AN ABSTRACT OF THE THESIS OF Paola M. Carrera-Ubidia for the degree of Master of Science in Wildlife Science presented on December 12, 2006. Title: Giant Otters (Pteronura brasiliensis) and Humans in the Lower Yasuní Basin, Ecuador: Spacio-temporal Activity Patterns and Their Relevance for Conservation Abstract approved: ___________________________________ Dr. Selina S. Heppell Giant otters (Pteronura brasiliensis) and humans in the Lower Yasuní Basin (Ecuador) have similar food and space requirements: they consume comparable arrays of fish species, and they use similar aquatic and terrestrial habitats. Resource partitioning could facilitate coexistence by allowing each species exclusive access to some resources. My research examines the correlations between the use of spatial resources by giant otters and humans and the hydrological pulse of their ecosystem. My objectives were (1) to estimate the extent of terrestrial and aquatic habitat available for giant otters and humans; (2) to recognize the main patterns of space occupancy and its overlap between them; (3) to explain these patterns in relation to natural gradients in the watershed; (4) to describe the giant otter’s diet; and (5) to depict the foraging activities of giant otters and humans relative to the distribution of prey. Between October 2004 and March 2005, I surveyed the Jatuncocha and Tambococha Creeks (Yasuní National Park) for direct and indirect signs of giant otters and humans, and I collected giant otter scat. Habitat availability was estimated by a geo-referenced map model that integrated virtual and field data, portraying four seasonal scenarios. Space use overlaps between giant otters and humans are a function of water level and the distance between terrestrial and aquatic habitats. The floodplain comprises 43% of the total study area during the flooding season, and is reduced to 25% of the total area at minimum water levels. Polygons obtained containing suitable habitat for giant otters are in average 41% larger than those obtained for humans; these contain areas that are inaccessible to humans (isolated pools and swamps, tributaries, and the upper portions of the main channel). Differences in space availability for and use by giant otters and humans depend on water level fluctuations. Area occupancy by both species is proportional to the estimated availability; but more so for giant otters, as humans increase area occupancy during the driest periods. Giant otter activity was primarily concentrated around the largest tributaries of each creek, and secondarily wherever the distance between suitable terrestrial and aquatic habitat was smaller. Human activity signs were distributed along the hydrographical gradient, i.e. in the lower portion of the Jatuncocha System (lagoon) or in the middle portion of the Tambococha Creek (large tributary). To identify correlations between habitat use by giant otters and humans and prey availability, I analyzed scat samples and collected fish along several creek stretches. Giant otters consumed at least 47 of the 73 species available for them. Identifiable hard parts in the scat samples consisted primarily of Hoplias malabaricus (11.3%), Hypselecara termporalis (5.3%), Acestrorrhynchus sp. and Prochilodus nigricans (4.9% each). Foraging activity of giant otters was positively correlated with fish abundance and relative diversity, with some exceptions. Human activity patterns were related to fish abundance and diversity in Tambococha, but showed less correlation to fish distribution in Jatuncocha. Overlap in resource availability and habitat use by otters and humans is highly variable. In the floodplain, extent and depth are critical variables that determine the distribution of resources in time and space, as well as the amount of resource partitioning possible. Competitive interactions during stressful conditions could be reduced by ensuring the availability of exclusive resources for giant otters during the driest periods, allocating suitable habitats within a short distance from one another along the longitudinal gradient of each watershed. Locally adapted and biologically sound regulations within this and comparable areas of the YNP could promote the persistence of giant otters without compromising the well-being of the local human inhabitants. © Copyright by Paola M. Carrera-Ubidia December 12, 2006 All Rights Reserved Giant Otters (Pteronura brasiliensis) and Humans in the Lower Yasuní Basin, Ecuador: Spacio-temporal Activity Patterns and Their Relevance for Conservation By Paola M. Carrera-Ubidia A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented December 12, 2006 Commencement