title: Assessing uncertainty in sighting records: an example of the Barbary lion.
abstract: As species become rare and approach extinction, purported sightings can be controversial, especially when scarce management resources are at stake. We consider the probability that each individual sighting of a series is valid. Obtaining these probabilities requires a strict framework to ensure that they are as accurately representative as possible. We used a process, which has proven to provide accurate estimates from a group of experts, to obtain probabilities for the validation of 32 sightings of the Barbary lion. We consider the scenario where experts are simply asked whether a sighting was valid, as well as asking them to score the sighting based on distinguishablity, observer competence, and verifiability. We find that asking experts to provide scores for these three aspects resulted in each sighting being considered more individually, meaning that this new questioning method provides very different estimated probabilities that a sighting is valid, which greatly affects the outcome from an extinction model. We consider linear opinion pooling and logarithm opinion pooling to combine the three scores, and also to combine opinions on each sighting. We find the two methods produce similar outcomes, allowing the user to focus on chosen features of each method, such as satisfying the marginalisation property or being externally Bayesian.
authors.affiliation: Mathematical Institute, University of Oxford , UK.
authors.forename: Tamsin E
authors.initials: TE
authors.lastname: Lee
authors.affiliation: Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent , Canterbury, Kent , UK.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Black
authors.affiliation: Agence Nationale pour la Conservation de la Nature , Algiers , Algeria.
authors.forename: Amina
authors.initials: A
authors.lastname: Fellous
authors.affiliation: Department of Biological and Environmental Sciences, University of Qatar , Doha , Qatar.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamaguchi
authors.affiliation: Italian Foundation of Vertebrate Zoology (FIZV) , Rome , Italy.
authors.forename: Francesco M
authors.initials: FM
authors.lastname: Angelici
authors.affiliation: Office for Conservation of the Environment , Diwan of Royal Court , Sultanate of Oman.
authors.forename: Hadi
authors.initials: H
authors.lastname: Al Hikmani
authors.affiliation: Department of Biology, Tufts University , Medford, MA , USA.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Reed
authors.affiliation: Department of Ecology and Evolutionary Biology, Center for Conservation and Biodiversity, University of Connecticut , Storrs, CT , USA.
authors.forename: Chris S
authors.initials: CS
authors.lastname: Elphick
authors.affiliation: Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent , Canterbury, Kent , UK.
authors.forename: David L
authors.initials: DL
authors.lastname: Roberts
keywords: Critically endangered; Data quality; Extinct; IUCN red list; Panthera leo; Possibly extinct; Sighting record; Sighting uncertainty