November is courtship time for deer in forest preserves
Ready or not, we have launched into the holiday shopping season. There's no easing into it. By mid-November, we're bombarded by the signs of the season and its imperatives.
But there's a more nuanced kind of shopping season this month. November is the rutting season of our state mammal, the white-tailed deer. Known also as "the rut," it's the breeding season, when amorous bucks seek does with all the determination of shoppers on Black Friday.
The rut in northern Illinois begins in October and lasts through November or early December. The early rut is triggered by the steady decrease in daylight. (Not, as some might think, by cold weather.) Photoperiod is the term for the length of day and night. Scientists have found that photoperiod is the cue for the rut and many other seasonal cycles in animals and plants.
Increasing darkness in October triggers melatonin production in deer. The increase in melatonin sets in motion a cascade of hormonal changes. Bucks' testosterone surges, and does' estrogen levels increase. Early on, bucks' antlers harden, their necks grow thick, and they take on the machismo of Bambi's dad in the Walt Disney classic. While the guys are becoming buff, does get closer to estrus. Both males and females grow thick winter coats.
Courtship is a multisensory affair. The visual is important -- big, strong and intimidating is the look you go for if you're a buck. Posturing says a lot about you, and males put on airs for both females and rival males.
The sense of smell is a powerful force in the rut. In our species, males douse themselves with sprays named Excite and Dark Temptation in the hope of impressing their dates. In the same vein, bucks pour on the scent. In early and mid-rut they rub trees with their foreheads and scrape the ground with their feet. Rub-scrapes occur at night and serve as a nocturnal calling card for the ladies. Glands on the buck's forehead secrete scent on the trees as they rub. (The excoriated bark may serve as a visual cue as well -- certainly for hunters.) Bucks also deposit scent from glands between their toes. Scraping ensures that the scent gets worked into the ground. Adding to the odoriferous allure, they urinate on the scrape site. Altogether, the scents signal the presence, stature, and overall desirability of the buck.
Does do their share of olfactory advertising. Like bucks, they have scent glands between their toes. Thus, a doe leaves a message with every step she takes. This biochemical bulletin tells whether she's ready, or perhaps not quite ready, or indeed, past ready. It also communicates how recently she's been at that spot and the direction she's traveling. If you see a buck with his nose to the ground this time of year, you can bet he's reading a lady's love letter.
Another strong scent gland is located on the inside of the hind legs of both males and females. Called the tarsal glands, these let others know a deer's sex, dominance level, and virility. A buck's dark tarsals are covered with coarse hairs and catch urine. This is decidedly unromantic to us humans, but for deer it's part of the whole enticing message.
The rutting season brings out the rock star in bucks. Whitetail bucks may not bugle like elk, but they make an impressive array of sounds. Grunts, wheezes and snorts are all part of the rutting repertoire. While social grunts are made all year long, bucks emit trailing grunts when following a doe that has caught their fancy. At the height of rut, when a buck and his doe are together, he makes a sound called a tending grunt. Additionally, a buck may roar, signifying that he's super jazzed. If a buck encounters another deer (other than his doe), he does his best snort-wheeze. (Yes, snort-wheeze is a thing. Not recommended on first dates.)
Does speak up, too, during the rutting season. They bleat and grunt, and sometimes give distress calls.
The rutting behavior that most affects us is the chasing phase. When bucks' testosterone skyrockets, they become restless and reckless. They're keen on following does, wherever that may lead. It doesn't matter if a four-lane highway is between the buck and the object of his affection; he has only one thing on his mind.
Deer-auto collisions spike at this time of year. These unlucky encounters don't end well for the deer, the car, or the driver. If a car traveling just 25 miles per hour collides with a 200-pound animal, there will be damage to the vehicle and the deer. At 55 miles per hour, the result can be disastrous. Often, cars are totaled, and collisions may be fatal for both human and deer.
Compounding the risk of deer collisions is the fact that deer are most active at dusk and dawn. Our vision is poor in the shadows of twilight. To make matters worse, the glare of artificial lights on the road further restricts our vision of shadowy, dark objects. A deer can appear suddenly in your headlights, seeming to come out of nowhere. Since deer have never mastered the "look both ways before crossing the street" rule, it's imperative that we stay on the alert for them -- especially at the height of the rut.
The seasonal calendars of holiday shoppers and love-struck deer overlap. As you're rushing around in holiday mode, be aware of the rutting season. Pause from the frenzy of the season to take a walk in the woods. You might catch a glimpse of a majestic buck and some beautiful does in the snow -- as pretty as a Christmas card.
• Valerie Blaine is a lifelong naturalist, recently retired from the Forest Preserve District of Kane County. You may reach her at firstname.lastname@example.org.