title: Toward accurate and precise estimates of lion density.
abstract: Reliable estimates of animal density are fundamental to understanding ecological processes and population dynamics. Furthermore, their accuracy is vital to conservation because wildlife authorities rely on estimates to make decisions. However, it is notoriously difficult to accurately estimate density for wide-ranging carnivores that occur at low densities. In recent years, significant progress has been made in density estimation of Asian carnivores, but the methods have not been widely adapted to African carnivores, such as lions (Panthera leo). Although abundance indices for lions may produce poor inferences, they continue to be used to estimate density and inform management and policy. We used sighting data from a 3-month survey and adapted a Bayesian spatially explicit capture-recapture (SECR) model to estimate spatial lion density in the Maasai Mara National Reserve and surrounding conservancies in Kenya. Our unstructured spatial capture-recapture sampling design incorporated search effort to explicitly estimate detection probability and density on a fine spatial scale, making our approach robust in the context of varying detection probabilities. Overall posterior mean lion density was estimated to be 17.08 (posterior SD 1.310) lions >1 year old/100 km2, and the sex ratio was estimated at 2.2 females to 1 male. Our modeling framework and narrow posterior SD demonstrate that SECR methods can produce statistically rigorous and precise estimates of population parameters, and we argue that they should be favored over less reliable abundance indices. Furthermore, our approach is flexible enough to incorporate different data types, which enables robust population estimates over relatively short survey periods in a variety of systems. Trend analyses are essential to guide conservation decisions but are frequently based on surveys of differing reliability. We therefore call for a unified framework to assess lion numbers in key populations to improve management and policy decisions.
authors.affiliation: Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, Recanati-Kaplan Centre, Tubney House, Abingdon Road, Tubney, Oxfordshire, OX13 5QL, U.K.|Mara Lion Project, Kenya Wildlife Trust, P.O. Box 86-00502 Karen, Nairobi, Kenya.
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Elliot
authors.affiliation: Statistics and Mathematics Unit, Indian Statistical Institute - Bangalore Centre, Bengaluru - 560059, India.|Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, U.K.
authors.forename: Arjun M
authors.initials: AM
authors.lastname: Gopalaswamy
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D003247:Conservation of Natural Resources; D005260:Female; D007630:Kenya; D008045:Lions; D008297:Male; D011156:Population Density; D015203:Reproducibility of Results
keywords: Maasai Mara; Panthera leo; SECR; captura-recaptura espacial; densidad; density; precision; precisión; spatial capture-recapture