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Preliminary Report on Heat Stress in Working Llamas - 1991

Gwen Ingram


Heat-stress research is one part of our ongoing effort to establish performance parameters for pack llamas. This year, we conducted heat-stress research in several phases.

First, we researched normal body temperature fluctuation, its causes, and factors interfering with body cooling for all species. Although llamas do not react exactly like other species, some idea of what is to be expected and normal precautions a responsible person takes with other working species is pertinent.

Second, we had to establish normal temperatures and fluctuations for nonexerting and exerting classic-woolled llamas (llamas with short neck wool, hair only -- no wool -- on the legs, and guard hair fibers in the coat) so that meaningful data could later be collected to identify, quantify and confirm variables.

Third, we recorded pertinent temperatures and fluctuations for several adult llamas before and after varied treatments intended to reduce heat retention after exertion. We have added information concerning actual heat stress occurrences (1991 only), but only when data were actually taken. This year, we focused on studies of preventive measures; next year, we plan to study remedial measures.

The eight-member study group consisted of both castrated and intact adult male llamas and an adult intact male guanaco for comparison. Young llamas were not used because juveniles of any species have higher body temperatures and greater fluctuations. Females were not used because pregnancy and estrus cycles are known to affect rectal temperature. With the relatively small number of llamas available to us for study, we try to repeat studies several times to reduce the chances of unusual llamas or circumstances changing the outcome, and to allow each llama to serve as his own "control" whenever possible.

All research is influenced to some extent by the researcher(s), and so repetition of studies by another party is always desirable before accepting any conclusions as absolute. We would be glad to assist anyone who is interested in participating in or repeating our research.

Jim Krowka deserves special recognition for repeated personal exertion to facilitate data collection.

Normal Body Temperatures and Normal Fluctuations

In published reports of normal temperature ranges for adult llamas, the low-normal temperatures range from 99 °F to 99.5 °F, and the high normal temperatures from 101.5 °F to 102 °F. Temperatures in our study llamas ranged from 98.8° to 104.2° under a variety of conditions.

According to all our sources, body temperature fluctuates diurnally (throughout the day) in all species of mammals. The normal amount of fluctuation is determined by the animal's body mass: Larger animals experience less fluctuation than smaller animals (Reibel).

Data collected during our studies indicate that llamas experience diurnal temperature fluctuations between 1 °F and 2 °F, which is within the normal range for other animals of similar size. This implies that "normally" active (not working or stressed) classic-type llamas are quite capable of regulating their body temperature satisfactorily in comparison with other mammals.

In all mammals, normal body temperatures and normal temperature fluctuations also vary seasonally. Acceptable and normal temperatures and fluctuation ranges are higher in the summer and lower in the winter.

Data collected during our studies indicate that llamas also experience this phenomenon. Each individual experienced normal resting temperatures about 1°F less in winter. Camels normally experience an average of almost 4 °F diurnal and seasonal temperature fluctuation, which is definitely dissimilar from lamoids (Gauthier-Pilters/Dagg).

In our study group, the heat-resistant llamas averaged morning and cool-weather resting temperatures from 99.6 °F to 99.8 °F, with both diurnal and seasonal fluctuations of 1-1.5 °F. Most of the less heat-resistant llamas averaged about 1 °F higher in the mornings and during cooler weather, and diurnal fluctuations were closer to 2 °F.

A final important question to answer is, What exactly does constitute a significant difference in llama body temperature? At this point, a 0.1-0.2 °F variance seems to have little significance; one published article on heat stress in llamas indirectly, through various references, indicates that 0.4 °F difference or greater should probably be considered "significant" (Evans).


Existing Lamoid-Specific Body Temperature Studies

We found only one account of a lamoid body temperature study, involving a male and a female guanaco. To summarize, when water was withheld from a female guanaco for five days, her body temperature remained "within a normal range." When water was withheld from a male guanaco for four days and at an ambient temperature of up to 84°, he experienced "no elevation in body temperature." Immediately after the male's primary dehydration study, he was subjected to an ambient temperature of 113° for six hours. His body temperature elevated 1.8°, and at this point, his respiratory rate increased "two- or three-fold." It was postulated that the cooling effect of the increased respiratory rate was directly responsible for allowing the guanaco to resist greater body temperature increase (Fowler). (These studies should be considered primarily in relation to resting temperatures and not to body temperature under exertion.)

