The evolution of the urban deer

Discussions about urban deer usually revolve around whether we want them in our gardens.

By Barbara Julian

Discussions about urban deer usually revolve around whether we want them in our gardens, some seeing them as a gorgeous addition and others as a threat to plants. We seldom ask, where do they think they are, when in our gardens?

Deer map their world and recognize territory through smell, not vision. We see them in the road and wonder why they don’t get out of the way, but cars don’t emit the pheromones that carry information for deer (the tiny molecules that carry odors from one object or body to another).

Deer must wonder why we don’t warn them we’re coming. Vision is of limited help to them; their eyes see best in the half-light of dawn and dusk, and poorly in bright light or darkness. They respond to sound and body language however, and are often visibly uncertain whether to trust the tall two-legged ones -— us — to walk on by, or whether this will be one of the times they will start shouting and waving their arms.

Biologist Roger Caras called pheromones the “fundamental source of communication” among living things, antecedent to the evolution of voices, ears and eyes. These molecules float in air and water and cling to everything, yet we are unaware of the trails of scent they create that criss-cross our gardens, parks and streets. For deer, they map the landscape. We and deer live in different worlds.

Deer use pheromones to communicate among themselves, revealing whose territory is here and whose rutting dip over there. They emit pheromones from glands in their hind legs, on their foreheads, under their eyes, between their toes and near their tails. When you see a buck rubbing his head and antlers against a tree he is not scratching an itch, he is sending a message to his fellows. When a doe is looking for a safe place to leave her fawns during an evening of browsing, she must often be confused by the acres of pavement, tall buildings and glass windows that don’t emit usable signals or disclose the paths her relatives have made.

Even the plants which deer eat send and receive chemicals and scents that brim with meaning. In his recent book What a Plant Knows, David Chamovitz tells us that plants too detect volatile compounds in air and produce a physiological response: they may close or open up, wilt or emit a toxic substance in turn, depending on whether they are dealing with a predator, a pollinator or a symbiont. 

The deer who visit our gardens are experiencing a vigorous exchange of information with the plants that grow there, which we’re not even privy to. Deer consume plant matter but they also stimulate growth by pruning, and by fertilizing soil with manure. If they did to their native forests what some people fear they might do to the urban landscape -— strip it bare — there would have been no coastal temperate forest at all. In fact plants and animals co-evolve in complex ecosystems, and we must learn to preserve that as much as possible within cities if we want them to remain a living rather than an artificial environment.

Plants, insects, birds and animals co-exist for mutual benefit, and we urban dwellers can get more pleasure from fitting in with than from fighting our co-residents. Peaceful co-existence in any relationship, whether human-to-human or human-to-animal, always comes down to gauging the other participant’s point of view — or of smell.