When they fall in the latrine and nobody can get them out, generally they die. Sad, I know. This is one reason people generally cover their latrine holes. It's also one of the most icky things I've ever contemplated, unless you count my visit yesterday to PCV Kurt, whose neighbors very kindly brought over breakfast for our little delegation: shima, soy pieces, and charred mice.
I ate the soy pieces but pictured those burnt little bodies with every bite.