Table 5. A Summary of Distribution of All Species of Megachiropteran Bats Known from the Solomons. Only Islands Well Known Faunistically Are Listed.

Subspecies
R. amplexicaudatusXXXXXXX
P. atrataXXXX
Pt. hypomelanusX
Pt. admiralitatumXXXXX
Pt. tonganusX
Pt. howensisX
Pt. rayneriXXXXXXXXXX
Pt. woodfordiXXXX
Pt. mahaganusXX
D. inermisXXXXXXXXXXXX
M. lagochilusXXXXXXX
M. woodfordiXXXXXX
M. aurantiusXX
N. albiventerXXXXXX
N. majorXXXX
N. malaitensisX
Totals89614464354103231

Santa Ysabel has six species of megachiropterans and 10 occur on Guadalcanal ([Table 5]). These two islands, separated by about 100 miles of water, share five species (Rousettus amplexicaudatus, Pteralopex atrata, Pteropus rayneri, Dobsonia inermis, and Nyctimene albiventer). The Nggela Group, in which Florida is the largest island and the only one from which bats have been collected, is 50 miles southeast of Santa Ysabel and 30 miles north of Guadalcanal ([Fig. 16]). Four species of megachiropterans are known from Florida (Dobsonia inermis, Macroglossus lagochilus, Melonycteris aurantius, and Nyctimene major). Three of these are known from Guadalcanal and one occurs on Santa Ysabel. This situation resembles the one involving Fauro, Bougainville, and Choiseul because none of the large bats (Pteropus and Pteralopex) is known from Florida, even though two species of large bats that occur on Santa Ysabel to the northwest occur also on Guadalcanal to the south. Possibly Florida and the smaller islands that comprise the Nggela Group are ecologically unsuitable for large bats, or perhaps these small islands can support only limited numbers of individuals during part of a year.

Fig. 16. The number of megachiropteran species known from individual islands (number within a circle) is compared with the number of species common to two different islands (number without a circle). For names of islands see [Fig. 2].

Some of the small islands in the Solomons have populations of large fruit bats. For example, Pteropus admiralitatum and P. hypomelanus have been reported from the small islands in the Russell Group ([Table 5]). Possibly these species do not live concurrently in the Russells; specimens of the two were obtained in different years. Two small megachiropterans, P. woodfordi and Melonycteris woodfordi, also inhabit the Russells. Shortland, a small island about 15 miles south of Bougainville, supports one large bat, P. admiralitatum, as well as smaller megachiropterans.

Kolombangara and Vella Lavella are about the same size and are separated by about 15 miles of water. Rousettus amplexicaudatus, Pteropus rayneri, P. woodfordi, Macroglossus lagochilus, and Nyctimene albiventer have been collected on Kolombangara but only P. admiralitatum, P. rayneri, and Dobsonia inermis have been found on Vella Lavella. The difference in the known megachiropteran faunas is more striking when one compares each island with adjacent islands. Two species on Vella Lavella occur also on Choiseul, which is about 35 miles northeastward, and two species occur also on Shortland, which is 120 miles northwestward ([Fig. 16]). Four of the five megachiropterans on Kolombangara also have been found on Choiseul, about 50 miles northward ([Table 5]). Pteropus rayneri is the only megachiropteran known from both Kolombangara and Vella Lavella, even though the islands are separated by only a few miles of water. Inadequate data possibly account for the differences in the megachiropteran fauna, but I suspect that some other factors are involved. Although Vella Lavella and Kolombangara do have one species (P. rayneri) in common, a different subspecies occurs on each island—rubianus on Kolombangara and lavellanus on Vella Lavella ([Fig. 17] and [Table 6]). This indicates that some factor or factors are operating to keep megachiropterans from moving frequently or easily from one island to the other.

Each of several subspecies of species in the genus Pteropus are known from one or two small islands separated by only a few miles from other islands on which different subspecies occur (see [Fig. 6]). Judging from this kind of distribution, these bats do not move frequently from island to island. Possibly this is because they cannot easily cross water barriers, or are not inclined to do so because food is abundantly available throughout the year on their home island. Because "flying foxes" frequently are seen in flight over water several hundred yards from shore, the first factor probably is unimportant—at least where short distances are involved. It seems most likely that when abundant food is available these bats have no reason to move even moderate distances.