underfur

例句：

1. 1. The fox was found with its underfur ripped open by hunters.
   猎人发现这只狐狸的下层毛皮被撕裂了。
2. 2. The animal's underfur is soft and warm to the touch.
   这种动物的下层毛皮柔软且温暖。
3. 3.The underfur of the rabbit provides insulation against the cold.
   兔子的下层毛皮提供了对寒冷的隔热保护。