Buck Rubs: Bright Beacons Of Scent Communication and Visual Signals
As fall unfolds and the breeding season approaches for White-tailed Deer, testosterone increases in bucks, triggering the drying and shedding of velvet from their antlers. Bucks rub their antlers against shrubs and trees in order to remove the dried velvet, a process which is normally completed within 24 hours. Generally small-trunked, smooth-barked trees and shrubs ½ to 4 inches in diameter and without lower branches are preferred (Staghorn Sumac is often chosen, as depicted). Research shows on healthy habitat, rub densities can vary from a few hundred to nearly 4,000 rubs per square mile.
Rubs are far more than just a velvet-removal site, however. They serve as billboards posted for deer of both genders. Through specialized forehead skin glands, a buck deposits pheromones that convey social status, suppress the sex drives of younger bucks and stimulate does. Aggressive rubbing as well as increased testosterone strengthen neck and shoulder muscles, equipping them for battle with another buck should it vie for the same doe.
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Female Sumac Gall Aphids Leaving Galls To Colonize Moss
The sac-like galls, often referred to as “Red Pouch Galls,” found on Staghorn and Smooth Sumac are anywhere from marble to ping pong ball-size, and usually become obvious in late summer and early fall when they often acquire a rosy pink blush. Inside the thin walls of these galls is one big hollow cavity, teeming with tiny orange woolly aphids (Melaphis rhois) referred to as Sumac Gall Aphids.
In the spring, female aphids lay an egg on the underside of a sumac leaf, causing the plant to form an abnormal growth, or gall, around the egg. The egg hatches and the aphid reproduces asexually within the gall. Thus, all the aphids inside the gall are identical clones of one another. In late summer or early fall, the winged females fly to patches of moss, where they establish asexually reproducing colonies. At some point these clonal colonies produce males and females which mate and it’s these mated females that fly off to lay eggs on sumac leaves in the spring.
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White-tailed Deer Scent-Marking
Scent-marking plays an important communication role in the animal world. A variety of species use glandular secretions to convey (for some distance) messages. From beavers spreading castoreum on scent mounds to fishers leaving their scent every time their hind feet touch the ground, the woods are alive with messages often undetected by most humans. Some of these are left by White-tailed Deer, which have two primary scent-marking behaviors: antler rubbing and scrapes.
One used to associate an antler rub with the act of a buck removing drying velvet from its antlers. However, it turns out that very few rubs are made by deer removing antler velvet, a process that’s normally completed within 24 hours. Instead, most rubs are made by relatively few dominant bucks to signal their readiness to breed and to mark their territory.
All White-tailed Deer possess specialized forehead glands that become increasingly active in autumn, particularly in adult males. All bucks spread their scent by rubbing their foreheads (which contain specialized scent glands) against trees and shrubs that have smooth bark, few, if any, lower limbs and are ½” to 4” in diameter. (Older bucks also will rub trees six or more inches in diameter.) In the Northeast, Trembling Aspen, Staghorn Sumac, Red Maple, and willows are often used for this purpose.
Mature, socially high-ranking bucks exude greater amounts of the glandular secretion than do younger males or females. They begin marking their territory soon after losing velvet and continue marking until they cast their antlers in December or January. The chemical signals left at a rub site tend to suppress the aggressiveness and sex drive of young males. However, those same signals stimulate females. The amount of rubbing an individual buck does depends on the level of testosterone in his blood, which in turn is largely determined by the animal’s age and dominance status.
We may not be able to detect the chemicals on a rub, but it’s hard to miss the sight of the light-colored blazes that magically appear in the woods at this time of year. (Photo: White-tailed Deer rub on Staghorn Sumac. Thanks to Chiho Kaneko and Jeffrey Hamelman for photo op.)
Female Sumac Gall Aphids Leaving Galls & Heading For Moss
The sac-like galls found on Staghorn and Smooth Sumac are anywhere from marble- to ping pong ball-size, and usually become obvious in late summer when they often acquire a rosy pink blush. Inside the thin walls of these galls is one big hollow cavity, teeming with tiny orange woolly aphids (Melaphis rhois) referred to as Sumac Gall Aphids.
In the spring, female aphids lay an egg on the underside of a sumac leaf, causing the plant to form an abnormal growth, or gall, around the egg. The egg hatches and the aphid reproduces asexually within the gall. Thus, all the aphids inside the gall are identical clones of one another. In late summer or early fall, the winged females fly to patches of moss, where they establish asexually reproducing colonies. At some point these clonal colonies produce males and females which mate and it’s these mated females that fly off to lay eggs on sumac leaves in the spring.
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White-tailed Deer Breeding Season Winding Down
The breeding season of White-tailed Deer extends from late October to mid-December. Fresh buck rubs, where bucks literally rub the velvet off of their antlers as well as communicate with other deer via their scent, can be found throughout this period of time.
Mature bucks make two distinct types of visual and olfactory signposts —early-season and breeding rubs. The early-season scraping of antlers builds up neck and shoulder muscles, designates a buck’s territory (both visually and by scent deposited from forehead glands) and releases aggression caused by rising testosterone levels. Later in the season, once the rut begins, bucks move out of their home ranges into doe territory, where they make breeding rubs. These rubs announce the bucks’ presence to does, and are thought to hormonally suppress small bucks to the point where their testosterone levels stay so low that they do not attempt to mate.
When a deer or moose strips bark off a tree to eat it, the de-barked area is torn only at one end — the deer grabs one end of the strip of bark and tears it off of the tree. The rubbing of an antler leaves ragged bits of bark at both the top and bottom of the rub. Staghorn Sumac, as pictured, is a favorite rubbing substrate.
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Winged Female Woolly Aphids Leaving Sumac Leaf Galls
The sac-like galls found on Staghorn and Smooth Sumac are anywhere from marble- to ping pong ball-size, and usually become obvious in late summer when they often acquire a rosy pink blush. Inside the thin walls of these galls is one big hollow cavity, teeming with tiny orange woolly aphids (Melaphis rhois). In the spring, female aphids lay an egg on the underside of a sumac leaf, causing the plant to form an abnormal growth, or gall. A number of parthenogenic generations are produced inside the gall, and then in late summer or early fall, the winged females fly to patches of moss, where they establish asexually reproducing colonies. According to biologist D.N.Hebert, these colonies produce the males and sexual females responsible for recolonizing sumac each spring.
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