Making her tail into a pillow?

Question
Hello,
I have a female pet rat named Oreo. She's less then a year old, I got her from Petcetera, she has a 3 level cage, with wood shavings that she can burrow in. I give her a rat food (giving her a full bowl which lasts her a couple days) and we play with her every day for at least 20 minutes. We don't know what breed she is, but here's a picture

We have a couple questions about her behavior. We were wondering why she compulsively cleans herself, why she uses her tail as a pillow, and why she buries her food. We also bought a big enough ball for her to run around the floor with, but she just sits there, inside the ball, grooming herself. We've rocked the ball back and forth, and she still doesn't get the clue that she's supposed to run. How can we get her to run.

Sorry for all the questions, but could you help me/us please?

Thanks,
Arden

Answer
Hi Arden;
Rats are, without a doubt, one of the cleanest animals I know of. They have immaculate grooming habits, and are always very conscious of their current grooming condition. This is all very normal; and don't expect it to change. In fact, if a rat suddenly quits grooming herself and allows herself to look/feel/smell dirty (including hair sticking up, feces and urine stuck to the coat, etc.) there's something wrong. Grooming is a good thing!

Just like cats, rats curl up into comfortable positions. To them, they're comfortable using their tails as pillows. Also, very normal.

Rats generally don't appreciate exercise balls -- they're a little too smart for them, and they can actually be quite dangerous, breaking toes and tails and if they happen to roll off of any surface (tables, couches, down flights of stairs, etc.) or slam into anything. I recommend ditching the ball and instead letting her play with you one-on-one.. rats love and appreciate human companionship and camaraderie.

Good luck!