Seeing your dog run for cover under your bed can be disturbing, especially if it's a new behavior. While in most cases this is natural, you might want to talk to your veterinarian if the problem worsens or if hiding is interfering with your dog's normal eating and playing behavior.
Back to Basics
In the wild, dogs -- especially the young and the weak -- survive by adapting to den behavior. While it's difficult to think of your cuddly pup as being connected to his wild ancestors, the den instinct is still alive in many dogs. Small covered spaces feel safe to dogs; hiding under the bed recreates this. This explains why many dogs hide under the bed when they are stressed, scared or confused.
Reasons for Hiding
There are many reasons for a dog to hide under the bed, including illness, fear, comfort, the search for a safe sleeping area, the need to avoiding punishment or simply being upset due to changes in the household. Sudden changes often indicate a more serious problem. For example, your dog might be hiding under the bed to avoid being picked up, which could be related to pain or fear. Dogs with serious phobias to noise and change could take to hiding under the bed to escape loud noises.
Alternatives to Hiding
If your dog only hides the bed once in a while, you might consider just letting him do it. Once the stress wears off, he'll come out on his own. If he's hiding under the bed constantly and you find the behavior troublesome, try providing a dog crate near the bed with a comfy bed inside to see if he'll adopt that as his own den. Add a favorite toy or one of your own shirts so he feels more comfortable and safe.
Other Ways You Can Help
If Fido is hiding under the bed because of fear, you can try "blocking" the cause as much as possible. For example, if he's hiding because of loud noises, try turning on the radio or TV to block out the sound. You can help him associate a more positive place with safety. Feed him certain treats when he retreats to his crate or sleeps on his bed rather than under yours.