I'm Japanese and we habitually use katakana in for the kind/species of animals, fish, plants, flowers, vegetables, fruits, etc, for example, キツネ、アジ、サクラ、バラ、ナス、リンゴ、etc. Since I'm not an expart of the Japanese language, I don't know why we use katakana for them though they are Japanese word. There might be histories for that, so please wait for the correct answer. Anyways, I hope this was helpful.