Protecting and caring for their young is instinctive in female domesticated dogs, just as it is for canines in the wild. If a litter of puppies remains with Mama long enough, their memory is imprinted and she will recognize the adult dogs as hers in later years.
A dog's long-term memory is not like a human's. Dog memory depends more on imprinting, a biochemical process stimulated by sight and smell. Imprinting is an innate behavior or response to a learned stimulus and occurs at a particular time in an animal's life known as "the sensitive time."
This happens in a mother dog after giving birth and triggers her protective instinct. This instinct is reinforced as the puppies grow, and if they stay with the dam long enough, remains with her for life, says animal behaviorist Steven Lindsay. As the puppies mature, Lindsay believes the physiological response is strengthened in both mother and puppies, creating a bond that allows them to recognize each other later in life.
Although doggie DNA has changed over centuries, dogs are descended from wolves and the canine maternal memory is rooted there. Wolf puppies remained with the family pack for one to three years until adulthood, so it was natural to maintain family ties. In the wild, keeping the family together served as protection for the pack. Although this is not the case with domestic dog litters, the bitch's instinct to protect the young remains and she will guard them even from dogs she knows who live in the same house. This maternal instinct allows her to remember her offspring if they remain with her through the formative three- to four-month period following their birth, according to Lindsay.
When Memory Fails
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It is important to socialize young puppies while they are in the litter with their mother, but not to wean or remove them too early. Any of these can result in puppies with behavioral or training issues later on.
Socialization prepares young puppies to meet and interact with people of all ages, from children to adults. Once the puppies are old enough, usually around 4 weeks of age, visitors who pet and play with them individually help them prepare for life outside the litter. Puppies who are not socialized can be shy or reserved after they leave the litter.
When puppies are taken too early, complete imprinting does not occur and the mother dog will not recognize her offspring. Typically, puppies begin to be weaned between 4 and 6 weeks of age, but the litter remains with the mother until they are at least 8 weeks old.
You may not recognize a dog's greeting for her grown puppies when they meet. They don't squeal and leap in happy greeting. Observe carefully though, and you will see extended sniffing and wagging between a mother dog and her grown offspring. If the offspring becomes overly exuberant, the bitch may turn tail and depart, ready to return to a puppy-free existence.