Integration of multimodal cues does not alter mean but reduces variance in avian responses to predators: a systematic review and meta-analysis

Abstract

Despite a wealth of studies documenting prey responses to perceived predation risk, researchers have only recently begun to consider how prey integrate information from multiple cues in their assessment of risk. We conduct a systematic review and meta-analysis of studies that experimentally manipulated perceived predation risk in birds and evaluate support for three alternative models of cue integration: redundancy/equivalence, enhancement, and antagonism. One key insight from our analysis is that the current theory, generally applied to study cue integration in animals, is incomplete. These theories specify the effects of increasing information level on mean, but not variance, in responses. In contrast, we show that providing multiple complementary cues of predation risk simultaneously does not affect mean response, but rather, reduces variance in responses across studies. We propose this may arise via maximum-likelihood estimation (MLE) integration. Although the MLE framework has been applied to study cue integration in humans, to date, it has not been applied to studies of cue integration in non-human animals. We highlight the broad applicability of MLE integration for information integration problems and propose avenues for future work. Our meta-analysis illustrates how explicit consideration of variance in responses can yield important biological insights.