Systematics of Megachiropteran Bats in the Solomon Islands.
by Carleton J. Phillips.
INTRODUCTION
The Solomon Islands const.i.tute an archipelago east of the large island of New Guinea and more than a thousand miles off the northeastern coast of Australia. This archipelago, which is princ.i.p.ally of volcanic origin although sedimentary layers of calcareous rocks occur on many islands (Lever, 1934; Belkin, 1962), consists of a double chain of islands having a northwest-southeast axis of more than 600 miles. The archipelago is more or less an extension of New Guinea and in fact is connected to it in stepping-stone fashion by New Britain, New Ireland, and numerous smaller islands (see Fig. 1).
Australia and New Guinea have many kinds of mammals but the only terrestrial mammals in the Solomon Islands are a species of the genus _Phalanger_ (order Marsupialia), and several species of four genera of rodents, one genus of which probably was introduced by man.
Additionally, several kinds of bats have reached and colonized the Solomon Islands.
[Ill.u.s.tration: FIG. 1. Showing the Solomon Islands in relation to major adjacent land ma.s.ses.]
In the past 100 years at least 43 species and subspecies of Chiroptera of 16 genera have been recorded from the Solomon Islands; of these 27 species and subspecies of seven genera are in the suborder Megachiroptera. At least one genus of Megachiroptera is endemic as are numerous species of other genera, and subspecies of still other species.
In 1963 and 1964, the Bernice P. Bishop Museum sent several collecting parties to the British Solomon Islands Protectorate and the Australian Trust Territory of New Guinea. In the Solomons, J. Linsley Gressitt, Philip Temple, Peter Shanahan, and Ray Straatmann visited many of the larger and more accessible islands and collected a wealth of zoological materials. I have had the opportunity to study and report on specimens of mammals, especially bats, collected by the persons named and deposited in the Bishop Museum. This report is the third in a series on bats from the Solomons (Phillips, 1966; 1967). Other specimens, mostly obtained in 1944 by personnel of United States military units, are stored in the United States National Museum and have been available for study. Aims of the following report are to (1) identify the megachiropteran bats to species and subspecies and (2) discuss distribution of these bats in the Solomon Islands.
In all, 27 kinds (subspecies and monotypic species) of the order Megachiroptera are known from the Solomon Islands. These pertain to three subfamilies of the one family Pteropodidae.
The 43 Solomon Islands, having a total land area of more than 15,300 square miles (see Belkin, 1962:42-43), are listed in the gazetteer (see also Figure 2). Politically, all of the Solomon Islands except Buka and Bougainville, which are included in New Guinea Trust Territory under mandate to Australia, are in the British Solomon Islands Protectorate.
The Solomons are within 300 to 700 miles of the equator and have a fairly constant tropical climate, except at high elevations. The temperature varies little; monthly mean temperature is between 81 and 83 F. and at sea level ranges from about 70 to 93 F. yearly (Belkin, 1962:42).
Southeast tradewinds are relatively constant from May to October and this period, in general, is a dry season except at higher elevations on windward coasts. From December to March prevailing winds are from the north and precipitation throughout the island group is especially heavy.
Rainfall on the island of Tulagi averages about 120 inches per year (Bryan, Edwin H., 1941; MS, p. 2, at Pacific Sci. Information Center, Bishop Museum) and up to 300 inches have been recorded on the north coast of Guadalca.n.a.l (Belkin, 1962:42-43). Occasional dry periods occur even in the period of December to March.
Most islands of the Solomon Group support dense tropical rain forest.
Much of it has been modified by man. Some clearings and scattered coconut plantations are found along coasts. On some of the larger islands (for example, Guadalca.n.a.l) coastal scrub (especially on leeward coasts) and extensive gra.s.sy areas are to be found. Additional notes on vegetation are in the gazetteer.
The 165,000 persons living on the Solomon Islands are mostly Melanesians but some are mixed Papuan, Malay, and Polynesian. These native peoples are notorious for their cannibalistic tendencies; the eating of human flesh usually was related to warfare, although malefactors and human sacrifices accounted for some of the cannibalism (Cranstone, 1961:29). Prior to the Second World War few Europeans visited the Solomons and several islands still remain beyond reach of modern-day technology. For example, Rennell and Bellona islands, south of the main part of the archipelago, are visited only rarely, and then only by a medical officer or the Resident Commissioner. According to Troughton (1936:341), the islanders in the interior of Bougainville as late as 1935, were p.r.o.ne to kill and feast upon strangers. In 1932, Lewis (1951:37) felt that the natives of Malaita Island were especially resistant to outside interference by Caucasians and reported that no "white man or foreigner" was safe on Malaita.
Troughton (1936), who listed Melanesian names for mammals, indicated that the native peoples distinguished between kinds of bats that closely resembled one another. Of these, the only bats that seem to be used as food belong to the genus _Pteropus_.
GAZETTEER
In the following list, currently-used names of islands are given; when available, older names and variant spellings are indicated in parentheses. For certain islands, especially those visited by field parties from the Bishop Museum or those frequently mentioned in previous literature on bats, some descriptive and ecological information also is provided.
