For the purposes of this report we have divided the means of communication into two groups according to the manner of employment. How applicable this division will continue to be as the study progresses is not known, but it is useful at this stage to think of bighorn communication in terms of being either voluntary or involuntary, dynamic or static, active or inactive. And since a communication to be complete must have a receiver as well as a transmitter each means must be considered in two parts: the method of transmission and the method of reception; that is, the sound must be heard, the touch felt, the odor smelled, and the action seen.
The largest and most dominant of the two groups, the voluntary-dynamic-active category is headed by the voice, snorting, stamping, and "clonking" involving four methods of transmission, with the ear and the sense of hearing as the common receiver.
Since it is possible to observe a band of bighorn constantly for days or even weeks at a time without hearing the sound of a single bleat from them, many observers have concluded as Seton (1929, p. 558) put it, "The Bighorn is one of the most silent of animals. The lambs up to 6 months old often bleat exactly as do the domestic kind; but I have never heard any sound from the old sheep except a loud snort or 'snoof.'"
Present evidence indicates a variation in the use of the voice both by age class and sex and by season.
On February 21, 1956, at Furnace Creek Wash, our notes record that a 3-week-old lamb "got lost (couldn't see its mother) twice today. Both times bleated several small bleats. This is the third time, third day, this has happened. Mother stops eating, listens, looks, decides nothing really wrong, never answers, goes on eating. Lamb eventually finds her without help." And of the same band when the two lambs were about 6 weeks old, March 16, "Once today mama missed them and climbed a 4-foot ridge in wash and gave three guttural calls, and both lambs came from the creosote [bush] full tilt. This is the first sound we have heard from the adults this year."
It was not until about 5 o'clock in the evening of April 10, when her lamb was 10 weeks old, that "old Mama seemed to suddenly realize that (she and her lamb) had been feeding in shadow for some time. She abruptly raised her head almost with a 'double take' effect and scanned the horizon all around. She looked at the lamb and gave one of her rare, muffled, squeezed-sounding, gurgling grunts which passes with her for a bleat. The lamb as usual responded instantly by going to her. She took off across the wash to the north and in 20 minutes had crossed the eastern extremity of Paleomesa and disappeared into the canyon behind Red Mountain." Old Mama's voice as described above should not be considered characteristic of all adult bighorn ewes.
The "bleat" of adult bighorn tends to be deeper than that of domestic sheep and sometimes so vebrato as to be almost comical. In general, the "bleat" of the adult ram is probably somewhat deeper than that of the ewe, but we have observed no evidence of the two sounds close enough together for actual comparison.
The lamb's voice is the expected appealing complement to the general concept of the lamb's personality and is probably used more before weaning than during any other period of its life. As in most young animals, its primary instinctual drives are at least partially expressed by "voicing" its demands for food and protection from its mother and, to a lesser degree, its social demands from playmates.
Once the lamb is weaned, its voice is no longer useful in securing food but is still employed in the quest for security by calling for help when lost. Young animals sometimes appear to be engaging in a mutual exchange of distant identification and recognition with no other objective in view.
There is probably a correlation between the frequency of voice use and population density or, more specifically, the number of sheep in the band. In the Desert Game Range in 1953 we found bands of 15 to 20 ewes, with lambs not uncommon and with the urge for identification and recognition between mothers and offspring frequently and loudly observable.
Returning in our jeep truck to Joe May camp in the Desert Game Range on a moonless night in March, we came directly upon a large band of ewes and lambs bedded among the Joshua trees on a knoll at the edge of the wash. We shut off the lights and motor and listened for 15 minutes to a veritable din of anxious bleating, calling, and answering, which gradually subsided into quieter and plainly recognizable tones of recognition and reassurance, then finally silence when the last anxious mother touched her lamb in the dark.
Later the same week we watched a "babysitting" break up with a less anxious din of high and low voices as the lambs dropped off the cliff into the dense ground cover of the wash. Here the ewes waited where they were, head high, looking and guiding by call as the lambs bobbed about through the brush, calling in return and locating their mothers with surprising efficiency.
