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      Spatio‐temporal changes in chimpanzee density and abundance in the Greater Mahale Ecosystem, Tanzania


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          Species conservation and management require reliable information about animal distribution and population size. Better management actions within a species' range can be achieved by identifying the location and timing of population changes. In the Greater Mahale Ecosystem (GME), western Tanzania, deforestation due to the expansion of human settlements and agriculture, annual burning, and logging are known threats to wildlife. For one of the most charismatic species, the endangered eastern chimpanzee ( Pan troglodytes schweinfurthii), approximately 75% of the individuals are distributed outside national park boundaries, requiring monitoring and protection efforts over a vast landscape of various protection statuses. These efforts are especially challenging when we lack data on trends in density and population size. To predict spatio‐temporal chimpanzee density and abundance across the GME, we used density surface modeling, fitting a generalized additive model to a 10‐year time‐series data set of nest counts based on line‐transect surveys. The chimpanzee population declined at an annual rate of 2.41%, including declines of 1.72% in riparian forests (from this point forward, forests), 2.05% in miombo woodlands (from this point forward, woodlands) and 3.45% in nonforests. These population declines were accompanied by ecosystem‐wide declines in vegetation types of 1.36% and 0.32% per year for forests and woodlands, respectively; we estimated an annual increase of 1.35% for nonforests. Our model predicted the highest chimpanzee density in forests (0.86 chimpanzees/km 2, 95% confidence intervals (CIs) 0.60–1.23; as of 2020), followed by woodlands (0.19, 95% CI 0.12–0.30) and nonforests (0.18, 95% CI 0.10–1.33). Although forests represent only 6% of the landscape, they support nearly one‐quarter of the chimpanzee population (769 chimpanzees, 95% CI 536–1103). Woodlands dominate the landscape (71%) and therefore support more than a half of the chimpanzee population (2294; 95% CI 1420–3707). The remaining quarter of the landscape is represented by nonforests and supports another quarter of the chimpanzee population (750; 95% CI 408–1381). Given the pressures on the remaining suitable habitat in Tanzania, and the need of chimpanzees to access both forest and woodland vegetation to survive, we urge future management actions to increase resources and expand the efforts to protect critical forest and woodland habitat and promote strategies and policies that more effectively prevent irreversible losses. We suggest that regular monitoring programs implement a systematic random design to effectively inform and allocate conservation actions and facilitate interannual comparisons for trend monitoring, measuring conservation success, and guiding adaptive management.

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              Defaunation in the Anthropocene.

              We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this "Anthropocene defaunation"; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet's sixth mass extinction and also a major driver of global ecological change. Copyright © 2014, American Association for the Advancement of Science.

                Author and article information

                Ecol Appl
                Ecol Appl
                Ecological Applications
                John Wiley & Sons, Inc. (Hoboken, USA )
                30 September 2022
                December 2022
                : 32
                : 8 ( doiID: 10.1002/eap.v32.8 )
                : e2715
                [ 1 ] School of Biological and Environmental Sciences Liverpool John Moores University Liverpool UK
                [ 2 ] School of Built and Natural Sciences University of Derby Derby UK
                [ 3 ] Greater Mahale Ecosystem Research and Conservation Project Dar es Salaam Tanzania
                [ 4 ] Department of Anthropology University College London London UK
                [ 5 ] School of Mathematics and Statistics University of St. Andrews St. Andrews UK
                [ 6 ] Department of Animal Biology Faculdade de Ciencias da Universidade de Lisboa Lisbon Portugal
                [ 7 ] Department of Conservation Science The Jane Goodall Institute Washington District of Columbia USA
                [ 8 ] Institute of Biodiversity and Ecosystem Dynamics University of Amsterdam Amsterdam Netherlands
                Author notes
                [*] [* ] Correspondence

                Joana S. Carvalho

                Email: j.carvalho@ 123456derby.ac.uk

                Author information
                © 2022 The Authors. Ecological Applications published by Wiley Periodicals LLC on behalf of The Ecological Society of America.

                This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

                : 23 February 2022
                : 07 September 2021
                : 16 June 2022
                Page count
                Figures: 4, Tables: 1, Pages: 15, Words: 9999
                Funded by: Arcus Foundation , doi 10.13039/100016681;
                Funded by: Frankfurt Zoological Society , doi 10.13039/501100003183;
                Funded by: The Nature Conservancy , doi 10.13039/100014596;
                Funded by: National Aeronautics and Space Administration (NASA) , doi 10.13039/100000104;
                Funded by: United States Agency for International Development (USAID) , doi 10.13039/100000200;
                Funded by: Jane Goodall Institute , doi 10.13039/100017812;
                Funded by: Tanzania Wildlife Research Institute , doi 10.13039/501100005914;
                Custom metadata
                December 2022
                Converter:WILEY_ML3GV2_TO_JATSPMC version:6.2.7 mode:remove_FC converted:06.04.2023

                conservation,density surface modeling,detection function estimation,eastern chimpanzee,generalized additive models,great apes,line‐transect distance sampling,spatially explicit models


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