It's the first litter of that species ever born there.

这是该物种在这里诞生的第一窝小宝宝。

Wolf pups in the first two litters tested showed little interest in playing ball.

头两窝被测试的小狼对玩球没有兴趣。

In fact, the most cautious pup from the second litter was bolder than the boldest pup from the first litter!

事实上，第二窝中最谨慎的幼崽都比第一窝中最大胆的幼崽要勇敢！

Females live alone as adults unless they have cubs. Females will have their first litter in the wild at about 3 years of age.

雌性成年后独自生活，除非它们有幼崽。雌性将在大约 3 岁时在野外产下第一胎。