the size of their prey（猎物）: With prey like deer, only around six to eight wolves are needed, while hunting wild ox requires a pack of nine to thirteen. Their prey also uses this concept to protect themselves from predators — deer tend to live in large herds to reduce the chance of any individual becoming prey. So obviously they are assessing the number of individuals in their groups for their everyday life situations.

Despite these many examples of numerical competence in animals, this subject has not gotten many first-hand studies. “Many of these behavioral findings in the wild have usually been collected as by-products or accidental findings of other research questions,” says Nieder. He argues that more research needs to be done to fully understand the numerical competence.

28. The phenomenon of animals having their own numerical competence shows that .

A. all groups of animals are related in some ways

B. numerical competence must have a survival benefit

C. the intelligence of animals varies with different environments

D. animals’ numerical competence is determined by their adaptability

29. What role does numerical competence play in wolves’ hunting?

A. It helps them form hunting groups.

B. It gives them more options to hunt.

C. It makes them discover more prey.

D. It offers them new skills to hunt.

30. How does the author mainly develop this text?

A. By listing figures.

B. By asking questions.

C. By giving examples.

D. By making comparisons.

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