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Voysey MD, de Bruyn PJN, Davies AB. Are hippos Africa's most influential megaherbivore? A review of ecosystem engineering by the semi-aquatic common hippopotamus. Biol Rev Camb Philos Soc 2023; 98:1509-1529. [PMID: 37095627 DOI: 10.1111/brv.12960] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 03/30/2023] [Accepted: 04/03/2023] [Indexed: 04/26/2023]
Abstract
Megaherbivores perform vital ecosystem engineering roles, and have their last remaining stronghold in Africa. Of Africa's remaining megaherbivores, the common hippopotamus (Hippopotamus amphibius) has received the least scientific and conservation attention, despite how influential their ecosystem engineering activities appear to be. Given the potentially crucial ecosystem engineering influence of hippos, as well as mounting conservation concerns threatening their long-term persistence, a review of the evidence for hippos being ecosystem engineers, and the effects of their engineering, is both timely and necessary. In this review, we assess, (i) aspects of hippo biology that underlie their unique ecosystem engineering potential; (ii) evaluate hippo ecological impacts in terrestrial and aquatic environments; (iii) compare the ecosystem engineering influence of hippos to other extant African megaherbivores; (iv) evaluate factors most critical to hippo conservation and ecosystem engineering; and (v) highlight future research directions and challenges that may yield new insights into the ecological role of hippos, and of megaherbivores more broadly. We find that a variety of key life-history traits determine the hippo's unique influence, including their semi-aquatic lifestyle, large body size, specialised gut anatomy, muzzle structure, small and partially webbed feet, and highly gregarious nature. On land, hippos create grazing lawns that contain distinct plant communities and alter fire spatial extent, which shapes woody plant demographics and might assist in maintaining fire-sensitive riverine vegetation. In water, hippos deposit nutrient-rich dung, stimulating aquatic food chains and altering water chemistry and quality, impacting a host of different organisms. Hippo trampling and wallowing alters geomorphological processes, widening riverbanks, creating new river channels, and forming gullies along well-utilised hippo paths. Taken together, we propose that these myriad impacts combine to make hippos Africa's most influential megaherbivore, specifically because of the high diversity and intensity of their ecological impacts compared with other megaherbivores, and because of their unique capacity to transfer nutrients across ecosystem boundaries, enriching both terrestrial and aquatic ecosystems. Nonetheless, water pollution and extraction for agriculture and industry, erratic rainfall patterns and human-hippo conflict, threaten hippo ecosystem engineering and persistence. Therefore, we encourage greater consideration of the unique role of hippos as ecosystem engineers when considering the functional importance of megafauna in African ecosystems, and increased attention to declining hippo habitat and populations, which if unchecked could change the way in which many African ecosystems function.
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Affiliation(s)
- Michael D Voysey
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
| | - P J Nico de Bruyn
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
| | - Andrew B Davies
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
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Subalusky AL, Sethi SA, Anderson EP, Jiménez G, Echeverri-Lopez D, García-Restrepo S, Nova-León LJ, Reátiga-Parrish JF, Post DM, Rojas A. Rapid population growth and high management costs have created a narrow window for control of introduced hippos in Colombia. Sci Rep 2023; 13:6193. [PMID: 37062768 PMCID: PMC10106455 DOI: 10.1038/s41598-023-33028-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 04/06/2023] [Indexed: 04/18/2023] Open
Abstract
The introduction of hippos into the wild in Colombia has been marked by their rapid population growth and widespread dispersal on the landscape, high financial costs of management, and conflicting social perspectives on their management and fate. Here we use population projection models to investigate the effectiveness and cost of management options under consideration for controlling introduced hippos. We estimate there are 91 hippos in the middle Magdalena River basin, Colombia, and the hippo population is growing at an estimated rate of 9.6% per year. At this rate, there will be 230 hippos by 2032 and over 1,000 by 2050. Applying the population control methods currently under consideration will cost at least 1-2 million USD to sufficiently decrease hippo population growth to achieve long-term removal, and depending on the management strategy selected, there may still be hippos on the landscape for 50-100 years. Delaying management actions for a single decade will increase minimum costs by a factor of 2.5, and some methods may become infeasible. Our approach illustrates the trade-offs inherent between cost and effort in managing introduced species, as well as the importance of acting quickly, especially when dealing with species with rapid population growth rates and potential for significant ecological and social impacts.
