Scent marking in shelter dogs: Effects of sex and age

• Previous studies of scent marking in dogs have focused on juveniles and adults.
• I studied instead marking behavior of juvenile, adult, and senior shelter dogs.
• Marking with urine, but not feces, differed between the sexes and among age classes.
• Ground scratching did not differ between the sexes and was rarely done by juveniles.
• Changes in some scent-marking behaviors occur even after adulthood has been reached.

Development of scent-marking behavior from the neonatal period to early adulthood has been well studied in dogs, but there is a distinct lack of information for older dogs. I studied scent-marking behavior during single walks of 500 male and female dogs at two shelters (Tompkins County SPCA and Cortland Community SPCA). My sample included juveniles, adults, and seniors. I found a significant effect of age on frequency of urination (P < 0.0001 at both shelters): seniors urinated more frequently than adults (contrast significant at the Cortland shelter; P < 0.07 at the Tompkins shelter), which urinated more frequently than juveniles. Age also influenced likelihood of directing urinations at targets in the environment (P < 0.0001 at both shelters): seniors directed more of their urinations than did adults (significant at Cortland shelter only), which directed more of their urinations than did juveniles. I found that males urinated more frequently than females (P < 0.0001 at both shelters) and directed more of their urinations (P < 0.0001 at both shelters). Significant age and sex differences did not characterize defecation at either shelter. Ground scratching, whether after urination or defecation, was rarely performed by juveniles (% that ground scratched at least once: Tompkins shelter, <14%; Cortland shelter, 0%), so I excluded juveniles from analyses of this behavior. Ground scratching after urination was not associated with sex or age (adults versus seniors) at either shelter, but was positively associated with number of directed urinations (Tompkins shelter, P < 0.0001; Cortland shelter, P < 0.002). Ground scratching after defecation was not associated with sex at either shelter, but was associated with age at the Tompkins shelter (P < 0.03; % that ground scratched after at least one defecation: 28% of adults; 42% of seniors); a similar pattern occurred at the Cortland shelter (29% of adults; 50% of seniors), but the association failed to reach statistical significance perhaps due to smaller sample sizes. Finally, at the Tompkins shelter, ground scratching after defecation was positively associated with number of urinations followed by ground scratching (P < 0.0001); here, again, a similar pattern occurred at the Cortland shelter but the association failed to reach statistical significance. These data reveal new relationships between scent-marking behaviors; indicate that some marking behaviors continue to change even after a dog has reached adulthood; and highlight the differential effects of sex and age on urination, defecation, and ground scratching.