Hunted Woolly Monkeys (Lagothrix poeppigii) Show Threat-Sensitive Responses to Human Presence

Sarah Papworth,E J Milner-Gulland,Katie Slocombe

doi:10.1371/journal.pone.0062000

Abstract

Responding only to individuals of a predator species which display threatening behaviour allows prey species to minimise energy expenditure and other costs of predator avoidance, such as disruption of feeding. The threat sensitivity hypothesis predicts such behaviour in prey species. If hunted animals are unable to distinguish dangerous humans from non-dangerous humans, human hunting is likely to have a greater effect on prey populations as all human encounters should lead to predator avoidance, increasing stress and creating opportunity costs for exploited populations. We test the threat sensitivity hypothesis in wild Poeppigi's woolly monkeys (Lagothrix poeppigii) in Yasuní National Park, Ecuador, by presenting human models engaging in one of three behaviours “hunting”, “gathering” or “researching”. These experiments were conducted at two sites with differing hunting pressures. Visibility, movement and vocalisations were recorded and results from two sites showed that groups changed their behaviours after being exposed to humans, and did so in different ways depending on the behaviour of the human model. Results at the site with higher hunting pressure were consistent with predictions based on the threat sensitivity hypothesis. Although results at the site with lower hunting pressure were not consistent with the results at the site with higher hunting pressure, groups at this site also showed differential responses to different human behaviours. These results provide evidence of threat-sensitive predator avoidance in hunted primates, which may allow them to conserve both time and energy when encountering humans which pose no threat.

Highlights

Anti-predator responses can incur opportunity costs, reducing time available for feeding and other activities, or physical costs from energy expenditure or injury [1]
Prey which can distinguish between dangerous and non-dangerous individuals of a predator species and respond appropriately will reduce the costs of antipredator behaviour [4]. This threat sensitive predator response, first suggested by Helfman [5], involves the prey altering their response depending on the magnitude of the threat
This study aims to compare primate antipredator responses to different types of human behaviour, the crucial contrast is the change in behaviour from before experimental presentation to afterwards

Summary

Introduction

Anti-predator responses can incur opportunity costs, reducing time available for feeding and other activities, or physical costs from energy expenditure or injury [1] These costs can be reduced if prey are able to distinguish between dangerous and nondangerous individuals of a single predator species. Prey which can distinguish between dangerous and non-dangerous individuals of a predator species and respond appropriately will reduce the costs of antipredator behaviour [4]. This threat sensitive predator response, first suggested by Helfman [5], involves the prey altering their response depending on the magnitude of the threat. Threat sensitive predator reactions translates to increased responses when the threat, and risk, is greatest

Objectives

Methods

Results