Dogs have been man’s best friend since they were first domesticated thousands of years ago. A friendly bark, a comforting nuzzle — dogs find plenty of ways to charm us. But a hearty tail wag may be the domestic dog’s most distinctive behavior. Tail-wagging isn’t observed in other canids, like wolves, although some animals will exhibit tail movements to signal things like status or intimidation. Conspicuous tail-wagging behavior is limited to domestic dogs — and scientists still aren’t sure exactly why. In early 2024, a team of researchers published an article featuring a series of hypotheses meant to explore the question: Why do dogs wag their tails? The published hypotheses could drive future research into domestic dog behavior, potentially strengthening our already strong bond with our canine friends.
Scientists Wonder: Why Do Dogs Wag Their Tails?
The article, which was originally published in The Royal Society’s Biology Letters, explains that visual signals like tail-wagging “are used as communicative cues in both human-dog and dog-dog interactions.” Humans use this visual information to “infer the inner states of dogs” — in other words, to determine how dogs are feeling. Tail-wagging is, of course, generally associated with a happy or excited dog. But when did dogs develop this behavior, and why?
According to the article, a “structured theoretical framework” for tail-wagging has yet to be established. While the article did not establish such a framework, the authors did identify several hypotheses about the behavior’s origins. Compiling these hypotheses in one place may allow for future research into the specifics of this charming canine behavior.
Dogs Likely Evolved to Wag Their Tails
The team cited behavioral differences between dog and wolf pups to explain the evolution of tail-wagging in dogs. In one study cited in the article, wolf pups and puppies were hand-raised and then researchers observed behavioral differences when the pups were exposed to positive stimuli. They found that four- to five-week-old puppies frequently started to wag their tails; by contrast, wolf pups almost never wagged their tails. This study emphasizes that tail-wagging appears to be an evolutionary trait in dogs that have evolved from wolf origins. But, again — why?
While the team did not confirm why dogs wag their tails, the article did cite numerous hypotheses that could explain the evolution of the behavior:
- Deferential behavior hypothesis: This hypothesis suggests that tail-wagging was developed by dogs in response to their human caretakers, as a “direct expression of docility.”
- Emotional reactivity hypothesis: This hypothesis suggests that a dog’s tail-wagging behavior is naturally linked to their emotional state.
- Domesticated rhythmic wagging hypothesis: This suggests that tail-wagging behavior may have been one target of the domestication process. Per this hypothesis, humans may have consciously or unconsciously selected dogs “who wagged their tails more often, and potentially more rhythmically.”
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While the team outlined numerous hypotheses, including those listed above, they did not delve further into the research necessary to test these hypotheses. They noted, “We invite testing of these hypotheses through neurobiological and ethological experiments, which will shed light on one of the most readily observed yet understudied animal behaviors.”
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