Technical Report #183.
Scheffler, P.Y., D. Foote, C.F. Perry, K. Schlappa, and C.P. Stone.
2012. Population dynamics of introduced rodents in Hawai'i Volcanoes
National Park 1986-1990.
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We determined seasonal and geographical distribution patterns for four
species of introduced rodents in Hawai‘i Volcanoes National Park from
1986-1990. We surveyed black rats (Rattus rattus), Polynesian
rats (R. exulans), Norway rats (R. norvegicus) and house
mice (Mus musculus) along an elevation gradient ranging from
90–1,820 m above sea level in five different sites using baited snap
traps. Rodent community structure differed by elevation: there were more
mice at montane sites and more Polynesian rats in the lowlands. We found
that breeding occurred throughout the year for all species at all sites
but that seasonal peaks in reproductive activity were common.
Reproduction tended to be more common in the summer months at higher
elevation sites and in the winter months at lower elevations. Rodents of
all species were more abundant in our study in the winter than in the
summer, but the differences were not significant. The overall sex ratio
did not vary from a 1:1 ratio, but seasonally there were differences in
sex ratio which varied with species and site. We calculated the minimum
distance traveled from an assessment line and found that larger-bodied
species traveled longer average distances. Pelage color in black rats
was darkest in wet forest which may have adaptive value. Black and
Polynesian rats were widespread in almost all habitat types, whereas
mice were limited to dry and mesic sites; Norway rats were the rarest
component of our sampling and found only in wet montane forest (‘Ōla‘a