Those who hunt by night will tell you that the wildest, most vicious of all animals is the tiny shrew.
The shrew feeds only by the dark of night. He must eat his own body weight every few hours or stave to death. The ravenous shrew eats everything, bones, flesh, marrow… everything.
Intro from Attack of the Killer Shrews 1959
PCs camp for the night in a dry pine forest. Fire skill of the person that made it is usually pretty good, but during the first watch the unexpected happens: a spark lights the surrounding woods and a brush fire quickly starts. Be quick or it could turn into a disaster that could affect the entire region.