Complementary Specialization of Male and Female Reproductive Structures in the Bear Macaque, Macaca arctoides

Abstract

IN 1872 Anderson¹ first noted the strikingly aberrant structure of the glans penis of the red-faced stump-tailed bear macaque, Macaca arctoides I. Geoffroy, 1831 (= M. speciosa Blyth, 1875; for nomenclatural discussion of this species see ref. 2). Further characterizations of the unusual penis of this monkey have been provided by other authors^3–7. The glans of the bear macaque differs from that of other macaques in being long, slender and lanceolate instead of short, blunt and rounded (Fig. 1). In the bear macaque the glans is 5–7 cm long, dorso-ventrally flattened, and tapers in breadth from about 1 cm at the base to less than 0.5 cm at the tip. In other macaques the glans is less than 2.5 cm long and is generally helmet-shaped⁴, approximately as in man. The penis bone, which provides skeletal support for the glans in macaques and most primates, is also about 6 cm long in the bear macaque (Fig. 2), more than twice as long as in other species of the genus^4,8.