Post date: Jun 29, 2013 2:29:34 PM
MSUcares.com - Behavior of the white-tailed deer is certainly one of the more interesting areas of study to sportsmen, not only in Mississippi, but also throughout all areas in the range of this subspecies. Deer enthusiasts simply want to know what a deer of either sex is doing, why it is doing it and where it is doing it. Encounters with deer vary from happenstance roadside viewing and backyard visits to the purposeful pursuit of deer for sport hunting with the desire to harvest the animal. As the deer enthusiast's knowledge of deer behavior increases, their chance of being in an area at the proper time to encounter a deer increases. Outings by sportsmen then become more productive and more satisfying when deer activity is observed and to some degree is understood.
CommunicationDeer are social creatures and, much like man, have a definite social structure. With this social structure comes a complex set of rules with which every deer in the herd must comply. These rules within the deer herd demand a method of communication whereby deer can react and respond to each other, establish herd hierarchy, or pecking order, and mutually warn each other of potential danger.
A socially intact deer herd, which is complete with doe/fawn family groups and buck groups, can intermingle with relative calm because dominance is established. Deer understand the difference between dominance and leadership. For example, a mature doe may be in a subordinate role to a specific buck, but clearly be the leader of the deer herd. The deer, like most of the animal world, reacts, cooperates, and communicates with other members to increase chances for survival.
Methods of communication include vocal, visual, and olfactory (smell) cues. These cues are utilized individually, or in some cases in combination, to reinforce a particular response.
Visual
When deer detect a potential threat all of their senses are directed toward that area of concern. The deer assumes what is called a stereotypic alert posture. This posture includes the cocking forward of both ears and erection of the hair, particularly along the back. The deer is then immediately prepared to either fight or flee. At this time, much the same as in humans, adrenaline is released, which prepares the animal to most efficiently react to the situation. Should the potential threat continue, or if a deer is unsure as to the actual presence of a threat, it will usually stomp a forefoot in an effort to evoke a response from the unknown object. Other deer in the immediate area are then warned of the possibility of danger. The possibility exists in this instance that deer may even be able to communicate by the ground vibrations generated by these foot stomps. Repeated foot stomps readily occur, probably for the same purposes as already mentioned. If or when the threat is identified as danger, deer will erect their tails, providing another cue to other deer of the imminent danger. In addition to the tail-up response, deer will erect the rump and tail hairs providing an immediate cue to flee the area. Mature does will flee the area of danger waving their enormous white flags as they depart. This highly visible flag waving provides a ready reference for her young fawns as they attempt to follow her. whitetail bucks do not seem to be as conspicuous as they flee from an area of danger. Bucks, of course, do give the tail-up warning, but in some instances, immediately lower the tail after giving the cue.
As assorted deer of either sex meet throughout the year, visual communication cues readily display the intentions and social status of the animals. During most of the year, physical contact and especially eye contact is avoided. However, many encounters of deer during the early spring and summer are for the purpose of establishing dominance. When two bucks who have not established this strict order of dominance meet in the early spring/summer, visual cues immediately begin which will terminate in dominance being established. The conflict is usually initiated by one of the bucks initiating an aggressive posture toward the other. If this threatening posture, which is characterized by laying back the ears, erecting hair, and lowering the head, is answered by a similar posture from the threatened buck, a fight usually develops. During this fight both deer rise to their hind feet and maneuver for position. After a few slashes with their forelegs the fight is over.
These fights are not limited solely to bucks. Does also fight after the same routine of threat followed by a corresponding aggressive posture from the threatened doe. Most people think that only bucks fight and then only with their antlers, but both bucks and does have numerous bouts with each other throughout the year. This type of skirmish is usually settled quickly with most of the fighting being done with the hooves. Once dominance is established, sometimes after several of these battles, the deer then quickly recognize each other in relation to their respective position in the pecking order. Harmony can then exist between the members in the herd until an animal, because of age, condition, or other factors, necessitates a change.
With the arrival of fall comes the hardening of antlers, a drying of antler velvet and an increasing number of sparring matches. These sparring matches are little more than bouts of shoving, which assist in confirming rank in the social hierarchy. At the end of many of these bouts a clear winner is not apparent. The two combatants will leisurely stop sparring and begin to browse together as if nothing has occurred. This type of sparring is usually terminated by the arrival of the breeding season.
A similar yet unmistakably different battle takes place between bucks during the rut. The fight begins in much the same manner, but now both animals have hardened, polished antlers and deep seated motives, altering the fighting conditions and stakes for both deer. Bucks are fighting now for territory and dominance, but a different twist raises the stakes: the right to breed the doe(s) in this area. Normally the two bucks exchange threatening glances and at times a sidling, circling and stiff-legged walk, which is followed by a clashing and pushing done with the antlers until the larger or more aggressive buck gains the upper hand. Bucks seldom fight with members of their own group, but occasionally a younger buck will get ambitious or a transient buck will pass through. These battles can be brief or can last for several minutes, depending upon how evenly matched the two deer are. Occasionally the two bucks will lock antlers resulting in the death of both deer. These cases are the exception rather than the usual, since this situation largely requires mature bucks existing in herds with a tight buck/doe ratio. Competition for does is greater in this situation than in a typical deer herd in Mississippi.
