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Modeling Sighting Heterogeneity and Abundance in Spatially Replicated Multiple-Observer Surveys

RICHARD J. BARKER,1 DAVID M. FORSYTH,2  MATTHEW WOOD,3

11 Department of Mathematics and Statistics , University of Otago, P.O. Box 56, Dunedin , New Zealand

2Department of Sustainability and Environment , Arthur Rylah Institute for Environmental Research , 123 Brown Street , Heidelberg, VIC 3084 , Australia

3Australian Ecological Research Services Ltd., 341 Princes Highway , Portland, VIC 3305, Australia

ABSTRACT

Failure to account for dependencies among observers in multiple-observer capture-recapture studies will lead to biased inference yet methods that account for dependencies are poorly developed. We combined hierarchical capture-recapture models and finite sampling theory to infer population abundance of koala (Pbascolarctos cinereus) in the 5,812-ha Mount Eccles National Park, southeastern Australia. We used plot replication to build a Bayesian hierarchical model of koala sightings by multiple observers. Given the number of koala present on a plot, we modeled counts of koala by a multinomial log-linear model with interaction terms to account for between-observer dependencies. We modeled total numbers using a Poisson log-linear model with covariate and random effects. We estimated the number of koala as 1.9 koala/ha (95% CI = 1.6, 2.4). We found evidence of between-observer interactions, highlighting the importance of having at least 3 observers in multiple observer studies.

  • All
  • 2013
  • Biogeography
  • Biology
  • Chlamydia
  • Diet
  • Disease
  • Ecology
  • Ellis
  • Eucalyptus
  • Genetics
  • Habitat
  • Infection
  • Interventions
  • Koala
  • Lunney
  • Threats
  • Timms
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