Most animals don't like the smell of Isopropyl Alcohol. Tiny bottles are available from chemist's shops/drug stores (for 'cleaning records', you have to say that)for a test case. It isn't a poison, it has warnings on the label because some desperate people drink it.

A firm here soaks Attapulgite/cat litter with several repellants, incuding Isopropylene, for outdoor use, but you have to keep it dry.