AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 92:521-538 (19931 Latitudinal and Insular Variation of Skull Size in Crab-Eating Macaques (Primates, Cercopithecidae: Macaca fascicularis) JACK FOODEN AND GENE H. ALBRECHT Division of Mammals, Field Museum of Natural History, Chicago, Illinois 60605 (J.F.); Department of Anatomy and Cell Biology, University of Southern California, Los Angeles, California 90033 (G.H.A.) KEYWORDS Geographic variation, Latitude, Islands ABSTRACT Macaca fascicularis is broadly distributed in Southeast Asia across 30° oflatitude and 35° oflongitude (Indochinese Peninsula, Isthmus of Kra, Malay Peninsula, Greater and Lesser Sunda Islands, Philippine Islands, and numerous small, neighboring islands). The range is divisible into 1) a core area comprised of mainland Southeast Asia, Borneo, Sumatra, and Java (large land masses interconnected during the last glacial maximum, 18,000 B.P.); 2) shallow-water fringing islands, which are smaller islands connected to the core area during the last glacial maximum; and 3) deep-water fringing islands, which are peripheral islands not connected to the core area during the last glacial maximum. Skull length was used to study effects of latitude and insularity on patterns of size variation. The data are from 802 adult M. fascicularis specimens from 140 core-area localities, 63 shallow-water is- lands, and 29 deep-water islands. Sex-specific polynomial regressions of skull length on latitude were used to describe skull length variation in the core area. These regressions served as standards for evaluating variation among samples from shallow-water and deep-water islands. The core area exhibits Bergmannian latitudinal size dines through most of the species range. Thus, skull length decreases from about 8°S (Java) to the equator (Sumatra and Borneo), then increases as far north as about 13°N (Isthmus of Kra). Farther north, to the northernmost Indochinese localities at about 17°N, skull length inM. fascicularis decreases with increasing latitude, contrary to Bergmann's rule. Latitudinal size variation in shallow-water fringing islands generally parallels that in the core area. However, skull length tends to be smaller than in the core area at similar latitudes. Deep-water fringing islands are mark- edly more variable, with relatively small specimens in the Lesser Sunda Islands and relatively large specimens in the Nicobar Islands. These analyses illustrate how a primate species may vary in response to latitudinal tempera- ture variation and to isolation. © 1993 Wiley-Liss, Inc. Macaca fascicularis (Raffles, 1821}-vari- ously known as the crab-eating, cynomol- gus, kra, or longtail macaque--is broadly distributed in Southeast Asia across 30° of latitude and 35° of longitude (Fig. 1). The range includes southernmost Bangladesh, the southern part of the Indochinese Penin- sula, the Isthmus of Kra, the Malay Penin- sula, the Greater Sunda Islands of Sumatra, Borneo, and Java, the Lesser Sunda Islands from Bali to Timor, and the Philippine Is- lands. The range of M. fascicularis also in- cludes many small, neighboring islands throughout the region. The breadth and geo- morphic diversity of this species' range and the relative abundance of museum speci- mens combine to make M. fascicularis favor- Received February 5, 1993; accepted June 28, 1993. Address reprint requests to Jack Fooden, Division of Mam- mals, Field Museum of Natural History, Chicago, IL 60605.