None of us holds a terribly high opinion of David.
I'd probably leave him as either a raccoon or a skunk. Both have EXTREMELY good survival skills, but they are sufficiently small that it would take them awhile to go anywhere, and Tobias or Ax would notice them attempting to go somewhere.
Have you ever seen an angry raccoon? Those things can get larger than 40 lbs. They are MEAN little cusses.
They are also extremely intelligent, dextrous, and talented at obtaining food and escaping danger.
They climb trees and swim VERY well, and they can eat virtually anything. Even wolves hesitate to tick them off. Furthermore, they can live a very long time, in mammal terms.
The skunk would just be funny, and it would also survive well.