Sexual dimorphism in the squirrel monkey, Saimiri sciureus (Linnaeus, 1758) and Saimiri ustus (I. Geoffroy, 1844) (Primates, Cebidae)

Causes and implications of sexual dimorphism have been studied in several different primates using a variety of morphological characters such as body weight, canine length, coat color and ornamentation. Here we describe a peculiar coat color characteristic in the squirrel monkey that is present only in adult females over five years old and which increases with age. Neither males nor young animals manifest this phenomenon, which is characterized by a spot of black hairs located anteriorly to the external ear (pinna). This characteristic could be used to discriminate adult females of Saimiri sciureus in the wild without the need of capture techniques

The Sensory Systems of Alouatta: Evolution with an Eye to Ecology

Our knowledge about the perceptual world of howler monkeys is unevenlydistributed between the fi ve senses. Whereas there is abundant knowledge about thesense of vision in the genus Alouatta , only limited data on the senses of hearing,smell, taste, and touch are available. The discovery that howler monkeys are theonly genus among the New World primates to possess routine trichromacy hasimportant implications for the evolution of color vision and therefore has been studiedintensively. Detailed information about the genetic mechanisms and physiologicalprocesses underlying color vision in howler monkeys are available. Although thesound production, vocal repertoire, and acoustic communication in the genusAlouatta have been well documented, basic physiological measures of hearing performancesuch as audiograms are missing. Similarly, despite an increasing numberof observational studies on olfactory communication in howler monkeys, there is acomplete lack of physiological studies on the effi ciency of their sense of smell.Information about the senses of taste and touch is even scarcer and mainly restrictedto a description of their anatomical basis. A goal of this chapter is to summarize ourcurrent knowledge of the anatomy, physiology, genetics, and behavioral relevanceof the different senses in howler monkeys in comparison to other platyrrhines.</p