Wildlife and Wildlife Habitat of American Samoa. Ii. Accounts of Flora and Fauna
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WILDLIFE AND WILDLIFE HABITAT OF AMERICAN SAMOA. II. ACCOUNTS OF FLORA AND FAUNA By A. Binion Amerson, Jr., W. Arthur Whistler, and Terry D. Schwaner Environment Consultants, Inc., Dallas, Texas Edited by Richard C. Banks U.S. Fish and Wildlife Service Washington, D.C. UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE Washington, D.C. 1982 FOREWORD A survey of the status of the wildlife and wildlife habitat of American Samoa, an unincorporated Territory of the United States, was recommended by administrative officials of the U.S. Fish and Wildlife Service (FWS) in the early 1970's. Environ- ment Consultants, Inc. (ECI), based in Dallas, Texas, was selected to conduct a2-year survey with A. Binion Amerson, Jr., as Principal Investigator. The contract was administered through the Division of Federal Aid in FWS Region I, Portland, Oregon. The primary objectives of the survey were to define the major ecosystems and to inventory their physical components, vegetation, and wildlife constituents; to prepare maps of these ecosystems; to identify any threatened or endangered species of wildlife; and to recommend wildlife management opportunities and needs. The report of the survey was to be in two parts. - The first was to be a non-technical account suitable for wide general distribution; the second was to include the technical aspects of the data and data gathering, with accounts of the wildlife species. This volume represents the second part of ECI's report. The final report submitted by ECI contained more than 1,200 pages, 200 figures, and 110 tables, many of the latter several pages long. The FWS felt that the report was too lengthy for publication in the form submitted. The task of editing and con- densing ECI's report into publishable form, without altering its essentials, was assigned to Richard C. Banks, National Fish and Wildlife Laboratory (now Museum Section), FWS, Washington, D.C. Claudia J. Angle assisted with revision of the figures, and Linda Wolfe retyped the tables and some of the text. Contents Page Foreword.. .....................................................................ii Abstract.. .....................................................................1 Introduction ...................................................................2 Climate .....................................................................3 Soils ........................................................................5 Methods.. .....................................................................5 Study Plots and Their Vegetation ..................................................7 Plants.. .......................................................................17 Dicotyledonae ................................................................18 Monocotyledonae ............................................................27 Pteridophyta .................................................................31 VertebrateAnimals ..............................................................36 Amphibians and Reptiles .......................................................36 Birds.. ......................................................................54 Mammals.. ..................................................................73 Acknowledgments ..............................................................76 References. .....................................................................77 Tables.. .......................................................................80 Wildlife and Wildlife Habitat of American Samoa. 11. Accounts of Flora and Fauna A. Binion Amerson, Jr., W. Arthur Whistler, and Terry D. Schwaner Environment Consultants, Inc. Dallas, Texas Abstract A survey of the status of the terrestrial vertebrate wildlife and the wildlife habitat of American Samoa was conducted from 15 June 1975 to 21 December 1976. Data were collected from42 study plots representing 16 vegetation communities and habitat types on the seven islands and from 98 linear survey routes. A checklist of plants includes 489 species of which 33 tree species are first reported for American Samoa. Eleven flowering plants are endemic to American Samoa. One amphibian and 15 reptiles occur in American Samoa. The amphibian, Bufo marinus, and a gecko, Hemidactylusfrenatus, are recent introductions. The Pacific boa, Candoia brbroni, is first reported from American Samoa, and 37 insular distribution records are reported. In number of individuals, reptiles are the most abundant vertebrates on the islands. The avifauna of American Samoa includes 53 species; the occurrence of 4 others is hypothetical. Four species are reported from a single occurrence, and the listing of seven sea birds is