June 2007 Master of Science Thesis for Paola M. Carrera-Ubidia presented on December 12, 2006. APROVED: _________________________________________ Major Professor, Representing Wildlife Science ___________________________________________ Head of the Department of Fisheries and Wildlife ____________________________ Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. ______________________________________________ Paola M. Carrera-Ubidia, Author ACKNOWLEDGEMENTS This page is not enough room to express my infinite gratitude to the people that made my research and the final version of this document possible. I will be forever thankful To my parents, José Carrera and Magdalena Ubidia, who supported me at all times and contributed with moral and financial aid whenever needed. To the Fulbright Commission, for honoring me with a two year scholarship that made my masters degree possible, and particularly to Dr. Suzana Cabeza de Vaca, and the Fulbright staff in Ecuador, who believed in my ability to cope with this challenge and encouraged me to take a chance that so radically changed my life. To the Office of International Education at Oregon State University, which honored me with a full tuition waiver at OSU; a very special thanks to my International Advisor, Marybeth Trevino, who was a source of infinite support and friendship. To Selina Heppell, my advisor, and Scott and Dylan Heppell, who, even without knowing much about me, welcomed me in their lives. Selina has been a source of inspiration as a scientist and as a woman; her example, patience, constant support and friendliness were a permanent source of motivation for me ever since I arrived to OSU. I will be always grateful for the trust you placed in me Selina, and I am so fortunate and honored to have had the chance to be your student… Thank you! To my committee members, Drs. Douglas Markle and Mary Santelmann for their support and contribution with many ideas that improved this document; their experience and scientific advice were always helpful and insightful. To Dr. Nicole Duplaix, who contributed with so many valuable comments to this document and has been a light of guidance and hope during the toughest moments. Always willing to share giant otter stories, and pictures, her experience and knowledge were enormous contributions to my papers. Je vous remercie énormement, Nicole … Merci beaucoup! To my friends at the Heppell Lab and elsewhere, particularly Giana Gómez, Brett Gallagher, Megan Petrie, Brianna Paterson, Brooke Martin, Abigail McCarthy, Marisa Litz, Craig Tinus, Josie Thompson, Kate Boersma, Jeremiah Osborne-Gowey, and Jed Moore, for the support and the fun, for being such generous comrades, confidents, friends, and even accomplices… I will miss you all! To my field assistants, David “Chino” Grefa, and Antonio “Mocho” Jota; without their help and skills I would have lost either one of my extremities, my mental sanity or my life. Their trust in me and willingness to help at all times and in any conditions, their contributions with useful ideas, their endurance, friendship and sense of humor in the field will always be appreciated. Gracias panitas! To the Rodas family in Nuevo Rocafuerte who provided logistic support and welcomed me in their home as one of their own… I will always be in debt for your help… ¡Muchas gracias por todo Don César, Doña Inmelda, Kerlita, Natalie, Vanessa e Isabel! To the Tambococha park guards, Don Belisario Hualinga and family, Don Eduardo López, and Don Genaro Merino †. Their knowledge, experience and insight were priceless contributions to my understanding of giant otters and of the rainforest. To the members of the local community that provided useful information for this study, in particular Don Abel Grefa† and family, Don Carlos Cox, Don Jaime Cabrera, Don Sandro and Hugo Ramos. A special thanks to the members of the Nuevo Rocafuerte Marina, in particular Cptn. Stalin Naranjo, for providing logistic and communications support to this project. To Tom Koerber from the Department of State’s Institute of International Education in San Francisco, California; his permanent support and patience made it possible for me to stay and extend my legal status in the USA. To the Wildlife Conservation Society – Ecuador, especially to Victor Utreras and Esteban Suárez, for their institutional support in Quito, and to Efrain “Frencho” Tenorio and the WCS-Coca staff for their technical and physical support in the field. To Dr. Dawn Wright (GeoSciences) and Dr. Collette Coiner (OSU Outreach Extension), for important advise and technical contributions to the GIS portion of this dissertation. To Dr. Rodrigo Sierra and MSc.