Sight or smell: which senses do scavenging raptors use to find food?

Simon Potier,Jean-Louis Liegeois,Francesco Bonadonna,Olivier Duriez,Aurélie Célérier

doi:10.1007/s10071-018-1220-0

Abstract

Raptors are usually considered to be mainly visually dependent, and the use of other sensory modalities has rarely been studied in these birds. Here, we investigated experimentally which senses (vision and/or olfaction) Turkey vultures (Cathartes aura) and Southern caracaras (Caracara plancus) use to find hidden food. First, two identical stainless-steel perforated balls, one containing a putrefied piece of meat and the other an odorless control, were presented to birds in binary choice experiments. Both species interacted more with the smelling ball than with the control, suggesting that they were attracted by the odor of the hidden meat. In a second experiment, individuals were accustomed to eat in one specifically colored ball (blue or green). In the test phase, the meat was hidden in the opposite color with respect to the one each bird had become accustomed to. Vultures still interacted more with the smelly ball disregarding the color, while caracaras interacted equally with the two balls. The prevalence of olfaction in Turkey vultures may partly explain why they are the first raptors to find carcasses in tropical forests. In contrast, caracaras forage on the ground opportunistically, a strategy where both olfaction and sight may be involved. Our experiments suggest that both species are able to use olfactory cues for foraging. However, olfaction could be the predominant sense in Turkey vultures while olfaction and sight could play an equivalent role in Southern caracaras.

Highlights

Vox populi often generalizes the sensory abilities of different animals
While it is well accepted that many birds do have a functional sense of smell (Caro et al 2015), the relative importance of olfaction compared to other senses, such as vision, remains poorly studied, especially for a specific function such as foraging
We found clear evidence that both Turkey vultures and Southern caracaras can smell, and find, the hidden food

Summary

Introduction

Animals experience a variety of different ecological conditions throughout their lives, which may favor the use of different sensory abilities (Ruzicka and Conover 2012; Vander Wall et al 2003), even in those organisms that “are known” to rely predominantly on one sense. Despite the work of a few pioneers in the 1970s who discovered that some bird species rely on olfaction for navigation (Papi et al 1972) and sometimes for foraging (Wenzel 1971), birds were, and still are, predominantly considered to be visual foragers, even though species that live in environments where visual cues are limited (e.g., dense vegetation) or almost absent (e.g., oceans) could have evolved alternative sensory abilities such as olfaction (Nevitt et al 1995).

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