In the low-density, small-band population of Death Valley where more than two nursing lambs are seldom seen together, the problem of identity and the development of recognition by voice between ewes and lambs has seldom been observed. On March 16, 1956, when the new band joined Old Mama and her lamb in Furnace Creek Wash, the lamb, never having seen other sheep before, became confused and tried to nurse each animal as it came to it, even the year-old ram. Its mother watched for some time and then made one of her rare vocal efforts which brought the lamb to her at once.
Probably the most dramatic use of the voice by the Death Valley bighorn is the challenge of the rams in the mating season.
Our first introduction to this was on July 9, 1955, at Willow Creek, when a 2-year-old ram "called" to other sheep across the canyon as he made his way down the cliff toward them. This was probably one of his first efforts, and we did not recognize it as the "challenge" he apparently was trying to make.
The much overworked word "apparently" is used to emphasize the hesitancy with which we approach the semantic barrier which arises at this point, and to remind us that we do not speak the bighorn language and that we can only guess what a sound or sign may mean after we have observed the manner of its transmission and reception and the subsequent reaction to it. Even then, positive interpretation must be withheld until repetition has established empirical authority for conclusions.
Another case in point was recorded of a band of five on Paleomesa on December 1, 1956, and has been described under "Curiosity." This was the behavior of the 9-year-old ram, Tight Curl, when two prospectors began descending Pyramid Peak from their claim about 1-1/2 miles away. His repeatedly uttered nasal growl was used to communicate his uneasiness.
In both the above incidents we have recorded a transmission by rams in the presence of ewes but eliciting no observable response from them. The young ram at Willow Creek seemed to be trying to communicate with the other sheep; the older ram on the mesa, on the other hand, appeared to direct his communique to the approaching prospectors and both his growling concern and the prospectors were ignored by the four ewes with him.
The question arises as to whether these reactions are due to the difference between the general nature of rams and ewes or to a difference in personal experience of the animals involved. The possibility of both factors being present is suggested by an observation made on a captive ram ("The Old Man" in our horn-growth photos) at the Desert Game Range on January 16, 1957. This observation includes not only voice but introduces movement, the sense of touch, and possibly the sense of smell as factors in communication.
When we were here on our last year's trip this ram was so "spooky" that it took me 2 days to get two rather poor closeups to show his horn development. At that time he and the two captive ewes seemed determined to keep the greatest possible distance within their fenced enclosure between themselves and us.
This year the ram had a different approach. His belligerence toward anyone who ventured inside the compound had been increasing year by year, earning him the local nickname of "Old Nasty," but this was the first time that he had challenged me right through the fence to "put up my horns and fight like a ram." As a matter of fact, you would think by his actions that it was the middle of the mating season, he was so willing to fight with anybody or anything.
The foot-thick almond tree in one corner of the small compound took a beating all day long. Standing about 20 feet from it, he would rear sideways on his hindlegs and with his head cocked on one side, his forelegs hanging almost crossed before him, he would advance to within about 10 feet of the tree; then, with a sharp increase in speed, his forequarters would drop toward the ground, his neck would arch, his head would come down, and he would lunge squarely into the tree, striking with all his speed and weight an instant before his forefeet touched the ground. It struck me that he seemed to be trying to show me what he would do to me if I would only come inside. If I remained motionless for any length of time, he would forget about me and wander off until I moved, then back he would dash until he was about 20 feet away, and then up he would rear on his hindlegs and sidle toward me with a walleyed stare down the side of his nose that would have been most discomfiting had there not been a strong fence between us.
He usually dropped to the ground a few feet short of striking the fence, although I knew that sometimes he didn't. I was trying to take a movie of this business by holding the camera a few feet out in front of me and guessing at having him in the frame as he advanced. This allowed me to stand 2 feet back from the fence in case he decided to make good his threat.
This he finally did, and with such force that the woven wire gave sufficiently under his weight to inflict a blow so painful to my thigh that I could hardly walk for almost an hour.
