How insects sense olfactory patches – the spatial scaling of olfactory information

Abstract

When searching for resources in heterogeneous environments, animals must rely on their abilities to detect the resources via their sensory systems. However, variation in the strength of the sensory cue may be mediated by the physical size of the resource patch. Patch detection of insects are often predicted by the scaling of sensory cues to patch size, where visual cues has been proposed to scale proportional to the diameter of the patch. The scaling properties of olfactory cues are, however, virtually unknown. Here, we investigated scaling rules for olfactory information in a gradient of numbers of odour sources, relevant to odour‐mediated attraction under field conditions. We recorded moth antennal responses to sex pheromones downwind from pheromone patches and estimated the slope in the scaling relationship between the effective length of the odour plumes and the number of odour sources. These measurements showed that the effective plume length increased proportional to the square root of the number of odour sources. The scaling relationship, as estimated in the field experiment, was then evaluated against field data of the slope in the relationship between trap catch and release rate of chemical attractants for a wide range of insects. This meta‐analysis revealed an average slope largely consistent with the estimated scaling relationship between the effective plume length and the number of odour sources. This study is the first to estimate the scaling properties of olfactory cues empirically and has implications for understanding and predicting the spatial distributions of insects searching by means of olfactory cues in heterogeneous environments.

Spatial Patterning of Prey at Reproduction to Reduce Predation Risk: What Drives Dispersion from Groups?

“…Note, however, that the encounter-detectability relationship is dependent on how detectability is modelled. Because the nature of prey detections in our wolf-caribou system is unknown, we used the inverse square law to model detectability as the square root of group size (Andersson et al 2013). This approach is likely not an exact representation of how wolves detect caribou and may be biologically liberal when group sizes are large (e.g.…”

“…For this analysis, we assumed that the primary means of prey detection by wolves is by olfaction or audition, particularly in forested environments (Mech and Boitani 2003). We assumed that detection distances for these senses are predominantly influenced by the olfactory or auditory intensity of the point source and that this intensity increases linearly with the number of caribou in a group (Andersson et al 2013). We therefore modelled the relationship between group size and detectability using the inverse square law, which states that the influence of a point source emitting a physical quantity will decay as the square root of the distance from the point source (Self et al 2009).…”

Context dependence of the olfactory perceptual range in the generalist land snail Cornu aspersum

“…The perceptual range is not fixed but depends, for instance, on the physical characteristics of the environment (Olden et al 2004), the size of the stimulus (Andersson et al 2013), and the sensory mode(s) involved (visual or olfactory; Öckinger and Van Dyck 2012). These elements may alter either the distance at which a stimulus is perceived by an animal (i.e., the perceptual range sensu stricto), the distance at which it triggers a behavioural response (the perceptual range sensu lato, which is more frequently measured, and depends on the perceptual range sensu stricto and the response tendency or bias of organisms; Fletcher et al 2013), or both.…”

“…Previous studies generally focused on visual perceptual ranges (e.g., Mech and Zollner 2002;Auburn et al 2009). However, many animals, including many invertebrates, rely heavily on olfactory cues to inform their orientation decisions (Öckinger and Van Dyck 2012;Andersson et al 2013). Investigations of olfactory perceptual ranges have been, to date, mostly limited to specialised stimuli towards which specific detection processes may have evolved (e.g., a host for a highly specialised species or sexual pheromones; Andersson et al 2013;Fletcher et al 2013).…”

“…However, many animals, including many invertebrates, rely heavily on olfactory cues to inform their orientation decisions (Öckinger and Van Dyck 2012;Andersson et al 2013). Investigations of olfactory perceptual ranges have been, to date, mostly limited to specialised stimuli towards which specific detection processes may have evolved (e.g., a host for a highly specialised species or sexual pheromones; Andersson et al 2013;Fletcher et al 2013). By contrast, information is lacking on the perceptual range of generalists using olfactory cues, and in particular, how it varies depending on resource quality and (or) resource heterogeneity.…”