Body Temperatures of Malaysian Rain Forest Mammals 
Robert L. Rudd 1 
ABSTRACT: Rectal temperatures of 23 species of Malaysian mammals were re- 
corded during the course of an intensive mark-recapture program in rain forest. 
Repeated capture allowed repetitive readings for many individuals over several 
months. Individual variations and group comparisons are tabulated and discussed. 
Comparisons are made with body temperatures of arctic and temperate mammals. 
It was concluded that mean temperature for all tropical mammals described in this 
study was lower than in higher latitude forms, but that comparisons, to be mean- 
ingful, should be restricted to equivalent taxonomic groups. 
Body temperatures of tropical mammals are 
poorly known. Most published records refer to 
single individuals of exotic groups not having 
counterparts in more northerly latitudes. Often 
temperature data are taken from animals held 
in captivity for long periods (particularly in 
zoos), and the reliability of such data from ani- 
mals living in captive environments may be 
questioned. This paper reports the temperatures 
of 23 species of Malaysian mammals of four 
orders, many individuals of which were repeat- 
edly captured and on which multiple readings 
were possible (Table 1). 
Rodbard (1950) has suggested that the mean 
body temperature of mammals weighing less 
than 1 kg bears a simple and direct proportion 
to body weight. In an effective refutation, Mor- 
rison and Ryser (1952) point to an essentially 
constant mean body temperature in most mam- 
mals. These authors, along with Scholander et 
al. (1950) and Wislocki and Enders (1935), 
agree however that certain groups of mammals 
(notably the monotremes, marsupials, eden- 
tates, and chiropterans) either maintain a con- 
sistently low body temperature or show a great 
temperature lability. Moreover, but without sup- 
porting data, Morrison and Ryser (1952) point 
out the possibility that within certain selected 
homogeneous groups of good regulators body 
temperatures may be significantly different from 
the general mammalian norm of 37.8° C. The 
present paper illustrates such a condition, par- 
ticularly in the comparisons of 11 species of 
1 Department of Zoology, University of California, 
Davis. Manuscript received September 8, 1965. 
sympatric murid rodents and of 4 species of 
sciurid rodents. Illustrated as well is individual 
variation in body temperatures and to a lesser 
extent behavioral relationships to temperature. 
MATERIALS AND METHODS 
All data derive from a single locality — Ulu 
Gombak, 20th mile Pahang Road, y 2 m ^ e NE 
Genting Simpah Youth Hostel, State of Selan- 
gor, Malaysia. The elevation at this location is 
about 1,900 ft. The climate in Malaya (about 
3° N) is remarkably constant; the photoperiod 
varies only about 20 minutes over a year. Hu- 
midity and rainfall are generally high, although 
both daily and "seasonal” variations occur. 
With the exception of the bats and of the 
single bamboo rat all mammals were taken in 
an area of 14 acres in primary and old secon- 
dary rain forest marked off in a trapping grid at 
intervals of 50 ft. For the entire trapping 
period (1 November 1963—22 May 1964) 225 
live traps were maintained on the ground. In 
trees at varying heights small platforms were 
built on which traps were maintained, of which 
50 were kept throughout the period and another 
25 were added about halfway through. Nor- 
mally traps were open four nights a week and 
were baited with coconut meat and banana. 
Trapped animals were brought each morning to 
a small shelter on the edge of the grid where 
temperature and other data were taken. Animals 
were then toe-clipped for individual identifi- 
cation, if not previously marked, and were re- 
turned to the station of capture for release. 
A total of 29,189 trap nights resulted in the 
472 
