Scientific American - USA (2012-12)

Source:

“Lifetime Mobility of an Arctic Woolly Mammoth,” by Matthew J. Wooller et al.,

in^ Science,

Vol. 373; August 2021 (

map reference

)

GRAPHIC SCIENCE
Text by Tess Joosse | Illustration by Beth Zaiken, Maps by Jen Christiansen

Pulp cavity

Time

Newer tusk

material

Older tusk

material

Mammoth

Travels

Chemical layers in a tusk reveal

an epic journey across Alaska

Mammoths are among the best-known inhabitants of the

last ice age. Fossils usually offer a static snapshot of an ani-

mal’s life, but researchers recently used one to track every

place a male mammoth traveled from birth to death. By

analyzing the chemicals in a 17,100-year-old tusk, scientists

found the mammoth walked far enough to loop around the

world twice—likely in search of food and a mate.

“Tusks are like time lines,” adding layers each year

that contain chemicals from the environment, says

Matthew  J. Wooller, a paleoecologist at the Universi-

ty of Alaska Fairbanks. He and his colleagues sliced

a five-and-a-half-foot-long tusk in half, then mea-

sured chemical ratios in each layer to re-create the

mammoth’s itinerary. Over 28 years the animal

walked nearly 80,000 kilometers across what is now

Alaska. The team plans to apply the same technique

to more tusk fossils in the future. “We have hundreds,”

Wooller says.

How

Tusks Grow

After growing and losing a first

set of “milk tusks” between six

months and a year old, mammoths

develop a permanent pair. Adult tusks grow

outward by adding cones of bone to

a hollow center extending from the

mammoth’s gums, continuing

throughout the animal’s life.

The resulting tusk’s tip is from

the animal’s younger years, and

its inner layers are from

its later years.

One Mammoth’s Journey

The alkaline earth metal strontium comes in different versions called isotopes, each with a unique atomic mass.

Proportions of these isotopes vary in soils around the world, and small amounts of strontium become part

of a mammoth’s bones, teeth and tusks when it eats plants. By analyzing each tusk layer’s strontium isotopes,

researchers traced where the mammoth roamed during each stage of its life.

0 500 kilometers

Ice (during

the Last Glacial

Maximum) Gulf of Alaska

Today’s Alaskan

coastline

Arctic C

ircle

Frequently Visited Regions during Youth Frequently Visited Regions during Adulthood Frequently Visited Regions during Final Two Years

Location

of death

76 Scientific American, December 2021