Vocal
During the above-mentioned aggressive behavior between deer, and their visual communication efforts to mutually warn fellow members of potential danger, other cues are being used simultaneously to reinforce the visual cues. These signals are called vocal cues, some of which are anecdotal. Others are simply the sounds deer make to communicate with each other. These vocal cues may certainly be used solely to communicate a response which visual cues may fail to elicit.
Reports vary as to the exact number and purpose of the known deer vocalizations. Some eight stereotypic sounds made by whitetails have been recorded, and behavior unique to the specific call has been described. The foot stomp is certainly another tool (not vocal but auditory) which deer utilize to communicate.
Probably the most commonly heard vocalization by deer is the alert snort. It is almost always preceded by the foot stomp. Mature and yearling deer of both sexes uses the alert snort when imminent danger is detected. Many times deer will escape to the edge of what they consider the danger area and give repeated warning snorts to alert other deer. This vocalization is made with the mouth closed while the deer forcefully expels a single blast of air primarily through the nostrils. Deer in family groups more commonly give alert snorts; members of buck groups rarely give a repeated series of this call.
Deer make another vocalization during times of acute distress. It is commonly referred to as the distress call. This apparently uncontrollable outcry is typically made when a deer is severely distressed, such as during an attack by a predator or when the deer is critically wounded. During our efforts of capturing and tagging deer this response was typically made by deer caught in a net or while they were being handled. Deer of both sexes and all age classes seem to be capable of this vocalization. Much like the snort, other deer are instantaneously and acutely alerted when a deer makes this sound. Apparently, individual deer recognition is possible to members of the family group as this call is made.
Vocalization between does and fawns are also common. Both the fawns and their dam (mother) make vocalizations to find each other when separated. This is one of the sounds commercial deer call manufacturers attempt to emulate. The call can best be described as a low bleat. Bleating intensity by the fawn appears to be related to the response generated from the bleat. If maternal care is not acquired after repeated bleating, intensity greatly increases, and conversely, a mothered fawn rarely bleats. Still another vocalization utilized between doe and fawn is the nursing whine made by the fawn during feeding periods. Maternal bonds are certainly reinforced by this vocalization, but other purposes for the whine may exist as well.
Undeniably, the most talked about sound during recent years is the grunt of bucks made while trailing an estrous doe. Commercial calls imitating this sound, as well as testimonials to the effectiveness of the call, seem to dominate hunter conversation during the rut each year. A dominant buck is apparently challenged by the possibility of another buck "grunting" a doe in his territory and, in many cases, responds accordingly. Females have been detected emitting the grunt as well. The grunt is utilized by does during dominant-subordinate interactions as well as to call fawns and initiate nursing interactions.
Two final vocalizations made by deer of both sexes are the aggressive snort and the snort/wheeze. Deer emit these sounds to challenge other deer either hierarchically or territorially at any time during the year, but especially by males prior to serious fighting associated with the rut. The level of arousal that the deer experiences apparently determines which of these two sounds will be made. The aggressive snort is the more serious of the two.
Olfactory
Substances secreted from several glands on the body of deer enable deer to communicate by scent or olfactory cues. Breeding condition, individual deer recognition, territory marking and possibly even danger are all communicated within a deer herd by scent. The acute ability of deer to apparently recognize differing scents from a variety of sources gives us some clues to the ability of deer to communicate with this medium. There are theories based on relatively valid parametric indicators that deer may in effect be able to detect olfactory signals some one hundred times more acutely than humans.
When the tail and rump hairs are erected during times of imminent danger, deer have been observed to erect the hair surrounding the tarsal glands as well. Other deer in the immediate area are unmistakably alerted as this behavior is displayed. The possibility that scent cues are emitted, which reinforce the presence of danger, certainly is likely.
Tarsal gland activity noticeably fluctuates during the lifetime of a deer as well as during any one year of the life of the animal. In actuality, these darkened patches of thickened hair, located on the inside of each hind leg, are not glands at all since they possess no exterior duct. As a newborn fawn and up to at least several days old, the gland appears, based on human observance, to be virtually scentless. Urination on the tarsal glands by deer of both sexes and all age classes seems to have a major impact on the scent emitted from the gland. Deer engaged in this rub urination hold both hind legs together and rub the tarsal glands together as they urinate over them. During peak breeding activity, the musky odor is clearly perceptible by humans even some distance away from the deer. The tradition that the glands must be removed immediately after the kill, "else the meat will be tainted" continues in many deer camps.
