85 © Springer Science+Business Media New York 2015 M.M. Kowalewski et al. (eds.), Howler Monkeys, Developments in Primatology: Progress and Prospects, DOI 10.1007/978-1-4939-1960-4_4 Chapter 4 Evidence of Alternative Dietary Syndromes and Nutritional Goals in the Genus Alouatta Paul A. Garber, Nicoletta Righini, and Martín M. Kowalewski Abstract Howler monkeys exploit difficult-to-digest and potentially toxic food items such as mature leaves and unripe fruits; persist across an extreme range of habitat types, including highly disturbed forests; and have the most widespread geo- graphical distribution of any genus of New World primate. Given evidence of dietary variability in the amount of monthly fruit, leaf, and flower consumption, howler monkeys provide an instructive model for examining relationships among foraging strategies, activity budgets, and patterns of habitat utilization. In this chap- ter we examined evidence for interspecific differences in dietary patterns and nutri- tional ecology within the genus Alouatta and identified three dietary “syndromes” that are generally consistent with howler monkey phylogeny and biogeography. Specifically, we show that Mesoamerican howler monkeys and A. seniculus are characterized by a balanced leaf and fruit diet, Amazonian species by a fruit enriched diet, and Atlantic Forest and southern howler monkeys by a leaf-enriched diet. Finally, to be able to identify species-specific dietary strategies and syndromes across the primate Order, we recommend an approach that includes collecting data on feeding rates and the nutritional composition of the diet. Resumen Los monos aulladores consumen alimentos difíciles de digerir y que potencialmente contienen compuestos secundarios tóxicos como hojas maduras y frutos inmaduros; habitan en tipos de ambientes muy variados, incluyendo áreas altamente fragmentadas, y tienen la distribución geográfica más amplia de cualquier otro género de primates neotropicales. Debido a las conspicuas fluctuaciones men- suales en las cantidades de frutos, hojas y flores consumidos, los monos aulladores constituyen un modelo útil para examinar las relaciones entre estrategias de forrajeo, P.A. Garber (*) Department of Anthropology, University of Illinois, Urbana, IL, USA Program in Ecology, Evolution, and Conservation Biology, University of Illinois, Urbana, IL, USA e-mail: p-garber@illinois.edu N. Righini Department of Anthropology, University of Illinois, Urbana, IL, USA M.M. Kowalewski Estación Biológica Corrientes, Museo Argentino de Ciencias Naturales, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina