104 
PACIFIC SCIENCE, Vol. IX, April, 1955 
NATURAL HISTORY NOTES AND OBSERVATIONS 
J. C. Greenway, Jr . 2 
Mr. Stetson was clearly an educated, ob- 
servant man but apparently not an experienced 
naturalist. As is most often the case when the 
history of such islands is studied, the incom- 
plete records of the past are, at least in part, 
at variance with what is known (or thought) 
to be true at the present. In any event this is 
the most graphic first hand account of the 
infestation of a small island by rats in ex- 
istence. 
Mr. Stetson assumed that the rats that 
troubled him belonged to the species variously 
called Ship Rat, Black Rat, Grey Rat, Roof 
Rat, Jungle Rat and Plague Rat (Rattus rattus ). 
These together with a larger, stronger species, 
usually called Brown Rat have escaped from 
wrecked ships and those beached for repairs, 
have taken to the forests and wrought havoc 
on islands ever since Europeans have sailed 
the Pacific Ocean. They are said to have 
moved in armies on South Island, New Zea- 
land in 1840, causing farmers to abandon 
fields (Thomson, 1922: 79). In 1919, soon 
after the wreck of a ship on the shores of tiny 
Lord Howe Island, 300 miles off the east 
coast of Australia, that island was overrun by 
rats and four endemic forms of birds were 
extirpated (Hindwood, 1940). If rats of How- 
land Island were in truth of this species this 
account would have been interesting, but its 
importance is much increased by the strong 
probability that they were actually Polynesian 
Rats ( Rattus exulans). The only specimens 
known from Howland Island were collected 
in September 1924 by George C. Munro. At 
that time the island was said to be overrun 
by Polynesian Rats of both brown and black 
varieties (Emory, 1934). Through the kind- 
ness of E. H. Bryan of the Bernice P. Bishop 
Museum, Honolulu, four of these were made 
available to Miss B. Lawrence, curator of 
2 Museum of Comparative Zoology, Cambridge, 
Massachusetts. 
mammals in the Museum of Comparative 
Zoology at Harvard College, who affirms the 
identification on the basis of the generally 
small size of the specimens, including small 
bullae and small teeth. The pellage of two 
is gray, resembling that of R. rattus\ that of 
the others is brown as in Polynesian Rats 
{exulans). A like dimorphism in exulans is 
reported by J. T. Marshall on Arno Atoll in 
the Marshall Islands. He suggests the possi- 
bility of hybridization, but the little that is 
known of their ecology, and also the rarity 
of morphologically intermediate individuals, 
make this hypothesis dependent upon further 
study. 
Certainly to those who know Polynesian 
rats in life, the behavior of those on Howland 
Island is surprising, for they are character- 
istically shy and retiring compared to the 
other species and indeed were thought for a 
time to have been extirpated from Hawaii 
and New Zealand by introduced rats. Their 
staple in nature is generally seeds and fruits, 
however, they are known to be almost om- 
nivorous in captivity, and it is not impossible 
that having lived up to and above the point 
of subsistence on such a small island as How- 
land their behavior might have adjusted to 
those special conditions. 
J. D. Hague who visited Howland Island 
about the year I860 says of them (Hague, 
1862): "Rats were found on all these islands 
[the guano islands, Baker, Jarvis, Phoenix, 
and others] especially on Howland’s where 
they had become astonishingly numerous. 
They are of very small size, being hardly 
larger than a large mouse, and, I think must 
have degenerated from their original state in 
consequence of the change of climate food 
and condition of life ... I have known over 
3,300 to have been killed in one day by a few 
men ..." Thus Stetson’s account is corro- 
borated. 
