The information available in canine urine is astounding. From a proper sniff, dogs can learn about the sex, reproductive status, diet and stress level of dogs who have been there before. Urine is used to communicate about territories, to mask the smell of other dogs, to detect females who are likely to be reproductively receptive and to compete with other individuals. It’s no wonder that our canine friends find urine so compelling that they are irresistibly drawn to it. As anyone who has spent even a little time with dogs knows, urine sniffing is a favorite pastime.
A recent study called “Length of time domestic dogs (Canis familiaris) spend smelling urine of gonadectomised and intact conspecifics” was conducted to investigate whether gonadectomy (being spayed or neutered) affects urine-sniffing behavior. Since gonadectomy has significant impacts on body chemistry, it has long been suggested that it disrupts the flow of information available through urine that dogs have evolved to detect over many generations.
Researchers tested the affects of gonadectomy in urine sniffing by recording how long dogs sniffed urine from intact versus gonadectomized individuals. They found that dogs spent more time sniffing urine from spayed or neutered dogs than from intact ones. One possibility is that the dogs are spending a longer time sniffing such urine because they are trying to figure out the information it contains. Because it may have a combination of chemicals that is different than the range of compounds that the dogs have evolved to understand, it may be harder for them to make sense out of it.
Interestingly, this study contradicts the findings of Lisberg and Snowdon, whose 2009 paper also analyzed the investigation patterns of unfamiliar urine and found that dogs spent more time sniffing urine from intact dogs than from gonadectomized ones. One possible explanation for the difference may be that for the current paper, the dogs were tested indoors, but for the 2009 paper, the study took place outside. (Fewer distractions inside may also explain an average sniff length of nearly 13 seconds in this paper compared with just over 5 seconds in the older study.) Another difference between the results of the two studies is that the recent research found no difference in sniffing time related to what kind of dog was doing the sniffing (male or female, intact or gonadectomized) but Lisberg and Snowdon found that neutered males and intact females both spent more time sniffing urine from intact males than from neutered males.
More research is definitely needed if we want to understand the complicated behavior of urine sniffing, which may involve many interactions between environment and individual traits of the dogs—both those who are the sources of urine and those who sniff if. Research is time intensive and can be costly, which is why I’m so impressed by this particular study. It was conducted in a single home in which the 12 dogs recruited to be sniffers all live, there was no funding source for the study and all of the urine in the study came from out of state to insure that the urine came from unfamiliar dogs. Kudos to the authors for taking the initiative to conduct a cool and clever experiment!