BONACCORSO: A PANAMANIAN BAT COMMUNITY


 ACKNOWLEDGEMENTS

 This study was funded by NSF Grant GB-36068 to J. H. Kaufman, NIH Biomedical
Sciences Grant No. RR7021-07 from the Division of Sponsored Research, University of
Florida, to S. R. Humphrey, and the Environmental Sciences Program, Smithsonian
Tropical Research Institute. The Florida State Museum and Smithsonian Tropical
Research Institute provided logistical support.
 B. K. McNab, both in his writings and classroom d' 2cussions, induced and encour-
aged the germ plasm of interest that launched me into the study of the ecology of
tropical bat communities. S. R. Humphrey provided help and encouragement through
all phases of the study, including assistance with field work in January 1973. J. H.
Kaufmann, E. Leigh, A. S. Rand, N. Smythe, A. F. Carr, D. H. Hirth, and T. C. Emmel
took time to provide constructive guidance. Robin Foster verified my seed identifica-
tions and cultured in me a deep appreciation for tropical plant ecology. Clark Sandford,
Julie Wiatt, Bill Biven, and Janet Hall faithfully assisted with fieldwork and laboratory
preparations under trying conditions. Nancy Halliday and Sylvia Scudder used their
creative talents to render the illustrations. Insects eaten by bats were identified by
Terry Zinn. Finally, I wish to thank the scientists, students, and visitors coinciding
with my residence on BCI, as well as the Smithsonian staff, for providing encourage-
ment, friendship, intellectual atmosphere, and volleyball at an isolated field station.

 STUDY AREA

 The primary research site was Barro Colorado Island (BCI), which lies within
 freshwater Lake Gatun, Panama Canal Zone, at 90 10' N Lat, 790 51' W Long. This site
 was selected because it has a rich bat fauna, relatively undisturbed mature moist
 forest, modern living and laboratory facilities, and reference collections of animals and
 plants. A second site was located on the mainland opposite BCI at the base of Buena
 Vista Peninsula (Fig. 1).
 The climate of this lowland area of Panama is warm and humid, with a 7-month (May
 through November) wet season and a 3-month (January through March) dry season.
 Dry season months each receive less than 60 mm of rain, whereas wet season months
 typically receive in excess of 250 mm of rain. April and December are transition months
 between the dry and wet seasons and receive amounts of rain that vary considerably
 from year to year. Thus in years when April and December are very dry, the dry season
 may last for five months. Average annual rainfall since 1926 has been 2820 mm
 (Smythe 1974). Monthly sums of rainfall for 1973 are shown in Figure 3.
 During night-time sampling of bats, relative humidity under the forest canopy never
 fell below 80 percent. Measurements were made at 2 m above ground with sling
 pyschrometer. Daily temperatures on the forest floor fluctate from a mean minimum of
 22.1C to a mean maximum of 28.0"C, with no significant seasonal variation (Smythe
 1974).
 Barro Colorado is in the Tropical Moist Forest life zone (Holdridge 1967). This 15
 km2 island is covered with forest that is over 60 years in age. The only physical disturb-
 ance results from recutting forest trails, maintaining a small laboratory clearing, and
 an undetermined amount of poaching. Further details on the geology, climate, biology,
 and history of the island are given by Kaufmann (1962) and Foster (1973).

 MATERIALS AND METHODS
 There were 17 sampling stations in an approximately 2 km2 central strip of BCI and
 one station on Buena Vista Peninsula (Fig. 1). Habitats sampled during the study were
 classified as mature forest (14 stations on BCI), creeks (3 stations on BCI), and second