For those of us that use fleece as bedding in our cages, this may come as a huge disappointment. Fleece is soft, comfortable, dust-free, safe, and it looks great too. But the truth is, fleece does not absorb urine. In fact, as a hydrophobic fabric, it does the opposite!!
Fleece wicks moisture, transferring it from one area to another. So what happens when your rat pees on fleece? Either the urine soaks through and pools on the shelf below, or the urine sits on the surface of the fleece, releasing ammonia and odor back into the air for both you and your rats to breathe!
In the interest of keeping this short and sweet, I won't get too science-y. However, the bottom line is that natural fabrics, like bamboo or cotton, break surface tension, holding approximately 80% their weight in water, while man made materials like polyester (this is what our fleece is made from!!) does NOT break surface tension, making it unable to hold water. In layman's terms, this means that fleece does not absorb water...or urine. In fact, it's well known that fleece doesn't hold water and it is often recommended for outdoor activities because of it's ability to keep you dry by wicking moisture away from your body (the same way it will wick urine into the air)!
I did a quick test to show you how absorption works between fleece and a 100% cotton towel.
Consider this: How does your fleece feel when it's straight out of the washing machine? Chances are, it may feel damp but overall, feels pretty dry. How quickly does it dry once you put it into the dryer? Almost immediately! This proves that fleece doesn't hold liquid well, and that it's not a good choice to use as bedding in our rat cages.
So what can you use as bedding?
I've been using underpads (or incontinence pads) for over 2 months now and they're literally made for absorbing urine! Not only do they hold up to chewing way better than fleece, but they also absorb way better than fleece too. That, of course, results in less cage cleanings for me which is quite nice. You can buy a pack of 4 washable underpads here.
Another great option is paper bedding. Only use paper bedding that is dust, fragrance, and baking soda free. Carefresh is a well known brand that is widely available at any pet store. You can also use other brands such as Eco Paper Bedding.
In order for fleece to work properly, you will need an absorbent layer underneath. The fleece will wick the urine, directing it to the next best source - the absorbent fabric. Without the extra layer, the urine will dry and evaporate...into your rattie's lungs!! Absorption is ONLY due to a second layer, not the fleece.
Futhermore, the second layer needs to be firmly secured to the fleece, preferably tightly sewn in a quilted fashion, for the technique to work well. If there is any space or air between the two fabrics, it won't work. But when you have two tightly bound fabrics, the fleece will remain relatively dry making a comfortable living environment for your rats.
BOTTOM LINE: Using ONLY fleece as bedding in your rat's cage isn't good for their sensitive respiratory systems as it releases the urine back into the air. If you use fleece with an absorption layer underneath, you will get much better results - helping save the health of your rats as well as saving your nose from the stench of ammonia.
Use this as a reminder
Just because the majority of the rat community recommends something, does not mean that you're a bad rat parent if you go against it. Instead of accepting and following poor advice, consider questioning why you're following that advice in the first place. Why should rats be in cages rather than tanks? Why should I quarantine new rats? Why is fleece considered the best bedding for rats when it causes more harm than good?