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Assessing Population Trends of Species with Imperfect Detection: Double Count Analyses and Simulations Confirm Reliable Estimates in Brown Frogs.
Falaschi, Mattia; Gibertini, Chiara; Lo Parrino, Elia; Muraro, Martina; Barzaghi, Benedetta; Manenti, Raoul; Ficetola, Gentile Francesco.
Affiliation
  • Falaschi M; Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy.
  • Gibertini C; Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy.
  • Lo Parrino E; Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy.
  • Muraro M; Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy.
  • Barzaghi B; Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy.
  • Manenti R; Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy.
  • Ficetola GF; Department of Environmental Science and Policy, University of Milan, Via Celoria 10, 20133 Milan, Italy.
Animals (Basel) ; 12(16)2022 Aug 15.
Article in En | MEDLINE | ID: mdl-36009675
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.
Key words

Full text: 1 Collection: 01-internacional Database: MEDLINE Type of study: Diagnostic_studies Language: En Journal: Animals (Basel) Year: 2022 Document type: Article Affiliation country: Italia Country of publication: Suiza

Full text: 1 Collection: 01-internacional Database: MEDLINE Type of study: Diagnostic_studies Language: En Journal: Animals (Basel) Year: 2022 Document type: Article Affiliation country: Italia Country of publication: Suiza