Morphology and somatometric growth of long-tailed macaques (Macaca fascicularis fascicularis) in Singapore

Abstract

Crab-eating, or long-tailed, macaques [Macaca fascicularis (Raffles, 1821)] have been studied extensively throughout their distribution in South and South-east Asia. Despite this extensive body of research, the island population of long-tailed macaques from Singapore remains virtually undescribed. In the present study, we compare the morphometric variability and patterns of growth observed in a population sample from Singapore with a composite sample from Thailand, north of the Isthmus of Kra. The results of our analyses indicate that there are statistically significant differences between the two populations in adult size and shape. For both males and females, the Singapore population is smaller than the Thai population. Relative to body length, the Singapore macaques exhibit significantly longer tails, and, relative to cranial length, they exhibit significantly more narrow faces than the Thai macaques. Although levels of sexual dimorphism for most morphometric traits are very similar, indicating similar levels of male-male competition for females, the Singapore males exhibit a significantly larger testicular volume relative to body weight, suggestive of an alternative male reproductive strategy. In addition to adult somatometric size and shape, comparisons of growth patterns relative to age and body size reveal significant differences between the two population samples. Combined, these results suggest either that statistically significant differences in adult morphology and patterns of growth can occur in presumably reproductively cohesive subspecies, or the Singapore macaques may be taxonomically distinct.

Latitudinal variation in cranial dimorphism in Macaca fascicularis

“…The authors of that study did not, however, find a relationship between island area and the degree of body size change. A recent comparison of insular populations of M. fascicularis without reference to mainland core populations also did not find a significant relationship between island size and body size [Schillaci et al, 2008].…”

“…The study of latitudinal and insular variation in the genus Macaca has been a topic of considerable research [e.g., Albrecht, 1978Albrecht, , 1980Albrecht, , 1983Fooden, 1975Fooden, , 1979Fooden, , 1991Fooden, , 1995Fooden, , 2006Fooden & Albrecht, 1993, 1999Hamada et al, 2008;Schillaci et al, 2007Schillaci et al, , 2008. Most of this research has identified latitudinal trends in macaque body size that are often, though not always, consistent with Bergmann's [Bergmann, 1847] and Allen's [Allen, 1877] rules.…”

Anatomical and radiographic appearance of the capuchin monkey thoracic cavity (Cebus apella)

“…Corroborating this, the cardiac image was also described in radiographic studies of the cardiac silhouette in monkeys of the Macaca nigra and Macaca tonkeana species (Schillaci et al 2007(Schillaci et al , 2008.…”

“…Radiographs in ventrodorsal projection favored the visualization of the pleural reϐlec-tion along the line where the accessory and left caudal lung lobes meet (Schillaci et al 2007). In these animals, the boundaries of diaphragmatic cupola could be distinguished, regardless of the x-ray beam angle, the opposite to what occurs with dogs and cats (Alves et al 2009).…”

“…Breeding in captivity is already a reality (Csatadi, Leus & Pereboom 2008); but there has been little discussion on the use of minimally invasive investigative techniques for primate thoracic radiography focusing on the cardiac silhouette (Medd 1971, Silverman 1975, Silverman & Morgan 1980. Other related studies were conducted in western primates concerning the radiographic anatomy of the thoracic cavity (Wagner & Kirberger 2005, Schillaci et al 2007, Schillaci 2008 and some studies evaluated the Cebus apella reproductive tract (Alves et al 2007, Domingues et al 2007. However, there is no reference to the capuchin monkey and it is worth mentioning that the Cebus apella anatomy is not as well known as that of other monkeys, perhaps due to its restriction to the South American Continent.…”