This article is from the Chihuahua Breed FAQ, by email@example.com (Melinda 'Bob' Casino) with numerous contributions by others.
It is a characteristic of the Chihuahua to prefer to sleep under a
cloth or a blanket. They will even get under pillows in order to feel
If you are raising a pup, be sure to provide them with a soft towel
or blanket in their sleeping area so they can burrow underneath it.
So don't be surprised if your Chihuahua scrambles under your blankets
at night, even though your house or apartment may not be particularly
cold. This is known as the "moley-effect." (1).
(1) "moley-effect": I made this term up, and if you use it in front of
veterinarians or other Chihuahua owners, you may receive a blank stare.