Published information on the heat tolerance of llamas as a species consists of a number of anecdotal accounts including reports of assumed, but unverified, heat stress incidents. Most references conclude either that some individuals are abnormally prone to heat stress when compared with their peers, or that llamas as a species are unusually prone to heat stress. When the data from the guanaco study referenced above are considered, the question of why llamas also do not show great heat and dehydration tolerance can be raised. Have some unobservable genetic traits governing heat dispersion been lost through breeding choices when humans have domesticated and selected llamas to suit their own needs? Or are llamas less heat tolerant only because of the obvious physical differences between the two "species" (or as they should more properly be referred to, breeds )?


Actions Increasing Temperature

In all species, exertion will raise body temperature. Exhaustion and stroke from overexertion alone is common, and the likelihood of heat disorders increases in warm environments. This is true of relatively naked species such as humans, horses, and short-haired dogs and cannot be considered a danger exclusive to llamas.

Also true of all species, recovery time (the time it takes for a normal temperature to be achieved after the temperature-elevating activity has ceased) is increased if exertion is ceased without continuing movement to dissipate heat from muscle tissue. In cases of an extreme temperature increase, cessation of movement can result in continuing heat build-up, rather than cooling (Mackay-Smith). Data we took on one adult llama pushed to high body temperatures through exertion during hot weather suggest that llamas also experience a continued temperature rise if prevented from moving. After extreme exertion, the study llama's temperature was 103.4 °F. He was turned out to pasture and allowed the freedom to act as he wished. The llama wandered head down, aimlessly and continually. His temperature fell to 102.6 °F, a decline of 0.8 °F, in 10 minutes and had reached his normal temperature for that time of day and season (99.8°) when checked three hours later. On another occasion, the same llama's temperature was a very comparable 103.6° after extreme exertion in hot weather. He was tethered, and his body temperature climbed to 104.2° in 10 minutes, an increase of 0.6 °F, at which point he was cooled immediately. The 1.4° difference between a decline of 0.8° and an increase of 0.6° within 10 minutes is highly significant.

All studied data indicate that all animals who have experienced even "mild" heat stress or heat stroke are unusually prone to heat stress for several days afterward. We recorded this phenomenon in two llamas that experienced moderate heat stress. One llama did not recover a fully normal resting temperature for 48 hours. The second recorded a subnormal temperature after 12 hours, but showed an extremely fast and abnormal temperature increase during exertion for the following two days.

Dehydration increases any animal's susceptibility to heat stress. Although the aforementioned study indicates that guanacos resist heat even when dehydrated, the study also clearly shows that dehydration compromised the male guanaco's cooling ability. Anecdotal evidence indicates that llamas who are comfortable drinking water on the trail and who are provided with water throughout the day (natural and packed sources) show a noticeable increase in willingness and stamina. This phenomenon merits further study.

Exposure to full sun (solar heat), with or without other factors, is a primary contributor to body-temperature increase in all other species. The most heat-resistant llama in our study experienced mild heat stress only after his movement was restricted after packing 65 miles over the course of three days in full sun. Heat absorption is higher in dark-colored objects, though heat dissipation is unaffected by color, and so exposure to full sun could theoretically increase the body temperature of dark-colored llamas more than that of white llamas. However, the data obtained from this study group showed absolutely no correlation between wool color and either a higher normal or higher exertional body temperature. In fact, all of the "hottest" llamas in the study group were white llamas. One was obese, a second was overweight and densely-wooled, and a third had no mitigating factors other than experiencing higher-than-normal temperatures after exertion. This implies that even if wool color is actually a contributor to temperature increase, the effect is very minimal, especially when compared with the effects produced by obesity and wool type.

Stress can cause temperature elevation and reduces any animal's ability to regulate body functions including temperature. The second study llama that experienced mild heat stress also showed symptoms of mental stress. Although his temperature (104 °F) was not critically hot, his actions (staggering, collapse, extreme disorientation) were comparable with those reported in 106-108° heat stressing. The combination of heat-building factors and mental stress had affected this particular llama similarly in the past.

It is well known that llamas have a unique behavior that increases body temperature: assuming the "kush" position. Llamas purposely employ this strategy when the environmental temperature drops. Unfortunately, llamas also kush when exhausted. An unburdened and mentally alert llama assumes one of a number of altered positions to allow better airflow to the haired portions of the body. However, kushing often results in heat retention and increase when the llama is exhausted, has been exerting, is experiencing other heat-building factors, or is already mentally affected by heat stress.


Actions Decreasing Temperature

Sweating is a common means of reducing temperature, but not all species sweat from their entire body surface: dogs, notably, have limited sweating abilities. A llama does have sweat glands over his entire body, including the wooled areas and foot pads. The llama's sweat glands are more dense in the hair areas and less dense in the areas covered by wool (Fowler). Anecdotal reports indicate that the neck may also have more sweat glands than the body proper.