The day was very cold and windy, and at one time I was lying down close to the fence behind a mesquite thicket when he saw me and immediately and rapidly approached to within a foot of where I lay. Here he stood motionless, head down, staring fixedly at me with one eye about a foot from mine. After a few moments of this I became curious as to what his reactions might be if I slowly put my hand through the fence and took hold of his left horn.
He never moved a muscle until I began to push against his horn. He then arched his neck slightly and pushed against my pressure until I reversed the process by pulling instead of pushing on his horn. Rocking slowly backward and forward he pushed when I pushed and pulled when I pulled. This went on for possibly 10 minutes until I finally tired of it and stopped, whereupon he stood stock still for a moment, then leaned forward, proffering his horn for another round.
Later he approached me again while I was standing by the fence and once more we began a friendly tug of war. While this was in progress, Biologist Devan and a visitor came up, and on seeing that I had hold of one of the ram's horns, Devan called to me to hold on to him and we would examine his pelt to see if the wool could be seen at the base of the long winter-coat hair.
The ram became very uneasy as they approached, and by the time they reached me to offer assistance it was all I could do to hold onto his horns with both hands. As a matter of fact, it became all that two of us could do to hold him, especially as others came running up to see what his hide felt like.
When everyone had felt his winter coat, looked down his ears for ticks or excess wax, and administered such other indignities, he was released, and this time he left the vicinity as far and as fast as possible.
I didn't see him any more that day. The next morning when I went out to see him he eyed me suspiciously from 100 yards away and gave out that same warning blow through the nose with which Tight Curl had signaled the approach of strangers.
Here is a picture of a frustrated ram, in the absence of another ram, seeking an outlet for his drives through contact with a substitute species of animal. Evidently the conditions of the engagement were satisfactory up to the point of being detained against his will and subjected to disturbing, unfamiliar activity contributing nothing to his satisfaction.
Both his initial overtures and subsequent reaction would appear to reflect not only the fundamental nature of the ram but his personal experience as well. It might be argued that the entire incident reflected frustrations of captivity, but that it might not have been entirely so is indicated by an incident which occurred in the Red Amphitheater during the rutting season, October 29, 1957. It is included here in full as it was reported to us on that day by one of the participants, Geologist James McAllister. His field notes of that date are as follows:
Here again there seems to be no doubt that a ram, this one wild and uninhibited by captivity, was trying to communicate with a man. Repeated observations of parallel activity between two rams as a preliminary to a joust indicate the probability that this ram was extending the same invitation to McAllister.
It is not necessary to assume that the ram mistook the man for another ram; it is just as likely that he was simply seeking to fulfill his complete destiny as a ram, which includes the satisfaction of an urge to hurl himself into a headlong colliding contest with an opponentpreferably another ram, but lacking that, anything of a comparable size that moves, and lacking that, a tree, or a boulder, or the solid wall of a mountain, all of which we have recorded repeatedly.
"Clonking," the reverberating crash of a lone ram's horns against a solid object, serves as a communication in that it reaches the attention of other lone rams who often seem to accept it as a challenge and seek him out to offer contest. The action is voluntary, but whether it is intended as a communication is not known and so remains unclassified.
Stamping, smelling, and other actions were observed and reported by Park Naturalist Don Curry during Regional Biologist Lowell Sumner's second Death Valley bighorn survey in 1939 (Curry, 1939).
This is an excellent and enlightening report, but the purposes of this discussion would not be fully served were it not suggested that here again it is not necessary to assume that the ram mistook the geologist for another ram or that he was definitely impelled by "curiosity or pugnaciousness." Further, the report suggests that the ram's actions were an effort to determine the man's intentions toward him, that he decided the man "was harmless and of no interest to him." This is one interpretation but it also seems possible that the ram actually had hoped to engage in a fight, rather than to avoid one.
Exact interpretation becomes more probable when both the transmission and reception of a communication can be observed within the same frame of reference. A geologist's reception and reaction to a ram's challenge to a dual is not likely to throw much light on the ram's original intent or the content of his message because of the geologist's unfamiliarity with the medium of communication at hand, the bighorn "language."
