The effects of sex, gonadectomy and status on investigation patterns of unfamiliar conspecific urine in domestic dogs, Canis familiaris

Little is known about social roles of urine marking and mark investigation in interpack communication in canids beyond mate acquisition, or of the influence of gonadal hormones on interpack urinary communication. We studied the responses of male and female, intact (nonoestrous) and gonadectomized Labrador retrievers to urine from unfamiliar dogs of the same four reproductive categories. We compared two measures of subject social status within subjects' home groups and measured the effect of subject status on urine investigation duration. We also compared the responses of subjects to urine from familiar and unfamiliar dogs. All subjects showed high interest in unfamiliar urine samples, but differed in their preference for particular unfamiliar urine types. Intact males, intact females and spayed females investigated urine from intact males and females equally, whereas neutered males investigated urine from intact males longer than urine from intact females. Urine from intact males and females elicited longer investigation than did urine from gonadectomized sources. Males showed no difference in investigation of familiar and unfamiliar urine, whereas females showed a nonsignificant tendency to investigate urine from unfamiliar dogs longer than urine from groupmates. Low-status subjects investigated urine longer than high-status subjects. Sex, status and familiarity patterns suggest that males and females, both intact and gonadectomized, have strong interest in unfamiliar urine and investigate urine to assess unfamiliar conspecifics in multiple social contexts, including mate and threat assessment. These results also suggest that gonadal hormones may affect urine investigation patterns both by increasing sexually motivated urine investigation in males and by creating signals in urine that allow assessment of potentially risky conspecifics.