Question: Zootopia makes an effort to include mammals at almost every scale from every possible environment. There's Tundratown, Sahara Square, the Jungle place, home to animals from artic shrews to elephants. However, I didn't see any large aquatic mammals. Are there dolphins or whales that I missed? If there aren't, has the production team publicly discussed why there aren't any?

Answer: 
According to the artbook ["Art of Zootopia](https://youtu.be/b4awFMpUbZk?t=2m54s)", it was simply too difficult for the film's concept artists to work out how to include large aquatic creatures (and other non-mammal animals) in the city. So they were just gently *airbrushed* out of the picture.

> 
> *The team spoke with zoologists, animal behavior specialists, and
>  scientists who study animal evolution. Based on what they discovered,
>  the filmmakers decided to limit the film’s animals to mammals,
>  although “reptiles and birds and other animals do exist on this
>  planet. We just don’t go to those continents,” says screenwriter and
>  co-director Jared Bush. This constraint led to an “aha!” moment that
>  became a central tenet of Zootopia—that mammals are divided into two
>  groups: predators and prey, and prey animals outnumber predators
>  ten-to-one.*
> 
> 
>
[![Hippo Subway](https://i.stack.imgur.com/jqOA9.png)](https://i.stack.imgur.com/jqOA9.png)

They show hippos, which are large aquatic mammals. Further we see that the hippo commuters use a special water-filled "subway" that presumably could be used by other aquatic mammals.