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Affiliation(s)
| | - Suresh A Sethi
- Fisheries, Aquatic Science, and Technology Laboratory, Alaska Pacific University, Anchorage, Alaska, USA
| | - Elizabeth P Anderson
- Department of Earth and Environment and Institute of Environment, Florida International University, 11200 SW 8Th St, Miami, FL, USA
| | - Germán Jiménez
- Departamento de Biología, Pontificia Universidad Javeriana, Carrera 7 No. 43-82, Edificio Jesús Emilio Ramírez, Bogotá, Colombia
| | - David Echeverri-Lopez
- Corporación Autónoma Regional de Las Cuencas de los Ríos Negro Y Nare (CORNARE), Carrera 59 44-48, El Santuario, Antioquia, Colombia
| | - Sebastián García-Restrepo
- Departamento de Ciencias Biológicas, Universidad de los Andes, Carrera 1 No. 18A-10, Bogotá, Colombia
| | - Laura J Nova-León
- Departamento de Biología, Pontificia Universidad Javeriana, Carrera 7 No. 43-82, Edificio Jesús Emilio Ramírez, Bogotá, Colombia
- Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, Bogotá D.C., Colombia
| | - Juan F Reátiga-Parrish
- Departamento de Biología, Pontificia Universidad Javeriana, Carrera 7 No. 43-82, Edificio Jesús Emilio Ramírez, Bogotá, Colombia
| | - David M Post
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT, USA
| | - Ana Rojas
- Department of Earth and Environment and Institute of Environment, Florida International University, 11200 SW 8Th St, Miami, FL, USA
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Bempah G, Kobby Grant M, Lu C, Borzée A. The direct and indirect effects of damming on the Hippopotamus amphibius population abundance and distribution at Bui National Park, Ghana. NATURE CONSERVATION 2022. [DOI: 10.3897/natureconservation.50.87411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Landscape changes resulting from human activities have resulted in range restrictions and substantial reductions in population sizes of most animals. The construction of hydroelectric dams has the same effect on species, but the study of their impact on semi-aquatic megafauna species is limited. We examined the response of a Hippopotamus amphibius population to the inundation of their habitat after the construction of a hydroelectric dam in Bui National Park, Ghana. We conducted an abundance and distribution survey of H. amphibius and compared the population size from our results with a pre-dam construction survey to determine changes in the abundance and distribution of the species within the focal area. Furthermore, we conducted a landscape analysis to estimate land cover before and after the dam construction and determined if the changes in land cover were related to the changes in population of H. amphibius. Finally, we conducted selected interviews to understand additional threats to the species perceived by the local population, as indirect effects of the dam construction. Contrary to our original hypothesis on an increase in the abundance of H. amphibius in the medium term (within a decade) through population recovery after the disturbances caused by the construction of the dam, we found lower numbers of H. amphibius after the dam construction, compared to the pre-dam results. The results indicated a reduced abundance from 209 H. amphibius individuals in 2003 to 64 H. amphibius individuals in 2021. Some individuals may have migrated to areas outside the reserve during damming when their habitat was disturbed. The amount of land covered by water increased from 0.41% before damming to 19.01% after damming, which flooded the resting and grazing sites of the H. amphibius. We conclude that the abundance and distribution of H. amphibius significantly and negatively decreased after the construction of the dam at the Bui National Park. We tentatively relate this decrease to the species’ semi aquatic ecology and sensitivity to changes in both the terrestrial and aquatic environment. The activities of human settlement encroachment such as poaching, as well as associated land cover changes, affected the stability of the H. amphibius population. However, as the species can survive in the medium to long term when effective management plans are implemented, we recommend H. amphibius to be given high conservation priorities by enhancing strict laws for habitat protection.
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Masese FO, Fuss T, Bistarelli LT, Buchen-Tschiskale C, Singer G. Large herbivorous wildlife and livestock differentially influence the relative importance of different sources of energy for riverine food webs. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 828:154452. [PMID: 35278569 DOI: 10.1016/j.scitotenv.2022.154452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 03/05/2022] [Accepted: 03/06/2022] [Indexed: 06/14/2023]
Abstract
In many regions of the world, large populations of native wildlife have declined or been replaced by livestock grazing areas and farmlands, with consequences for terrestrial-aquatic ecosystem connectivity and trophic resources supporting food webs in aquatic ecosystems. The river continuum concept (RCC) and the riverine productivity model (RPM) predict a shift of energy supplying aquatic food webs along rivers: from terrestrial inputs in low-order streams to autochthonous production in mid-sized rivers. In Afromontane-savanna landscapes, the shifting numbers of large mammalian wildlife present a physical continuum whose ecological implications for rivers is not clearly understood. Here, we studied the influence of replacing large wildlife (mainly hippos) with livestock on the fractional contribution of C3 vegetation, C4 grasses and periphyton on macroinvertebrates in the Mara River, which is an African montane-savanna river known to receive large subsidy fluxes of terrestrial organic matter and nutrients mediated by large mammalian herbivores (LMH), both wildlife and livestock, in its middle and lower reaches. Using stable carbon (δ13C) and nitrogen (δ15N) isotopes, we identified spatial patterns in the fractional contribution of allochthonous organic matter from C3 and C4 plants (woody vegetation and grasses, respectively) and autochthonous energy from periphyton for macroinvertebrates at various sites of the Mara River and its tributaries. Potential energy sources and invertebrates were sampled at 80 sites spanning stream orders 1 to 7, various catchment land uses (forest, agriculture and grasslands) and different loading rates of organic matter and nutrients by LMH (livestock and wildlife, i.e., hippopotamus). The fractional contribution of different sources of energy for macroinvertebrates along the river did not follow predictions of the RCC and RPM. First, the fractional contribution of C3 and C4 carbon was not related to river order or location along the fluvial continuum but to the loading of organic matter (dung) by both wildlife and livestock. Notably, C4 carbon was important for macroinvertebrates even in large river sections inhabited by hippos. Second, even in small 1st -3rd order forested streams, periphyton was a major source of energy for macroinvertebrates, and this was fostered by livestock inputs fuelling aquatic primary production throughout the river network. Importantly, our results show that replacing wildlife (hippos) with livestock shifts river systems towards greater reliance on autochthonous sources of energy through an algae-grazer pathway as opposed to reliance on allochthonous inputs of C4 carbon through a detrital pathway.
