Comp. Biochem. Physiol., 1972, Vol. 43A, pp. 219 to 222. Pergamon Press. Printed in Great Britain
SHORT COMMUNICATION
DOES THE DEVIL SWEAT ?
A. J. HULBERT 1 and R. W. ROSE 2
'School of Zoology, University of New South Wales, Kensington, Australia,
2033; and 2 Department of Zoology, University of Tasmania, Hobart, Australia,
7000
(Received 1 February 1972)
Abstract—1. The cutaneous water loss, respiratory rate and rectal temperature
of the Tasmanian devil (Sarcophilus harrisi) was measured before and during
heat stress.
2. There was a sevenfold increase in respiratory rate under heat stress indicating panting, whilst cutaneous water loss increased by only 50 per cent and
remained below levels considered indicative of thermal sweating.
3. No marsupials are now known to use sweating as a thermoregulatory
response when at rest. This response appears to be restricted to the primates
and some ungulates.
INTRODUCTION
ROBINSON & MORRISON (1957), in their extensive survey of the responses of
Australian mammals to heat, reported that the Tasmanian devil (Sarcophilus
harrisi) must sweat when exposed to a high ambient temperature. This oftencited report is interesting for two reasons. The first is that the Tasmanian devil is
a temperate zone dasyurid marsupial and while Hardy (1947) has shown that a
large number of marsupials possess epitrichial (apocrine) sweat glands it is the
only marsupial reported to sweat at rest under an external heat load. The other
point is that the adult Tasmanian devil weighs 5–8 kg and the interest here lies in
the fact that among the non-primates it seems that sweating is of major thermoregulatory importance only in the large (> 50 kg) ungulates (Robertshaw &
Taylor, 1969).
The presence of sweating was assumed because the Tasmanian devil did not
show any significant increase in respiratory rate when exposed to 40°C but was
able to maintain a constant body temperature. The control (pre-exposure) body
temperature and respiratory rate both appear to be quite high and were probably
not indicative of true resting levels. For this reason it was decided to measure
actual cutaneous evaporation as well as body temperature and respiratory rate of
the Tasmanian devil at rest both with and without heat stress.
MATERIALS AND METHODS
The present work was carried out on two adult animals. The Tasmanian devil is a
dasyurid marsupial weighing approximately 5—8 kg and is carnivorous, solitary and
nocturnal.
219
A. J. HULBERT AND R. W. ROSE
220
Cutaneous water loss was measured using two desiccant capsules. The capsules contained Drierite (CaSO 4) in their outside chamber and were placed on either side of the
animal on a shaved area of the flank, just caudal to the diaphragm. Both capsules were
sealed and weighed before and after each 20-min run. The weight gained during this time
was the water lost from the skin underlying the capsule and was expressed in g H 2O/m2
per hr.
Respiratory rate was determined at 5-min intervals by counting flank movements with a
stopwatch. Rectal temperature was measured on only one animal with a standardized
thermometer inserted to a depth of 10 cm immediately after each run. There was minimal
disturbance to this animal.
To prevent excessive movement the animals were kept in a narrow box with a straw
floor. They were allowed 12-2 hr at each temperature before any measurements were made.
RESULTS AND DISCUSSION
All three parameters increased under an external heat load (Table 1). The
relative increases were, however, quite different, there was a 720 per cent increase
in respiratory rate while the increase in cutaneous water loss was only 50 per cent.
TABLE 1-BODY TEMPERATURE, RESPIRATORY RATE AND CUTANEOUS EVAPORATION OF
THE TASMANIAN DEVIL (S. harrisi) IN RESPONSE TO HEAT STRESS
Control
Heat stress
Ambient
temperature (°C)
19-21°C
39-41°C
Rectal
temperature (°C)
34 5°C
39 0°C
20 ± 2* (n = 7)
144 ± 27 (n = 7)
.
.
24 3 ± 5 6 (n = 2)
36 8 ± 6 4 (n = 3)
Respiratory
1
rate (min- )
Cutaneous
water loss
(g H 2O/m2 per hr)
.
.
.
.
* Mean ± S.E.M.
