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Lundgren EJ, Ramp D, Middleton OS, Wooster EIF, Kusch E, Balisi M, Ripple WJ, Hasselerharm CD, Sanchez JN, Mills M, Wallach AD. A novel trophic cascade between cougars and feral donkeys shapes desert wetlands. J Anim Ecol 2022; 91:2348-2357. [PMID: 35871769 PMCID: PMC10087508 DOI: 10.1111/1365-2656.13766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 06/08/2022] [Indexed: 12/14/2022]
Abstract
Introduced large herbivores have partly filled ecological gaps formed in the late Pleistocene, when many of the Earth's megafauna were driven extinct. However, extant predators are generally considered incapable of exerting top-down influences on introduced megafauna, leading to unusually strong disturbance and herbivory relative to native herbivores. We report on the first documented predation of juvenile feral donkeys Equus africanus asinus by cougars Puma concolor in the Mojave and Sonoran Deserts of North America. We then investigated how cougar predation corresponds with differences in feral donkey behaviour and associated effects on desert wetlands. Focusing on a feral donkey population in the Death Valley National Park, we used camera traps and vegetation surveys to compare donkey activity patterns and impacts between wetlands with and without cougar predation. Donkeys were primarily diurnal at wetlands with cougar predation, thereby avoiding cougars. However, donkeys were active throughout the day and night at sites without predation. Donkeys were ~87% less active (measured as hours of activity a day) at wetlands with predation (p < 0.0001). Sites with predation had reduced donkey disturbance and herbivory, including ~46% fewer access trails, 43% less trampled bare ground and 192% more canopy cover (PERMANOVA, R2 = 0.22, p = 0.0003). Our study is the first to reveal a trophic cascade involving cougars, feral equids and vegetation. Cougar predation appears to rewire an ancient food web, with diverse implications for modern ecosystems. Our results suggest that protecting apex predators could have important implications for the ecological effects of introduced megafauna.
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Affiliation(s)
- Erick J Lundgren
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark.,Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus C, Denmark.,Centre for Compassionate Conservation, TD School, University of Technology Sydney, Ultimo, Australia
| | - Daniel Ramp
- Centre for Compassionate Conservation, TD School, University of Technology Sydney, Ultimo, Australia
| | | | - Eamonn I F Wooster
- Centre for Compassionate Conservation, TD School, University of Technology Sydney, Ultimo, Australia
| | - Erik Kusch
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark.,Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus C, Denmark
| | - Mairin Balisi
- La Brea Tar Pits and Museum, Los Angeles, California, USA.,Raymond M. Alf Museum of Paleontology, Claremont, CA, USA
| | - William J Ripple
- Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, USA
| | - Chris D Hasselerharm
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
| | - Jessica N Sanchez
- One Health Institute, School of Veterinary Medicine, University of California at Davis, Davis, CA, USA
| | - Mystyn Mills
- Department of Botany & Plant Sciences, University of California Riverside, Riverside, CA, USA
| | - Arian D Wallach
- Centre for Compassionate Conservation, TD School, University of Technology Sydney, Ultimo, Australia
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Cooke R, Gearty W, Chapman ASA, Dunic J, Edgar GJ, Lefcheck JS, Rilov G, McClain CR, Stuart-Smith RD, Kathleen Lyons S, Bates AE. Anthropogenic disruptions to longstanding patterns of trophic-size structure in vertebrates. Nat Ecol Evol 2022; 6:684-692. [PMID: 35449460 DOI: 10.1038/s41559-022-01726-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 03/07/2022] [Indexed: 11/09/2022]
Abstract
Diet and body mass are inextricably linked in vertebrates: while herbivores and carnivores have converged on much larger sizes, invertivores and omnivores are, on average, much smaller, leading to a roughly U-shaped relationship between body size and trophic guild. Although this U-shaped trophic-size structure is well documented in extant terrestrial mammals, whether this pattern manifests across diverse vertebrate clades and biomes is unknown. Moreover, emergence of the U-shape over geological time and future persistence are unknown. Here we compiled a comprehensive dataset of diet and body size spanning several vertebrate classes and show that the U-shaped pattern is taxonomically and biogeographically universal in modern vertebrate groups, except for marine mammals and seabirds. We further found that, for terrestrial mammals, this U-shape emerged by the Palaeocene and has thus persisted for at least 66 million years. Yet disruption of this fundamental trophic-size structure in mammals appears likely in the next century, based on projected extinctions. Actions to prevent declines in the largest animals will sustain the functioning of Earth's wild ecosystems and biomass energy distributions that have persisted through deep time.
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Affiliation(s)
- Rob Cooke
- UK Centre for Ecology & Hydrology, Wallingford, UK. .,Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden. .,Gothenburg Global Biodiversity Centre, Gothenburg, Sweden.
| | - William Gearty
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Abbie S A Chapman
- Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Jillian Dunic
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Graham J Edgar
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
| | - Jonathan S Lefcheck
- Tennenbaum Marine Observatories Network and MarineGEO Program, Smithsonian Environmental Research Center, Edgewater, MD, USA
| | - Gil Rilov
- National Institute of Oceanography, Israel Limnological and Oceanographic Research, Haifa, Israel
| | | | - Rick D Stuart-Smith
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
| | - S Kathleen Lyons
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Amanda E Bates
- Biology Department, University of Victoria, Victoria, British Columbia, Canada
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