Increasing the rate of respiration also dissipates heat. Data we collected indicate that llamas also employ this strategy. Some individuals increased their respiration rate more readily than others; data showed some correlation between these individuals and improved recovery rates and heat resistance. This correlation is supported by the guanaco study cited above.

Avoidance of exposure to solar heat prevents temperature increases and can allow heat to dissipate from a warmed individual. Again, our data confirm that this applies to llamas also. Anecdotal accounts state that some individual llamas do not readily remove themselves from full sun. Exposing the hair areas by lying in lateral recumbency (on the side) may be more beneficial than not, but certainly sternal recumbency (kushed) in full sun is of no advantage to the llama if shade is available. Our personal experience indicates that llamas experiencing mild heat stress may not move out of full sun because of confusion resulting from that heat stress.

Some species "pant" to dissipate heat; this requires physiology that allows breathing through the mouth. Llamas can breathe through the mouth and do "pant," alternatively referred to as "mouth-breathing," "huffing," and "open-mouth breathing." Popular literature on llamas generally equates huffing with heat stress. In fact, our data conclusively show that there is no correlation between the onset of huffing and an increase in temperature. This suggests that llamas do dissipate heat by huffing and that huffing should be encouraged as a heat stress preventative.


Characteristics Increasing Temperature

In all mammals, body fat is the greatest nonbehavioral and nonenvironmental factor in increased body temperature. Fat alone retains normal metabolic heat. Fat also retains heat received from other heat-producing sources: exertion, sun, and higher environmental temperature. Fat also contributes to dehydration during exertion: Great amounts of water are required to metabolize fat. The data we collected show that fat llamas definitely have higher resting temperatures than their fit counterparts.

Body fiber also retains heat. The only working animals with amounts of body fiber similar to that of llamas are some breeds of dogs. Dogs that generally work in warm climates have short, coarse hair; dogs with longer, denser, and finer hair generally originated in cooler climates. However, another important point to note is that lamoids are the only species - working or otherwise - that have two distinct, differently-fibered body regions, with a large, very short-fibered region apparently existing solely for the purpose of body-temperature regulation. Still, wool is considered in popular literature to be the primary or even the only cause of heat stress in llamas. This year, the bulk of our temperature and heat-stress studies focused on this aspect.


Studies - Temperature Recovery Time

Examining the time elapsed between exertion-induced temperature increase and recovery of normal temperature (for individual, time of day and season) is pertinent to preventing heat stress in llamas in several ways. First, once normal and acceptable ranges for temperature-recovery (T-R) times have been established, deviances indicating potential for overheating can be treated before clinical signs of heat stress even occur. This was highly important for protection of the individual llamas participating in the studies.

Second, establishing normal T-R times helps to identify individuals who excel in minimizing both increase and recovery times; to isolate common features that contribute to superior temperature control; and to isolate features that do not significantly affect temperature control. This can assist packers in choosing better pack llamas, and for pack llama breeders, this can eventually lead (through selective breeding) to fewer pack llamas prone to heat stress, and possibly even recovery of the demonstrated heat resistance of the guanaco, if that has indeed been lost in the llama.

Third, T-R times can identify individuals who do not consistently achieve safe increases and recovery times and help to isolate common features that contribute to inferior temperature control. This helps us avoid heat stress in llamas by choosing suitable individuals whenever possible and alerts us to those llamas needing precautionary measures. It also aids in removing any inherited factors from the gene pool.

Finally, we wanted to identify and evaluate all means to normalize temperature increases and recovery times in inferior llamas without compromising the health of those same llamas under both normal pasture conditions and when used for backcountry packing. This helps us to maximize the use of poorer animals, and may also further the performance of better llamas as well.


Normal Temperature-Recovery Times

One of our goals this year was to begin to establish normal recovery times for llamas. The resting and exertion temperatures of horses are surprisingly similar to llamas, and a drop of 1 °F every 10-15 minutes after ceasing exertion is considered a normal range (Hillenbrand/Lang). In our study, Jim took a portion of the study llamas running on several occasions to increase their temperature. We then allowed the llamas to recover under conditions simulating those generally available on the trail. The recovery of the llama currently considered most heat resistant did match the rate of the horse.

One llama did not experience an exertion temperature significantly exceeding his normal afternoon temperature and so did not have a "recovery time." The llamas considered to have inferior resistance to heat stress did not experience any significant decline for 20-40 minutes and then registered a "sudden" 1 °F decline 30-50 minutes after ceasing exertion. The results for these llamas did not alter whether environmental temperature was high (90 °F) or low (48 °F).