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Affiliation(s)
- Frank O Masese
- University of Eldoret, Department of Fisheries and Aquatic Science, P.O. Box 1125-30100, Eldoret, Kenya; Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany.
| | - Thomas Fuss
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Lukas Thuile Bistarelli
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Caroline Buchen-Tschiskale
- Thünen Institute of Climate-Smart Agriculture, Bundesallee 65, 38116 Braunschweig, Germany; Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Straβe 84, 15374 Müncheberg, Germany
| | - Gabriel Singer
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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Hippopotamus population trends in Ndumo Game Reserve, South Africa, from 1951 to 2021. Glob Ecol Conserv 2021. [DOI: 10.1016/j.gecco.2021.e01910] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Dutton CL, Subalusky AL, Sanchez A, Estrela S, Lu N, Hamilton SK, Njoroge L, Rosi EJ, Post DM. The meta-gut: community coalescence of animal gut and environmental microbiomes. Sci Rep 2021; 11:23117. [PMID: 34848778 PMCID: PMC8633035 DOI: 10.1038/s41598-021-02349-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/08/2021] [Indexed: 01/04/2023] Open
Abstract
All animals carry specialized microbiomes, and their gut microbiota are continuously released into the environment through excretion of waste. Here we propose the meta-gut as a novel conceptual framework that addresses the ability of the gut microbiome released from an animal to function outside the host and alter biogeochemical processes mediated by microbes. We demonstrate this dynamic in the hippopotamus (hippo) and the pools they inhabit. We used natural field gradients and experimental approaches to examine fecal and pool water microbial communities and aquatic biogeochemistry across a range of hippo inputs. Sequencing using 16S RNA methods revealed community coalescence between hippo gut microbiomes and the active microbial communities in hippo pools that received high inputs of hippo feces. The shared microbiome between the hippo gut and the waters into which they excrete constitutes a meta-gut system that could influence the biogeochemistry of recipient ecosystems and provide a reservoir of gut microbiomes that could influence other hosts. We propose that meta-gut dynamics may also occur where other animal species congregate in high densities, particularly in aquatic environments.
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Affiliation(s)
- Christopher L Dutton
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St., New Haven, CT, 06511, USA.
- Department of Biology, University of Florida, Gainesville, FL, USA.
| | - Amanda L Subalusky
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St., New Haven, CT, 06511, USA
- Department of Biology, University of Florida, Gainesville, FL, USA
| | - Alvaro Sanchez
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St., New Haven, CT, 06511, USA
- Microbial Sciences Institute, Yale University, New Haven, CT, USA
| | - Sylvie Estrela
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St., New Haven, CT, 06511, USA
- Microbial Sciences Institute, Yale University, New Haven, CT, USA
| | - Nanxi Lu
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St., New Haven, CT, 06511, USA
- Microbial Sciences Institute, Yale University, New Haven, CT, USA
| | - Stephen K Hamilton
- W.K. Kellogg Biological Station and Department of Integrative Biology, Michigan State University, Hickory Corners, MI, USA
- Cary Institute of Ecosystem Studies, Millbrook, NY, USA
| | | | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Millbrook, NY, USA
| | - David M Post
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St., New Haven, CT, 06511, USA
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7
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Iteba JO, Hein T, Singer GA, Masese FO. Livestock as vectors of organic matter and nutrient loading in aquatic ecosystems in African savannas. PLoS One 2021; 16:e0257076. [PMID: 34495982 PMCID: PMC8425544 DOI: 10.1371/journal.pone.0257076] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 08/23/2021] [Indexed: 11/19/2022] Open
Abstract
Populations of large wildlife have declined in many landscapes around the world, and have been replaced or displaced by livestock. The consequences of these changes on the transfer of organic matter (OM) and nutrients from terrestrial to aquatic ecosystems are not well understood. We used behavioural data, excretion and egestion rates and C: N: P stoichiometry of dung and urine of zebu cattle, to develop a metabolism-based estimate of loading rates of OM (dung), C, N and P into the Mara River, Kenya. We also directly measured the deposition of OM and urine by cattle into the river during watering. Per head, zebu cattle excrete and/or egest 25.6 g dry matter (DM, 99.6 g wet mass; metabolism) - 27.7 g DM (direct input) of OM, 16.0-21.8 g C, 5.9-9.6 g N, and 0.3-0.5 g P per day into the river. To replace loading rates OM of an individual hippopotamus by cattle, around 100 individuals will be needed, but much less for different elements. In parts of the investigated sub-catchments loading rates by cattle were equivalent to or higher than that of the hippopotamus. The patterns of increased suspended materials and nutrients as a result of livestock activity fit into historical findings on nutrients concentrations, dissolved organic carbon and other variables in agricultural and livestock areas in the Mara River basin. Changing these patterns of carbon and nutrient transport and cycling are having significant effects on the structure and functioning of both terrestrial and aquatic ecosystems.
