Ecology of Manana Island, Hawaii — Tomich et AL. 
361 
Fig. 6. Wild tobacco plant ( Nicotiana tabacum ) 
on Manana with bark gnawed, and roots exposed and 
eaten, by rabbits. (Photo by K. Wodzicki, February 
29 , 1964 .) 
crater, all foods identified from each rabbit 
examined were available to rabbits living in 
any of the vegetated parts of the island. How- 
ever, there are differences in abundance of the 
food plants; for example, Trichachne insularis 
is very common within the crater, but uncom- 
mon on the outer slopes. We suspect that the 
rabbit population is more concentrated in the 
heavily vegetated main crater than in any other 
part of the island, and that individually the 
rabbits may be quite localized. Shifts in range, 
with the rise and recession of forage plants and 
of number of rabbits, are quite likely. 
Mus musculus 
The house mouse, Mus musculus L., is the 
only other mammal on Manana. Rats are not 
now present and never have been reported. 
Mice possibly have inhabited the island longer 
than rabbits, through early accidental introduc- 
tion by Hawaiians. Tinker (1938) was ap- 
parently the first to report Mus on Manana, 
but he offers no detailed information. Richard- 
son and Fisher (1950) briefly discuss this 
species. 
On February 29-March 1, 1964, we found 
mice commonly active in late afternoon and 
at night along the beach, on the slopes above 
the beach, and in the main crater. Fifteen traps 
set overnight caught three mice, and three others 
were caught easily by hand at dusk and at night. 
Mice seen in full daylight early in the morn- 
ing were noticeably wary. 
One mouse was a juvenile weighing 5.4 g; 
the others were adult. A male weighed 20.0 g, 
and three females were 22.4, 18.2, and 17.3 g, 
for a mean weight of 19.5 g (the fifth adult 
was partly eaten by ants). These are remark- 
ably large mice for Hawaii. For example, on 
the island of Hawaii adults range generally 
from 9 to 14 g, and seldom reach 17 g (Tom- 
ich, unpublished). A parallel case is reported 
by Berry (1964) in Scotland. 
Reproductive data on the mice from Manana 
were as follows. The male was in breeding con- 
dition, three females were lactating and one 
female was parous-inactive. One had just borne 
a litter, as was shown by six prominent uterine 
scars; another was in estrus. From this small 
series, it appears that reproduction was at a 
high level in a mature population, and that 
weanling offspring were just appearing above 
ground. Two museum specimens were pre- 
served. 
The stomach contents of six mice were 
examined but identification of foods was dif- 
ficult. Because of thorough mastication and 
digestion, very few recognizable fragments re- 
mained (Table 4). It was not possible to esti- 
mate relative volumes of different foods con- 
sumed, nor to compile a list of all materials 
used by the mice. We conclude, however, that 
the mice tend to subsist on foods such as seeds, 
fruits, and insects rather than coarse bulky 
stems or leaves. 
ECTOPARASITES 
Parasites of isolated animal populations are 
expected to be few in number of species be- 
