203 © 2020 The Linnean Society of London, Biological Journal of the Linnean Society, 2020, 131, 203–219 Biological Journal of the Linnean Society, 2020, 131, 203–219. With 8 figures. Being hunted high and low: do differences in nocturnal sleeping and diurnal resting sites of howler monkeys (Alouatta nigerrima and Alouatta discolor) reflect safety from attack by different types of predator? THAYS JUCÁ 1, , SARAH BOYLE 2 , GITANA CAVALCANTI 3 , THIAGO CAVALCANTE 1 , PAVEL TOMANEK 4 , SALATIEL CLEMENTE 5 , TADEU DE OLIVEIRA 6 , and ADRIAN A. BARNETT 1,7,8,9, * 1 Amazonian Mammals Research Group, National Institute for Amazonian Research (INPA), Manaus, Amazonas 69067-001, Brazil 2 Department of Biology, Rhodes College, Memphis, Tennessee 31270-901, USA 3 Department of Ecology, Conservation and Wildlife Management, Institute of Biological Science, Federal University of Minas Gerais (UFMG), Belo Horizonte, Minas Gerais 31270-901, Brazil 4 Department of Animal Science and Ethology, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Prague 165 00, Czech Republic 5 Ecology and Natural Resource Management, Federal University of Acre (UFAC), Acre 69920-900, Brazil 6 Department of Biology, Maranhão State University (UEMA), São Luís, Maranhão 65080-805, Brazil 7 Zoology Department, Amazonas Federal University (UFAM), Manaus, Amazonas, 69077-000 Brazil 8 Centre for Research in Evolutionary Anthropology, University of Roehampton, London SW15 5PJ, UK 9 Department of Zoology, Federal University of Pernambuco (UFPE), Recife, Pernambuco 50670-420, Brazil Received 6 February 2020; revised 1 June 2020; accepted for publication 5 June 2020 Predation risk is important in influencing animal behaviour. We investigated how the choice of nocturnal sleeping and diurnal resting sites by two species of primates was influenced by the most likely forms of attack (diurnal raptors and nocturnal felids). We recorded vertical and horizontal patterns of occupancy for 47 sleeping and 31 resting sites, as well as the presence of lianas or vines on trees. We compared the heights of trees used as resting or sleeping sites by the monkeys with those of 200 forest trees that the monkeys did not use. Trees used as nocturnal sleeping sites were taller than those used as diurnal resting sites, and taller than trees that the monkeys did not use. However, while trees used as diurnal resting sites were not significantly taller than non-used trees, diurnal resting sites were located on branches closer to the ground, closer to the main trunk of the tree and in trees with more lianas/vines than nocturnal sleeping sites. The differences in site location can be explained by the type of predator most likely to attack at a particular time: raptors in the day and felids at night. ADDITIONAL KEYWORDS: Amazonia – predation risk – primate – risk sensitivity. Though’ I know I’ll be hunting high and low … There’s no end to the lengths I’ll go to. a-ha (lyrics: Pål Waaktaar) INTRODUCTION Predator-sensitive behaviour is widespread in animals and permeates many aspects of their biology including foraging, movement, group-dynamics and refuge occupation (Caro, 2005). Such responses have been documented in a wide variety of organisms [spiders (Reichert & Hedrick, 1990); insects (Kortet et al., 2007); molluscs (Hamilton & Heithaus, 2001); *Corresponding author. E-mail: adrian.barnett1.biology@ gmail.com Downloaded from https://academic.oup.com/biolinnean/article/131/1/203/5887841 by guest on 10 November 2023