Exclusion Performance in Dwarf Goats (Capra aegagrus hircus) and Sheep (Ovis orientalis aries)

Christian Nawroth,Jan Langbein,Eberhard Von Borell,Alan Mcelligott

doi:10.1371/journal.pone.0093534

Christian Nawroth, Jan Langbein + Show 2 more

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https://doi.org/10.1371/journal.pone.0093534

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Abstract

Using a comparative approach, we investigated the ability of dwarf goats and sheep to use direct and indirect information about the location of a food reward in an object-choice task. Subjects had to choose between two cups with only one covering a reward. Before making a choice, subjects received information about the baited (direct information) or non-baited cup (indirect information). Both goats and sheep were able to use direct information (presence of food) in the object choice task. After controlling for local enhancement, we found that goats rather than sheep were able to use indirect information (i.e., the absence of food) to find a reward. The actual test setup could not clarify whether individual goats were able to inferentially reason about the content of the baited cup when only shown the content of the non-baited cup or if they simply avoided the empty cup in that situation. As browsing species, feral and wild goats exhibit highly selective feeding behaviour compared to the rather unselective grazing sheep. The potential influence of this species-specific foraging flexibility of goats and sheep for using direct and indirect information to find a food reward is discussed in relation to a higher aversion to losses in food acquisition in goats compared to sheep.

Highlights

A fundamental question in comparative studies of the cognitive abilities of non-human animals is to distinguish between a gradual development in performance due to associative learning mechanisms and complex cognition, such as sudden insightful solutions [1]
Of main interest was to analyse if the information provided across conditions, species and/or effects of local enhancement had an impact in solving the task
We investigated whether goats and sheep are able to use direct as well as indirect information to choose the correct location of a reward in an object-choice task

Summary

Introduction

A fundamental question in comparative studies of the cognitive abilities of non-human animals is to distinguish between a gradual development in performance due to associative learning mechanisms and complex cognition, such as sudden insightful solutions [1]. By introducing a new item and giving the animal the choice between a familiar and a new label, subjects infer by choosing the new label that it must refer to the new item [7,8] Another approach frequently used to study inferential reasoning is the matching-tosample paradigm, in which a subject is trained to a conditional discrimination [9]. The matching to sample procedure has been applied to test inference by exclusion in chimpanzees, sea lions, bottlenose dolphins and pigeons [10,11,12,13,14] Some of these experimental approaches have been criticised because the artificial setting hampers animals from exhibiting spontaneous behaviour. It requires massive pre-training of the animals, and it is often difficult to exclude the possibility that they acted on the basis of previously learned associations [6,15,16]

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