based on sight records of birds flying over or near the islands. Six northern hemisphere shorebirds and one cuckoo are known only as migrants. Two species, Columba Ifvia and Pycnonotus cafer, are introduced; only the latter is well estab- lished. One species, Gymnomyzasamoensis, is probably extirpated. The friendly quail-dove, Gallicolumba stalri, is reported from American Samoa for the first time. The mammalian fauna includes two native bats, a third hypothetical species, four introduced mice and rats of which one, Rattus exulans, probably represents an old introduction, and feral pigs. Introduction American Samoa is a group of seven islands at about 14" The natural vegetative cover of most of American Samoa south latitude and 170" west longitude, along the crest of a is tropical rain forest. Nearly two-thirds of the rain forest has submarine ridge. From west to east in the chain, the islands been destroyed or damaged by man's activities; undisturbed are Tutuila, Aunu'u, Ofu, Olosega, Ta'ii, and Rose Atoll forest exists only on steep slopes. Despite the low fertility of (Fig. 1). The seventh, Swains Island, is about 320 km north- the soil, plantation land is the most extensive type of vegeta- northwest of Tutuila. The island group is about 4,180 km tion (34%). Secondary forest (20%) is another major vegeta- southwest of Honolulu and about 925 km northeast of Fiji tion type; if undisturbed for along time, the secondary forest (Fig. 2). The total land area is about 197 km2. Individual will revert to a condition nearly indistinguishable from islands range in size from Tutuila (about 142 km2)to Rose primary forest. The only relatively undisturbed vegetation Atoll (0.04 km2). The maximum elevation of 966 m is on types are cloud forest, montane and littoral scrub, and lit- Ta'ii; in contrast, Rose Atoll and Swains Island are flat and toral strand. low, rising only about 9 m above sea level. Figures 3-5 show For the purposes of this study, "wildlife" was restricted to the topography of the individual islands and place names birds, terrestrial mammals, reptiles, and amphibians. used in this report. The islands are inhabited except for Rose Atoll, which is a National Wildlife Refuge of the U.S. Fish and Wildlife Service. OCEAN - OLU IS. A FU IS' wq OLOSEGA IS. .I TA'~IS. ROSE ATOLL , Fig. 1. The islands of American Samoa and their relationship to Western Samoa. , Climate Temperature. -The average annual temperature of associated with the proximity of small tropical storms, bands American Samoa is about 23" C (Fig. 6). The southern of converging winds, or low-pressure systems higher in the hemisphere winter months of June, July, and August are the atmosphere, all conditions that help make summer the rainy coolest and the summer months of January, February, and season. At other times, the absence of the tradewinds is March are the warmest. However, the mean annual range of marked by periods of light and variable winds. Westerly and temperature is less than 2" C, in contrast to a mean daily northerly winds are then more frequent; strong at times, range of about 7" C. Afternoon temperatures ordinarily these winds often reflect the nighttime drainage of cooled air reach slightly more than 30" C in summer and slightly less from the mountains west and north of the airport. than that figure in winter; night temperatures fall to about Hurricanes move into the area generally from the north, 25" C in summer and about 22" C in winter. The highest occasionally from the east or west. According to historical temperatures recorded at the Pago Pago Airport were about records, Samoa experienced at Ieast 39 hurricanes between 33 " C and the lowest about 16" C. Minimum temperatures 1831 and 1926; of these, 2 occurred in November, 7 in from April 1964 to March 1966, when the weather station December, 11 in January, 3 in February, 12 in March, 3 in was about 0.8 km farther inland, appear to have been April, and 1 at an unspecified time. Some have been intense somewhat lower than those at the present location nearer the and highly destructive. On 29-30 January 1966, a hurricane shore. battered Pago Pago with gusts of more than 110 mph, Winds.-The prevailing winds throughout the year are the deposited 15-36 cm of rain, and caused five deaths and an easterly tradewinds. These tend to be more directly from the estimated $4.3 million in property damage. east from December through March, but from the east- Precipitation.-Rainfall averages more than 3 18 cm an- southeast and southeast in the rest of the year. Monthly nually at the Pago Pago Airport, but varies greatly over small average wind speeds are 4-10 knots (Fig. 6). The trade winds distances because of the rugged topography. Pago Pago are less consistent in summer than in winter. At Pago Pago Village, less than 6.5 km north of the airport at the head