Abstract
Common hippopotamus (Hippopotamus amphibius) (hereafter hippos) are iconic and understudied ecological engineers in African aquatic and terrestrial systems. Temporal changes in hippo group size in response to changes in wading areas have been described in river systems, but hippo group dynamics remain generally understudied and have not been quantified in a seasonal floodplain. We used monthly census data collected with an unmanned aerial vehicle between August 2016 and July 2017 to identify changes in hippo distribution, density, and group size at the most used wading areas in the seasonal floodplain in Ndumo Game Reserve, South Africa. We found that hippos congregate into large groups when the wading area decreases in seasonal floodplain systems, similar to perennial river systems. Moreover, as the inundation area increased, overall individual and group density decreased, hippo abundance decreased, and the mean distance between groups increased. Periods of low water availability tend to coincide with periods of food scarcity; thus, competition for water may compound with competition for food, likely affecting cycles of population growth or decline. Increased unpredictability in seasonal and annual rainfall patterns because of climate change will affect the predictability and availability of hippo wading areas, which will likely affect the distribution, size, and persistence of hippo populations. The results of our study provide additional information necessary for the conservation and management of hippos in seasonal floodplain systems in the context of climate change.
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Data for this study are available at: https://doi.org/10.5281/zenodo.4781018. Reproducible code used for the analyses is available at https://doi.org/10.5281/zenodo.6535966.
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Acknowledgements
We are grateful to Ezemvelo KZN Wildlife, C. Hanekom, and A. Thembe for permission to work in NGR. We would also like to thank all the rangers at NGR and especially B. Nyathi. In addition, this work would not have been possible without the help of all the research assistants involved, in particular C. Price, S. McPherson, V. Thabethe, H. Aronsson, T. Caine, and H. Thatcher. We thank the National Research Foundation (ZA, Grant 98404), the University of KwaZulu-Natal (ZA), the Rufford Trust (UK), the Phoenix Zoo (USA) and the Hans Hoheisen Charitable Trust (ZA) for funding. We thank the Ford Wildlife Foundation (ZA) for vehicle support. MP was supported by grants from the Claude Leon Foundation and the Swiss National Science Foundation. We thank M. Thornhill for his UAV expertise and for servicing the UAV. We thank Planet Imagery for supplying satellite imagery. We thank the reviewers for their constructive comments that improved the manuscript.
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This work was supported by National Research Foundation (ZA, Grant 98404), the Rufford Trust (UK, 0e95d7-1), the Phoenix Zoo (USA), the Hans Hoheisen Charitable Trust (ZA), and the Ford Wildlife Foundation (ZA). MP was funded by the Claude Leon Foundation (ZA) and the Swiss National Science Foundation (CH).
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Fritsch, C.J.A., Plebani, M. & Downs, C.T. Inundation area drives hippo group aggregation and dispersal in a seasonal floodplain system. Mamm Biol 102, 1811–1821 (2022). https://doi.org/10.1007/s42991-022-00286-8
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DOI: https://doi.org/10.1007/s42991-022-00286-8