Götz Schürholz
Götz Schürholz is a forester and wildlife biologist. He is at the FAO Regional Office for Latin America in Santiago, Chile.
A doe in a socially well-defined herd of red deer was repeatedly immobilized for certain tests. During the time the doe was under the effect of the drug, both the social and sexual patterns of behaviour in the herd changed. The author's observations of these changes are followed by some possible explanations.
During the course of an experiment in spring 1972, the repeated immobilization of the same red deer doe became necessary. As a result, it was possible to observe changes in the attitude of others in the group toward this doe and a change in the whole social organization of the group.
The experiment involved recording the animals' activities. In order to attach a mechanical recording device by a neck collar, it was necessary to capture the doe using a tranquillizer dart fired from a special pistol or rifle. The doe which was the test animal in this case lived within a group of six red deer in a 6-hectare enclosure in the Black Forest, Federal Republic of Germany. The group consisted of a 23-year-old stag, a 22-year-old doe, a 10-year-old doe which had lost her calf during the previous winter, a 3-year-old doe with a calf, and an 18-month-old stag.
Red deer, being socially organized, normally define the positions of individuals within their group through the establishment of a certain rank order (Gossow, 1971; Buetzler, 1970, Schloeth, 1966). The occupancy of rank positions is determined by a combination of factors, both physical (sex, age, weight, size and shape of antlers, and overall condition) and psychological (such as predisposition toward inferiority or aggressivity). Experience has shown that the individual deer's privileges, which have to be defended continuously in order to maintain its specific position within the social organization of the group, are linked to each animal's single rank. This implies a permanent readiness of individuals to demonstrate dominance.
In a well-defined linear social hierarchy - as was found in this group - the rank defence is exhibited by a wide scale of agonistic encounters, mostly directed toward subordinate animals. The expression of aggressive behaviour ranges from display threats to vicious biting, kicking and pursuing of the subordinate animal. The results of a quantitative and qualitative analysis of social encounters within this group demonstrated this well-defined linear social hierarchy.
An over-aged stag was the top-ranking animal, while an over-aged doe was pushed down to the lowest rank of the group (Schürholz, 1972). The old stag, being readily recognized as the dominant animal, did not have to prove his dominance to the same extent as the other members of the group. This advantage allowed him to be the first at the feeding places and to stay there as long as he pleased, although the other animals were usually waiting impatiently to get to the troughs, showing highly agonistic behaviour among themselves during this period of psychological stress. Thus, the over-aged stag was well fed and showed no signs of physical weakness. In contrast, an over-aged doe (not the test animal) was pushed about and chased away from the feeding trough by all the group members. Even a calf participated in discriminating against this doe, albeit playfully. The old doe was very careful to keep a safe distance from the others in the group, but her basic drive to socialize was so strong that she was rarely seen to be separated from the group.
Comparing aggressive encounters within this enclosed group with those of free-ranging animals in a group of similar size, it can be seen that both the frequency and the intensity of threatening behavioural events are much less within the former. A possible explanation could be that animals in an enclosure come to know each other well and consequently do not have to engage in testing each other with agonistic encounters as do free-ranging animals. The latter, however, also have permanently changing grouping patterns for various reasons.
The beta or second-ranking position within the enclosed group was held by an 18-month-old stag with spike antlers, the third position by a 10-year-old doe, and the fourth by a leading doe with a male calf. The 10-year-old doe was chosen as the test animal because of her good integration in the group, where she held a well-defined medium rank in the social hierarchy. This is a very important aspect for such studies, since experience has shown that any sign of physical weakness of a group number can result in an immediate aggressive response from the subordinate animals. This behaviour could be observed at various times during the study, when the three year-old doe and the calf were maltreating the tranquillized test animal. The doe and the calf usually approached the lying darted animal cautiously, the doe in the lead with a long neck stretch. They would circle the bedding place, continuously muzzling the ground, approach the test animal and strike it viciously with the forelegs until the writer separated the attackers from their helpless victim.
