Yes, you can train your pet rat to use a litter box. Rats are intelligent animals and can be litter trained similar to how you would train a cat. Start by placing the litter box in a corner of the cage where your rat tends to do its business. Use a rat-safe litter material such as paper-based bedding. Encourage your rat to use the litter box by placing some soiled bedding or droppings in the box to attract them. Be patient and consistent with the training, rewarding your rat with treats when they use the litter box correctly. With time and positive reinforcement, your pet rat can learn to use the litter box consistently.