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Falaschi M, Gibertini C, Lo Parrino E, Muraro M, Barzaghi B, Manenti R, Ficetola GF. Assessing Population Trends of Species with Imperfect Detection: Double Count Analyses and Simulations Confirm Reliable Estimates in Brown Frogs. Animals (Basel) 2022; 12:ani12162085. [PMID: 36009675 PMCID: PMC9405163 DOI: 10.3390/ani12162085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/25/2022] [Accepted: 08/11/2022] [Indexed: 11/16/2022] Open
Abstract
Most animal species are detected imperfectly and overlooking individuals can result in a biased inference of the abundance patterns and underlying processes. Several techniques can incorporate the imperfect detection process for a more accurate estimation of abundance, but most of them require repeated surveys, i.e., more sampling effort compared to single counts. In this study, we used the dependent double-observer approach to estimate the detection probability of the egg clutches of two brown frog species, Rana dalmatina and R. latastei. We then simulated the data of a declining population at different levels of detection probability in order to assess under which conditions the double counts provided better estimates of population trends compared to naïve egg counts, given the detectability of frog clutches. Both species showed a very high detection probability, with average values of 93% for Rana dalmatina and 97% for R. latastei. Simulations showed that not considering imperfect detection reduces the power of detecting population trends if detection probability is low. However, at high detection probability (>80%), ignoring the imperfect detection does not bias the estimates of population trends. This suggests that, for species laying large and easily identifiable egg clutches, a single count can provide useful estimates if surveys are correctly timed.
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Affiliation(s)
- Mattia Falaschi
- Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy
| | - Chiara Gibertini
- Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy
- Correspondence:
| | - Elia Lo Parrino
- Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy
| | - Martina Muraro
- Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy
| | - Benedetta Barzaghi
- Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy
| | - Raoul Manenti
- Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy
| | - Gentile Francesco Ficetola
- Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy
- Laboratoire d’Écologie Alpine, University Grenoble Alpes, University Savoie Mont Blanc, CNRS, LECA, F-38000 Grenoble, France
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Brooks GC, Haas CA. Using historical dip net data to infer absence of flatwoods salamanders in stochastic environments. PeerJ 2021; 9:e12388. [PMID: 34760383 PMCID: PMC8557685 DOI: 10.7717/peerj.12388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 10/04/2021] [Indexed: 11/20/2022] Open
Abstract
Local extinction and undetected presence are two very different biological phenomena, but they can be challenging to differentiate. Stochastic environments hamper the development of standardized monitoring schemes for wildlife, and make it more challenging to plan and evaluate the success of conservation efforts. To avoid reintroductions of species at risk that could jeopardize extant populations, managers attempting translocation events require a higher level of confidence that a failure to confirm presence represents a true absence. For many pond breeding amphibians, monitoring of the breeding population occurs indirectly through larval surveys. Larval development and successful recruitment only occurs after a sequence of appropriate environmental conditions, thus it is possible for a breeding population of adults to exist at a site but for detectability of the species to be functionally zero. We investigate how annual variability in detection influences long-term monitoring efforts of Reticulated Flatwoods Salamanders (Ambystoma bishopi) breeding in 29 wetlands in Florida. Using 8 years of historic dip net data, we simulate plausible monitoring scenarios that incorporate environmental stochasticity into estimates of detection probability. We found that annual variation in environmental conditions precluded a high degree of certainty in predicting site status for low-intensity monitoring schemes. Uncertainty was partly alleviated by increasing survey effort, but even at the highest level of sampling intensity assessed, multiple years of monitoring are required to confidently determine presence/absence at a site. Combined with assessments of habitat quality and landscape connectivity, our results can be used to identify sites suitable for reintroduction efforts. Our methodologies can be generally applied to increase the effectiveness of surveys for diverse organisms for which annual variability in detectability is known.
