英语听力：猛玛象进城记—6
The puma may have been more able to adapt because its diet is more varied and includes small prey. The grizzly bear also lived through the post Ice Age changes and now thrives in North America. Once again, a varied diet of meat and plants made it a versatile survivor.
The moose is now the largest browser on the continent. During the last Ice Age, moose were restricted to the far north, but after the ice melted, they spread south. They took the place of mastodons and the larger stag-moose, both of which became extinct.
Bison, too, were to benefit from the post Ice Age changes. They managed to survive the draught, eventually expanding in number to replace the horse as dominant grazer. As ruminants with multi-chambered stomachs, bison can extract more nutrients from grass and this may help explain why they survived when other grazers such as the wild horses did not.
While all these creatures were adapting to their changing landscape, another animal was just beginning to make North America its home. It’s thought the dog arrived with early people and its descendents are still with us today. The Carolina dog lives in the woods of South Carolina. Like most primitive dogs, it makes its den in the ground or in hollow tree trunks. The Carolina dog is often called the American dingo. It does look like its Australian relative, but links between the two may go deeper than that. Genetic analysis of the Carolina dogs suggests they are closely related to primitive wild dogs like the dingo.
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