And he was with the wild beasts...

Immediately the Spirit impelled Him to go out into the wilderness. And He was in the wilderness forty days being tempted by Satan; and He was with the wild beasts, and the angels were ministering to Him. (Mark 1:12-13)

Why does Mark give us this little detail about the wild beasts? Matthew (ch. 4) and Luke (ch. 4) both omit the phrase in their own accounts of the temptation narrative.

Is Mark emphasizing the loneliness of Jesus--"no one was around except for the animals"? Maybe.

I wonder if Mark has Isaiah 11 in mind. The vision in that chapter is one of universal peace, even between man and animals, at the time that the root from Jesse appears. Or even if not this precise chapter, maybe Mark is thinking of this theme of universal peace, which is a feature of other eschatological passages (Hos. 2:18). Jesus in the wilderness, even while he's being tempted by Satan, experiences a foretaste of the messianic peace that his own ministry will usher in.