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Baldwin RW, Beaver JT, Messinger M, Muday J, Windsor M, Larsen GD, Silman MR, Anderson TM. Camera Trap Methods and Drone Thermal Surveillance Provide Reliable, Comparable Density Estimates of Large, Free-Ranging Ungulates. Animals (Basel) 2023; 13:1884. [PMID: 37889800 PMCID: PMC10252056 DOI: 10.3390/ani13111884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/28/2023] [Accepted: 06/02/2023] [Indexed: 10/29/2023] Open
Abstract
Camera traps and drone surveys both leverage advancing technologies to study dynamic wildlife populations with little disturbance. Both techniques entail strengths and weaknesses, and common camera trap methods can be confounded by unrealistic assumptions and prerequisite conditions. We compared three methods to estimate the population density of white-tailed deer (Odocoileus virgnianus) in a section of Pilot Mountain State Park, NC, USA: (1) camera trapping using mark-resight ratios or (2) N-mixture modeling and (3) aerial thermal videography from a drone platform. All three methods yielded similar density estimates, suggesting that they converged on an accurate estimate. We also included environmental covariates in the N-mixture modeling to explore spatial habitat use, and we fit models for each season to understand temporal changes in population density. Deer occurred in greater densities on warmer, south-facing slopes in the autumn and winter and on cooler north-facing slopes and in areas with flatter terrain in the summer. Seasonal density estimates over two years suggested an annual cycle of higher densities in autumn and winter than in summer, indicating that the region may function as a refuge during the hunting season.
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Affiliation(s)
- Robert W. Baldwin
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (R.W.B.); (M.M.); (J.M.); (G.D.L.); (M.R.S.); (T.M.A.)
| | - Jared T. Beaver
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (R.W.B.); (M.M.); (J.M.); (G.D.L.); (M.R.S.); (T.M.A.)
- Wake Forest University Center for Energy, Environment, and Sustainability, Wake Forest University, Winston-Salem, NC 27109, USA
- Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717, USA
| | - Max Messinger
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (R.W.B.); (M.M.); (J.M.); (G.D.L.); (M.R.S.); (T.M.A.)
- Wake Forest University Center for Energy, Environment, and Sustainability, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Jeffrey Muday
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (R.W.B.); (M.M.); (J.M.); (G.D.L.); (M.R.S.); (T.M.A.)
| | - Matt Windsor
- Pilot Mountain State Park, North Carolina State Parks, 1792 Pilot Knob Park Rd, Pinnacle, NC 27043, USA;
| | - Gregory D. Larsen
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (R.W.B.); (M.M.); (J.M.); (G.D.L.); (M.R.S.); (T.M.A.)
- Wake Forest University Center for Energy, Environment, and Sustainability, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Miles R. Silman
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (R.W.B.); (M.M.); (J.M.); (G.D.L.); (M.R.S.); (T.M.A.)
- Wake Forest University Center for Energy, Environment, and Sustainability, Wake Forest University, Winston-Salem, NC 27109, USA
| | - T. Michael Anderson
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA; (R.W.B.); (M.M.); (J.M.); (G.D.L.); (M.R.S.); (T.M.A.)
- Wake Forest University Center for Energy, Environment, and Sustainability, Wake Forest University, Winston-Salem, NC 27109, USA
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Keller AG, Grason EW, McDonald PS, Ramón-Laca A, Kelly RP. Tracking an invasion front with environmental DNA. Ecol Appl 2022; 32:e2561. [PMID: 35128750 DOI: 10.1002/eap.2561] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/21/2021] [Accepted: 12/14/2021] [Indexed: 05/03/2023]
Abstract
Data from environmental DNA (eDNA) may revolutionize environmental monitoring and management, providing increased detection sensitivity at reduced cost and survey effort. However, eDNA data are rarely used in decision-making contexts, mainly due to uncertainty around (1) data interpretation and (2) whether and how molecular tools dovetail with existing management efforts. We address these challenges by jointly modeling eDNA detection via qPCR and traditional trap data to estimate the density of invasive European green crab (Carcinus maenas), a species for which, historically, baited traps have been used for both detection and control. Our analytical framework simultaneously quantifies uncertainty in both detection methods and provides a robust way of integrating different data streams into management processes. Moreover, the joint model makes clear the marginal information benefit of adding eDNA (or any other) additional data type to an existing monitoring program, offering a path to optimizing sampling efforts for species of management interest. Here, we document green crab eDNA beyond the previously known invasion front and find that the value of eDNA data dramatically increases with low population densities and low traditional sampling effort, as is often the case at leading-edge locations. We also highlight the detection limits of the molecular assay used in this study, as well as scenarios under which eDNA sampling is unlikely to improve existing management efforts.
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Affiliation(s)
- Abigail G Keller
- School of Marine and Environmental Affairs, University of Washington, Seattle, Washington, USA
| | - Emily W Grason
- Washington Sea Grant, University of Washington, Seattle, Washington, USA
| | - P Sean McDonald
- School of Aquatic & Fishery Sciences, University of Washington, Seattle, Washington, USA
| | - Ana Ramón-Laca
- CICOES, University of Washington at Northwest Fisheries Science Center, Seattle, Washington, USA
| | - Ryan P Kelly
- School of Marine and Environmental Affairs, University of Washington, Seattle, Washington, USA
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