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Affiliation(s)
- Jacob O. Iteba
- Department of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria
- Department of Fisheries and Aquatic Sciences, University of Eldoret, Eldoret, Kenya
| | - Thomas Hein
- Department of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria
- WasserCluster Lunz, Lunz am See, Austria
| | - Gabriel A. Singer
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
- Department of Ecology, University of Innsbruck, Innsbruck, Austria
| | - Frank O. Masese
- Department of Fisheries and Aquatic Sciences, University of Eldoret, Eldoret, Kenya
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
- Aquatic Science and Ecosystems Group, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa
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Utete B. A review of some aspects of the ecology, population trends, threats and conservation strategies for the common hippopotamus, Hippopotamus amphibius L, in Zimbabwe. AFRICAN ZOOLOGY 2020. [DOI: 10.1080/15627020.2020.1779613] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Beaven Utete
- Department of Wildlife Ecology and Conservation, Chinhoyi University of Technology, Chinhoyi, Zimbabwe
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Masese FO, Kiplagat MJ, González-Quijano CR, Subalusky AL, Dutton CL, Post DM, Singer GA. Hippopotamus are distinct from domestic livestock in their resource subsidies to and effects on aquatic ecosystems. Proc Biol Sci 2020; 287:20193000. [PMID: 32345142 PMCID: PMC7282896 DOI: 10.1098/rspb.2019.3000] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 03/31/2020] [Indexed: 12/31/2022] Open
Abstract
In many regions of the world, populations of large wildlife have been displaced by livestock, and this may change the functioning of aquatic ecosystems owing to significant differences in the quantity and quality of their dung. We developed a model for estimating loading rates of organic matter (dung) by cattle for comparison with estimated rates for hippopotamus in the Mara River, Kenya. We then conducted a replicated mesocosm experiment to measure ecosystem effects of nutrient and carbon inputs associated with dung from livestock (cattle) versus large wildlife (hippopotamus). Our loading model shows that per capita dung input by cattle is lower than for hippos, but total dung inputs by cattle constitute a significant portion of loading from large herbivores owing to the large numbers of cattle on the landscape. Cattle dung transfers higher amounts of limiting nutrients, major ions and dissolved organic carbon to aquatic ecosystems relative to hippo dung, and gross primary production and microbial biomass were higher in cattle dung treatments than in hippo dung treatments. Our results demonstrate that different forms of animal dung may influence aquatic ecosystems in fundamentally different ways when introduced into aquatic ecosystems as a terrestrially derived resource subsidy.
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Affiliation(s)
- Frank O. Masese
- Department of Fisheries and Aquatic Sciences, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
| | - Mary J. Kiplagat
- Department of Fisheries and Aquatic Sciences, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
| | | | - Amanda L. Subalusky
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06511, USA
| | - Christopher L. Dutton
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06511, USA
| | - David M. Post
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06511, USA
| | - Gabriel A. Singer
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
- Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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Shurin JB, Aranguren-Riaño N, Duque Negro D, Echeverri Lopez D, Jones NT, Laverde-R O, Neu A, Pedroza Ramos A. Ecosystem effects of the world's largest invasive animal. Ecology 2020; 101:e02991. [PMID: 31994172 DOI: 10.1002/ecy.2991] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 12/04/2019] [Indexed: 11/06/2022]
Abstract
The keystone roles of mega-fauna in many terrestrial ecosystems have been lost to defaunation. Large predators and herbivores often play keystone roles in their native ranges, and some have established invasive populations in new biogeographic regions. However, few empirical examples are available to guide expectations about how mega-fauna affect ecosystems in novel environmental and evolutionary contexts. We examined the impacts on aquatic ecosystems of an emerging population of hippopotamus (Hippopotamus amphibus) that has been growing in Colombia over the last 25 yr. Hippos in Africa fertilize lakes and rivers by grazing on land and excreting wastes in the water. Stable isotopes indicate that terrestrial sources contribute more carbon in Colombian lakes containing hippo populations, and daily dissolved oxygen cycles suggest that their presence stimulates ecosystem metabolism. Phytoplankton communities were more dominated by cyanobacteria in lakes with hippos, and bacteria, zooplankton, and benthic invertebrate communities were similar regardless of hippo presence. Our results suggest that hippos recapitulate their role as ecosystem engineers in Colombia, importing terrestrial organic matter and nutrients with detectable impacts on ecosystem metabolism and community structure in the early stages of invasion. Ongoing range expansion may pose a threat to water resources.
