Other species of canids — dogs, wolves — hunt in packs, but her life is a lonely one.

其他的犬——狗、狼，都是群体狩猎，但是鬃狼却是孤军作战。

So do certain canids and crows.

某些犬鸦也是如此。

Not everyone's convinced that Prohesperocyon was a canid, though.

不过，并非所有人都相信 Prohesperocyon 是犬。

But other groups, like canids, bears, and whales, were fully fledged.

但其他群体，如犬、熊 鲸鱼，已经完全成熟。

These canids are relatively small, at about  60 cm in length and weighing just over 3kg.

这些犬相对较小，长约 60 厘米，重量仅超过 3 公斤。

Their scientific name, vulpes  lagopus means hare-footed fox, as this furry pad adaptation  is unique among canids.

它们的学名 vulpes lagopus 意思是兔足，因为这种毛茸茸的垫子适应性在犬中是独一无二的。

Today there are 34 species of canids, from the leggy maned wolf to the big-eared fennec fox.

今天有 34 种犬，从长腿鬃狼到大耳耳廓。

One species in this genus—Epicyon haydeni—was the biggest of the big, thought to be the largest canid of all time.

该属中的一个种——Epicyon haydeni——是大型犬中最大的，被认为是有史以来最大的犬。

The only important thing that Epicyon has in common with your golden retriever or whatever is that they're both canids.

Epicyon 与您的金毛猎犬或其他任何的唯一重要共同点是它们都是犬。

So two out of the three canid subfamilies are dead and gone.

所以犬的三个亚中有两个已经死去。

Because, just like cats, they had fully retractable claws, a trait that canids eventually lost.

因为，就像猫一样，它们有完全可伸缩的爪子，犬最终失去了这一特征。

Today canids include wolves, foxes, coyotes and dogs, all over the world.

今天，犬包括世界各地的狼、狸、土狼狗。

But in canids, they're especially big, and it's thought that these extra large spaces help dogs and wolves hear low-frequency sounds.

但在犬中， 它们特别大，人们认为这些超大空间有助于狗狼听到低频声音。

And the biggest canids that ever lived were the borophagines, also known as the bone-crushing dogs, which I've talked about before.

有史以来最大的犬是 borophagines，也被称为碎骨犬，我之前已经谈过。

If anything, dogs resemble juvenile rather than fully adult canids, a sort of arrested development which accounts for the way they remain dependent on their human owners throughout their lives.

如果说狗与犬确有相似性，那么也只是像未成年而非成年犬。这种类似发育停滞的现象可以解释狗为何一生都如此依 赖主人。

But around 30 million years ago, a new subfamily of canids appeared: Caninae, or canines, the true dogs.

但大约 3000 万年前， 出现了一个新的犬亚：Caninae，或犬， 真正的狗。

Canids have hollow bony structures toward the back of their skulls called auditory bullae that protect the delicate bones of the middle ear.

犬的头骨后部有中空的骨结构，称为听觉大泡，可保护中耳的脆弱骨骼。

Now, some experts think the earliest canid was a small, weasel-like creature called Prohesperocyon, which first appeared about 36 million years ago in southern Texas.

现在，一些专家认为最早的犬是一种名为 Prohesperocyon 的小型、类似黄鼠狼的生，大约 3600 万年前首次出现在得克萨斯州南部。

Bovids, equids and, in particular, canids, were put to work by H.sapiens; felids always took a slightly different view of the matter, but were indulged for their rodent-catching talents.

牛、马，尤其是犬，都是由智人分工的；猫略有不同，但受宠的原因主要是捕捉啮齿类生的天性。

So while the canines went on with their own set of prey and long-distance hunting strategies, the bone-crushers, once the most dominant of the canids, found themselves struggling for survival.

因此，当犬继续使用它们自己的一套猎长距离狩猎策略时，曾经是犬中最强大的碎骨者却发现自己在为生存而苦苦挣扎。