It's less that Strange has chosen to be on wolf watch, more that he wants somewhere to be while his hare licks her wounds and they catch their breath (that berserker thing was useful and worrying at the same time.)

Bell is watching the wolf from afar: the hare is laying on the ground, ears down, attention focused on the wolf. Strange is playing around with magic. There's a silver coin in his hand that he's been moving around and staring at for the past few minutes. It's a bit hard to see what he's doing with the coin from afar but it's obviously something that's grabbed his attention.

"Hmm?" Strange turns to look at the wolf as he sighs. "That's an understatement. Has he even let us go near the thing since he arrived?"