It is possible that this destruction of the wolves is due to some disease among them, perhaps to hydrophobia, a terrible malady from which it is known that they suffer greatly at times.

Perhaps the bear is helped by its habit of hibernating, which frees it from most dangers during winter; but this cannot be the complete explanation, for in the South it does not hibernate, and yet holds its own as well as in the North.

What makes it all the more curious that the American wolf should disappear sooner than the bear is that the reverse is the case with the allied species of Europe, where the bear is much sooner killed out of the land.
Indeed the differences of this sort between nearly related animals are literally inexplicable.

Much of the difference in temperament between such closely allied species as the American and European bears and wolves is doubtless due to their surroundings and to the instincts they have inherited through many generations; but for much of the variation it is not possible to offer any explanation.

In the same way there are certain physical differences for which it is very hard to account, as the same conditions seem to operate in directly reverse ways with different animals.