Observations on the Endemic Pygmy Three-Toed Sloth, Bradypus pygmaeus of Isla Escudo de Veraguas, Panamá

Sam Kaviar,Jakob Shockey,Peter Sundberg,Alistair Robert Evans

doi:10.1371/journal.pone.0049854

Abstract

Our objective was to ascertain the population status of the Pygmy Three-toed Sloth, Bradypus pygmaeus, an IUCN Critically Endangered species, on Isla Escudo de Veraguas, Panama. Bradypus pygmaeus are thought to be folivorous mangrove specialists; therefore we conducted a visual systematic survey of all 10 mangrove thickets on the island. The total mangrove habitat area was measured to be 1.67 ha, comprising 0.024% of the total island area. The population survey found low numbers of B. pygmaeus in the mangrove thickets and far lower numbers outside of them. The connectivity of subpopulations between these thickets on the island is not established, as B. pygmaeus movement data is still lacking. We found 79 individuals of B. pygmaeus; 70 were found in mangroves and 9 were observed just beyond the periphery of the mangroves in non-mangrove tree species. Low population number, habitat fragmentation and habitat loss could lead to inbreeding, a loss of genetic diversity, and extinction of B. pygmaeus.

Highlights

The Pygmy Three-toed Sloth, Bradypus pygmaeus, was first described as a species in 2001 [1]
Bradypus pygmaeus is morphologically distinct from Bradypus variegatus, most obviously in their reduced body size, genetic differentiation has not been shown [2]
We attempted to falsify the hypothesis that B. pygmaeus are obligate mangrove specialists by attempting to track individuals that were outside the mangroves and observe one eating from a non-mangrove tree

Summary

Introduction

The Pygmy Three-toed Sloth, Bradypus pygmaeus, was first described as a species in 2001 [1]. Researchers have only observed pygmy sloths in the red mangroves (Rhizophora mangle) of Isla Escudo’s tidal areas, leading to the working hypothesis of obligate red mangrove dietary specialization within the species [1]. The dwarfism of B.pygmaeus may be due to their folivorous dietary specialization [4], this hypothesis is not entirely supported [2]. For the three weeks we searched for more B. pygmaeus outside the mangrove thickets but did not find any. Our research focused on assessing the total population size of B. pygmaeus and delineating the distribution of this population on Isla Escudo.

Objectives

Methods

Results

Conclusion