Place the cage in a busier part of your house, this way the rats will see you move around giving them some visual stimulation throughout their day. In terms of the size of the cage, there is no such thing as a cage that is too big. Rats are incredibly smart and thus need stimulation. Having a rat live couped up in a tiny cage for most of their lives is just plain cruel. At the minimum their cage should be around 24 by 12 inches but it can be as high as you like. Double, triple or even four times this space would be ideal for them.
It’s also important to make sure there is proper ventilation in their habitat. Rat droppings give off ammonia when they start decomposing and this can irritate the respiratory tract creating health problems. Placing some litter on the floor of the cage can help slow down this decomposition process by absorbing the moisture from it. One can never stop the release of ammonia completely though. Ventilation allows the air to move freely inside the cage and dilute it’s potency and effects. Wood shavings are the most popular type of litter but just make sure you get good quality wood shavings, not sawdust, as this creates unnecessary dust for the rats. Also avoid red cedar shavings, paper bedding with drops of aromatic oils or any wood or paper-based bedding that is especially dusty as this can cause breathing problems for rats.
A good option is called Bio-Catolet which is a cat litter made from recycled paper. It’s designed to be dust-free, sterile and many times more absorbent than wood shavings. It is a little more expensive than wood shavings but it’s also a lot more effective which means it works out cheaper. You can use less of it and change it less often, resulting in real savings. Instead of changing the cage’s litter twice a week, you now only need to change it once a week. That’s a huge difference. When you run out of cage litter, shredded paper towels can be used for an emergency until you buy some more real litter. However, this should not be used for more that 24 hours. Never use cat litter for rats under any circumstances as the dust can be very harmful to their lungs.
For rat bedding, use shredded paper from a pet store. Newspapers tend to be printed with toxic ink and this can cause problems as well as stain their coats. Straw and hay do very little to absorb moisture so avoid them if possible.
If one of your rats is already suffering from a respiratory illness, then your first port of call is to check that they are getting adequate ventilation. Cages made from wire are by far the best choice for rats since their structure makes for a perfect climbing wall for them. There is enough space between the bars to feed them and you can easily see how they are doing inside. Air, smells and sounds are let through easily, making their environment that much more interesting for them. They do however need a little sheltered box to sleep in so they can stay warm.
Some fun things to add to the cage are ropes, shelves, ladders, hammocks, flowerpots and tree branches. These will turn any ordinary cage into a rat paradise. Since floor space is usually restricted in the average home, but there is plenty of height available, you can take advantage of this and get your rat a really tall cage. This increases the space they have available, while keeping your room from getting too crowded. This allows them to climb up high and go on little adventures. Shelves can be made out of a material called melamine which can be cut to size, slid in-between the bars and fastened easily, as well as cleaned when necessary without a problem.
There are companies which make very high-quality parrot and cockatiel cages and these are generally just perfect for rats. Prices for cages vary drastically so it makes sense to do a bit of shopping around. Check Craigslist and animal exhibitions and chances are you will find a bargain. When you first get the cage make sure you give it a thorough cleaning and disinfecting. Avoid cages which have wire floors designed for ferrets. These are not ideal for rats and can cause severe health problems for them. There is no advantage ammonia-wise in having the wire floors either, contrary to what many believe. A solid floor with litter is always the healthiest option for rats and solid floors are easier to clean as well. Aquariums can work if there is an open lid and a fan or home-made aircon or ventilation system made. However, for the added expense, the extra cleaning required and risk that the system fails when you are out of the house, it makes sense to stick with a simple wire mesh cage. Rabbit hutches are sometimes used to keep the rats outdoors but they usually have extra insulation as well as good ventilation. Like all cages though, they need to be cleaned often. A nestbox also needs to be made and it needs to be made as entertaining as possible.
Baby rats love toys almost as much as human babies do. Great ideas for toys include drainpipe sections, glass jars, boxes, old clothes and balls. Some rats love wheels while others will never use them and find them boring. Keep in mind that wheels with spokes are dangerous, especially if two or more rats share the same cage (which they should). A rat can easily get their tail or foot caught in them so opt for solid flooring for your wheels where possible. Most toys that are intended for parrots or ferrets are ideal for rats, just use your common sense or ask the store owner questions when in doubt.