Foods of Rodents in the Hamakua District, Hawaii 1 
Harry T. Kami 2 
ABSTRACT : The food habits of Rattus exulans, R. rattus, R. norvegicus, and Mus 
mus cuius captured in sugar cane fields, in gulches adjacent to cane fields, and in 
areas of human habitation, were determined from the stomach contents of 1205 
rodents collected in 12 consecutive monthly samples. In cane fields the diet of R. 
exulans and R. rattus was primarily the internodes of sugar cane, while Mus fed 
principally on insects and grass seeds. In gulches R. exulans subsisted mainly on 
sugar cane, but R. rattus fed heavily on grass stalks and fruits. Mus from this habitat 
consumed kukui nuts and insects to a large extent, while the few R. norvegicus 
found here took a variety of foods. The foods of R. rattus and R. norvegicus 
captured near human habitations consisted mainly of garbage, other waste materials, 
and mixed livestock rations. 
Nutrition is a primary requirement for the 
support of animal populations, and its quality 
is considered by some ecologists to be the 
ultimate factor which controls the growth or 
decline of such populations. Hence, knowledge 
of food habits is an important element in the 
understanding of rodent ecology. In Hawaii 
early investigations by Caum (1922), Spencer 
(1938), and Doty (1945) provided basic in- 
formation for their programs directed toward 
control of rodents which damage sugar cane. 
The present investigation was undertaken as 
part of extensive research on the reservoirs and 
vectors of bubonic plague. Three species of 
rats, Rattus rattus (L.), R. norvegicus (Berken- 
hout), and R. exulans (Peale), and a mouse, 
Mus mus cuius L., make up the rodent complex 
of the Hamakua district on the northeast coast 
of the island of Hawaii. Because plague bacilli 
have been detected many times in humans, ro- 
dents, and rodent fleas in the area extending 
from the village of Kukuihaele on the west to 
that of Paauhau on the east, trapping effort for 
rodent collections was concentrated within that 
area. 
1 This investigation was supported, in part, by 
Public Health Service research grant AI-02886- 
06TMP, from the Institute of Allergy and Infectious 
Diseases, Dr. C. M. Wheeler, Principal Investigator. 
Manuscript received March 15, 1965. 
2 Plague Research Unit, Department of Health, 
State of Hawaii. 
I wish to thank the Rodent Surveillance and 
Control Crew, Department of Health, Honokaa, 
supervised by Mr. R. Baker, for rodents from 
the many villages scattered throughout the dis- 
trict; Dr. Kaoru Noda and Dr. Satyu Yamaguti, 
University of Hawaii, for identification of 
nematodes ; Dr. Dale H. Habeck, University of 
Florida, for identification of insects; and Dr. 
P. Quentin Tomich for his valuable suggestions 
during the course of the work and for his 
critical reading of the manuscript. 
DESCRIPTION OF SELECTED HABITATS 
Sugar Cane Fields 
Permanent trap lines were established in 
sugar cane fields which varied in crop age from 
recently planted seedlings to mature cane, ready 
for harvest. In fields of young cane the area 
between the rows is bare of weeds and other 
cover. After a time, the ground is often over- 
grown by seed-producing forbs and grasses, 
and so littered by the fallen leaves and stalks 
of cane that penetration of the field is nearly 
impossible. 
Gulches 
Trap lines were also established in two 
gulches, Ouhi gulch near Paauhau and an un- 
named gulch adjacent to cane fields near Waipio 
Valley. The section of Ouhi gulch studied 
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