Doctoral Dissertation Improvement: A Comparative Analysis of Ateline Functional Anatomy and Locomotor Performance

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Upright postures and below branch, suspensory behaviors are key locomotor innovations that led to the anatomical and ecological divergence of apes. However, understanding how and why these behaviors evolved is complicated by an inadequate fossil record and the behavioral diversity of living apes. Unlike the apes, the New World subfamily Atelinae, which includes howler monkeys, woolly monkeys, spider monkeys and woolly spider monkeys, exhibits a broad spectrum of suspensory behaviors and associated morphologies. Thus, this family of monkeys provides a useful model for understanding the relationships between anatomy and behavior in a group of closely related species that rely on suspensory behaviors to different degrees. This study examines the anatomical and behavioral gradient exhibited by atelines and may ultimately inform our understanding of locomotor evolution which is of particular importance in interpreting the behavior of primates, such as the Miocene apes, which are known only by their fossil remains. Although positional frequency data are available for some atelines, differences in functional anatomy and locomotor style are not well quantified. This study analyzes the frequency of specific locomotor modes and examines video based motion analysis data of 3 species of wild atelines including: Alouatta seniculus (howler monkeys), Lagothrix lagothricha (woolly monkeys) and Ateles belzebuth (spider monkeys). These data will be used to generate predictions relating differences in positional behavior to variation in the anatomy of the shoulder, elbow, back, tail and hip. Ten months of behavioral data have already been collected at Tiputini Biodiversity Station in the lowland rainforests of eastern Ecuador. Postcranial skeletal data will be collected, using museum specimens, allowing for the examination of functional anatomical differences among atelines and hominoids. This study is innovative in that it integrates traditional approaches quantifying morphology and locomotor frequencies with canopy level, video based motion analysis techniques previously underutilized in wild primate studies. The overall goals of this research are: (1) to provide comparable, detailed, quantitative documentation of ateline anatomy and locomotor behavior; (2) to illuminate the functional significance of upright/suspensory postcranial features; (3) to further pioneer the use of video based kinematic analyses under non-laboratory conditions; and (4) to evaluate "hominoid" vs. "ateline" adaptations to below branch suspensory behavior.The broader impacts of this study include the mentoring of Ecuadorian and American undergraduates participating in tropical ecology programs at Tiputini Biodiversity Station (TBS), and the prominent participation of women who tend to be underrepresented in the scientific community. Data from this and other ongoing research at TBS also contributes to conservation policies impacting the pristine forests surrounding the station.