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Affiliation(s)
- Jonathan B Shurin
- Section of Ecology, Behavior and Evolution, University of California San Diego, La Jolla, California, 92093-0116, USA
| | - Nelson Aranguren-Riaño
- Unidad de Ecología en Sistemas Acuáticos-UDESA, Universidad Pedagógica y Tecnológica de Colombia, Avenida Central del Norte 39-115, Tunja, Boyacá, Colombia
| | - Daniel Duque Negro
- Unidad de Ecología en Sistemas Acuáticos-UDESA, Universidad Pedagógica y Tecnológica de Colombia, Avenida Central del Norte 39-115, Tunja, Boyacá, Colombia
| | - David Echeverri Lopez
- Corporación Autónoma Regional de las Cuencas de los Ríos Negros y Nare-CORNARE, Calle 13, No. 9-29, Municipio de la Unión, Antioquia, Colombia
| | - Natalie T Jones
- Section of Ecology, Behavior and Evolution, University of California San Diego, La Jolla, California, 92093-0116, USA.,School of Biological Sciences, The University of Queensland, St. Lucia, Queensland, 4072, Australia
| | - Oscar Laverde-R
- Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Sede Bogotá, D.C., Colombia
| | - Alexander Neu
- Section of Ecology, Behavior and Evolution, University of California San Diego, La Jolla, California, 92093-0116, USA
| | - Adriana Pedroza Ramos
- Unidad de Ecología en Sistemas Acuáticos-UDESA, Universidad Pedagógica y Tecnológica de Colombia, Avenida Central del Norte 39-115, Tunja, Boyacá, Colombia
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12
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Potential ecological and socio-economic effects of a novel megaherbivore introduction: the hippopotamus in Colombia. ORYX 2019. [DOI: 10.1017/s0030605318001588] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
AbstractIntroduced species can have strong ecological, social and economic effects on their non-native environment. Introductions of megafaunal species are rare and may contribute to rewilding efforts, but they may also have pronounced socio-ecological effects because of their scale of influence. A recent introduction of the hippopotamus Hippopotamus amphibius into Colombia is a novel introduction of a megaherbivore onto a new continent, and raises questions about the future dynamics of the socio-ecological system into which it has been introduced. Here we synthesize current knowledge about the Colombian hippopotamus population, review the literature on the species to predict potential ecological and socio-economic effects of this introduction, and make recommendations for future study. Hippopotamuses can have high population growth rates (7–11%) and, on the current trajectory, we predict there could be 400–800 individuals in Colombia by 2050. The hippopotamus is an ecosystem engineer that can have profound effects on terrestrial and aquatic environments and could therefore affect the native biodiversity of the Magdalena River basin. Hippopotamuses are also aggressive and may pose a threat to the many inhabitants of the region who rely upon the Magdalena River for their livelihoods, although the species could provide economic benefits through tourism. Further research is needed to quantify the current and future size and distribution of this hippopotamus population and to predict the likely ecological, social and economic effects. This knowledge must be balanced with consideration of social and cultural concerns to develop appropriate management strategies for this novel introduction.
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Acreman M, Hughes KA, Arthington AH, Tickner D, Dueñas M. Protected areas and freshwater biodiversity: a novel systematic review distils eight lessons for effective conservation. Conserv Lett 2019. [DOI: 10.1111/conl.12684] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Affiliation(s)
- Michael Acreman
- Centre for Ecology & Hydrology Wallingford UK
- Hydro‐ecology Consulting Ltd Wallingford UK
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14
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Dutton CL, Subalusky AL, Hill TD, Aleman JC, Rosi EJ, Onyango KB, Kanuni K, Cousins JA, Staver AC, Post DM. A 2000-year sediment record reveals rapidly changing sedimentation and land use since the 1960s in the Upper Mara-Serengeti Ecosystem. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 664:148-160. [PMID: 30739850 DOI: 10.1016/j.scitotenv.2019.01.421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/29/2019] [Accepted: 01/31/2019] [Indexed: 06/09/2023]
Abstract
The Mara River basin is a trans-boundary basin of international importance. It forms the headwaters of the Nile River and serves as the primary dry season water source for an estimated 1.1 million rural people and the largest remaining overland migration of 1.4 million wildebeest in the Serengeti-Mara Ecosystem. Changes throughout the basin are impacting the quantity and quality of the Mara River, yet the historical context of environmental conditions in the basin is not well known. We collected sediment cores throughout the wetland at the mouth of the Mara River, and we used isotopic dating methods and a suite of analyses to examine historical patterns of sediment quantity and source, mercury contamination, and carbon and nutrient loading. Our results show that ecological conditions in the Mara River basin were fairly stable over paleoecological time scales (2000-1000 years before present), but there has been a period of rapid change in the basin over the last 250 years, particularly since the 1960s. A shift in the source and quantity of sediments in the river began in the late 1700s and became much more pronounced in the 1950s and 1960s, coincident with increasing mercury concentrations. The quantity of sediment from the Upper Mara increased, particularly since 1960, but the proportion of total sediment from this region decreased as the Talek and Middle Mara portions of the basin began producing more sediment. The decadal oscillation in sediment accumulation was congruent with known periods of extreme precipitation events. Carbon and nitrogen loading also increased since the 1960s, and the shift in the isotopic ratio of nitrogen provides evidence for increased anthropogenic loading. Altogether, these data likely reflect patterns of change also experienced in other basins throughout East Africa.
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Affiliation(s)
- Christopher L Dutton
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA.
