I was at a gathering of emeritus faculty members at my university, and a small group of us were standing around drinking coffee and nibbling on cookies while discussing matters that were neither political, philosophical, or earthshaking. At one point during the conversation, one of my colleagues took the opportunity to pose a question. She said, "I'm going to visit my dog's breeder this weekend and my husband and I were debating whether Siegfried [her Labrador Retriever] will remember his mother, Ashley. Since I am surrounded by behaviorally knowledgeable people I was wondering if any of you had an opinion?"
The first response came from a behavioral biologist who mused, "Well I can't imagine that the DNA of dogs has changed all that much from the DNA of the wolves that they descended from. The social hierarchy in a wolf pack is really based on family structure. It is set up so that the parents hold the highest status and are the pack leaders. That means that the pups must have an inherited ability which allows them to recognize and remember their mother simply because, for the pack to function well, she must be obeyed. I wouldn't be surprised if that recognition of parents also comes with a sense of kinship and affection. On the flip side, the mother should recognize her own offspring since she has gone through a period of rearing them when her whole focus is on guarding, nourishing and protecting the pups."
A social psychologist in our little group disagreed. She argued, "While it may be the case that family structure and recognition of kinship is necessary for wild canines, it's not the case with domestic dog litters. Our dogs don't stay in a family grouping for long, but rather, after only a couple of months, the litter is generally disbanded as puppies go to their new families. After that, the majority of pups will never see their parents again."
Then she added an interesting twist to her argument, saying, "I am also struck by the fact that there are some behaviors that seem to be incompatible with the idea that adult dogs recognize their mothers. In particular, it seems to me that dogs demonstrate that they lack any recognition of their biological relatives by violating basic social psychological principles. I'll give you the example which convinced me. When my dog was about 3 years of age he met his mother again. Although he seemed happy to see her it took less than half an hour before he was trying to mate with her! It seems to me that this is something which he certainly would not do if he recognized her as his mother."
I felt a poke in my ribs from another faculty member who is also a long-time friend. I looked at him and he asked in a questioning tone that seemed to require my response, "Certainly you must have run into some kind of real empirical data which can answer this question?"
It took me a few moments to scrounge through my memory, but I did manage to recall a convincing set of experiments which were done a while back by Peter Hepper, from the School of Psychology at Queens University of Belfast, in Northern Ireland. It involved a number of litters of puppies and their mothers (multiple sets of Labrador retrievers, golden retrievers, and German shepherds). At the time of testing, the pups were aged between 4 and 5.5 weeks of age.
To assess whether puppies recognize their own mothers, two wire enclosures were placed at the end of a room. The puppy's mother was placed in one of these, while a female dog of the same age and breed was placed in the other. A puppy would enter at one end of the room and the experimenter recorded which of the areas he went to first and how long he spent attending to the dog in that place. The results were unambiguous, with 84 percent of the puppies preferring their own mother.
The second experiment modified the situation by placing puppies from the test pup's own litter in one of the enclosures and puppies of the same breed, age, and gender in the other. Again the pups showed recognition of their own relatives by preferring their siblings 67 percent of the time.
Hepper went on to show that it is the scent cues which are important in the recognition of which dogs a puppy was biologically related to. This was done by repeating the experiments, only now, instead of having an actual live dog in each of the wire pens, he used a large square of toweling cloth that target dogs had slept on for two days. The results were very similar to the previous experiments. When pups were given a choice of a cloth impregnated with their mother's odor versus one impregnated with the odor of a similarly aged, unfamiliar female of the same breed, 82 percent showed a preference for the scent of their mother. When pups were given a choice of a cloth impregnated with their siblings' odor compared to one impregnated with the odor of a dog of similar age and breed but from a different litter, 70 percent showed a preference for the scent of their littermates.
The results of these two experiments clearly show that young puppies recognize their own mother and littermates, and it also shows that this recognition is based upon scent cues.
However, the question that was actually being raised by my colleague is whether, when the pups grow into adult dogs, will they still recognize their biological mother. This indicates that the tests must be conducted using adult dogs rather than young puppies. To do this, Hepper gathered a set of dogs that were approximately 2 years of age. These dogs had been separated from their mother when they were around 8 weeks of age and had not seen her again up to the time of testing. He now repeated the previous set of experiments starting with an assessment of whether the canine mothers still recognized their offspring after all of this time apart, based upon scent alone.
The results were quite clear, with 78 percent of the mothers sniffing the cloth containing the scent of her offspring longer than they sniffed the scent of an unfamiliar dog of the same breed, age, and gender. So obviously canine moms recognize their offspring even after they are adults and after a long separation.
To see whether the offspring still recognize their mothers, the experiment was now revised so that the targeted scent was that of the dog's mother compared to another female dog of the same breed and age. The results were almost the same as in the case of the mothers recognizing their offspring, with 76 percent of the dogs showing a preference for the cloth impregnated with their mother's scent. This was impressive because the puppies had by now grown into adults and had not seen their mother for around two years.
"So," I went on to explain to my colleague, "at least as far as the data is concerned, it appears clear that a dog, even as an adult, will still recognize its biological mother.
"However, although that answers the initial question (concerning a dog's ability to remember his mom after a long separation) it does not tell us how that former puppy, having now reached adulthood, will act around its mother once they are finally reunited. Contrary to the beliefs of our social psychologist here, the fact that a male offspring might try to mate with his mother during their reunion should not be taken as evidence that he has failed to recognize her as his parent. Rather than demonstrating that he is not aware of his familial relationship to his mother it simply demonstrates the fact that dogs do not have the same system of morality that is accepted by people. Specifically it tells us that the concept of incest, although repugnant to humans, is completely alien to dogs. Even if the dog recognizes that the canine that he has encountered is his mother, it just doesn't arouse any taboo which might halt his amorous attempts."
Stanley Coren is the author of many books, including Gods, Ghosts and Black Dogs; The Wisdom of Dogs; Do Dogs Dream? Born to Bark; The Modern Dog; Why Do Dogs Have Wet Noses? The Pawprints of History; How Dogs Think; How To Speak Dog; Why We Love the Dogs We Do; What Do Dogs Know? The Intelligence of Dogs; Why Does My Dog Act That Way? Understanding Dogs for Dummies; Sleep Thieves; and The Left-hander Syndrome.
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Hepper, Peter G. (1994). Long-term retention of kinship recognition established during infancy in the domestic dog. Behavioural Processes, 33(1-2), [Special Issue: Individual and social recognition] pp. 3-14.