In Planet Zoo, your animals all have various needs that you must meet in order to keep their well-being as high as possible. One of the things that all the animals in the zoo will need is the Hard Shelter.
Hard Shelter is a place in their habitat where they can go where they feel safe. While your animals enjoy their habitat, they also like to have a place where they can feel protected and can protect them from the elements.
How to build a hard shelter
You can purchase pre-built hard shelters from the Habitat menu. Just click on the Habitat tab at the bottom of the screen, then click on the Shelter icon with the sleeping Zs floating above it. This will then show you all of your available Hard Shelter options.
You can, if you wish, build a hard shelter from scratch. This is done by placing objects, such as stone, to build your own. The important thing to remember is that a hard shelter should be closed on three sides, have an entrance and a roof. Without these elements, the cover will not be adequate and will not be considered as a hard shelter.
Another thing to keep in mind is the number of animals in the habitat. It may be necessary to build more than one rigid shelter, or a very large one, depending on the number of animals in the habitat and the size of those animals. To check and see if the animals in the habitat have enough shelter, just click on any of them. On the Animal Information tab, click the Terrain tab. The first bar will show you the amount of free disk space available. If it's 100%, you will need to build another shelter.