Lat.i.tude and longitude of islands are from publication no. 881 of the Hydrographic Office of the United States Navy Department (Anonymous, 1944); names of islands were checked against a list by Brigham (1900); descriptive information mostly is from reports by Temple and Straatmann (1964, field notes, at the Department of Entomology, Bishop Museum).
ALU.--7 07" S, 155 54" E.
BANIKA.--9 05" S, 155 13" E.
BARA (Gera).--9 31" S, 160 31" E.
BELLONA (Bello).--11 18" S, 159 48" E.
BOUGAINVILLE (Mamamolimo).--6 12" S, 155 15" E. This is the largest island in the Solomon Group, being 127 miles long (northwest to southeast) and about 59 miles across at the widest place. The highest elevations are 9850 and 10171 feet, at the tops of active volcanoes.
Ecologically, Bougainville is mostly dense rain forest, which is less dense on the summits of higher mountains.
BUKA.--5 15" S, 154 38" E.
CHOISEUL.--7 04" S, 157 01" E. This island, formed along a northwest-southeast line of low mountains (maximum elevation of 3500 feet), is about 90 miles long and 20 miles wide. Most collecting was at Malangona (Sasamunga on some maps) on the southwestern coast.
FAURO.--6 55" S, 156 07" E. This small island, about 14 miles long (north-south) and six miles wide (east-west), lies about 10 miles south and east of Bougainville. Fauro is formed around a volcanic cone having a maximum elevation of 1925 feet; it has considerable dense mangrove swamp along the west coast, and mature rain forest with little understory growth. Most collecting was at Toumoa, on one of two southern peninsulas.
FLORIDA (Nggela).--9 05" S, 160 16" E. Florida, the main island in the Nggela Island Subgroup, is mountainous and except for some small gra.s.sy areas, supports dense rain forest. It is nearly 25 miles long (east-west) and nine miles wide (north-south), with a maximum elevation, at Mount Barnett, of about 1366 feet. Most collecting was at Haleta, on the southwestern coast. At this locality there were scattered mangrove swamps, rain forest, and gardens inland.
GANONGGA (Ronogo, Ronongo).--8 03" S, 156 35" E.
GATUKAI.--8 47" S, 158 12" E.
GHIZO (Gizo, Keso).--8 05" S, 156 59" E.
GOWER (N"dai).--7 54" S, 160 34" E.
GUADALCa.n.a.l (Guadalcanar).--9 15" S, 159 35" E. Guadalca.n.a.l is mostly of volcanic origin and has an irregular chain of mountains along the southern coast. The highest elevation is 8005 feet at Mount Popomanasiu.
This large island is nearly 80 miles long (east-west) and 25 miles wide (north-south). Most of the northwestern part of Guadalca.n.a.l supports _alang-alang_ gra.s.s. The remainder of the island is heavily wooded.
KILINAILAU (Cartaret).--4 44" S, 155 28" E.
KOLOMBANGARA (Duki, Kulambangara).--8 00" S, 157 05" E. Kolombangara, formed from an extinct volcano, is about 18 miles in diameter and nearly circular. The highest peaks, rising as precipitous cliffs in some places, reach a maximum elevation of about 5000 feet. The vegetation is mostly virgin rain forest. Mangrove swamp and small coconut groves occur along the coast. Field parties from the Bishop Museum were able to reach the highest elevations, and concentrated their work along the southwestern side of the island.
[Ill.u.s.tration: FIG. 2. Solomon Islands. Princ.i.p.al islands are named.]
MALAITA (Mala, Malanta, Malayta).--9 00" S, 161 00" E. This long (104 miles northwest to southeast), narrow (about 23 miles at its widest spot) island, between Santa Ysabel and San Cristobal islands, is basically of volcanic origin with some limestone (coral) deposits along the coast. Mount Kolovrat, having an elevation of 4275 feet, is the highest point. The Bishop Museum field party lived at Dala, in dense rain forest about 12 miles north of Auki on the northwestern coast of Malaita.
MALAPA.--9 49" S, 160 53" E.
MONO (Treasury).--7 22" S, 155 35" E. This is a small island (maximum elevation 1150 feet) in the Treasury Island Subgroup just south of Bougainville. Mono is about nine miles long (east-west) and five and one half miles wide (north-south). The basic volcanic core is described in field notes as topped with coral limestone.
NEW GEORGIA (Kausagi).--8 20" S, 157 30" E. The New Georgia Subgroup is composed of 11 moderate-sized islands and islets. New Georgia Island, the main member of the subgroup, is 50 miles long (northwest to southeast) and from five to 30 miles wide. On the northern side several volcanic peaks attain an elevation of about 3000 feet. The entire island is forested.
NGGELA (Florida Islands).--4 31" S, 154 11" E. This subgroup consists of several small to medium-sized islands between Guadalca.n.a.l and Malaita. Florida is the main island.
NISSAN (Green, Sir Charles Hardy"s).--4 31" S, 154 11" E.
NUk.u.mANU (Le Maira, Tasman).--4 32" S, 159 25" E.
ONTONG JAVA (Lord Howe Atoll, Liuniuwu).--5 25" S, 159 30" E.
PAVUVO.--9 04" S, 159 08" E.