Testing the effect of medical positive reinforcement training on salivary cortisol levels in bonobos and orangutans.

Verena Behringer,Erich Möstl,Dieter Selzer,Gottfried Hohmann,Tobias Deschner,Jeroen M G Stevens,Martine Hausberger

doi:10.1371/journal.pone.0108664

Abstract

The management of captive animals has been improved by the establishment of positive reinforcement training as a tool to facilitate interactions between caretakers and animals. In great apes, positive reinforcement training has also been used to train individuals to participate in simple medical procedures to monitor physical health. One aim of positive reinforcement training is to establish a relaxed atmosphere for situations that, without training, might be very stressful. This is especially true for simple medical procedures that can require animals to engage in behaviours that are unusual or use unfamiliar medical devices that can be upsetting. Therefore, one cannot exclude the possibility that the training itself is a source of stress. In this study, we explored the effects of medical positive reinforcement training on salivary cortisol in two groups of captive ape species, orangutans and bonobos, which were familiar to this procedure. Furthermore, we successfully biologically validated the salivary cortisol assay, which had already been validated for bonobos, for orangutans. For the biological validation, we found that cortisol levels in orangutan saliva collected during baseline conditions were lower than in samples collected during three periods that were potentially stressful for the animals. However, we did not find significant changes in salivary cortisol during medical positive reinforcement training for either bonobos or orangutans. Therefore, for bonobos and orangutans with previous exposure to medical PRT, the procedure is not stressful. Thus, medical PRT provides a helpful tool for the captive management of the two species.

Highlights

Over the past few decades, the management of captive animals has been improved in a variety of ways
When subjects were exposed to potentially stressful events, salivary cortisol levels were elevated compared to the baseline condition
For each of the three potentially stressful events, salivary cortisol levels were significantly higher compared to the baseline condition (Table 3), with the effect being most pronounced on the day of the transfer (Table 3)

Summary

Introduction

Over the past few decades, the management of captive animals has been improved in a variety of ways. One effective element was the establishment of specific enrichment programs that contributed to the improvement of the well-being of captive individuals [1] Another one concerns the establishment of positive reinforcement training (PRT) as a tool to facilitate interactions between caretakers and animals during examinations [1]. PRT with a clicker is commonly used in different animal species and has become a common training method in nonhuman primates [5,8,9] This kind of training gives the animal the choice to cooperate or not [4], and the training of medical procedures is a helpful tool in monitoring physical health [10,11,12]

Methods

Results

Discussion

Conclusion