| | - Amanda L Subalusky
- Cary Institute of Ecosystem Studies, 2801 Sharon Turnpike, Millbrook, NY 12545, USA
| | - Troy D Hill
- South Florida Natural Resources Center, National Park Service, 950 N. Krome Avenue, Homestead, FL 33030, USA
| | - Julie C Aleman
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, 2801 Sharon Turnpike, Millbrook, NY 12545, USA
| | | | - Kanuni Kanuni
- WWF-Tanzania, Plot No. 350, Regent Estate Mikocheni, Dar es Salaam, Tanzania
| | - Jenny A Cousins
- WWF-UK, The Living Planet Centre, Rufford House, Brewery Rd, Woking GU21 4LL, UK
| | - A Carla Staver
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA
| | - David M Post
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA
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Schoelynck J, Subalusky AL, Struyf E, Dutton CL, Unzué-Belmonte D, Van de Vijver B, Post DM, Rosi EJ, Meire P, Frings P. Hippos ( Hippopotamus amphibius): The animal silicon pump. SCIENCE ADVANCES 2019; 5:eaav0395. [PMID: 31049394 PMCID: PMC6494503 DOI: 10.1126/sciadv.aav0395] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 03/21/2019] [Indexed: 05/10/2023]
Abstract
While the importance of grasslands in terrestrial silicon (Si) cycling and fluxes to rivers is established, the influence of large grazers has not been considered. Here, we show that hippopotamuses are key actors in the savannah biogeochemical Si cycle. Through a detailed analysis of Si concentrations and stable isotope compositions in multiple ecosystem compartments of a savannah-river continuum, we constrain the processes influencing the Si flux. Hippos transport 0.4 metric tons of Si day-1 by foraging grass on land and directly egesting in the water. As such, they bypass complex retention processes in secondary soil Si pools. By balancing internal processes of dissolution and precipitation in the river sediment, we calculate that hippos affect up to 76% of the total Si flux. This can have a large impact on downstream lake ecosystems, where Si availability directly affects primary production in the diatom-dominated phytoplankton communities.
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Affiliation(s)
- Jonas Schoelynck
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Amanda L Subalusky
- Cary Institute of Ecosystem Studies, Millbrook, NY, USA
- Yale University, Department of Ecology and Evolutionary Biology, New Haven, CT, USA
| | - Eric Struyf
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Christopher L Dutton
- Yale University, Department of Ecology and Evolutionary Biology, New Haven, CT, USA
| | - Dácil Unzué-Belmonte
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Bart Van de Vijver
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
- Botanic Garden Meise, Nieuwelaan 38, 1860 Meise, Belgium
| | - David M Post
- Yale University, Department of Ecology and Evolutionary Biology, New Haven, CT, USA
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Millbrook, NY, USA
| | - Patrick Meire
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Patrick Frings
- Department of Geosciences, Swedish Museum of Natural History, Box 50007, Stockholm, Sweden
- Section 3.3 Earth Surface Geochemistry, GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany
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Subalusky AL, Dutton CL, Njoroge L, Rosi EJ, Post DM. Organic matter and nutrient inputs from large wildlife influence ecosystem function in the Mara River, Africa. Ecology 2018; 99:2558-2574. [PMID: 30179253 DOI: 10.1002/ecy.2509] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 07/19/2018] [Accepted: 07/27/2018] [Indexed: 11/11/2022]
Abstract
Animals can be important vectors for the movement of resources across ecosystem boundaries. Animals add resources to ecosystems primarily through egestion, excretion, and carcasses, and the stoichiometry and bioavailability of these inputs likely interact with characteristics of the recipient ecosystem to determine their effects on ecosystem function. We studied the influence of hippopotamus excretion/egestion and wildebeest carcasses, and their interactions with discharge, in the Mara River, Kenya. We measured nutrient dissolution and decomposition rates of wildlife inputs, the influence of inputs on nutrient concentrations and nutrient limitation in the river and the influence of inputs on biofilm growth and function in both experimental streams and along a gradient of inputs in the river. We found that hippopotamus excretion/egestion increases ammonium and coarse particulate organic matter in the river, and wildebeest carcasses increase ammonium, soluble reactive phosphorus, and total phosphorus. Concentrations of dissolved carbon and nutrients in the water column increased along a gradient of wildlife inputs and during low discharge, although concentrations of particulate carbon decreased during low discharge due to deposition on the river bottom. Autotrophs were nitrogen limited and heterotrophs were carbon limited and nitrogen and phosphorus colimited upstream of animal inputs but there was no nutrient limitation downstream of inputs. In experimental streams, hippo and wildebeest inputs together increased biofilm gross primary production (GPP) and respiration (R). These results differed in the river, where low concentrations of hippo inputs increased gross primary production (GPP) and respiration (R) of biofilms, but high concentrations of hippo inputs in conjunction with wildebeest inputs decreased GPP. Our research shows that inputs from large wildlife alleviate nutrient limitation and stimulate ecosystem metabolism in the Mara River and that the extent to which these inputs subsidize the ecosystem is mediated by the quantity and quality of inputs and discharge of the river ecosystem. Thus, animal inputs provide an important ecological subsidy to this river, and animal inputs were likely important in many other rivers prior to the widespread extirpation of large wildlife.
