It sounds like you might be thinking of a few different behaviors:
* Burrowing: Some dog breeds, especially those with a heritage of digging (like terriers), may dig holes in the ground. This is a natural instinct stemming from their ancestors' need to find shelter, hunt prey, or cool down. They might dig in your garden, at the park, or even in your house!
* Sleeping in a den: Dogs often seek out enclosed spaces to sleep, like under a blanket or in a dog bed. This is a natural instinct for safety and comfort. They feel more secure when they can't be easily seen or approached.
* Hiding: A dog might hide if they are feeling scared, anxious, or ill. If your dog is hiding, it's important to try to understand why and offer comfort and support.
* Playing: Some dogs may engage in "burrowing" play by digging into piles of leaves, blankets, or even toys. This is usually just a fun and playful activity.
It's important to consider the context and your dog's individual behavior to understand what they are doing. If you are concerned about your dog's behavior, it's always best to consult with a veterinarian or a certified dog behaviorist.