Tag: buck rub

Buck Rubs

Autumn is mating season for white-tail deer. The bucks sport fully formed antlers and bulked up necks and shoulders, and they’re busy sparring, posturing, and otherwise asserting their suitability as mates. Antler rubs are an important part of the bucks’ demonstrations. To make a rub a buck approaches a sapling or small tree and works its antlers up and down against the trunk. The rough surfaces at the antler bases act like rasps to remove the bark, and the tips of the tines leave rough gouges. In the center of the rub the exposed wood is bright and relatively smooth, and dislodged bark fibers may hang from the roughened margins.

Buck rubs are only made on living trees, and vertical trunks that have an unobstructed approach are preferred. Buck rubs are generally located between 1 and 3 1/2 feet off the ground and can be found on both hardwoods and conifers up to 10 inches in diameter. The light color of the exposed wood is eye-catching, but the most important part of the message is invisible. The buck deposits chemicals from scent glands in its skin by rubbing its forehead against the surface of the rub. In the process of making a rub a buck stops periodically to sniff the surface. Later, visiting does sniff the rub and take in olfactory messages that reveal the health and status of the rub maker.

Contrary to common belief, buck rubs are not connected with the removal of the velvet, the highly vascularized tissue which nourished the antlers as they grew. By late summer the rack is fully formed, and the velvet is beginning to wither and slough off. This process is assisted when the animals thrash their antlers against shrubs and small trees. By the time the rut begins in earnest the velvet is long gone.

An individual tree may be hit more than once, and a popular one may take on a whimsical appearance. Damage like that shown in the photo above may be enough to kill a young tree.

Rubs from previous years are often found among fresh rubs. Old rubs like the one in the photo below are dulled by weathering and are usually rimmed by callus formed in the growing season following the assault as the tree attempted to heal the wound.

Other animals also remove bark from woody plants, but there are usually clues that help to identify the culprit. Squirrels strip bark from stems and branches to use for nest lining, and stripped stems can look similar to buck rubs. Dead trees or branches are often the source for squirrel nest lining, and in that case we know it can’t be a buck rub. But sometimes the bark fibers are harvested from a living tree or shrub, such as the honeysuckle in the photo below. The lack of abrasion on the debarked area and the undamaged hanging strips signal squirrel rather than deer. Squirrels can gather fibrous bark from stems at any height, and the debarked areas in the photo are closer to the ground than an antler rub would be. If nearby stems or branches obstruct the stripped stem it’s also unlikely to be the work of a deer. And finally, as in the photo, stems harvested by squirrels may not be vertical while buck rubs usually are.

Debarking can also be a result of chewing. In the photo below you see a stem fed on by a cottontail rabbit. The irregular removal of bark and outer wood differs from the vertical bands left by the up and down rubbing of an antler. Rabbit feeding is also usually closer to the ground than would be expected in an antler rub, but keep in mind that deep snow can result in elevated rabbit chews. Porcupines and beavers also chew on shrubs and trees at varied heights. But like the rabbit chew, the tooth marks left by these animals are different enough from the abraded surface left by antler action to separate their chews from buck rubs.

Antler rubs are part of a suite of behaviors that allow male white-tail deer to establish dominance and demonstrate their prowess, but that’s not all there is to it. These behaviors also trigger changes in the females that prime them for mating. Sniffing a rub sends chemical signals to a doe that precipitate a flood of hormones and prepare her for reproduction. Buck rubs are part of an intricate interplay of behaviors that results, if things go well, in the appearance of offspring about 6 1/2 months later.

Looking On The Bright Side

The leaves are down, and the colorful spectacle of autumn is behind us. The forest has gone from a kaleidoscope of color to a narrow spectrum of browns and grays. But wait, what’s that pale streak glinting among the tree trunks? If you look closely you can see it in the center of the featured photo. Moving closer we can see that it’s a buck rub, bright wood laid bare by a hormone-driven male deer. This is rutting season for whitetail deer, and the bucks are roaming the landscape seeking receptive does. They leave their calling cards on living trees–anything from very young saplings to substantial trunks 8 inches or more in diameter. To make a rub the animal lowers its head and rakes its antlers up and down against the stem. Rough areas around the bases of the antlers work like files to abrade the outer bark down to the light colored sapwood.

