Their guard hairs are actually also hollow, which also helps with their insulation.

它们的外层粗毛实际上也是中空的，这也有助于它们保温。

The otter's slick outer coat is made from coarse oil-covered guard hairs.

水獭光滑的外衣是一层粗糙且附有油脂的针毛。

Although their coat appears white, both their guard hairs and underfur are actually translucent.

虽然它们的皮毛看起来是白色的，但它们的外层粗毛和下层绒毛实际上都是半透明的。

It consists of two layers of transparent hair, a soft thick undercoat and a layer of hollow guard hairs.

它有两层透明皮毛，一层是柔软厚实的皮毛，另一层是中空的护毛。

Only guard hairs from the tail will do.

只有尾巴上的护毛可以。

But for many mammals, hair grows in two layers consisting of a shorter undercoat of ground hairs covered by longer guard hairs.

许多哺乳动物的毛发生长为两层，由较短的毛作为底层毛发，上面覆盖较长的保护毛。