366 
relationships do not seem particularly signifi- 
cant, but we hasten to add that this may be 
because they have never been probed deeply. 
For instance, it is conceivable that the rabbits 
affect the vegetation in such a way that favor- 
able conditions for nesting by certain birds are 
maintained. Nesting colonies of Sooty Terns, 
which one of us (Lamoureux) has observed on 
several of the Leeward Hawaiian Islands, tend 
to be in more open areas covered with grasses 
and low herbs, rather than in areas covered with 
shrubs. It is quite possible that the presence of 
the rabbit on Manana contributes to the rela- 
tive scarcity of shrubs there. In turn, the selec- 
tive development of the rabbit strain on Manana 
may have been guided by a vegetation richly 
fertilized with bird guano, infusing in it a 
vitality sufficient to permit at least a bare sur- 
vival of the rabbits in times of crisis. Without 
question, the ecology of birds, rabbits, and 
vegetation on Manana is complex, and very 
likely there are key interdependencies not real- 
ized at this time. 
A decision now to eliminate rabbits because 
of some presumed interference with nesting of 
birds would be premature. We recommend, 
instead, an intensive program of ecological study 
to embrace particularly birds, rabbits, and vege- 
tation. Because of the unique relationships 
observed between some species of ectoparasites 
and birds and mammals, careful attention 
should be paid to all of the fauna. The 
following immediate suggestions are made for 
projects that would lead gradually to an under- 
standing of the island’s more prominent eco- 
logical relationships. 
1. Construction of a 20 X 50 m (open) and 
several 2 X 2 m (covered) exclosures to test 
the responses of vegetation in the absence of 
rabbits and the presence of birds only, and in 
the absence of both. 
2. Establishment of permanent vegetation 
transect points and periodic recording of vege- 
tation changes by photographic and other 
means. 
3. Monthly or quarterly population estimates 
of birds, rabbits, and mice, with particular 
regard to season of year and condition of vege- 
tation. The mark and release of trapped mam- 
mals would allow access to information on age 
PACIFIC SCIENCE, Vol. XXII, July 1968 
composition, nutritional condition, reproductive 
cycles, and ectoparasite infestation of the popu- 
lations. 
4. Behavioral studies of rabbits and birds, 
with particular attention to social relationships 
of rabbits to surface- and burrow-nesting birds. 
5. Study of energy relationships to deter- 
mine the degree of dependence of the vegeta- 
tion, and hence the rabbits, upon bird guano 
as a primary nutritive source. 
The possible importance of the rabbit strain 
on Manana as an experimental animal in par- 
ticular problems of medical or biological re- 
search should not be overlooked (Thomsen 
and Evans, 1964), and a thorough study of the 
population as it is related to other populations 
of the species in Hawaii and in the world is a 
need of special significance. 
Further intentional introduction to Manana 
of organisms of any sort in the near future is 
not recommended. Ecological studies should be 
carried out with as little disturbance as possible 
of the present biota. The ecosystem on Manana 
has much scientific potential in its present con- 
dition and is within easy reach of the intellec- 
tual center of the state. This value will increase 
in time and in proportion to the effort made to 
understand and interpret this singular Hawaiian 
resource. 
ACKNOWLEDGMENTS 
The authors are particularly indebted to Dr. 
Kazimierz Wodzicki, former Director of the 
Ecology Section, D.S.I.R., New Zealand, for 
his sustained interest in the rabbits of Manana, 
for encouraging the present project, and for 
advice and assistance during the 1964 visit to 
the island. David H. Woodside arranged the 
trip, skillfully directed our landing and depar- 
ture in rough weather, and gave us much assis- 
tance from his extensive knowledge of Hawaiian 
fauna. Ronald L. Walker and William J. Voss 
rendered valuable aid during the expedition. 
Dr. Theresa Clay and Dr. C. M. Clifford iden- 
tified the Mallophaga and Metastigmata, respec- 
tively, and P. C. Bull provided advice and 
services in the search for internal parasites of 
rabbits. Dr. R. W. Strandtmann visited Manana 
in March 1963 and collected ectoparasites, the 
records of which he placed at our disposal. 
