Until now there has been no evidence of prey animals responding to the direction of a predator's eye-gaze, which may be a common signal in mammalian predators, despite the functional advantage it could provide (particularly for competitive socially feeding prey species, where even small competitive advantages can be very important). We investigate responses to aspects of predator orientation, including eye-gaze direction, which is a very subtle and somewhat overlooked cue of predatory risk.
While responses to conspicuous indicators (such as looming predators or fleeing conspecifics) are well documented, responses to subtle predator cues have been studied in less depth. the effect of being in a group: theory reviewed by Bednekoff & Lima (1998)) or on the predator's characteristics (the threat-sensitivity hypothesis: Helfman 1989). The risk may depend on the current situation of the prey (e.g. However, long-term costs of anti-predator responses (review by Lima 1998) provide an incentive to delay or reduce feeding only when really necessary, adjusting behaviour in line with the current level of risk. Because the costs of failing to identify predation risk can be high, animals are expected to overestimate the risk of predation ( Kavaliers & Choleris 2001) and to maintain a baseline expectation of risk at all times ( Lima & Dill 1990). 2004), feeding often reduces vigilance ( Lima & Bednekoff 1999 Devereux et al. While vigilance and feeding are not always mutually exclusive activities ( Cresswell et al. By correctly assessing lower risk and returning to feeding activity earlier (as in this study), the animal gains a competitive advantage over conspecifics that do not respond to the subtle predator cue in this way.Īll prey animals are under pressure to be vigilant against predation. Starlings respond in a functionally significant manner: when the predator's gaze was averted, starlings resumed feeding earlier, at a higher rate and consumed more food overall. We present wild-caught European starlings ( Sturnus vulgaris) with human ‘predators’ whose frontal appearance and gaze direction are manipulated independently, and show that starlings are sensitive to the predator's orientation, the presence of eyes and the direction of eye-gaze. We describe the first explicit demonstration of a bird responding to a live predator's eye-gaze direction. A predator's head orientation and eye-gaze direction are good candidates for subtle but useful indicators of risk, since many predators orient their head and eyes towards their prey as they attack. Prey responses to conspicuous indicators of risk (such as looming predators or fleeing conspecifics) are well documented, but there should also be strong selection for the detection of more subtle cues. Very few designers go for the eyes at the side of the head look, with the notable exception of Rod Hull's Emu.For prey animals to negotiate successfully the fundamental trade-off between predation and starvation, a realistic assessment of predation risk is vital. While interesting to learn about adaptions in the real world, it turns out it should not be applied to fictional animals for a very simple reason: all of them – from Big Bird to Spongebob Squarepants – turn out to be predators. Meanwhile, predators do tend to have eyes at the front of their heads, giving them a wider field of binocular vision (and the depth perception that comes with it) helping them to focus on their prey. The horizontal pupil also enhances the image quality of horizontal planes and this enhanced view at ground level is also an advantage when running at speed to escape." "This allows them panoramic vision along the ground to help detect potential predators as early as possible. Having a horizontal pupil enhances the amount of light they can receive in front of and behind them while reducing the amount of light from above and below," Gordon Love, professor of physics at Durham University and author of a paper on the topic explained in the Conversation in 2015. "Having eyes towards the side of their head helps them to see nearly all around them.