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Affiliation(s)
- George C Brooks
- Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, Virginia, United States
| | - Carola A Haas
- Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, Virginia, United States
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Dupont P, Milleret C, Tourani M, Brøseth H, Bischof R. Integrating dead recoveries in open‐population spatial capture–recapture models. Ecosphere 2021. [DOI: 10.1002/ecs2.3571] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- P. Dupont
- Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life Sciences PB 5003 ÅsNO‐1432Norway
| | - C. Milleret
- Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life Sciences PB 5003 ÅsNO‐1432Norway
| | - M. Tourani
- Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life Sciences PB 5003 ÅsNO‐1432Norway
| | - H. Brøseth
- Department of Terrestrial Ecology Norwegian Institute for Nature Research PB 5685 Torgarden TrondheimNO‐7485Norway
| | - R. Bischof
- Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life Sciences PB 5003 ÅsNO‐1432Norway
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Ibouroi MT, Arnal V, Cheha A, Dhurham SAO, Montgelard C, Besnard A. Noninvasive genetic sampling for flying foxes: a valuable method for monitoring demographic parameters. Ecosphere 2021. [DOI: 10.1002/ecs2.3327] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mohamed Thani Ibouroi
- Centre for Functional and Evolutionary Ecology (CEFE UMR 5175) EPHE PSL Research University, CNRS University of Montpellier, SupAgro, IRD, INRA Montpellier F‐34293 France
- Sustainable Development Task Force (GIDD) Moroni Hamramba Comores
| | - Véronique Arnal
- Centre for Functional and Evolutionary Ecology (CEFE UMR 5175) EPHE PSL Research University, CNRS University of Montpellier, SupAgro, IRD, INRA Montpellier F‐34293 France
| | - Ali Cheha
- Sustainable Development Task Force (GIDD) Moroni Hamramba Comores
| | | | - Claudine Montgelard
- Centre for Functional and Evolutionary Ecology (CEFE UMR 5175) EPHE PSL Research University, CNRS University of Montpellier, SupAgro, IRD, INRA Montpellier F‐34293 France
| | - Aurélien Besnard
- Centre for Functional and Evolutionary Ecology (CEFE UMR 5175) EPHE PSL Research University, CNRS University of Montpellier, SupAgro, IRD, INRA Montpellier F‐34293 France
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Using an individual-based model to assess common biases in lek-based count data to estimate population trajectories of lesser prairie-chickens. PLoS One 2019; 14:e0217172. [PMID: 31100093 PMCID: PMC6524812 DOI: 10.1371/journal.pone.0217172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 05/06/2019] [Indexed: 11/19/2022] Open
Abstract
Researchers and managers are often interested in monitoring the underlying state of a population (e.g., abundance), yet error in the observation process might mask underlying changes due to imperfect detection and availability for sampling. Additional heterogeneity can be introduced into a monitoring program when male-based surveys are used as an index for the total population. Often, male-based surveys are used for avian species, as males are conspicuous and more easily monitored than females. To determine if male-based lek surveys capture changes or trends in population abundance based on female survival and reproduction, we developed a virtual ecologist approach using the lesser prairie-chicken (Tympanuchus pallidicinctus) as an example. Our approach used an individual-based model to simulate lek counts based on female vital rate data, included models where detection and lek attendance probabilities were <1, and was analyzed using both unadjusted counts and an N-mixture model to compare estimates of population abundance and growth rates. Using lek counts to estimate population growth rates without accounting for detection probability or density-based lek attendance consistently biased population growth rates and abundance estimates. Our results therefore suggest that lek-based surveys used without accounting for lek attendance and detection probability may miss important trends in population changes. Rather than population-level inference, lek-based surveys not accounting for lek attendance and detection probability may instead be better for inferring broad-scale range shifts of lesser prairie-chicken populations in a presence/absence framework.