The photo below is a close-up of the rub in the first photo. Rubs are usually between one and four feet above the ground, and their edges are often rough or stringy. Gouges made by the short tines near the antler bases are often present–look for them just above the debarked area. The brightness of the freshly exposed wood is what attracts our attention, and it may do the same for deer. But buck rubs also carry scent messages, deposited when the animal rubs its forehead against the newly bared surface. We’re not equipped to detect these chemical signals, but to a visiting doe they convey a wealth of information about the age, health, and even individual identity of the rub maker.

The light colored areas in the photo below have also been denuded of bark, but this wood was exposed by feeding rather than by rubbing. A porcupine climbed these yellow birch trees and chewed through the outer bark to get at the cambium, the living cells that produce both bark and wood during the growing season. There’s no mistaking this example for a buck rub, but porcupine chews are sometimes found close enough to the ground to be confusing. In both cases the light wood stands out against the bark, but there are several clues that distinguish rubs from chews.

Instead of a smooth surface, wood that has been exposed by porcupine feeding is textured by tooth grooves, and the margins are more irregular, as in the photo below. The tooth marks are just deep enough to reach the nutritious tissue, and are organized with a neatness that speaks of feeding efficiency. Along the margins of chews there are often tooth marks instead of the stringy fibers that mark the edges of rubs.

Beavers, like porcupines, rely on the cambium of woody plants for much of their winter diet. Being larger than porcupines, beavers’ wider incisors give their chews a more robust appearance. And rather than climb to access food, beavers bring the food down to their level by felling trees. The beaver that felled the log in the photo below stood on its back feet to feed, anchoring its upper incisors in the bark and drawing its lower incisors upward to scrape up the cambium. It moved systematically along the log, leaving the row of shallow upper incisor digs in the bark and the longer lower incisor marks below them. Like the porcupine, the beaver penetrated just deep enough to scrape up the nutritious cambium.

Not all bark chewers show this kind of efficiency. The sumac stem below was chewed by a rabbit, and its ragged appearance contrasts with the more orderly work done by beavers and porcupines. Rabbits only feed on small stems, and their chews show varying depths of penetration with projecting splinters of bark and wood. Like beavers they are limited to what they can reach from the surface they’re standing on, but if there’s a deep snow pack or heavy snow that bends branches down, rabbit chews can be found in some surprising places.

Here’s another kind of feeding that might catch your eye in the autumn woods. Woodpeckers worked on this standing dead tree to get at the insects in the outer layers of wood. The beak strikes left pits, partially lifted slivers, and gouges (best seen on the right edge of the tree). This kind of woodpecker work can be located at any height, and may even be found on downed logs, but unlike the previous examples, it only occurs on dead trees.

Here’s a final example of eye-catching brightness. As the weather gets colder, squirrels leave their leafy tree-top dreys and make nests in hollow trees or other protected places. They gather fibrous bark for nest lining, and in the process, leave freshly debarked wood for us to find. The dead, fallen branch in the photo below was stripped of its fibrous inner bark by a squirrel. Although there’s a vague resemblance to a buck rub, the position of the branch and its non-living status indicate squirrel work rather than deer.

When squirrels harvest fiber from woody plants they may leave another clue. In the photo below you can see the paired marks of a squirrel’s incisors. Much of the bark removal is done by pulling up long strips, but occasionally the squirrel leaves a bite mark as it grasps the bark with its teeth.

Squirrel stripping is also found on living stems–I’ve seen it on honeysuckle and red cedar–and these are more likely to be mistaken for buck rubs. But areas shredded by squirrels are often in places a deer wouldn’t be able to reach, higher on a trunk, within multi-stemmed shrubs, or on stems guarded by projecting branches. Deer prefer sites with straight stems and unobstructed approaches, and any small branches or twigs are usually broken off by the vigorous action of making a rub.

I love this time of year–the leaves are down, and I can see for greater distances through the trees. Many signs of animal activity are hidden by fallen leaves, but others have become more visible. And every once in a while a bright patch shining among the duller tones draws me in and opens up a new and interesting discovery.