Journal of Herpetology , Vol. 48, No. 3, 338–342, 2014 Copyright 2014 Society for the Study of Amphibians and Reptiles Researcher Disturbance Has Minimal Impact on Natural Predation of Caiman Nests in Central Amazonia JOSE ´ ANT ´ ONIO LEMOS BAR ˜ AO-N ´ OBREGA, 1,2 BORIS MARIONI, 3 FRANCISCO VILLAMARI ´ N, 4 AMADEU M. V. M. SOARES, 1,5 WILLIAM E. MAGNUSSON, 6 AND RONIS DA SILVEIRA 7 1 Departamento de Biologia, Universidade de Aveiro–UA, Campus de Santiago, 3810-193, Aveiro, Portugal 3 Amazonian Caiman Conservation Program–Piaga ¸ cu Institute, Rua UZ n88 Cj Morada do Sol, 6900-000, Manaus-AM, Brazil 4 Instituto Nacional de Pesquisas da Amaz ˆ onia-Programa de P ´ os-Gradua ¸ c˜ ao em Ecologia e Programa de Capacita ¸ c˜ ao Institucional PCI/MCT/INPA. Av. Andre ´ Ara ´ ujo 2936, CEP 69060-001, Manaus-AM, Brazil 5 Centro de Estudos do Ambiente e do Mar–CESAM, Campus de Santiago, 3810-193, Aveiro, Portugal 6 Coordena ¸ c˜ ao de Biodiversidade, Instituto Nacional de Pesquisas da Amaz ˆ onia, CP 478, 69011-970, Manaus-AM, Brazil 7 Laborat ´ orio de Zoologia-Aplicada ` a Conserva ¸ c˜ ao, Departamento de Biologia, Instituto de Ci ˆ encias Biol ´ ogicas, Universidade Federal do Amazonas, Av. Gen. Rodrigo Ota ´vio 3000, CEP 69077070, Manaus, Amazonas, Brazil ABSTRACT.—Predation is one of the major causes of crocodilian egg mortality. Many studies have suggested that opening nests, handling eggs, and capturing attending females may increase predation rates, but the influence of such activities on nest predation has not been quantified. For that reason, we studied the impacts of different research activities on nests of wild Spectacled Caimans (Caiman crocodilus crocodilus) from a flooded forest (va ´ rzea) in the Piaga ¸ cu-Purus Sustainable Development Reserve, Central Amazonia. During the 2010 nesting season, predation on eggs in disturbed nests was generally higher than in nests without research activities found in the same area. However, natural predation rates in similar habitat were not significantly different, suggesting that predation rates on disturbed nests, though elevated, remain within the broad range found in undisturbed nests. We conclude that the benefits in knowledge gained from research activities will generally out-weigh the small increase in nest predation that could result from research activities. RESUMO.—A preda ¸ c ˜ao constitui uma das principais causas de mortalidade dos ovos em crocodilianos. Va ´rios autores sugerem que o abrir os ninhos, manusear os ovos e capturar as respetivas f ˆ emeas, podera ´ aumentar as taxas de preda ¸ c ˜ao. No entanto, o impacto destas atividades ainda n ˜ ao foi quantificado. Por esse motivo, n ´ os estudamos diferentes nı´veis de impacto de pesquisa nos ninhos e respetivas f ˆ emeas de jacaretinga (Caiman crocodilus crocodilus) na floresta de va ´rzea da Reserva de Desenvolvimento Sustenta ´vel Piaga ¸ cu-Purus, Amaz ´ onia Central. Durante a e ´poca de nidifica ¸ c ˜ao de 2010, a preda ¸ c ˜ao dos ovos em ninhos perturbados por actividades de pesquisa foi, de maneira geral, superior ao observado em ninhos n ˜ ao perturbados, encontrados no mesmo local. No entanto, as taxas de preda ¸ c ˜ao naturais em habitat semelhante n ˜ ao demonstraram ser significativamente diferentes, o que sugere que as taxas de preda ¸ c ˜ao em ninhos perturbados, mesmo apesar de elevadas, permanecem dentro do intervalo observado em ninhos n ˜ ao perturbados. Desta forma, concluı´mos que todo o conhecimento obtido durante actividades de pesquisa ira ´ compensar a possibilidade de um pequeno aumento na preda ¸ c ˜ao dos ninhos, que podera ´ surgir em consequ ˆ encia de abrir os ninhos e manusear os ovos ou as f ˆ emeas. Predation is a major source of egg mortality in many long- lived tetrapods (Gregoire and Gunzburger, 2008; Strickland et al., 2010; Somaweera et al., 2011). However, little is known about the factors that affect predation rates (Bowen and Janzen, 2005). Predators find reptilian eggs based on features related to nest structure or by visual and/or olfactory cues left by the attending female during nest construction and maintenance (Strickland et al., 2010). The relative importance of each cue varies with species and environmental conditions (e.g., wind, rain; Bowen and Janzen, 2005; Burke et al., 2005; Rollinson and Brooks, 2007). At least three of the four Amazonian caiman species nest in floodplain (va ´rzea) habitats during the annual dry season, when the river water levels in the Amazon Basin are at their lowest levels (Thorbjarnarson and Da Silveira, 2000; Da Silveira et al., 2010; Villamarı ´n et al., 2011). Information indicates that Jaguar (Panthera onca), Gold Tegu (Tupinambis teguixin), Brown Capuchin Monkey (Sapajus (formerly Cebus) apella; Alfaro et al., 2011), and local people (Homo sapiens; Da Silveira et al., 2010) are the main predators of caiman eggs and thus nest disturbance. Research activities (e.g., human scent and soil disturbance around the nest) may also affect nest predation rates (Burke et al., 2005; Strickland et al., 2010). However, few studies have investigated how human interference with nests, eggs, and nesting females may affect crocodilian nest predation, even though the nesting period is probably the most vulnerable life- history stage in crocodilians (Pough et al., 1993; Vitt and Caldwell, 2009). It has been suggested that opening the nest, handling the eggs, and capturing nesting females during scientific studies may cause the mother to abandon the nest, potentially increasing predation rates (Staton and Dixon, 1977; Campos, 1993; Ayarzagu ¨ ena and Castroviejo, 2008). However, little is known about the effects of human interventions on nests of wild crocodilians (Deitz and Hines, 1980; Campos and Mour ˜ ao, 2010). Our objective was to evaluate natural predation and the possible impacts that research activities (manipulating nests, eggs, and attending females) have on mortality of eggs in wild Spectacled Caimans (Caiman crocodilus crocodilus) living in two protected floodplain areas in the Amazon biome. MATERIALS AND METHODS Study Area.— Our study was conducted primarily in Piaga ¸ cu- Purus Sustainable Development Reserve (PP-SDR), located between the Purus and Madeira rivers (04805 0 S, 61844 0 W and 5820 0 S, 63820 0 W), approximately 350 km southwest of Manaus, Amazonas, Brazil. It encompasses about 834,245 ha of terra-firme forest (not flooded by major rivers) and seasonal flood plains known locally as va ´rzea or igap ´ o (Deus et al., 2010). Va ´rzea covers about 50% of the reserve, ranging from lakes and canals covered 2 Corresponding Author. E-mail: joseantonio@ua.pt DOI: 10.1670/13-081