Dangerous liaisons: the predation risks of receiving social signals

Abstract

Individuals are at risk when communicating because conspicuous signals attract both conspecifics and eavesdropping predators. This predation cost of communicating has typically been attributed to signalling individuals because of their conspicuous role, and is a core concept within sexual selection and communication ecology. But, if predators are attracted to signals, then receivers, both intended or otherwise, may also find themselves at risk of predation. Here, we review the theoretical basis and empirical evidence that receiving also carries a risk of predation. We distinguish between the risks of receiving and responding to signals, and we argue that receivers of signals that are long lived, are highly predictable in time or place and/or cannot be received quickly are likely to be at greater risk of predation compared to receivers of signals without these properties. We review recent empirical evidence from a variety of taxa that supports the hypothesis that receivers (including heterospecific prey) are aware of these risks and that they modify their behaviour to balance the risks against the benefits of receiving under predation threat. We also discuss the wider implications of risky receiving for receiving and signalling behaviour in prey, as well as for the prey's predators.

The dilemma of foraging herbivores: dealing with food and fear

“…Predation risk is often associated with indirect cues from the environment, including open habitat (Powell and Banks 2004) or moonlight , or for arboreal animals, being on the ground (Mella et al 2014); and with direct cues such as the scats and urine of predators (Apfelbach et al 2005). As these cues vary spatially and temporally (Carthey et al 2011;Hughes et al 2012;Price and Banks 2012), so does the landscape of fear (Laundre et al 2001;van der Merwe and Brown 2008). Animals will forage in safe areas if they can (Banks 2001;Verdolin 2006) but when they must forage in risky areas, they adopt many behaviours to manage their risk, including reduced time allocation, increased vigilance, central place foraging and group foraging (Lima and Dill 1990).…”

Breaking the cipher: ant eavesdropping on the variational trail pheromone of its termite prey

“…Even so, it is still possible, and common, for predators to use these signals through eavesdropping [2]. Predators must, however, be equipped with the right sensors in order to detect specialized prey signals [3][4][5] e.g. hornets can detect the alarm pheromones [6] and the aggregation pheromones [7] of honeybees, some ants can detect the trail odour [8], colony odour [9], and alarm pheromones of some termites [10], and the specialist zodariid spider can detect the alarm pheromone of its ant prey [11].…”

Predator odours attract other predators, creating an olfactory web of information

“…prey). This simple approach is unlikely to hold however, given the properties of olfactory cues in terms of longevity, spatial association and the need for close inspection to receive specific information [1]. It is likely that olfactory signals are of interest not only to the intended receiver but also to an array of eavesdroppers in the community who seek to gain beneficial information, including predators, prey, competitors and conspecifics.…”

“…It is likely that olfactory signals are of interest not only to the intended receiver but also to an array of eavesdroppers in the community who seek to gain beneficial information, including predators, prey, competitors and conspecifics. Olfactory cues in particular are vulnerable to eavesdropping, as unlike acoustic and visual cues, odours typically persist in the environment long after the creator has departed [1]. This creates potential for a complex olfactory web of interactions whereby receivers (intended or otherwise) may not only be responding to the signaller, but also to many other potential receivers.…”

“…visual, auditory, olfactory) by predators, prey, competitors and conspecifics is a well-established phenomenon in ecology (reviewed in [1,2]). In particular, numerous studies have investigated the response of prey to predator odours, and prey behaviours such as avoidance and reduction in feeding, activity or reproduction are thought to reduce predation risk from the donor species [3,4].…”