Inside of a Dog: What Dogs See, Smell, and Know by Alexandra Horowitz Page A

allowing them to mark repeatedly and often.
    And having left smells in their wake, they also come right up to investigate others' smells. From observations of the behavior of the sniffing dogs, it appears that the chemicals in the urine give information about, for females, sexual readiness, and for males, their social confidence. The prevailing myth is that the message is "this is mine": that dogs urinate to "mark territory." This idea was introduced by the great early-twentieth-century ethologist Konrad Lorenz. He formed a reasonable hypothesis: urine is the dog's colonial flag, planted where one claims ownership. But research in the fifty years since he proposed that theory has failed to bear that out as the exclusive, or even predominant, use of urine marking.
    Research on free-ranging dogs in India, for instance, showed how dogs behave when left entirely to their own devices. Both sexes marked, but only 20 percent of the markings were "territorial"—on a boundary of a territory. Marking changed by seasons, and happened more often when courting or when scavenging. The "territory" notion is also belied by the simple fact that few dogs urinate around the interior corners of the house or apartment where they live. Instead, marking seems to leave information about who the urinator is, how often he walks by this spot in the neighborhood, his recent victories, and his interest in mating. In this way, the invisible pile of scents on the hydrant becomes a community center bulletin board, with old, deteriorating announcements and requests peeking out from underneath more recent posts of activities and successes. Those who visit more frequently wind up being at the top of the heap: a natural hierarchy is thus revealed. But the old messages still get read, and they still have information—one element of which is simply their age.
    In the annals of animal urine marking, dogs are not the most impressive players. Hippopotami wave their tails as they spray urine, better to scatter it, sprinklerlike, in all directions. There are rhinoceroses who follow their high-powered urination onto bushes with destruction of the same bushes with horn and hoof—to ensure, presumably, that their urine is spread far and wide. Pity the owner whose dog is the first to discover the spreading-efficiency of high-powered, whirling-sprinkler urination.
    Other animals also press their rear ends against the ground to release fecal and other anal odors. The mongoose does a handstand and rubs itself against a high perch; some dogs do what gymnastics they can, seemingly deliberately relieving themselves on large rocks and other outcroppings. Although secondary to urine marking, defecation also holds identifying odors—not in the excreta itself but in the chemicals dolloped on top. These come from the pea-sized anal sacs, situated right inside the anus and holding secretions from nearby glands: extremely foul, dead-fish-in-a-sweatsock kind of secretions with apparently individual-dead-fish-in-individual-sweatsock odors for each individual dog. These anal sacs also release involuntarily when a dog is afraid or alarmed. It may be no wonder that so many dogs fright at their veterinarian's office: as part of a routine examination, vets often express (squeeze to release the contents of) the anal sacs, which can get impacted and infected. The smell, covered for us by the familiar scent of veterinary antibiotic soaps, must be all over the vets: they reek of epic dog fear.
    Finally, if these mephitic calling cards are insufficient, dogs have one other trick in their marking book: they scratch the ground after defecation or urination. Researchers think that this adds new odors to the mix—from the glands on the pads of the feet—but it may also serve as a complementary visual cue leading a dog to the source of the odor for closer examination. On a windy day, dogs may seem friskier, more likely to scratch the ground; they may in fact be leading others to a message that