Fenris isn't startled. He heard it and smelled it before it landed.

Okay, no, Fenris totally is startled. It's like opening an umbrella or inflating a garbage bag. Still, his urge to defend his pack overrides his urge to run around in panicky circles, so he darts between Jim and the birdthing, teeth bared and ears back, ready to pounce on it if it twitches wrong.

It doesn't smell right. "You are not of Midgard."