Notes 
369 
NOTES 
The Body Temperature of Wild Rattus spp. on the Island of Hawaii 
During the course of a recent study concern- 
ing methods for the control of sylvatic plague 
in the Hawaiian Islands (Kartman and Loner- 
gan, World Health Organ. Bui., in press), data 
were obtained on body temperatures of rats 
inhabiting Kaunamano Gulch in the Hamakua 
District of the Island of Hawaii. The rats con- 
cerned, Rattus norvegicus , R. rattus subspecies and 
R. hawaiiensis , were captured alive, subjected to 
ether anaesthesia (rarely to chloroform) and 
processed for certain physical data. Rectal tem- 
peratures were obtained with a mercury-filled 
glass thermometer after the animal had become 
quiescent. With few exceptions, temperature 
determinations were made at planes just below 
consciousness. This was fortunate since deeper 
planes of anaesthesia are thought to depress 
body temperature. Hypothermic effects in small 
animals are also known to be induced by certain 
microorganisms (Olitzki et. al., 1942, Jour. 
Immunol. 45: 237-248). The rats reported on 
here were not affected by any known infection, 
but the presence of "inapparent” or asympto- 
matic plague cannot be excluded (Meyer et al ., 
1943, Jour. Infect. Dis. 73: 144-157) even 
though it was not thought to have a high degree 
of probability. 
Table 1 shows the body temperatures of these 
rats in relation to arbitrary weight classes. The 
data are based on the first capture of each animal. 
Although the mean body temperature of all 
individuals in each species was 37.6°C, animals 
in the lowest weight class (youngest) for each 
species had lower mean body temperatures. Al- 
though this may be due to the fact that younger 
animals have a more variable body temperature 
since they are in the process of acquiring homo- 
eothermal ability it may have some relevance to 
current hypotheses concerning weight-temper- 
ature relations in mammals (Rodbard, 1950, 
Science 111: 465-466; 1953, Science 117: 256- 
257; Morrison and Ryser, 1952, Science 116: 
231-232). 
The overall mean body temperature of these 
wild rats closely approximates that recorded for 
the laboratory rat which is generally thought to 
be about 37.5°C. This correlation may be ex- 
pected insofar as the commensal species are 
concerned, but it seems surprising in regard to 
the native Rattus hawaiiensis. Furthermore, the 
mean body temperature of R. exulans on the 
island of Guam was found to be about 35.9°C. 
(Baker, 1946, Ecol. Monog. 16: 393-408), and 
this species is closely related to the Hawaiian 
TABLE 1 
Temperature (C.) of Rattus spp. by Weight Classes 
Weight Class 
(Gm.) 
Rattus he, 
twauensis 
Weight Class 
(Gm.) 
Rattus rattus * 
Rattus norvegicus 
Number 
examined 
Mean 
Number 
examined 
Mean 
Number 
examined 
Mean 
0-29 
25 
36.4 
0-99 
61 
37.0 
11 
37.2 
30-59 
121 
37.7 
100-199 
95 
37.9 
28 
37.7 
60-89 
86 
37.9 
200-299 
4 
37.8 
9 
37.6 
Total 
232 
37.6 
Total 
160 
37.6 
48 
37.6 
* .Rattus rattus rattus and R. r. alexandrinus. 