A goal for future study is to gather controlled data on how postexertion behavior (kushing, standing, and walking) affects recovery times.


Superior Temperature-Recovery Times; Common Features

As already reported above, color did not play a measurable part in temperature recovery rates; in fact, the best two performers were a black and a dilute original type, and the worst two, white. One of the conditions during the recovery period was keeping the llama in shade, rather than full sun, as would normally be done on the trail whenever possible. We plan to repeat the study with the recovery period in full sun to see if wool color will then play a role.

Wool length had no effect on heat tolerance in the llamas studied. The group's body wool length was essentially uniformly short, ranging between 2.5" and 4". Their neck wool also fell into the "classic" type: One llama's neck wool measured 2"; a male guanaco (for comparison) measured 1"; all others measured 1.5". The two llamas with the best temperature recovery times had body wool lengths of 3.5" and 4" and 1.5" neck wool. Guard hair lengths at mid-body in the study group ranged from 6" to 9"; a male guanaco (for comparison) measured 4.5". As with wool length, the guard hair length did not show any correlation to heat tolerance.

A very surprising tendency in the data was that the castrated llamas seemed to have lower resting temperatures in general. Two llamas had slightly lower resting temperatures after castration, but other factors may also have been involved. The study group is too small to draw any conclusion in this respect, and so no temperature-recovery studies were set up to evaluate the effect of castration, if any, on recovery times. This may merit further study in a large group of intacts and castrates of similar type and condition.


Inferior Temperature-Recovery Times; Common Features

During initial studies, two factors emerged as probable contributors to inferior temperature recovery times. The first is wool density. A coat with both a high percentage and density of wool fibers creates a greater insulating mass than does a normal, high-guard-hair­content coat. Initial studies indicate that densely-wooled llamas have higher resting temperatures as well as inferior recovery times and a predisposition to heat stress.

A condition creating an artificially high wool density is accumulation of dead wool felted to live wool fibers. Shearing does not reduce this artificial density increase. Combing out does return the llama's coat to its own normal density but does not further reduce density when the coat has a naturally high-wool-fiber content. Initial shearing is highly beneficial in facilitating rapid and complete combing-out. Combing out removes dead wool fibers, resulting in a coat through which a comb can be pulled freely all the way to skin level. Brushing, brushing out, and surface combing are not techniques comparable to combing out.

A second factor apparently contributing to inferior temperature recovery times is a type of wool distribution that can be referred to as "wool closure." The wool of some llamas "closes" completely around the chest area and encroaches on what is normally the hair area on the legs. Wool closure is common to alpacas and appears in "true" woolly llamas as well. However, short-wooled llamas with woolly llamas in their genetic background may also exhibit this trait. Llamas with greater "wool closure" also have higher resting temperatures as well as inferior recovery times and a predisposition to heat stress. Future studies will address artificially changing such a llama's wool distribution through spot-shearing.


Methods Tested to Alter Resting Temperature and Temperature Recovery

Shearing allows comparison of the effects of longer with shorter wool on the same llama. Data were taken during hot weather before and after shearing a classic-wooled llama with normal resting temperatures and inferior temperature recovery times - with surprising results. The initial intention was to shear a llama to 3-4", the normal length for a classic-wooled llama and within the range of the unshorn llamas in the studies. However, the wool on the llama to be shorn was matted very close to the skin, and the matts proved impossible to cut through, so we sheared the llama at 1-2" immediately under the matts. After we allowed ample time (several days) for the llama to dissipate latent abnormal heat after shearing, the llama's resting temperature decreased by 0.2 °F (insignificant). After exertion, the llama's temperature was also only 0.2 °F lower, and recovery time remained unacceptably long.

Combing out allows comparison of greater with lesser wool density on the same llama. We took data in cool weather at various intervals after combing classic-wooled llamas with varying resting temperatures and temperature-recovery times. Combing out appeared to affect afternoon resting temperatures by up to 1 °F. One llama with good temperature recovery times lowered exertion temperatures by an average of 0.5 °F. These effects lasted for an average of several weeks after combing out.

Future studies will include hot-weather combing data and, for comparison, combed-only data on the llama that was shorn this year.


Diagnosing Heat Stress in Llamas

We tried numerous methods of evaluation to diagnose heat stress in llamas. We found that, as in other species, the only reliable and accurate method of diagnosis is use of a rectal thermometer combined with data on the individual's normal resting temperatures.

"Huffing" (open-mouthed breathing) is commonly held to be a reliable indicator of heat stress. Temperature data taken on a llama when he was "huffing" was normal. Both llamas who heat-stressed this year did not "huff." Huffing appears to be a highly unreliable (and an unsafe) method of body-temperature evaluation.

