Special Issue: Defaunation’s impact in tropical terrestrial ecosystems Long-term exclosure of large terrestrial vertebrates: Implications of defaunation for seedling demographics in the Amazon rainforest Harald Beck a,⇑ , Joel W. Snodgrass a , Paporn Thebpanya b a Department of Biological Sciences, Towson University, 8000 York Road, Towson, MD 21252, USA b Department of Geography and Environmental Planning, Towson University, 8000 York Road, Towson, MD 21252, USA article info Article history: Received 30 September 2012 Received in revised form 17 February 2013 Accepted 8 March 2013 Available online xxxx Keywords: Defaunation Exclosure Herbivory Non-trophic interactions Peccaries Seedling demography Survival abstract ‘‘Empty forests’’ in which humans have driven large vertebrate species to extinction lack myriad direct and indirect species interactions. This may alter key ecosystem processes, including trophic cascades, dis- turbance regimes, and nutrient cycling. Past research concerning the effects of tropical forest defaunation mainly compared sites with an intact fauna with sites having degraded faunal communities. However, experimental studies on seedling demographics at individual sites, with the same abiotic and biotic con- ditions, over a long period of time are still scarce. In this research we conducted a 7-year experiment within a completely intact and pristine forest in Manu National Park, Peru to elucidate the effects of def- aunation on tree seedling demographics and densities. We constructed semipermeable exclosures that prevented access of large terrestrial vertebrates, but allowed free passage of small- and medium-sized species. New tree seedlings taller than 5 cm were tagged and followed. Jolly–Seber mark-recapture mod- els were used to estimate density, survival, and recruitment of seedlings. Seedling density in the exclo- sures continued to increase significantly after the first year of the study. Only during the first 2 years was seedling survival higher in the exclosures. The numbers of new recruits were consistently higher in exclo- sures when compared to open control plots throughout the study. In accord with increased density, sur- vival, and recruitment in exclosure plots, we also observed increased understory vegetation cover. Our results suggest that defaunation can have long-term effects on seedling demographics and density, which could ultimately influence the composition and diversity of the canopy tree community. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Overhunting of large vertebrates, primarily birds and mam- mals, has spread with alarming rates across tropical continents (e.g. Fa et al., 2002; Corlett, 2007; Redford, 1992; Wilkie et al., 2011). Many large game species have been either extirpated or persist only at greatly reduced densities (Corlett, 2007; Fa and Brown, 2009; Muller-Landau, 2007; Peres and Palacios, 2007; Wilkie et al., 2011). For example, over the last century white- lipped peccaries (Tayassu pecari) have been extirpated from over 21% of their historical range in Central and South America (Altrichter et al., 2012). Wilkie et al. (2011) argue that besides habitat lost, hunting is the principal threat to birds and mam- mals across much of the tropical regions. Defaunated or empty forests (Redford, 1992) lack myriad direct and indirect species interactions, including herbivory, seed predation, dispersal, and trampling of seedlings (Fig. 1), thus resulting in cascading changes in plant and animal composition (Dirzo, 2001; Peres and Dolman, 2000; Peres and Palacios, 2007; Wright, 2003; Wright et al., 2007a,b). In the absence of predation and dispersal of seeds, large seeds of many tree and palm species accumulate underneath their parents (e.g. Dirzo and Miranda, 1990; Galetti et al., 2006; Terborgh, 1988; Wang et al., 2007). These seeds may either start to germinate, which can result in monotypic seedling carpets or perish (Alvarez-Loayza and Terborgh, 2011; Beck, 2007; Dirzo and Miranda, 1991; Dirzo et al., 2007, Wright et al., 2007a). Furthermore, because different animal species preferentially consume seeds or cause mortality to different plant life stages, the response of tree communities to defauna- tion is likely to be complex and site dependent (Beckman and Muller-Landau, 2007; Brocardo et al., this issue; Stoner et al., 2007). To elucidate the effects of defaunation on plant communities, most studies have compared protected forest with ‘‘empty’’ forest sites (i.e. Beck, 2007; Dirzo and Miranda, 1990, 1991; Roldan and Simonetti, 2001; Terborgh et al., 2008; Wright et al., 2007a,b). For instance, Dirzo and Miranda (1991) found lower seedling den- sity but higher diversity and higher rates of vertebrate seedling herbivory in a protected forest compared to a hunted forest in Mexico. Similarly, Terborgh et al. (2008) reported higher overall 0006-3207/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biocon.2013.03.012 ⇑ Corresponding author. Tel.: +1 410 704 3125; fax: +1 410 704 2405. E-mail addresses: Hbeck@towson.edu (H. Beck), Jsnodgrass@towson.edu (J.W. Snodgrass), Pthebpanya@towson.edu (P. Thebpanya). Biological Conservation xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon Please cite this article in press as: Beck, H., et al. Long-term exclosure of large terrestrial vertebrates: Implications of defaunation for seedling demograph- ics in the Amazon rainforest. Biol. Conserv. (2013), http://dx.doi.org/10.1016/j.biocon.2013.03.012