As they are not playable as PCs, deriving them from the animal rules is easiest, though you will need to dig back into prior editions for the bits of the animal rules Mongoose snipped. The MGT animal tables look like someone with no exposure to anything outside a petting zoo decided to remove all the "oddities" because "animals can't do that".
Granted, "as PGMP" wasn't on the tables before, but you're stretching for the SST bugs as it is.