BIO150Y: Saving the Whooping Crane Exercise


Background to Whooping Crane Conservation

Whooping Cranes

Whooping Cranes are the tallest birds in North America, standing about 1.6 metres tall. The remaining wild population breeds in arctic wetlands in Wood Buffalo National Park, Northwest Territories, Canada. Cranes are slow to mature and do not breed until they are about 5 years of age. Long-lived, a female may breed for 15 years or more, but rarely will a pair rear more than one chick per year.
After the brief arctic summer, the crane families migrate south all the way to Texas, a distance of about 4,000 kilometres. On the way they must avoid collisions with powerlines, hunters and predators. On their wintering grounds on the Gulf coast, they are again at the mercy of weather and variable food supply.
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Whooping cranes were never very common even in the early 1800s prior to human intervention, when the total population may not have been more than a few thousand. They preferred the secluded wetlands of the prairies -- a habitat which was largely converted to farmland in the 1800s. As large, conspicuous birds they were viewed as a source of food and recreation by early settlers.
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Why did the cranes decline?

This Exercise

By 1941, the combination of habitat loss and overhunting had driven the population to an all-time low of 16 birds. Populations this small are at risk of extinction simply from random events. Fortunately, conservationists stepped in and implemented a series of measures which would ultimately ensure the survival of the species until the present day. But it was a close thing.

In this exercise, we will use the Whooping Crane example as a way to learn about population dynamics. We can't go back to 1941, or experiment directly with the cranes, but we can use computer simulations of the population demographics to recreate history and model the population growth of the cranes under two scenarios: unmanaged versus managed.

Now let's establish how we model population growth...

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