A dog separated from its mother as a puppy can recognize her even after years. The most reliable evidence comes not from a reaction to a chance encounter, but from controlled odor tests. They show that the mother and her grown offspring retain information about each other for at least two years after separation.
Smell lasts longer than image
The study by British scientist Peter Hepper, published in 1994 in the journal Behavioural Processes, followed the recognition of relatives in domestic dogs. Puppies were separated from their mothers between the ages of 8 and 12 weeks. When the animals were about two years old, they were given the opportunity to choose between the smell of their mother and that of an unfamiliar female.
Their behavior showed a preference for the smell of the mother. The mothers, in turn, also recognized the smell of their adult puppies. The important clarification is that the test tested a reaction to a smell, not a human-type memory of a specific shared story.
There is no exact moment when a dog “forgets“
Two years is not a shelf life of memory, but the longest period tested in this study. It cannot be concluded from it that the animal will necessarily forget its mother at the third, fifth or tenth year. There simply aren't enough controlled studies to set a longer limit.
A recent review of research on maternal behavior in dogs also found that mothers and offspring can recognize each other after a two-year separation. However, the author notes that knowledge about the mechanisms of this memory in dogs is still limited.
Why the encounter may seem ordinary
Recognition does not necessarily mean a violent reaction. When the dog meets again, it may sniff the other animal for a long time, follow it or show interest, but it may also remain relatively calm. Behavior depends on the character, age, environment and whether the animals have had additional contact.
“There is a so-called memory for smells – this is scientifically proven. "Dogs recognize animals they've known before, but not necessarily with the emotional depth that we humans would expect," dog trainer Katarina Marriott told PETBOOK.
With siblings, the results are more uncertain. In Hepper's study, dogs that lived on their own after being separated from the litter did not show the same ability to recognize their siblings. This suggests that a dog's memory for its mother and that for other dogs in the litter may be formed and maintained in different ways.
The most accurate answer is this: a dog may not "think" of its mother in the human way, but it carries her odor profile in its memory. After two years of separation, it can recognize her. For longer periods, science still does not have enough data to say exactly when this trace disappears.
Sources: petbook-magazine.com, whole-dog-journal.com