Gerbils that are kept in captive environments can develop a behaviour known as ‘Bar Rub’. This is where they continuously chew on the bars, sometimes so much that they can give themselves little sores around the mouth and rub away their hair. If the bar rub is very bad, then the gerbil’s teeth can become misaligned, which may prevent them from eating.
If your gerbil is constantly gnawing the bars of its cage, then you'll need to figure out the cause
There are lots of different reasons that gerbils chew the bars, such as boredom, or lack of space. To stop your gerbil doing this, you might want to try to understand what the cause is. We’ve listed some on our Gerbil Chewing Bars page, as well as offering some potential solutions. One of the easiest potential solutions is providing your pets with a chew or a gnaw. This provides them with something to nibble on should they feel the urge.