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Rats like to play with just about everything, but avoid providing these types of toys or your rat could get itself caught and seriously hurt itself. Rats like to drag their tails behind them, so it could get caught in a battery-powered toy or on a sharp piece of metal. Opt for soft, rounded toys instead. A rat wheel is one of the few exceptions to this. As long as the inside panel is completely covered, the rat shouldn't get its tail stuck in any moving parts. Buy a wheel specially made for rats, as mouse and hamster wheels are just too small for them to use. Cut out some rat-sized holes in a few small boxes, such as shoe boxes, and arrange them on top of each other randomly to create a tall structure for your rats to explore. Cut some holes in the tops of the boxes too so your rats can crawl around inside the fort. Arrange other accessories as you see fit, like small pieces of fabric to create curtains, or strips of cardboard to make ladders. Add treats wrapped in paper to the inside of the fort, which entices your rats into exploring for hidden treasure! PVC pipe is perfect for creating elaborate mazes for your rats. Go to your local hardware store for a variety of at least 2.5 in (6.4 cm) wide PVC pipes. Connect angled pipes, straight pipes, and pipe connectors together in random arrangements to create a tunnel maze. You can also make fabric tunnels by cutting the legs or sleeves of old clothes and stuffing them with toilet paper tubes.  PVC pipe is better for rats who like to chew a lot, whereas a fabric tunnel lets you keep an eye on where your rat is at in the maze. Simply disconnect the PVC pipes from each other when you are ready to take down the rat play area — you can create a different maze pattern next time you let the rats out! Fill a shallow dish, no more than 1 in (2.5 cm) deep, halfway with water. Place some rocks big enough to poke out of the water, and add some frozen peas. Your water-loving rats will love the chance to get wet and get a snack at the same time, while your water-fearing rats can safely stand on a rock or on the edge and grab peas that float by! A paint tray meant for paint rollers is great for this, as it has a deep end and a shallow end. Your rats can stand on one side and fish, or go for a dip in the deeper end. Fill a small garbage basket, one that you would keep under a desk, with crumpled paper, toilet paper rolls, extra pieces of cardboard, and other soft, safe materials for your rat to dig through. Rats love crunchy noises and collecting bits of trash for themselves, so use a variety of materials to entertain  your rat.  Root through your own trash and recycling bin for small objects that are safe for your rat if you want to conserve resources.  Don't add any discarded food or organic products, as if they have gone bad your rat might get sick. If you want to add food to the bin, add some rat snacks at the bottom before filling it with trash, as this entices your rats to dig in deeper. Fill a square plastic container halfway with regular, clean soil, then plant sprout seeds, wheat seeds, and grass seeds. Water the soil until its slightly saturated each day for about a week. When the sprouts start to show, let your rats dig around and munch on the greenery!  Rats can eat just about anything, but avoid planting poppy seeds in the digging pit. It's been shown that poppies can kill rats.  If you'd rather not wait for a week as the sprouts grow, simply bury some of your rats' favorite treats under the dirt and let them dig them out. Be sure to use clean soil, which you can buy at any gardening store. Rats also love chewing plants in general, so if you have plants that are dying and you plan to throw them out anyway, let your rats have some fun with them first!

Summary:
Use only toys and accessories with no sharp edges or moving parts. Build a cardboard "rat fort" inside the play area. Add some PVC pipe or fabric tunnels for your rat to crawl through. Create a pea fishing pond with a shallow dish and rocks. Add a small bin of trash for your rats to root around in. Create a digging pit with a plastic container, dirt, and veggie sprouts.