To what degree a human understanding of this "language" could develop is not known, but comparison of the above observations with our repeated observations of opposing rams in their preliminaries to butting bouts in the field reveal too many striking similarities for coincidence.
We have, for example, many observations such as these notations at Nevares on August 27, 1957:
This was the first of many observations we were to make of the ram's use of the voice in challenging other rams, seen or unseen, to contest. Here too, was a ram "butting a sage bush," apparently stimulated to do so by the "challenge" of another ram.
On September 6 in The Notch above Raven Spring at 9:10 a.m., we heard two "blowings," and there was Tight Curl again.
He looked to the south, and, as he looked, his back arched in a spasm. Then he started rapidly toward the springs, and we saw then that Brahma and her lamb were feeding on the thistles at Round Pool.
They saw the ram coming and went on with their eating. Tight Curl gave Brahma the rush and got a cold shoulder in return. Then he, too, decided eating was a good idea and turned away and began to eat grass as vigorously as Brahma and her lamb were eating thistles.
So the "sounding," "bellowing," "blowing" may be a mating call as well as a challenge to battle.
By 11:20 that day we were hearing "clonks" steadily from high on Nevares Peak where Tight Curl had been chasing Brahma. She had eluded him and taken to the shade, and the "clonking" we heard was caused by him in his gestures of frustrationhe had a cliff backed up against a mountain and was "blasting" it again and again! He banged it 15 or 20 times before he appeared to give Brahma up and took off for greener pastures.
By 6:15 that evening, however, a younger ram, Low Brow, had drunk from Raven Spring and was leaving via The Saddle when we heard a "call" and at once spotted a big ram running northward from The Narrows. There was Tight Curl again, and ahead of him, dropping into Red Wall wash, was Brahma and her lamb. Low Brow heard Tight Curl's bellow and immediately set off at a gallop to over take them.
In general, the systems of communication so far discussed depend on auditory reception. No extensive tests or experiments have been conducted to determine the quality of bighorn hearing. What little evidence we have, however, indicates a healthy, normal condition at least equal in sensitivity to ours. We have no evidence in Death Valley sheep of hearing impairment by ticks, as has been suggested by observers in other areas.
Touch as a means of communication is difficult to evaluate because transmission and reception involve the same sense and are expressed by the same means under intimate circumstances where other factors may be at work. One of the commonest examples observed, the "nursing touch" of the mother ewe just before walking away from her nursing lamb, may combine the sense of smell with the sense of touch because the contact is made with the nose. The common nuzzling of mothers for their lambs probably involves both systems, as does the identification-recognition activity which follows the age class segregation of "babysitting."
The stiff foreleg upthrust of the ram used on other rams in the preliminary to jousting and on ewes as a persuasion to mating is apparently more of a signal than a blow because no retaliatory action, or shrinking, has been observed.
Movement seems to serve in both a voluntary and involuntary capacity as a medium of communication. The change of posture and manner of walking in the "traveling look" of the leader is probably involuntary but usually is responded to by the rest of the band by cessation of browsing and an assumption of more or less the same posture and manner as the leader. The same is apparently true of a fear reaction; the retreating band will stop if the leader stops and will watch her closely for signs of her evaluation of the danger. If she relaxes and appears to dismiss the danger, the others usually follow her example.
Running seems to serve as an involuntary communication when the reason for the running is not readily recognizable to the rest of the band. The four-footed, drumming bound, however, seems to be responded to by all as a voluntary warning of danger.
The gesture of appeasement is widespread among animals. The bird may crouch to the ground with quivering wings outspread, and the dog may roll on its back with its throat and belly exposed. The bighorn holds its horns back from the fighting position and down on both sides of its neck by thrusting its nose forward, turning its head on one side, and advancing slightly sideways with mincing, quick, short steps, and an almost ludicrously placating manner.
