PROC. BIOL. SOC. WASH. 104(2), 1991, pp. 399^15 THE MAMMALS OF CATANDUANES ISLAND: IMPLICATIONS FOR THE BIOGEOGRAPHY OF SMALL LAND-BRIDGE ISLANDS IN THE PHILIPPINES Lawrence R. Heaney, Pedro C. Gonzales, Ruth C. B. Utzurrum and Eric A. Rickart ^^^^rac?.— Thirty-five species of mammals are known from Catanduanes Island, 28 of which are reported here for the first time; these include 1 insectivore, 24 bats, 1 primate, 5 rodents, 2 carnivores, and 2 ungulates. No endemic species are present, and all but one (the widespread Saccolaimus saccolaimus) are known from neighboring Luzon. All pop-ulations are morphologically similar to conspecifics on Luzon. Data are consistent with the prediction (based on depth of surrounding water) that Catanduanes should exhibit characteristics associated with being a small land-bridge island of the Luzon faunal region. The avifauna of Catanduanes shows similar biogeographic patterns. Although the mammalian fauna of Luzon Island is considered to be one of the best-known in the Philippine Archipelago, none of the small islands offshore of Luzon had been comprehensively surveyed at the time of the last faunal review (Heaney 1986, Heaney et al. 1987). This is unfortunate, since knowledge of the faunas of small is-lands often provides the basis for inferences about the dynamics of evolution and ex-tinction within island archipelagos (Case & Cody 1983, Heaney & Patterson 1986), and such studies within the Mindanao and Pa-lawan regions of the Philippines have been productive (Heaney 1986, Heaney et al. 1989). Accordingly, the small islands sur-rounding Luzon (which has a rich fauna of endemic murid rodents and pteropodid bats) may be expected to be especially interesting for studies of evolutionary biogeography. This paper reports the results of a survey of the mammals of Catanduanes Island, an island that lies adjacent to the southern pen-insula of Luzon. Published records previ-ously existed for only seven species of mam-mals (Heaney 1986). Because little has been published on the ecology of most species of small mammals in the Philippines, we in-clude here data on reproduction and de-scriptions of habitats where the animals were taken. Geographic variation in most Phil-ippines species is poorly documented, so we have provided external and cranial mea-surements wherever possible. We use these data to test several predictions of biogeo-graphic patterns proposed earlier (Heaney 1986, Heaney etal. 1989). Climate and Geology of Catanduanes Catanduanes is an island of 1 5 1 3 km^ that lies 8 km east of the nearest portion of the southeastern peninsula of Luzon. Because the highest point is 764 m, the island is below the elevation required to support more than small and localized areas of montane or mossy vegetation (Heaney et al. 1989, Whitmore 1984). In about 1970, primary forest was estimated to cover about 25% of the island, with about half of the remaining area covered by secondary forest (obser-vations by PCG). By 1988, the Philippine Bureau of Forest Development estimated that primary forest occupied about 5% of the island, with about 25% of the island covered by scattered patches of degraded primary and second-growth forest. Catanduanes lies in one of the principal typhoon tracks in eastern Asia, and rainfall is thus both high and seasonal. Mean annual rainfall at Baras, Pandan, and Virac is 548 1 ,
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