This behaviour indicates the continuous readiness of a group member not only to defend its own social position but also to take advantage of any possible chance of rising within the social hierarchy. Aggressive encounters are normally directed toward the next-ranking subordinate. The aggressive behaviour of the fourth leading doe toward the temporarily weakened third-ranking older doe is thus quite understandable.
The over-aged doe at the bottom of the social hierarchy reacted indifferently to the darted animal, as did the over-aged stag, who lived a solitary life and did not normally show much interest in the activities of the rest of the group.
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Posture in a red deer doe appears to be a key factor in causing sexual arousal in stags. The same posture-heads and neck lowered, back arched and tail lifted-occurs during the first minutes after a doe has been injected with a combination tranquillizer and muscle relaxant to immobilize it. |
But the young spike buck holding the beta position in the group behaved quite differently. As soon as the darted animal showed the first signs of ataxia (inability to coordinate voluntary muscular movements) the stag started to pursue it, muzzling the perineum of the continuously moving doe and mounting her incompletely several times. The stag usually approached the doe from behind, flicked his tongue at her perineum, placed his throat over her rump, rose up on his hindlegs, and straddled the doe with his forelegs, which were placed just anterior to her hindlegs. This behaviour is al so described by Struhsacker (1967) for rutting elk (Cervus canadensis). The much frightened doe tried to buck away from him, and the observer was forced to separate the spike from the darted animal in order to avoid injuries to the doe and to give her a chance to bed down.
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...among socially organized animals rank is determined by a combination of physical and psychological factors... |
Struhsacker (1967) defines the rut of a species as "the periodically sexual arousal of that species." The rutting time for red deer usually takes place in autumn. The current study was carried out in March/April. Consequently, the out-of-season rutting behaviour must be connected with the use of the immobilizer. The author has yet to see this type of behaviour in connexion with the use of any other drugs. The stimulation for sexual arousal could have been created by various chemical-biological factors, such as:
- Activation of the perineal glands due to a sudden release of hormones.- Hypoxy-phenomenon in the doe, connected with a stimulation of the cerebral sexual centre due to activation of the perineal glands.
- The injected substance, Rompun, may have been sexually stimulating for the stag.
The stimulation could also be explained quite simply as described by Buetzler (1970), who noted that certain positions and movements of a doe act as inviting key releasers for rutting behaviour, but during rutting time only. He observed that arching or hunching the back, simultaneously with sinking of the head and neck and tail-lifting by the doe are the key releasers for rutting stags and that this behaviour usually leads to a series of mounts, terminated by copulation with insemination. The darted doe in this case did indeed bend the neck and head and hunched the back, signs which are typical effects of the use of Rompun, as well as being typical for causing sexual arousal in stags.
On two occasions, observations of possible significance could be made of the young stag's behaviour after the darted doe had bedded down and was under the full effect of the drug. The spike slowly approached the motionless lying doe, muzzled her neck, back and flanks, flicked his tongue briefly at her perineum, and muzzled the ground intensely for five minutes while very slowly circling the doe. Then he softly touched the tips of her ears with his muzzle, waited a moment, then pushed his muzzle gently but distinctly between her ears, waited again, then touched her eyes with his muzzle, waited again, moved to the back of the lying animal, and pushed his muzzle from the side repeatedly between her hindquarter and belly. He then started muzzling her perineum again and slowly raised his muzzle slightly above the horizontal plane, holding his mouth open, but with the lips uncurled and unretracted, emitting no sound. This posture he held for several seconds without moving. He then started muzzling the ground once more, moving around the lying doe and muzzling her. His muzzling of the doe was interrupted 13 times in 26 minutes by the above described characteristic head-lifting, which seems to be identical with the flehmen described by Schneider (1930).
