Tapirs in trouble: estimating Baird's tapir densities in the Sierra Madre de Chiapas, Mexico

Marina Rivero,Christopher A Jordan,Gamaliel Camacho,J Antonio De La Torre,Rodrigo A Medellín,Rafael Reyna-Hurtado,Eduardo J Naranjo,Mathias W Tobler

doi:10.1017/s0030605320001076

Abstract

AbstractSpatial capture–recapture models have been widely used to estimate densities of species where individuals can be uniquely identified, but alternatives have been developed for estimation of densities for unmarked populations. In this study we used camera-trap records from 2018 to estimate densities of a species that does not always have individually identifiable marks, Baird's tapir Tapirus bairdii, in the Sierra Madre de Chiapas, southern Mexico. We compared the performance of the spatial capture–recapture model with spatial mark–resight and random encounter models. The density of Baird's tapir did not differ significantly between the three models. The estimate of density was highest using the random encounter model (26/100 km2, 95% CI 12–41) and lowest using the capture–recapture model (8/100 km2, 95% CI 4–16). The estimate from the spatial mark–resight model was 10/100 km2 (95% CI 8–14), which had the lowest coefficient of variation, indicating a higher precision than with the other models. Using a second set of camera-trap data, collected in 2015–2016, we created occupancy models and extrapolated density to areas with potential occupancy of Baird's tapir, to generate a population estimate for the whole Sierra Madre de Chiapas. Our findings indicate the need to strengthen, and possibly expand, the protected areas of southern Mexico and to develop an action plan to ensure the conservation of Baird's tapir.

Highlights

Baird’s tapir Tapirus bairdii is one of the last representatives of the megafauna that survived Pleistocene extinctions and is considered a living fossil because of its unique morphological and behavioural characteristics, which resemble those of primitive ungulates (Janis, )
Tapir images that could not be assigned to an individual were discarded for the spatial capture–recapture analysis, but were included as unmarked individuals for the spatial mark–resight analysis
We evaluated the accuracy of our best candidate model by calculating the area under the receiver operator characteristic (ROC) curve, which is obtained by plotting sensitivity vs − specificity

Summary

Introduction

Baird’s tapir Tapirus bairdii is one of the last representatives of the megafauna that survived Pleistocene extinctions and is considered a living fossil because of its unique morphological and behavioural characteristics, which resemble those of primitive ungulates (Janis, ). Baird’s tapir ranged from south-east Mexico to north-west Colombia (García et al, ). Populations are declining because of poaching, droughts and habitat loss caused by land-use change, and logging and fires (García et al, ). The extent of this decline is not well known because there is no reliable information on population density and size across most of the species’ range (Naranjo, ; Mejía-Correa et al, ; González-Maya et al, ; Carbajal-Borges et al, ; Lavariega-Nolasco et al, ; Botello et al, ). Adults, Baird’s tapir is categorized as Endangered on the IUCN Red List, (García et al, ), variations in estimates (Naranjo, ; García et al, ; Schank et al, ) reflect uncertainty about the size of the population With an estimated global total of c. , adults, Baird’s tapir is categorized as Endangered on the IUCN Red List, (García et al, ), variations in estimates (Naranjo, ; García et al, ; Schank et al, ) reflect uncertainty about the size of the population

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Conclusion