I think it depends on who designed each animal. Kosta, Boda and Afors cooperated from 1964 ownwards and joined together in 1971, but kept separate labels. If the animal were designed by Bertil Vallien, as I believe at least two of the elephants and some other animals were, they would have the Boda label, while the others, designed by Lindstrand, would have Kosta label. Around 1985 the label would be changed to Kosta Boda. Guesswork, I confess.
The key, I suppose, is that there is one series, the Zoo, and at least two designers, each working for a different company, or different branches of the company. What a complicated answer to a simple question and simple, but delightful, designs.