Inter-digital glands located between the toes of deer probably aid deer in individual deer recognition. Upon close inspection when the toes are spread apart, the gland appears as an indentation out of which a yellowish, waxy, ammonia-like scent is emitted. Interestingly, some other ungulates use the foot stomp to release scent cues that warn conspecifics of danger; the possibility may exist with whitetails.
Pre-orbital or lachrymal gland secretions by deer aid in the lubrication and cleansing of the eye. However, bucks are readily observed rubbing this gland on twigs, limbs, and branches during scrape and rub activity. This gland located at the anterior corner of the eye appears as a darkened, hollowed slit. Excretions from this gland tend to smell similar to ammonia and are detectable to humans. The possible message conveyed to other deer as they confront this scent remains a mystery.
The forehead of the buck also has some glandular function. An oily substance produced by this gland is rubbed on twigs and overhanging branches during scrape activity. This is certainly an olfactory cue of some sort to other deer.
A gland of unknown function is the metatarsal. Like the tarsal, no external duct is detectable on this gland-like structure. Theories abound that the gland, when in contact with the ground, may even serve as a sensor that can detect minute vibrations (such as approaching steps) as the deer beds. No discernable substance produced by the gland can be identified.
Another gland, the Jacobs gland, is located on the roof of the mouth of the deer. As in many other hoofed animals, it is used by the buck to detect an estrous female. The buck will extend his neck and chin to a 45-degree angle and will curl back his upper lip and nostrils for some 5 seconds in an activity called "flehmen." Apparently this effort intensifies olfactory stimulus and enables the buck to monitor scent cues emitted by the doe in her urine prior to and during peak estrous.
We know enough about deer communication by olfactory cues to make us appreciate the vast amount that we have no idea about. Scent cues surely are more important to deer than we are able to identify. We do know that deer rely on visual, vocal, and olfactory cues to communicate, and that the senses used by deer to detect and monitor these behavioral signals are many times more sensitive to the stimuli produced than that of man.
Signposts
The mystique involving rubs and scrapes will undoubtedly continue for years to come. The following is what we "think" we know about rubs and scrapes. In no way will this information be the definitive guide concerning signpost communication in the deer herd.
A rub is simply a shrub, bush, or tree from which a portion of the bark has been scraped away in a vigorous rubbing action. The bark is removed by the buck repeatedly pushing and scraping his antlers and forehead against the resiliency of the rub object. Differing types of rubs are made for several purposes at varying times. Initially in the late summer-early fall, bucks begin rub activity to remove the dried velvet from the antlers. This process has been observed to take from only a few hours up to several days. Most of the rubs made during this time of the year are small and not very apparent as visual communication cues. These rubs have been appropriately called "low visibility rubs." As the breeding season approaches bucks begin to more vigorously debark the trees and shrubs on which the rubs are made. A greater amount of the bark is removed as the bucks "spar" with the resilient saplings and trees. We notice bucks regularly marking these high visibility rubs with secretions from the glandular area on the forehead. Other deer of both sexes take notice of the rubs but do not react in a detectable (to humans) manner.
As noticed by most hunters, there seems to be some correlation between the size tree that the buck rubs and antler size of the buck making the rub. Bucks also seem to select trees that have an aromatic quality. Pine, cedar, and apple are good examples of this apparent selection. Bark from these and other trees that deer prefer to rub are even odoriferous to humans.
A scrape may be defined as a circular depression from which all debris has been pawed, some 3-6 feet under an overhanging limb or branch. The limb is marked with saliva (mouthed) and by glandular secretions from the forehead of the buck as he rubs his forehead and antlers through the leaves on the limb. Bucks may or may not rub-urinate in the scrape as the initial scrape is established or as he freshens the scrape at some irregular interval during the breeding season. Scraping activity by dominant bucks markedly increases just prior to and during the breeding season or rut. Scraping intensity is observed by hunters to greatly fluctuate during some years due to a variety of unknown factors.
Researchers have found that only dominant bucks produce a significant number of identifiable scrapes. Most of these scrapes appear to be made in precisely the same spot that a scrape was made 1 year earlier. The scraping activity peaks some 2 weeks prior to the peak in breeding. Immediately after peak breeding, scraping activity declines.
Does visit these scrapes during various periods of their estrous cycle. Olfactory messages are left at the site of the scrape by the doe as she urinates into the scrape and then departs. As routine checks at the scrape are made by the buck, notice is made of the previous visit by the doe, which is then trailed until found. The buck will follow the trail of the doe, keeping his nose close to the ground and emitting the low guttural grunt, which has been previously discussed.
As we begin to think we understand the purpose of the scrape we then observe activity by deer which will not fit the pattern that we have established. To illustrate this, recently we have found that does make scrapes too, and to further complicate matters, they make these scrapes regardless of the breeding season.
Reproduced with permission from MSUcares.com.
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