Very similar behaviour has been reported by Struhsacker for rutting elk (Cervus canadensis). He reports that: "Holding-mouth-open was most commonly seen in bulls that were tow-and-a-half-years or older. Spikes were seen behaving in this way on two occasions only. The pattern was preceded by the bull muzzling the ground, frequently where a cow had recently been lying, or muzzling the perineum of a cow" (Struhsacker, 1967). His observations support the statement that various of the described behavioural parameters are true indicators for rutting stags.
One further aspect of the described ear and eye touch, the muzzle-to-muzzle contact, and the belly-pushing, as observed for the stag, may be noted. Wildlife biologists who have had experience with immobilizers know how to recognize the depth of anaesthesia by simply testing the protective reflexes of the immobilized animal, touching its nostrils, ears and eyes. These tactile stimulations generally result in the immediate rising of any animal capable of doing so. The behaviour of the stag may also have been an attempt to awaken the doe. In this respect, cases of forkeln (stags using their antlers as deadly weapons) have been reported, occasionally involving immobilized animals (Schürholz, 1972). In general, however, what appears to be forkeln is probably not an attempt to kill a drugged animal, but rather an attempt to awaken it by means of a stronger stimulus than the ear, eye and muzzle touch.
It is also possible that by pushing his muzzle into the belly of the doe the stag was attempting to remedy a bloated condition in the doe. Bloating, which occasionally occurs in darted ruminants, can be easily remedied by raising the animal to a chest-downward position, keeping its head and neck down and gently massaging and pressing the belly. If this is not done, the drugged animal will die.
The behaviour of the spike stag, in any event, could not be mistaken for that of the leading doe and her calf. The incidents of obvious maltreatment were almost certainly rank-order debates, in which the leading subdominant doe tried to demonstrate social superiority over the normally dominant darted doe.
Immediately upon recovery of the doe, the social rank pattern within the herd returned to normal and the sexual behaviour of the young stag ceased. The doe had no difficulty in regaining her social rank. Nonetheless, on each of the four occasions when the author observed or assisted in immobilization of this doe, the same social and sexual aberrations were seen to occur.
The author would be interested to hear of instances of similar sexual or social rank behaviour patterns in cervine species or other animals as a result of immobilization.
Pharmacological studies with Rompun have indicated that the drug achieves unique effects, ranging from sedation to a condition similar to that of anaesthesia combined with relaxation of muscles and general analgesia, which vary considerably from species to species.
The drug, also designated Xylazin-Hydrochloride, is available as a dry substance, from which any desired concentration can easily be prepared. Rompun, developed and marketed by Bayer, can be administered by intramuscular or intravenous injection. It is designated chemically as 2-(2,6-xylidino)-5,6-dihydro-4H-1,3-thiazin-hydrochloride. The most favourable injection site is the musculature of the hindleg (Bayer, 1972). Injection of Rompun can be carried out by dart syringes propelled by specially designed weapons.
The onset of the first effects after the complete injection of the solution occurs after 10 to 15 minutes. The drugged animal should not be handled or approached before the effect of the drug is fully pronounced.
Bloating occasionally occurs in ruminants but can be avoided if they are given the prescribed care and treatment. The full recovery time ranges from 3 to 4 hours, during which the animal should not be left unguarded; this is the main disadvantage of Rompun.
Advantages of this drug include rapid action, lack of negative side effects, no need for antagonistic drugs, wide physiological tolerance, and the fact that it can be used repeatedly on the same animal.
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FARBENFABRIKEN BAYER AG. 1972. Information paper on Rompun. D17-731/34754. Leverkusen.
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SCHÜRHOLZ, G. 1973. Mechanical recording of ruminant activities. Paper presented at the 11th International Conference of Game Biologists, September 1973, Stockholm.
STRUHSACKER, T. 1967. Behaviour of elk (Cervus canadensis) during the rut. Zeitschrift für Tierpsychologie, 24: 80-114.