This gesture may be employed by one ram toward another during the joust and result in a temporary cessation of tilting. It is often used by a young ram meeting an older one on the trail; and it is almost universally employed by all rams in their initial approach to ewes. But probably the most striking use of it we have seen has been between ewes. On July 1 at Nevares two small bands met near the spring, and the ewes "stuck their noses far forward, crouched, and slunk" past each other.
Showing Rump Patch
Showing the rump patch is a purely involuntary signal of location to other animals. The bighorn cannot "flash" its rump patch in the manner described for the antelope, and we have no evidence to suggest its voluntary use in any way. However, the involuntary gleam of white in the sun may be of importance in getting rams and ewes together in the mating season.
Other specific forms of movement, touch, and so forth will be discussed under "Reproduction."
The vision of the bighorn has assumed legendary proportions. Eight-power binoculars are often used in comparison with it. We have no way of determining the quality of their vision beyond the most rudimentary experiments and observations. On January 19, 1956, while watching a band of eight about 1-1/2 miles away through 12x glasses, we determined by repeated trials that they could see a wave of the hand although they were barely discernible to the naked eye.
The fact that they have good vision is too well known to warrant general discussion. We have seen ample proof of this in distant vision and in the close vision associated with the incredible surefootedness of the species. (See "Play" and "Climbing Ability.") There is some question, however, involving their intermediate vision suggested by a seeming inability to recognize well-known objects within certain limits. Under "Response to Humans and Equipment" in this report, several instances of this seeming inability are recorded in detail. Much more work would be necessary to determine the cause of it.
Sense of Smell
The sense of smell of the bighorn has been variously described in degree from acute to nonexistent. Acute can be a relative degree; compared with the average human sense of smell it is acute; compared with the average canine sense of smell, it is not. On the other hand, no evidence points to its nonexistence; the lack of reaction to the transmission of human scent on a close wind does not necessarily indicate a lack of reception of the scent. Without exception, the bands involved in our prolonged observations have become indifferent to indications of our presence, whether by sight, sound, or scent, as long as acceptable conditions obtained. (See "Response to Humans and Equipment.")
The urination of a ewe and what seems to be some sort of olfactory analysis of it by a ram apparently plays a part in establishing the presence or imminence of oestrus in the mating cycle. The suggestion that the closely related sense of taste is also employed here has been considered.
That their sense of smell is developed enough for tracking of other sheep to a limited degree has been indicated repeatedly but not conclusively. For example, we have seen a lone ewe wander to certain outstanding but unfrequented points in the area to be traced (apparently) to the same spots by a ram an hour after she had disappeared. The route followed was not along an established trail and was traversed by the ram with head down and nose to the ground, much like a dog on the scent of a rabbit.
Lambs frequently will tarry at a spring for some time after the mother has sought shade out of sight on the mountainside. Occasionally the lamb has followed a most circuitous route, around the point of ridges, across boulder-strewn washes, turning back and leaping from the same rock to rock that its mother did and eventually finding her in her shaded resting place.
This type of behavior has all the appearance of the utilization of the sense of smell. What confuses the picture is the fact that they do not always follow this pattern. Sometimes a lamb will, on realizing that its mother is out of sight, give way to panic and run back and forth from one high point to another, employing only its eyesight and hearing in its effort to find its mother. Lambs lost during the rut-run have never been observed using their sense of smell to locate their mothers. Nor do adult sheep separated from the band seem to employ it successfully, apparently relying entirely on vision for the final solution.
According to Einarsen (1948), sheep have interdigital scent glands, but we have no data on their use, either on a voluntary or involuntary basis.
The establishment and maintenance of "signpost" areas seems to be common practice among the rams and this custom sometimes is casually observed by the ewes and lambs. We have observed two types of bighorn "signposts" in Death Valley, the commonest being "urination." How the first ram decided to urinate in a certain spot is not known, but once he has, it appears to be common practice for every other ram passing that way to stop, sniff elaborately, advance a step or two, and urinate at length in or near the same spot. The second in popularity seems to be the "bush-beating signpost," which, when once chosen, may eventually end in the complete destruction of the shrub or even the tree thus favored.
Almost all phases of communication will be further developed in the succeeding discussions of this report.