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Nilsen EB, Strand O. Integrating data from multiple sources for insights into demographic processes: Simulation studies and proof of concept for hierarchical change-in-ratio models. PLoS One 2018; 13:e0194566. [PMID: 29596430 PMCID: PMC5875752 DOI: 10.1371/journal.pone.0194566] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 03/06/2018] [Indexed: 12/02/2022] Open
Abstract
We developed a model for estimating demographic rates and population abundance based on multiple data sets revealing information about population age- and sex structure. Such models have previously been described in the literature as change-in-ratio models, but we extend the applicability of the models by i) using time series data allowing the full temporal dynamics to be modelled, by ii) casting the model in an explicit hierarchical modelling framework, and by iii) estimating parameters based on Bayesian inference. Based on sensitivity analyses we conclude that the approach developed here is able to obtain estimates of demographic rate with high precision whenever unbiased data of population structure are available. Our simulations revealed that this was true also when data on population abundance are not available or not included in the modelling framework. Nevertheless, when data on population structure are biased due to different observability of different age- and sex categories this will affect estimates of all demographic rates. Estimates of population size is particularly sensitive to such biases, whereas demographic rates can be relatively precisely estimated even with biased observation data as long as the bias is not severe. We then use the models to estimate demographic rates and population abundance for two Norwegian reindeer (Rangifer tarandus) populations where age-sex data were available for all harvested animals, and where population structure surveys were carried out in early summer (after calving) and late fall (after hunting season), and population size is counted in winter. We found that demographic rates were similar regardless whether we include population count data in the modelling, but that the estimated population size is affected by this decision. This suggest that monitoring programs that focus on population age- and sex structure will benefit from collecting additional data that allow estimation of observability for different age- and sex classes. In addition, our sensitivity analysis suggests that focusing monitoring towards changes in demographic rates might be more feasible than monitoring abundance in many situations where data on population age- and sex structure can be collected.
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Affiliation(s)
- Erlend B. Nilsen
- Norwegian Institute for Nature Research, Torgarden, Trondheim, Norway
- * E-mail:
| | - Olav Strand
- Norwegian Institute for Nature Research, Torgarden, Trondheim, Norway
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Goodwin CED, Hodgson DJ, Al-Fulaij N, Bailey S, Langton S, Mcdonald RA. Voluntary recording scheme reveals ongoing decline in the United Kingdom hazel dormouse Muscardinus avellanarius
population. Mamm Rev 2017. [DOI: 10.1111/mam.12091] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Cecily E. D. Goodwin
- Environment and Sustainability Institute; University of Exeter; Penryn Campus; Penryn TR10 9FE Cornwall UK
| | - David J. Hodgson
- Centre for Ecology and Conservation; University of Exeter; Penryn Campus; Penryn TR10 9FE Cornwall UK
| | - Nida Al-Fulaij
- People's Trust for Endangered Species; 3 Cloisters House 8 Battersea Park Road London SW8 4BG UK
| | - Sallie Bailey
- Forest Enterprise Scotland; Dumfries & Borders Forest District; Ae Village, Parkgate Dumfries DG1 1QB UK
| | - Steve Langton
- Hallgarth; Leavening Malton YO17 9SA North Yorkshire UK
| | - Robbie A. Mcdonald
- Environment and Sustainability Institute; University of Exeter; Penryn Campus; Penryn TR10 9FE Cornwall UK
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Gervasi V, Brøseth H, Gimenez O, Nilsen EB, Odden J, Flagstad Ø, Linnell JDC. Sharing data improves monitoring of trans-boundary populations: the case of wolverines in central Scandinavia. WILDLIFE BIOLOGY 2016. [DOI: 10.2981/wlb.00142] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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Rauset GR, Low M, Persson J. Reproductive patterns result from age-related sensitivity to resources and reproductive costs in a mammalian carnivore. Ecology 2015; 96:3153-64. [DOI: 10.1890/15-0262.1] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Galaverni M, Caniglia R, Fabbri E, Milanesi P, Randi E. One, no one, or one hundred thousand: how many wolves are there currently in Italy? MAMMAL RES 2015. [DOI: 10.1007/s13364-015-0247-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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