Gerbils need somewhere to hide in their enclosure, a place that they feel is safe and far away from anything that frightens them - even if this is just a human gazing in through the bars! Gerbils will need a lot of bedding, piled high in an area of their cage and several inches thick. This will enable them to satisfy one of their strongest natural instincts: tunnelling.
Gerbils like to create little tunnels in their bedding, but they will love any little hidey holes you supply them with, too
In the wild, gerbils usually live in large family groups or colonies. They would all live together in tunnel networks that they would all pull together to build and maintain. Those being kept in captivity still have these instincts, so owners will need to give them the materials they need in order to replicate this environment as closely as possible. You’ll want to give them enough bedding so that they can create their own tunnels and nests.