You can find the answer to this in Chapter 9. There, beginning on p. 169 in the paperback edition of the book, Diamond lists 6 major groups of reasons that can make one animal domesticable while another is not. These factors include:
- Diet. Some animals have diets that are not efficient for domestication. Carnivores have to eat too much. Herbivores are sometimes too picky in what they'll eat.
- Growth rate. If an animal does not get big very quickly, it is not good for domestication. You don't want to have to wait years (while feeding the animal the whole time) for it to get big enough to eat or use for work.
- Problems of captive breeding. Some animals simply won't breed in captivity.
- Nasty disposition. You can't domesticate an animal that is simply mean. Diamond lists a number of animals, including zebras, that are too mean to be domesticated.
- Tendency to panic. You don't want animals that will panic and stampede too easily. They will ruin your fences and be too much work to herd.
- Social structure. Hierarchical and social animals are easiest to breed because they will tolerate being in herds and they are more likely to obey humans.
These six factors are the ones that determine whether an animal species can be domesticated.