Timothy M. Eppley, Selwyn Hoeks, Colin A. Chapman, Jörg U. Ganzhorn, Katie Hall, Megan A. Owen, Dara B. Adams, Néstor Allgas, Katherine R. Amato, McAntonin Andriamahaihavana, John F. Aristizabal, Andrea L. Baden, Michela Balestri, Adrian A. Barnett, Júlio César Bicca-Marques, Mark Bowler, Sarah A. Boyle, Meredith Brown, Damien Caillaud, Cláudia Calegaro-Marques, Christina J. Campbell, Marco Campera, Fernando A. Campos, Tatiane S. Cardoso, Xyomara Carretero-Pinzón, Jane Champion, Óscar M. Chaves, Chloe Chen-Kraus, Ian C. Colquhoun, Brittany Dean, Colin Dubrueil, Kelsey M. Ellis, Elizabeth M. Erhart, Kayley J. E. Evans, Linda M. Fedigan, Annika M. Felton, Renata G. Ferreira, Claudia Fichtel, Manuel L. Fonseca, Isadora P. Fontes, Vanessa B. Fortes, Ivanyr Fumian, Dean Gibson, Guilherme B. Guzzo, Kayla S. Hartwell, Eckhard W. Heymann, Renato R. Hilário, Sheila M. Holmes, Mitchell T. Irwin, Steig E. Johnson, Peter M. Kappeler, Elizabeth A. Kelley, Tony King, Christoph Knogge, Flávia Koch, Martin M. Kowalewski, Liselot R. Lange, M. Elise Lauterbur, Edward E. Louis, Meredith C. Lutz, Jesús Martínez, Amanda D. Melin, Fabiano R. de Melo, Tsimisento H. Mihaminekena, Monica S. Mogilewsky, Leandro S. Moreira, Letícia A. Moura, Carina B. Muhle, Mariana B. Nagy-Reis, Marilyn A. Norconk, Hugh Notman, M. Teague O’Mara, Julia Ostner, Erik R. Patel, Mary S. M. Pavelka, Braulio Pinacho-Guendulain, Leila M. Porter, Gilberto Pozo-Montuy, Becky E. Raboy, Vololonirina Rahalinarivo, Njaratiana A. Raharinoro, Zafimahery Rakotomalala, Gabriel Ramos-Fernández, Delaïd C. Rasamisoa, Jonah Ratsimbazafy, Maholy Ravaloharimanitra, Josia Razafindramanana, Tojotanjona P. Razanaparany, Nicoletta Righini, Nicola M. Robson, Jonas da Rosa Gonçalves, Justin Sanamo, Nicole Santacruz, Hiroki Sato, Michelle L. Sauther, Clara J. Scarry, Juan Carlos Serio-Silva, Sam Shanee, Poliana G. A. de Souza Lins, Andrew C. Smith, Sandra E. Smith Aguilar, João Pedro Souza-Alves, Vanessa Katherinne Stavis, Kim J. E. Steffens, Anita I. Stone, Karen B. Strier, Scott A. Suarez, Maurício Talebi, Stacey R. Tecot, M. Paula Tujague, Kim Valenta, Sarie Van Belle, Natalie Vasey, Robert B. Wallace, Gilroy Welch, Patricia C. Wright, Giuseppe Donati, and Luca Santini
Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods. Therefore, we investigated predominantly arboreal, diurnal primate genera from the Americas and Madagascar that lack fully terrestrial taxa, to determine whether ecological drivers (habitat canopy cover, predation risk, maximum temperature, precipitation, primate species richness, human population density, and distance to roads) or species-specific traits (body mass, group size, and degree of frugivory) associate with increased terrestriality. We collated 150,961 observation hours across 2,227 months from 47 species at 20 sites in Madagascar and 48 sites in the Americas. Multiple factors were associated with ground use in these otherwise arboreal species, including increased temperature, a decrease in canopy cover, a dietary shift away from frugivory, and larger group size. These factors mostly explain intraspecific differences in terrestriality. As humanity modifies habitats and causes climate change, our results suggest that species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use.