… that’s where the repository of unofficial models might come handy. You will find models for a bat, bird, boar, bunny, sheep, etc. in there. As long as we do not have access to the game I guess the best we can try is to size our own stuff based on this models. E.g. I have tried to create a cow which does not feel too wrong from a size point of view (for me)… you can also find it under the mentioned link.
Btw. the male might be something like 19x33x14 and the female 17x31x13 voxels in size.