Ecological Factors on Manana Island, Hawaii 
P. Quentin Tomich , 1 Nixon Wilson , 2 and Charles H. Lamoureux 3 
ABSTRACT: A 25-ha islet occupied by seasonally nesting sea birds, feral rabbits, 
and house mice is considered. Rabbits presumably modified the unknown original 
vegetation in their 70 or more years on the island and reached an equilibrium with a 
plant cover composed largely of a few hardy introduced grasses. A total of 28 species 
of higher plants has been recorded from the island, only 6 of which are native to 
Hawaii. Rabbits occur in low to moderate numbers, sustained by a food source that 
is enriched by bird guano and subject to annual drought. Average body weight of 
the mouse is remarkably heavy at 19.5 g. Data on biological and food habits are 
presented for both mammals. Among 13 species of ectoparasites of birds and 
mammals are two unusual host adaptations: of the cat flea, Ctenocephalides felis 
felis, to Oryctolagus c uni cuius, and of the Oriental rat flea, Xenopsylla cheopis, to 
Mus muse ulus. Rabbits appear not to be detrimental to the nesting of birds, and their 
control or extermination is discouraged at present. The scientific importance of the 
island’s unique ecosystem is stressed, and proposals for its intensive study are 
outlined. 
Most of the lands in Hawaii were altered 
rapidly, in the hundred years or so following 
initiation in 1778 of sustained contact with 
outside cultures, through agricultural develop- 
ment and the spread of introduced plants and 
herbivorous animals. Then there came a period 
of lessened disturbance simply because purpose- 
ful exploitation of land was diminished and be- 
cause controls were exercised over some major 
pest species. In the past 50 years, many new 
balances have emerged among lands, plants, 
and animals. However, Hawaii is now in a 
second era of resource development that threat- 
ens to overrun not only the lands touched little 
or not at all by earlier disruptions, but also those 
which have achieved new levels of ecological 
stability. This is a universal problem that is not 
peculiar to Hawaii. Its solution lies in the ex- 
ercise of wise resource development based on 
present, as well as future, needs. Lands with 
prominent natural attributes often serve their 
highest use only when left undistrurbed. Pro- 
1 Plague Research Unit, State Department of Health, 
Honokaa, Hawaii 96727. 
2 Bernice P. Bishop Museum, Honolulu, Hawaii 
96819. 
3 Department of Botany, University of Hawaii, 
Honolulu, Hawaii 96822. Manuscript received 
August 4, 1967. 
posals for their manipulation should be pre- 
ceded by careful study of each individual case. 
This paper is concerned with Manana (Rab- 
bit) Island which lies about 1.3 km off the 
southeast tip of Oahu, Honolulu County. Its 
principal occupants are a depauperate flora, 
large numbers of seasonally nesting sea birds, 
a colony of feral rabbits, and house mice. Since 
1945 this island has been a Territorial and State 
bird reservation whose security from unautho- 
rized landings is now vested in the State De- 
partment of Land and Natural Resources. The 
basis for this status is that Manana has been one 
of the main nesting grounds for the Noddy 
Tern, Anous stolidus (L.), and the Sooty Tern, 
Sterna fuscata L., two species highly valued by 
fishermen in locating schools of aku, Katsu- 
wonus pelamis (L.), the principal commercial 
fish of Hawaiian waters. The terns and aku 
prey on the same species of forage fish, crust- 
aceans, and squids (Gosline and Brock, I960). 
Some ornithologists and conservationists have 
recommended destruction of the rabbits on 
Manana as an undesirable invader, in an attempt 
to enhance and possibly enlarge the colonies of 
terns and other birds, notably the Wedge-tailed 
Shearwater, Puffin us pad ficus (Gmelin). In 
1962 a program of rabbit extermination was 
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