prolonged periods of warmer, wetter climate allowed peat to spread.

With the rise of sea levels, though, this corridor was no longer present. Without the ability to move, the large mammals declined.

"Arctic climates are particularly unstable and are changing rapidly today," said Mann. "This means the Arctic is an interesting place to study how climate changes cause extinctions, and the past gives us many interesting examples of extinction there. Plus, bones are exceptionally well-preserved because of the frozen ground."

The findings are published in the journal Proceedings of the National Academy of Sciences.

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