Wolves have bulky coats consisting of two layers. The first
layer is made up of tough guard hairs that repel water and
dirt. The second is a dense, water-resistant undercoat that
insulates. The undercoat is shed in the form of large tufts
of fur in late spring or early summer (with yearly variations).
A wolf will often rub against objects such as rocks and branches
to encourage the loose fur to fall out.