Deception in Nature: Small dogs imitate big dogs' urine markings

Urine marking in male domestic dogs: honest or dishonest? B. McGuire et al. Journal of Zoology, https://doi.org/10.1111/jzo.12603

Abstract: Scent marking is a common mode of communication in mammals. Such marking is thought to communicate information about the signaler's size and corresponding competitive ability and accurately reflect the signaler's attributes (i.e., an honest signal). However, new data suggest that scent marking can be dishonest in certain circumstances. Via two studies, we tested the hypothesis that urine marking is a dishonest signal in adult male domestic dogs, which raise a hindlimb when marking vertical objects. In Study 1, we tested whether raised‐leg angle (i.e., during a urination, the angle between a dog's raised leg and the axis normal to the ground) is a proxy for urine mark height (n = 15 dogs) and, in Study 2, we tested whether small dogs exhibit larger raised‐leg angles than large dogs (n = 45 dogs). We videotaped urinations of adult male dogs and, afterwards, measured height of urine marks (Study 1) and degree of raised‐leg angles (Studies 1 and 2). In Study 1, we found significant positive relationships between both raised‐leg angle and height of urine mark and body size (using either body mass or height at withers) and height of urine mark; raised‐leg angle was a stronger predictor than either measure of body size. In Study 2, we found a significant negative relationship between body size (using either body mass or height at withers) and average raised‐leg angle. Our findings support raised‐leg angle as a proxy for urine mark height and provide additional evidence that scent marking can be dishonest. Assuming body size is a proxy for competitive ability, small adult male dogs may place urine marks higher, relative to their own body size, than larger adult male dogs to exaggerate their competitive ability. We did not control for over marking, which also may explain our findings.