Howler monkeys, genus Alouatta, are the sole survivors of a relatively long (middle Miocene to modern), geographically widespread, and ecologically and morphologically diverse clade (Rosenberger et al. 2014). The genus is currently represented by some 12 species of fruit, leaf, and flower feeding New World primates that range from southern Mexico to northern Argentina (see Cortés-Ortiz et al. 2014). In fact, Alouatta has the most widespread distribution of any platyrrhine genus and can exploit forest types that vary from undisturbed rainforest to severely anthropogenically impacted forest fragments adjacent to pastureland, agricultural fields, and human communities (Di Fiore et al. 2011; Estrada 2014). In many instances, howlers are the only primate species found in such highly disturbed habitats (Benchimol and Peres 2014). Their extended distributional range, their survival and exploitation of highly impacted forested patches, and their energy-minimizing behavior make them relatively easy to observe and this has resulted in numerous studies of their biology and behavior (see reviews in Crockett and Eisenberg 1987; Kinzey 1997; Milton 1998; Di Fiore et al. 2011). These include short-term and long-term field studies on the ecology, behavior, and demography of individual howler species, as well as studies of morphology, genetics, and physiology aimed at evaluating the evolutionary and adaptive history of this genus. Given this relatively robust literature on Alouatta, we have edited two volumes on howler monkeys. The goals of these two volumes are to bring together expert scholars, many from habitat countries, to contribute to a comprehensive corpus that reviews, integrates, and evaluates current information on howler behavior, ecology, nutrition, morphology, physiology, reproduction, evolution, and conservation. Moreover, recently published studies on howler systematics, functional morphology, physiology, and nutritional ecology highlight the growing importance of the genus Alouatta as a comparative model for examining platyrrhine evolution and the parallel social and ecological problems faced by species of prosimians, New World monkeys, Old World monkeys, and apes (Rosenberger et al. 2009; Kowalewski and Garber 2010; Di Fiore et al. 2011; Garber and Kowalewski 2011; Benchimol and Peres 2014; Halenar and Rosenberger 2013; Van Belle and Bicca-Marques 2014; Matsushita et al. 2014).
Youlatos, D., Kowalewski, M. M., Garber, P. A., & Cortés-Ortiz, L. (2015). New challenges in the study of howler monkey anatomy, physiology, sensory ecology, and evolution: Where we are and where we need to go? In Howler Monkeys: Adaptive Radiation, Systematics, and Morphology (pp. 403–414). Springer New York. https://doi.org/10.1007/978-1-4939-1957-4_15