They usually weigh 15 to 20 pounds more in the winter than in the summer due to a heavier fur coat, among other things. Wolves have a double layer of fur. A wooly underfur grows very thick in the fall and winter and keeps the wolf warm, while an outer layer of guard hairs repels snow and water, and keeps the underfur dry so it can trap air as an insulator. In this way, it can easily survive temperatures will below zero. During the spring, the thick underfur sheds so the wolf can survive the heat.
Wolves are social animals, living together in family groups called packs.
In order to live together peacefully, they have an elaborate system of rank order. This keeps order within the pack and minimizes fighting. Wolves howl for a variety of reasons. Pack members can recognize each other's howls, so when they are separated, they can locate each other. Sometimes wolves just howl for reasons we don't fully understand.