Report on Heat Stress in Working Llamas - 1991
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.
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.
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.
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.
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"
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.
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
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
Existing Lamoid-Specific Body Temperature
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
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
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
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
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
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
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
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
"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
- 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 °+
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.
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,
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.
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,
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
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: firstname.lastname@example.org
Copyright © 1992 by Gwen Ingram. All
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