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Affiliation(s)
- Amanda L Subalusky
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA.,Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
| | - Christopher L Dutton
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA
| | - Laban Njoroge
- Invertebrate Zoology Section, National Museums of Kenya, Nairobi, Kenya
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
| | - David M Post
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA
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Subalusky AL, Post DM. Context dependency of animal resource subsidies. Biol Rev Camb Philos Soc 2018; 94:517-538. [DOI: 10.1111/brv.12465] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 08/24/2018] [Accepted: 08/30/2018] [Indexed: 12/01/2022]
Affiliation(s)
- Amanda L. Subalusky
- Department of Ecology and Evolutionary Biology Yale University New Haven CT 06511 U.S.A
- Cary Institute of Ecosystem Studies Millbrook NY 12545 U.S.A
| | - David M. Post
- Department of Ecology and Evolutionary Biology Yale University New Haven CT 06511 U.S.A
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Dutton CL, Subalusky AL, Hamilton SK, Rosi EJ, Post DM. Organic matter loading by hippopotami causes subsidy overload resulting in downstream hypoxia and fish kills. Nat Commun 2018; 9:1951. [PMID: 29769538 PMCID: PMC5956076 DOI: 10.1038/s41467-018-04391-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 04/20/2018] [Indexed: 11/18/2022] Open
Abstract
Organic matter and nutrient loading into aquatic ecosystems affects ecosystem structure and function and can result in eutrophication and hypoxia. Hypoxia is often attributed to anthropogenic pollution and is not common in unpolluted rivers. Here we show that organic matter loading from hippopotami causes the repeated occurrence of hypoxia in the Mara River, East Africa. We documented 49 high flow events over 3 years that caused dissolved oxygen decreases, including 13 events resulting in hypoxia, and 9 fish kills over 5 years. Evidence from experiments and modeling demonstrates a strong mechanistic link between the flushing of hippo pools and decreased dissolved oxygen in the river. This phenomenon may have been more widespread throughout Africa before hippopotamus populations were severely reduced. Frequent hypoxia may be a natural part of tropical river ecosystem function, particularly in rivers impacted by large wildlife. Hypoxic (low oxygen) water conditions are generally thought to be uncommon in rivers and result from human impacts. However, Dutton and colleagues show here that waste from hippos in the Mara River contributes to frequent hypoxic events, suggesting hypoxia is a natural aspect of this system.
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Affiliation(s)
- Christopher L Dutton
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT, 06511, USA.
| | | | - Stephen K Hamilton
- W.K. Kellogg Biological Station, Michigan State University, 3700 E. Gull Lake Drive, Hickory Corners, MI, 49060, USA.,Department of Integrative Biology, Michigan State University, 288 Farm Lane, East Lansing, MI, 48824, USA
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Box AB, Millbrook, NY, 12545, USA
| | - David M Post
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT, 06511, USA
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Dutton CL, Subalusky AL, Anisfeld SC, Njoroge L, Rosi EJ, Post DM. The influence of a semi-arid sub-catchment on suspended sediments in the Mara River, Kenya. PLoS One 2018; 13:e0192828. [PMID: 29420624 PMCID: PMC5805331 DOI: 10.1371/journal.pone.0192828] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 01/31/2018] [Indexed: 11/19/2022] Open
Abstract
The Mara River Basin in East Africa is a trans-boundary basin of international significance experiencing excessive levels of sediment loads. Sediment levels in this river are extremely high (turbidities as high as 6,000 NTU) and appear to be increasing over time. Large wildlife populations, unregulated livestock grazing, and agricultural land conversion are all potential factors increasing sediment loads in the semi-arid portion of the basin. The basin is well-known for its annual wildebeest (Connochaetes taurinus) migration of approximately 1.3 million individuals, but it also has a growing population of hippopotami (Hippopotamus amphibius), which reside within the river and may contribute to the flux of suspended sediments. We used in situ pressure transducers and turbidity sensors to quantify the sediment flux at two sites for the Mara River and investigate the origin of riverine suspended sediment. We found that the combined Middle Mara-Talek catchment, a relatively flat but semi-arid region with large populations of wildlife and domestic cattle, is responsible for 2/3 of the sediment flux. The sediment yield from the combined Middle Mara-Talek catchment is approximately the same as the headwaters, despite receiving less rainfall. There was high monthly variability in suspended sediment fluxes. Although hippopotamus pools are not a major source of suspended sediments under baseflow, they do contribute to short-term variability in suspended sediments. This research identified sources of suspended sediments in the Mara River and important regions of the catchment to target for conservation, and suggests hippopotami may influence riverine sediment dynamics.
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Affiliation(s)
- Christopher L. Dutton
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, United States of America
- * E-mail:
| | - Amanda L. Subalusky
- Cary Institute of Ecosystem Studies, Millbrook, New York, United States of America
| | - Shimon C. Anisfeld
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, United States of America
| | - Laban Njoroge
- Invertebrate Zoology Section, The National Museums of Kenya, Nairobi, Kenya
| | - Emma J. Rosi
- Cary Institute of Ecosystem Studies, Millbrook, New York, United States of America
| | - David M. Post
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, United States of America
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Auty H, Cleaveland S, Malele I, Masoy J, Lembo T, Bessell P, Torr S, Picozzi K, Welburn SC. Quantifying Heterogeneity in Host-Vector Contact: Tsetse (Glossina swynnertoni and G. pallidipes) Host Choice in Serengeti National Park, Tanzania. PLoS One 2016; 11:e0161291. [PMID: 27706167 PMCID: PMC5051720 DOI: 10.1371/journal.pone.0161291] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 08/03/2016] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Identifying hosts of blood-feeding insect vectors is crucial in understanding their role in disease transmission. Rhodesian human African trypanosomiasis (rHAT), also known as acute sleeping sickness is caused by Trypanosoma brucei rhodesiense and transmitted by tsetse flies. The disease is commonly associated with wilderness areas of east and southern Africa. Such areas hold a diverse range of species which form communities of hosts for disease maintenance. The relative importance of different wildlife hosts remains unclear. This study quantified tsetse feeding preferences in a wilderness area of great host species richness, Serengeti National Park, Tanzania, assessing tsetse feeding and host density contemporaneously. METHODS Glossina swynnertoni and G. pallidipes were collected from six study sites. Bloodmeal sources were identified through matching Cytochrome B sequences amplified from bloodmeals from recently fed flies to published sequences. Densities of large mammal species in each site were quantified, and feeding indices calculated to assess the relative selection or avoidance of each host species by tsetse. RESULTS The host species most commonly identified in G. swynnertoni bloodmeals, warthog (94/220), buffalo (48/220) and giraffe (46/220), were found at relatively low densities (3-11/km2) and fed on up to 15 times more frequently than expected by their relative density. Wildebeest, zebra, impala and Thomson's gazelle, found at the highest densities, were never identified in bloodmeals. Commonly identified hosts for G. pallidipes were buffalo (26/46), giraffe (9/46) and elephant (5/46). CONCLUSIONS This study is the first to quantify tsetse host range by molecular analysis of tsetse diet with simultaneous assessment of host density in a wilderness area. Although G. swynnertoni and G. pallidipes can feed on a range of species, they are highly selective. Many host species are rarely fed on, despite being present in areas where tsetse are abundant. These feeding patterns, along with the ability of key host species to maintain and transmit T. b. rhodesiense, drive the epidemiology of rHAT in wilderness areas.
