Journal of Tropical Ecology (2007) 23:599–602. Copyright © 2007 Cambridge University Press doi:10.1017/S0266467407004294 Printed in the United Kingdom SHORT COMMUNICATION Synergistic impacts of ungulates and falling palm fronds on saplings in the Amazon Harald Beck ∗ Duke University, Center for Tropical Conservation, P.O. Box 90381, Durham, North Carolina 27708-0381, USA and Department of Biological Sciences, Towson University, 8000 York Road, Towson, Maryland 21252, USA (Accepted 4 May 2007) Key Words: animal–plant interaction, Iriartea deltoidea, litterfall, Manu National Park, peccaries, physical damage, saplings, Tayassuidae, ungulates Most seedlings and saplings remain in the forest under- storey for decades before becoming adults or dying, and thus may be exposed to various sources of physical disturbance (Clark & Clark 1991, 2001). Because tree species vary in their ability to recover after physical damage (Gillman et al. 2003, Guariguata 1998), this damage can act as an ecological filter and influence the juvenile community structure and species composition (Peters et al. 2004). Studies have demonstrated the occurrence and magnitude of stem breakage in juveniles caused by falling branches and other canopy debris (Clark & Clark 1989, 1991; Gillman & Ogden 2001, Scariot 2000). Surprisingly, little is known about the magnitude and ecological consequences of physical damage to juvenile plants by mammals, particularly large ungulates, including herbivory, trampling and uprooting (Gillman & Ogden 2003, Rold ´ an & Simonetti 2001). Studies that ignore mammalian activities that con- tribute to sapling damage may lead to erroneous con- clusions. For instance, Peters et al. (2004) reported that falling palm fronds led to higher rates of sapling damage underneath Iriartea deltoidea palms than away from the palms. The authors demonstrated that plant species composition underneath I. deltoidea differed from that away, and argued that falling fronds may select for species that can recover after frequently occurring disturbances. Because I. deltoidea is the dominant tree species within the western Amazon (Pitman et al. 2001), Peters et al. (2004) concluded that falling I. deltoidea fronds may act as an ecological filter and influence the sapling community composition across the Amazon. ∗ Email: hbeck@towson.edu However, falling fronds are not the only source of sapling damage underneath I. deltoidea. Throughout the Neotropics, palm fruits are a major food resource for frugivores (Beck 2005, 2006; Bodmer 1990, 1991; Terborgh 1986), and fallen I. deltoidea fruits attract many ungulates including tapir (Tapirus terrestris Linnaeus), brocket deer (Mazama spp.) (Bodmer 1990, 1991; Bodmer & Ward 2006, Rivero et al. 2005) and particularly collared (Tayassu tajacu Linnaeus) and white-lipped peccaries (T. pecari Link) (Beck 2006, Bodmer & Ward 2006). Among all neotropical mammals, white-lipped peccaries form the largest foraging groups (sometimes consisting of hundreds of individuals) and have the largest biomass (370 kg km −2 ) (Beck 2005, 2006; Silman et al. 2003). Peccaries forage primarily underneath palms, where most of the fallen seeds are located (Beck 2005, 2006; Beck & Terborgh 2002, Fragoso 1997) and their trampling and erratic foraging behaviour can damage juvenile plants growing underneath palms (Beck 2006, Fragoso 1997, Rold´ an & Simonetti 2001). Tapir and brocket deer species also forage for palm fruits underneath palms and browse saplings and understorey vegetation (Bodmer 1990, 1991; Bodmer & Ward 2006, Rivero et al. 2005). To test whether fallen palm fronds or foraging ungulates lead to higher incidences of sapling damage, I repeated the study of Peters et al. (2004) at two sites within a tract of > 1.5 million ha of the Peruvian Amazon. The first site, Cocha Cashu Biological Station (and the original site for the aforementioned study), is located within Manu National Park and Biosphere Reserve (11 ◦ 52 ′ S, 71 ◦ 21 ′ W) where hunting is prohibited (hereafter non- hunted site) and thus ungulates, in particular peccaries, are found at high densities (Silman et al. 2003). Because of its pristine setting and high species richness, in 1977 the UNESCO recognized Manu as a Biosphere Reserve