Why does my dog keep putting her puppy in her mouth?
Correspondingly, why does my dog put her puppies head in her mouth?
Canine mothers muzzle grab their puppies (sometimes accompanied by a growl) to deter them from suckling during weaning. A muzzle grab, therefore does not involve biting, just grabbing. This behavior helps develop a relationship of trust between both parties: "We don't hurt one another."
Additionally, why does my dog keep picking up her puppies?
Yes, a mother dog can reject her litter and turn on her puppies. This may happen because she feels unwell herself, or because a puppy seems too weak to be worthy of her care, or simply because of a lack of maternal instinct. Such behavior may appear from the moment she has given birth, or a few days or weeks later.
If your mother dog attacks her puppies, don't worry that you touching them was the cause. Sometimes mothers kill their puppies because they sense that they are sick. Other times mother dogs have more puppies than they can handle and get stressed, feeling the need to downsize.