Since there are more eyes, ears and noses to detect a stalking predator.
In a nearby clearing a young calf has become trapped in quicksand.
It is a scene that has been played throughout history
and one which has provided us with our richest source of fossil remains.
When predators like this coyote approach, they too can become trapped.
Fossils obtained from scenarios like this
have allowed us to reconstruct a
remarkably detailed portrait of North America during the Ice Age.
But there are many unanswered questions.
What we do know is that about ten thousand years ago,
global temperatures suddenly began to rise.
As the earth grew warmer, open prairies turned to forest
and plants that were once plentiful suddenly disappeared.
Animals that relied on these plants
were, in many cases, unable to adjust to the changes.
At around the same time the first human hunters arrived in North America.
With many species like the woolly
mammoth already weakened by environmental changes,
it didn't take much for human hunters to finish them off.
North America would never again
sustain such a diverse and plentiful mammal population.
The plains of Africa.
The vast diversity of animals here is a living reminder of the world
as it was before the Ice Age extinctions.
Africa's geographical position
protected most of its animals from the Arctic cold
permitting huge herds to migrate across its limitless terrain.
Today, Africa is still the home of the
world's most magnificent herds of large mammals.
Elephants are the largest land mammals on earth.
During the Ice Age, they enjoyed the boundless resources Africa provided.
Although they managed to survive the
climatic changes at the end of the Ice Age,
some of their distant relatives were less fortunate.
Mammoths migrated throughout the world.
But when the glaciers retreated and their food supply disappeared,
so did the mammoths.
Like the mammoths,
today's elephants travel in large herds over enormous tracts of land.
They require huge amounts of food.
Quantities that today's shrinking habitat can barely supply.
Grasses, shrubs and the bark from trees make up most of their diet.
They chew their food with huge block like teeth
that re-grow as they wear down.
In order to reach and manipulate food, elephants evolved trunks.
Though powerful enough to lift a
whole tree, the trunk is also acutely sensitive to smell and touch.
Stripping bark from trees and shrubs
enables elephants to utilize a food
source other animals can neither reach nor digest.
As they did during the Ice Age,
elephants travel great distances in search of water sources
capable of supplying each elephant with up to twenty gallons a day.
Often following the same paths
over time, elephant roads are carved through even the densest vegetation.
Female elephants live in groups of two or three sisters and their infants.
Mothers carry their young for twenty-two months
and closely defend them through childhood.
Elephant skin is highly sensitive so they bathe frequently
followed by a powdering with dust to prevent parasites and disease.
But dwindling food supplies and space
still make it likely they will follow their Ice Age cousins into extinction.
A group of African lion slumbers in the midday heat.
They've not changed much over millions
of years as they boast a design that has kept them on top of the food chain.
But their distant Ice Age relative was not so lucky.
During the Ice Age saber-tooth cats
used six-inch serrated fangs to slash open their prey.
But when their prey became extinct, so did the saber-tooth.
Today's African lions retain the basic characteristics of their extinct
But a tight social structure sets them
apart from many of today's other cat species.
Copulation serves a dual purpose as it also bonds members of the pride.
Ovulation is induced by the act of mating
and pairs may copulate up to thirty times a day.
The male dismounts quickly since
females sometimes become aggressive toward their partners.
Litters average three or four cubs
and enjoy a long period of parental care.
Support comes from all the females in the group
lending a nursery-like atmosphere to the pride.
Communal suckling is rare among mammals.
Lions are one of the few whose females
will actually nurse offspring other than their own.
Lions have the largest brains and are the most social of all cats.
Two traits that today, as they did during the Ice Age,
contribute immensely to their survival.
Females do most of the hunting and will teach their young at an early age.
Camouflage and stealth are the keys to a successful hunt.