The simplest answer is
they don’t.
In The Intelligence of Dogs,
author Stanley Coren gives us the
classical explanation of this myth: “All canids use urine ... to mark the
limits of their territories. In males this marking behavior is usually
accompanied by leg lifting to direct the urine against large objects (trees,
rocks, bushes) to place the scent at nose height for other dogs and to allow
the scent to radiate over a large area. Some African wild dogs ... scrabble as
high up the trunk of a tree as possible before squirting their message.”
First of all, dogs urinate
far beyond the boundaries of their so-called territory. Secondly,
males aren’t the only ones who lift their legs; some females (usually the
anxious type) do this as well. Thirdly, dogs don’t just urinate on large
objects, but on vertical objects (trees, posts), unfamiliar or inorganic
objects (tires, plastic bags, fire hydrants), and on top of another dog’s urine
(males usually urinate on top of another male’s scent, but not on top of a
female’s).
Coren is not responsible
for the myth. His offhand re-telling of it, as if it were a scientific
certainty, merely highlights a general tendency in science: in attempting to
dissect how an animal’s behavior might serve an adaptive purpose—in this case
marking would be a hypothetical means of limiting competition within a niche or
habitat—most scientists blur the line between what makes sense in terms of the
grand arc of evolution, and what an individual animal is capable of in terms of
its cognitive abilities.
Of course if a biologist
who witnessed the African wild dogs madly scrabbling up the tree trunks did so with
the belief that dogs urinate to send a message to other dogs, their behavior
would, no doubt, confirm his hypothesis. But if we approach this with
a clearer mind we might ask, how could these dogs possibly know the “nose
height” of another, purely hypothetical dog who might or might not come along
at some undetermined point in time?
In The Secret Life of Dogs,
anthropologist Elizabeth Marshall Thomas
compares a dog’s urine marks to Hansel and Gretel’s trail of
pebbles and bread crumbs: a means of finding their way home. But that would
mean the dog was planning for the potential (thus, hypothetical) possibility of
getting lost. I’ve never seen any evidence for that kind of thinking in any of
the dogs I’ve known. They live totally in the now moment.
Roger Caras, whose voice
used to be heard each year at the Westminster Kennel Club Dog Show
in New York, was fond of saying that when a dog sniffs a fire hydrant he’s
“reading his mail”. This is highly anthropomorphic, yet it’s hard to dispute
that a dog does get information from the scent of other dogs this way. The only
question is, did the dog who left the scent do so with the intention of
“sending a message?”
It doesn’t make sense that
any dog would have the intelligence necessary to leave messages for other dogs
in this manner because in order to do so he would have to be capable of
propositional and/or hypothetical thinking, directed fantasy, mental time
travel, not to mention a full-blown theory of mind. “If I mark this fence
(propositional thinking), Spike will come along some time in the future
(directed fantasy, hypothetical thinking, mental time travel), sniff it (more
fantasy, more hypothetical thinking), and know he’s in my territory (theory of
mind, abstract and conceptual thinking) and start to feel nervous about being here
(more theory of mind).”
That’s pretty complicated
thinking for a dog.
Territory is defined as an area which an animal will defend against intruders of the same species. But how is such an area delineated in the
animal’s mind? Are its boundaries visible and concrete or imaginary and
abstract? Is a dog capable of forming a mental image of where his territory
begins and ends? And if animals have no sense of self and other, how could they
think of a territory as “mine” or “belonging to me?”
Meanwhile, I got my first
glimpse into a more reasonable explanation of why dogs mark—one that has
nothing to do with “territory”—many years ago when I took my dog Freddie to a
training session I had with a six-month Maltese male named Buckwheat who hadn’t
had much socialization with other dogs. Freddie’s presence made Bucky a little
nervous, but not to the point that he couldn’t learn the games we were teaching
him. However, at several key points during the lesson—which was taking place in
the dining room—I put Freddie in a down /stay by a piano in the living room, to
keep him out of the way. Later Bucky’s owner told me that immediately after
Fred and I left, Bucky had gone over to the piano and had urinated on the spot
where Freddie was told to lie down.
Why did he do that? To
mark the limits of his territory? He was already inside his territory; in fact,
he was inside his “den.” Did he do it to send a message? No. The answer is
simple. The rug held remnants of Freddie’s scent, enough to make Bucky feel
nervous. So he put his own scent on top of it. Yes, in a sense, he marked the
carpet, but not to tell Freddie that it belonged to him. He just did it to
relieve his own internal tension.
A few years later, while
doing research for a subplot about kidney disease for my 4th novel, ‘Twas the Bite Before Christmas,
I learned that in mammals, the need to urinate is controlled, in large part, by
the neuropeptide vasopressin. Higher levels
of vasopressin increase water retention, reducing the need to urinate. Low
levels are associated with excessive urination, bedwetting, etc. Vasopressin
also has a converse relationship with the stress hormone, cortisol: when cortisol levels go up, vasopressin goes
down, suggesting that there’s a causal relation between stress and excessive
urination.
So it seems far more
likely that when one male detects the scent of another, (particularly an
unknown male), it could cause a perhaps low-level stress reaction, which would
then increase his need to urinate. As he does he would feel the pleasure of
releasing some of the tension and pressure in his body. This would
reinforce the behavior, making it a purely emotional response initially, which
becomes a Pavlovian response over time; it wouldn’t have to derive from any
kind of high-level cognitive ability.
Later, when this dog
smells a urine mark he’d made earlier, he would probably re-experience, on some
level, the original lessening of tension and the pleasure it produced. (Of the
five senses the sense of smell is the one most likely to evoke memories.) He
learns to mark in order to relieve emotional tension and to feel connected to
his environment.
This explanation is
simple, whole, and complete. It requires no complicated thinking. It obeys the rules of parsimony and logic. And it only requires that a
dog have the ability to experience tension and pleasure, and to form simple
physical and emotional associations.
“Life Is an Adventure—Where Will Your Dog Take You?”
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