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Affiliation(s)
- Harriet Auty
- Epidemiology Research Unit, SRUC, Drummondhill, Inverness, United Kingdom
- Division of Pathway and Infections Medicine, Centre for Infectious Diseases, School of Biomedical Sciences, Edinburgh Medical School, The University of Edinburgh, Edinburgh, United Kingdom
| | - Sarah Cleaveland
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Imna Malele
- Tsetse & Trypanosomiasis Research Institute (TTRI), Tanga, Tanzania
| | - Joseph Masoy
- Serengeti Biodiversity Project, Tanzania Wildlife Research Institute, Arusha, Tanzania
| | - Tiziana Lembo
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Paul Bessell
- The Roslin Institute, The University of Edinburgh, Easter Bush, Midlothian, United Kingdom
| | - Stephen Torr
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Kim Picozzi
- Division of Pathway and Infections Medicine, Centre for Infectious Diseases, School of Biomedical Sciences, Edinburgh Medical School, The University of Edinburgh, Edinburgh, United Kingdom
| | - Susan C. Welburn
- Division of Pathway and Infections Medicine, Centre for Infectious Diseases, School of Biomedical Sciences, Edinburgh Medical School, The University of Edinburgh, Edinburgh, United Kingdom
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Masese FO, Abrantes KG, Gettel GM, Bouillon S, Irvine K, McClain ME. Are Large Herbivores Vectors of Terrestrial Subsidies for Riverine Food Webs? Ecosystems 2015. [DOI: 10.1007/s10021-015-9859-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Dublin HT, Ogutu JO. Population regulation of African buffalo in the Mara–Serengeti ecosystem. WILDLIFE RESEARCH 2015. [DOI: 10.1071/wr14205] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Context The processes regulating ungulate populations have been the focus of numerous studies. For the African buffalo (Syncerus caffer Sparrman) population inhabiting the Mara–Serengeti ecosystem, rinderpest was the primary regulatory factor up to the mid-1960s. Following reduction of rinderpest and buffalo population increase, interspecific competition for food, notably with cattle and wildebeest (Connochaetes taurinus Burchell), was thought to be the primary regulatory factor in the ecosystem. Aims We analysed buffalo population trends and the relationship between buffalo population growth and rainfall and density dependence in the Mara–Serengeti ecosystem and discuss the findings in the context of the key ecosystem processes governing buffalo population dynamics in African savannas, namely, food limitation, competition, predation, disease and land use changes. Methods We analysed buffalo population dynamics in the Mara–Serengeti ecosystem in relation to rainfall and density dependence feedback between 1984 and 2010. Key results Buffalo population growth was both significantly density-dependent and positively correlated with the dry season rainfall after, but not before, a severe drought in 1993. Buffalo numbers crashed by 48.6% in 1984–85 and by 76.1% in 1993–94 during severe droughts when food availability was lowest and competition with the more numerous cattle and wildebeest was highest. Conclusions Recovery of buffalo numbers to pre-drought levels took 8–9 years after the 1984–85 drought but was much slower, with buffaloes numbering merely 36% of their 1993 population (12 895 animals) 18 years after the 1993–94 drought despite intermittent periods of high rainfall, probably due to demographic and/or reproductive factors, heightened competition with livestock, land use changes in the adjoining pastoral ranches, lion predation and recurrent severe droughts. Implications Our findings demonstrate how food limitation caused by droughts associated with the hemispheric El Niño–Southern Oscillation can cause severe declines in and threaten the persistence of large ungulate populations. The findings also portray how density-dependent food limitation, competition, predation, land use changes and other factors can accentuate the effect of droughts and greatly prolong population recovery.
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Kanga EM, Ogutu JO, Piepho HP, Olff H. Hippopotamus and livestock grazing: influences on riparian vegetation and facilitation of other herbivores in the Mara Region of Kenya. LANDSCAPE AND ECOLOGICAL ENGINEERING 2011. [DOI: 10.1007/s11355-011-0175-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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