The resting body temperature of 34 . 5°C is lower than that reported by MacMillen & Nelson (1969) for the Tasmanian devil but similar to values reported for
other marsupials (Dawson & Hulbert, 1970). In the heat stress situation body
temperature rose to 39 . 0°C, a level similar to that reported for the wallaby, Macropus eugenii, at the same ambient temperature (Dawson et al., 1969; Dawson &
Rose, 1970). This increase has the important effect of reducing the gradient between the animal and its surroundings and thus dramatically lessening inward
heat flow.
The sevenfold change in respiratory rate under heat stress conditions indicates
panting. There was a gradual increase in respiratory rate during heat stress with
periods of rapid shallow panting interspersed with deeper breathing.
DOES THE DEVIL SWEAT ?
221
Cutaneous evaporation increased under heat stress but even at 40°C the level
was well below the value of 50 g H 2O/m2 per hr which Allen & Bligh (1969)
considered to be the minimum value indicative of thermal sweating in a variety of
ungulates. Our value is not much above the 11–33 g/m 2 per hr found in humans
with congenital absence of sweat glands (Kuno, 1934). The increase in cutaneous
water loss under heat stress is probably largely due to an increased skin temperature. A greater skin temperature results in a greater water vapour pressure at the
skin surface and thus an increased gradient for passive water loss.
An important point is that both respiratory rate and body temperature in the
non-stress state are much lower than the corresponding values (116 min –1 and
37 . 6°C respectively) reported by Robinson & Morrison (1957). It seems that the
Tasmanian devil examined by these authors was already under a heat load (maybe
due to exercise and struggling during handling) and was panting in response.
"
No, the devil does not sweat " . It appears that the Tasmanian devil's principal
response to heat is panting. There is now no marsupial that is known to sweat
when at rest under a high external heat load. This thermoregulatory response
appears to be of prime importance in only two mammalian groups, the primates
and ungulates. Among the ungulates only animals greater than about 50 kg
depend primarily on sweating as their heat loss mechanism (Robertshaw & Taylor,
1969) but in the primates body size seems to have little effect as even the small
squirrel monkey (approximately 1 kg in weight) uses sweating as its main heat loss
mechanism in response to high ambient temperature (Stitt & Hardy, 1971).
Acknowledgements—We should like to thank Dr. Eric Guiler of the University of
Tasmania for the loan of the two Tasmanian devils, and R. Mawbey and T. Sward for
assistance in handling the animals. This work was supported by a C.S.I.R.O. post-graduate
studentship to A. J. H.
REFERENCES
ALLEN T. E. & BLIGH J. (1969) A comparative study of the temporal patterns of cutaneous
water vapour loss of domesticated animals with epitrichial sweat glands. Comp. Biochem.
Physiol. 31, 347–363.
DAWSON T. J., DENNY M. J. S. & HULBERT A. J. (1969) Thermal balance of the macropodid
marsupial Macropus eugenii Desmarest. Comp. Biochem. Physiol. 31, 645-653.
DAWSON T. J. & HULBERT A. J. (1970) Standard metabolism, body temperature, and
surface areas of Australian marsupials. Am.J. Physiol. 218, 1233-1238.
DAWSON T. J. & RosE R. W. (1970) Influence of the respiratory response to moderate and
severe heat on the blood gas values of a macropodid marsupial ( Macropus eugenii).
Comp. Biochem. Physiol. 37, 59–66.
HARDY M. H. (1947) The group arrangement of hair follicles in the mammalian skin.
Proc. R. Soc. Qld 58, 125-155.
KuNO Y. (1934) Human perspiration. Thomas, Springfield, Illinois.
MACMILLEN R. E. & NELSON J. E. (1969) Bioenergetics and body size in dasyurid marsupials. Am.'. Physiol. 217, 1246-1251.
ROBERTSHAW D. & TAYLOR C. R. (1969) A comparison of sweat gland activity in eight
species of East African bovids. Y. Physiol., Lond. 203, 135-143.
ROBINSON K. W. & MORRISON P. R. (1957) The reaction to hot atmospheres of various
species of Australian marsupial and placental animals. Y. cell. comp. Physiol. 49, 455-478.
222
A. J. HULBERT AND R. W. ROSE
STITT J. T. & HARDY J. D. (1971) Thermoregulation in the squirrel monkey (Saimir
sciureus). J. appl. Physiol. 31, 48—54.
Key Word Index—Perspiration; sweating; Marsupials; temperature control; Sarcophilus harrisi.