Skin temperature, evaluated by touch on the llama's head and chest, showed no correlation to rectal temperature. The area between the llama's flank and stomach radiated extreme heat in both heat-stressed llamas and might be considered one indicator that taking an immediate thermometer reading would be in order.

We could not rely on the presence or absence of sweating as an indicator of heat stress. Perspiration normally occurs in exerting llamas with normal body temperatures and can be felt on the chest, belly, and the short neck wool. In our study, both mildly heat-stressed llamas were sweating. However, dehydration reduces the llama's ability to sweat and results in temperature increase, and cessation of sweating is reported to accompany more severe heat stress.

Apparent surface wool temperature is the result of exposure to sun, not of internal body temperature. Continued exposure to sun may eventually result in increased body temperature, but the apparent surface wool temperature will be hot to the touch for a long period prior to actual temperature increase. We observed that the surfaces facing the sun were hot, but the shaded surfaces -- evaluated simultaneously -- were quite cool.


Suggested Temperature Evaluation Guidelines

"Huffing," increased skin temperature, and perspiration are all normal, heat-dispersing actions and must be expected in llamas and other animals when activity, environment, behavior, or a combination result in the need to dissipate heat. Absence of heat-dispersing actions is more likely to cause (and therefore accompany) heat stress. It is extremely important to recognize that a thermometer should be used to diagnose heat stress. From the data obtained in this year's studies, I have developed the following guidelines for evaluating my primary pack llama's body temperature. Whether they are satisfactory guidelines for a majority of llamas remains to be seen.

  • Normal AM/cool weather: 99.8 °
  • normal PM/warm weather: 100.8 °
  • normal when exerting, warm-weather : up to 101.8 °
  • reduce demands (slower pace, more rest/water): 102.2 °-102.8 ° (at this point it would be prudent to find out where the nearest water/cooling source is located and consider altering course, if necessary, to get there)
  • cease activity (except unburdened "cooling out"): 103 °+
  • treat llama for beginning stage heat stress: 104 °+ and rising
  • EMERGENCY: 106 °+


Future Studies

We have not addressed all questions involving heat stress in llamas. Future studies we plan to undertake (other than those mentioned above) include evaluation of the effects of dehydration on exerting llamas; evaluation of at least one other preventive heat-reduction measure; and evaluation of various remedial heat-reduction measures including methods available at home and on the trail. This will be a slow process, but one we feel is very worthwhile.

References Cited

Evans, C. Norman DVM. "Heat Stress," Llamas July/August 1991, 102-106.

Gauthier-Pilters, Hilde and Anne Innis Dagg. The Camel-Its Evolution, Ecology, Behavior and Relationship to Man. Chicago, Illinios: The University of Chicago Press, 1981.

Fowler, Murray E. Medicine and Surgery of South American Camelids. Ames, Iowa: Iowa State University Press, 1989.

Hillenbrand, Laura and Anne Wakeman Lang. "Fever," Equus June 1991, 50-54, 105-107.

Mackay-Smith, Matthew. "Warm-Up and Warm-Down," Equus July 1991, 52-56, 112-116.

Reibel, Jaime Issac. Caring for Livestock. New York, New York: Arco Publishing, 1984.


Additional References

Baum, Karen H. "Heat Stress in Llamas," Llama Banner June/July 1991, 104-105.

Burt,Sandi. Llamas-An Introduction to Care, Training and Handling. Loveland, Colorado: Alpine Publications, 1991.

Daugherty, Stannlynn. Packing with Llamas. Ashland, Oregon: Juniper Ridge Press, 1989.

Du Teil, Karen Kopp. "Summer Survival Tips," Equus August 1989, 51-54, 93-95.

Freeman, Myra. Heat Stress: Prevention, Management and Treatment in Llamas. N.p, 1988.

Fowler, Murray E. "Thermal Stress In Llamas," 3L Llama May/June 1985, 17-20.

Gatewood, Donna M. "Toxic and Matabolic Diseases of North American Llamas," Llama Banner October/November 1989, 71.

Hoffman, Clare and Ingrid Asmus. Caring for Llamas: A Health and Management Guide. Livermore, Colorado: Rocky Mountain Llama Association, 1989.

______, "Calm, Cool and Collected, " Equus August 1990, 93.

This report originally appeared in The Backcountry Llama, June 1992, and appears here with the permission of the author. Reproduction in any form is prohibited without the express written consent of the author. Address permission requests to: llamaprints@att.net

Copyright © 1992 by Gwen Ingram. All rights reserved.

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