Journal of Tropical Ecology (2009) 25:229–238. Copyright © 2009 Cambridge University Press doi:10.1017/S0266467409005860 Printed in the United Kingdom Short-term post-dispersal fate of seeds defecated by two small primate species (Saguinus mystax and Saguinus fuscicollis) in the Amazonian forest of Peru Laurence Culot ∗, ‡ ,1 , Marie-Claude Huynen ∗ , Paul G ´ erard† and Eckhard W. Heymann‡ ∗ Behavioural Biology Unit, University of Li ` ege, Belgium † Department of Mathematics, University of Li ` ege, Belgium ‡ Department of Behavioural Ecology and Sociobiology, Deutsches Primatenzentrum, G ¨ ottingen, Germany (Accepted 24 January 2009) Abstract: Post-dispersal fate of seeds dispersed by large primates is well studied but little is known about this process in small frugivores like tamarins. This study in the Amazonian forest of Peru aimed at investigating if characteristics related to the defecation patterns of tamarins (Saguinus mystax and Saguinus fuscicollis) affected short-term post- dispersal seed fate, through secondary seed dispersal by dung beetles and removal by seed predators. Data on dung beetle activity were based on direct observations of 49 defecations while seed fate was studied using semi-controlled experiments (N = 458 for secondary dispersal and N = 398 for predation). Tamarins produce small defecations with a low number of seeds. Thirty-five per cent of defecations were visited by an average of 1.5 dung beetles that usually transport the faeces as pellets. Twenty-four per cent of seeds were buried by beetles at a mean depth of 3.5 cm. With increasing quantities of faecal matter, the probability of secondary seed dispersal increased but not the depth of burial. Seed predation pressure was low (17.6%) after 4 d and higher in faeces of S. mystax than in faeces of S. fuscicollis. Despite their small size, tamarins could be considered as high-quality seed dispersers, with a potential role for forest regeneration. Key Words: Amazonia, dung beetles, Saguinus fuscicollis, Saguinus mystax, secondary dispersal, seed predation INTRODUCTION Primary seed dispersal provides the template on which subsequent events and processes like secondary seed dispersal and post-dispersal seed predation can act (Vander Wall & Longland 2005). Seeds dispersed in faeces can be accidentally incorporated into dung balls carried away and then buried, or directly buried by dung beetles digging tunnels beneath the faeces in order to feed or supply their nest with food (Hanski & Cambefort 1991). Most often, seeds are buried in an environment more suitable for germination or safer from detection by rodents (Andresen & Levey 2004, Estrada & Coates-Estrada 1991, Feer 1999, Shepherd & Chapman 1998). However, deep burial can also prevent seedling emergence (Andresen & Levey 2004). Likewise post-dispersal seed predation is one of the major factors affecting the recruitment of plant 1 Corresponding author. Address : Universit´ e de Li` ege, Unit´ e de Biologie du comportement : Ethologie et Psychologie animale, Quai Van Beneden, 22 B ˆ at. I1, 4020 Li` ege. Email: Laurence.Culot@student.ulg.ac.be species (Hulme 2002) and it can be very high and variable in space and time (Crawley 2000). Primates, constituting 25–40% of the frugivore biomass within the tropical forests they exploit (Chapman 1995), are among the main seed dispersers in these ecosystems. The majority of studies of primate seed dispersal, and particularly on the post-dispersal fate of primate-dispersed seed, focuses on large primates (Andresen 1999, Estrada & Coates-Estrada 1984, Kaplin & Lambert 2002, Kunz & Linsenmair 2007, Stevenson et al. 2002, Wrangham et al. 1994). Lack of information on the fate of seeds dispersed by small primates may partly be due to the difficulty of finding and following the fate of seeds in small defecations, but it is also related to the frequent assumption that larger primates are more effective seed dispersers because they produce large defecations with many seeds. However, this pattern has been considered disadvantageous to seed survival as clumped seeds are removed more rapidly than scattered seeds (Feer & Forget 2002). Effective seed dispersal depends on the quantity but also on the quality of