title: Mark-recapture and mark-resight methods for estimating abundance with remote cameras: a carnivore case study.
abstract: Abundance estimation of carnivore populations is difficult and has prompted the use of non-invasive detection methods, such as remotely-triggered cameras, to collect data. To analyze photo data, studies focusing on carnivores with unique pelage patterns have utilized a mark-recapture framework and studies of carnivores without unique pelage patterns have used a mark-resight framework. We compared mark-resight and mark-recapture estimation methods to estimate bobcat (Lynx rufus) population sizes, which motivated the development of a new "hybrid" mark-resight model as an alternative to traditional methods. We deployed a sampling grid of 30 cameras throughout the urban southern California study area. Additionally, we physically captured and marked a subset of the bobcat population with GPS telemetry collars. Since we could identify individual bobcats with photos of unique pelage patterns and a subset of the population was physically marked, we were able to use traditional mark-recapture and mark-resight methods, as well as the new "hybrid" mark-resight model we developed to estimate bobcat abundance. We recorded 109 bobcat photos during 4,669 camera nights and physically marked 27 bobcats with GPS telemetry collars. Abundance estimates produced by the traditional mark-recapture, traditional mark-resight, and "hybrid" mark-resight methods were similar, however precision differed depending on the models used. Traditional mark-recapture and mark-resight estimates were relatively imprecise with percent confidence interval lengths exceeding 100% of point estimates. Hybrid mark-resight models produced better precision with percent confidence intervals not exceeding 57%. The increased precision of the hybrid mark-resight method stems from utilizing the complete encounter histories of physically marked individuals (including those never detected by a camera trap) and the encounter histories of naturally marked individuals detected at camera traps. This new estimator may be particularly useful for estimating abundance of uniquely identifiable species that are difficult to sample using camera traps alone.
authors.affiliation: Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, United States of America; Western Ecological Research Center, Biological Resources Discipline, United States Geological Survey, Thousand Oaks, California, United States of America.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Alonso
authors.affiliation: National Marine Mammal Laboratory, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America.
authors.forename: Brett T
authors.initials: BT
authors.lastname: McClintock
authors.affiliation: Western Ecological Research Center, Biological Resources Discipline, United States Geological Survey, Carlsbad, California, United States of America.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Lyren
authors.affiliation: Western Ecological Research Center, Biological Resources Discipline, United States Geological Survey, Thousand Oaks, California, United States of America.
authors.forename: Erin E
authors.initials: EE
authors.lastname: Boydston
authors.affiliation: Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Crooks
mesh_terms: D000818:Animals; D002140:California; D060435:Carnivory / Q000502:physiology*; D017753:Ecosystem; D046008:Lynx / Q000502:physiology*; D008954:Models, Biological; D008962:Models, Theoretical; D010781:Photography / Q000295:instrumentation; D011156:Population Density; D011157:Population Dynamics; D013686:Telemetry / Q000295:instrumentation
references.citation: Biometrics. 2000 Jun;56(2):434-42
references.pmid: 10877301
references.citation: Mol Ecol. 2006 Jun;15(7):1733-41
references.pmid: 16689893
references.citation: Biometrics. 2009 Mar;65(1):237-46
references.pmid: 18479484
references.citation: Stat Med. 2009 Nov 10;28(25):3049-67
references.pmid: 19630097
references.citation: Ecology. 2009 Nov;90(11):3233-44
references.pmid: 19967878
references.citation: Ecology. 2013 Mar;94(3):553-9
references.pmid: 23687880
references.citation: Ecology. 2013 Jul;94(7):1464-71
references.pmid: 23951706
references.citation: Integr Zool. 2013 Sep;8(3):232-43
references.pmid: 24020463
references.citation: Biometrics. 2013 Sep;69(3):766-75
references.pmid: 23845216