Perceptual Range Research Articles

Anthropogenic noise weakens territorial response to intruder's songs

AbstractNoise pollution degrades natural acoustic conditions, potentially interfering with bird communication. However, exactly how noise impacts the ability of the signal receiver to detect and discriminate vocalizations from conspecifics remains understudied in field settings. We performed a natural experiment to determine the effect of noise pollution on the territory‐defense behaviors of two emberizid sparrows exposed to carefully constructed playbacks of conspecific intruder songs. Although all birds reacted to the playbacks, response latency increased with noise levels. This suggests that noise interferes with signal reception and may indicate impaired signal discrimination. We place these results in the context of a receiver's “listening area” and the significant impact of noise pollution on this receiver‐centric perceptual acoustic range. This work informs conservation efforts and provides a much needed field‐based examination of the disruptive impact of noise pollution on behaviors directly related to reproduction and fitness.

Grain-dependent functional responses in habitat selection

Context Spatial scale is an important consideration for understanding how animals select habitat, and multi-scalar designs in resource selection studies have become increasingly common. Despite this, examination of functional responses in habitat selection at multiple scales is rare. The perceptual range of an animal changes as a function of vegetation association, suggesting that use, selection and functional responses may all be habitat- and scale-dependent.

Erratum to: Using Reflectance Ratios to Study Animal Coloration

We used 8911 reflectance spectrophotometry measurements of plumage colours, made on museum skins of 135 species of finches in the family Estrildidae. For most species male and female specimens were measured, usually three specimens per species/sex, and multiple measurements of colour were made that include all the main body parts. This dataset will be described in detail elsewhere. Here we used visual models to estimate colour saturation of these spectra as the distance to the achromatic centre of an avian tetrahedral colour space (Endler and Mielke 2005; Stoddard and Prum 2008), either applying or not applying Fechner law. Reflectance values lower than 1 % were flattened to 1 %, and spectra were then analysed using the avian visual model of Vorobyev et al. (1998) as implemented in pavo (functions vismodel and tcs; Maia et al. 2013). Settings for the visual model without Fechner law (y-axes in Fig. 4) were as follows: average UV avian sensitivity, regular daylight illumination, von Kries correction, relative quantum catches, no Fechner law (i.e. not log-transforming quantum catches), and the remaining options set to default. For visual models with Fechner law (x-axes in Fig. 4) we first ran a model similar to the above but with Fechner law applied (i.e. log-transforming quantum catches), and with absolute rather than relative quantum catches. Then, as explained below, we rescaled log-transformed quantum catches to a biologically interpretable scale before normalization (i.e. dividing the signal of each photoreceptor cone type by the sum of signals of the four cone types) to obtain relative quantum catches. Rescaling log-transformed quantum catches is necessary because, as discussed by Stoddard and Prumm (2008; page 4 of the appendix), log-transformation changes colour spaces artefactually in a way that strongly depends on the arbitrary, unitless scale chosen for absolute quantum catches (from 0 for no stimulation of the photoreceptor, to an arbitrary value for stimulation by 100 % reflectance). Relative differences among log-transformed quantum catches are unaffected by the scale used or by the logarithmic base chosen, but the absolute values change so that normalizing log-quantum catches directly produces meaningless colour spaces. For example, software for analysis of spectral colour usually quantify quantum catches from 0 to an arbitrary value of 1; the resulting log-transformed quantum catches have negative values that, upon normalization, distort colour to the point that the relative strength of signals from the four cone types is reversed. The conceptual problem is that log-transformed quantum catches have no intrinsic minimum (as log(0) tends to minus infinity, though low values should be flattened because they reach beyond the perceptual range of animals and because The online version of the original article can be found under doi:10.1007/s11692-015-9328-5.

A stochastic movement simulator improves estimates of landscape connectivity.

Conservation actions often focus on restoration or creation of natural areas designed to facilitate the movements of organisms among populations. To be efficient, these actions need to be based on reliable estimates or predictions of landscape connectivity. While circuit theory and least-cost paths (LCPs) are increasingly being used to estimate connectivity, these methods also have proven limitations. We compared their performance in predicting genetic connectivity with that of an alternative approach based on a simple, individual-based "stochastic movement simulator" (SMS). SMS predicts dispersal of organisms using the same landscape representation as LCPs and circuit theory-based estimates (i.e., a cost surface), while relaxing key LCP assumptions, namely individual omniscience of the landscape (by incorporating perceptual range) and the optimality of individual movements (by including stochasticity in simulated movements). The performance of the three estimators was assessed by the degree to which they correlated with genetic estimates of connectivity in two species with contrasting movement abilities (Cabanis's Greenbul, an Afrotropical forest bird species, and natterjack toad, an amphibian restricted to European sandy and heathland areas). For both species, the correlation between dispersal model and genetic data was substantially higher when SMS was used. Importantly, the results also demonstrate that the improvement gained by using SMS is robust both to variation in spatial resolution of the landscape and to uncertainty in the perceptual range model parameter. Integration of this individual-based approach with other developing methods in the field of connectivity research, such as graph theory, can yield rapid progress towards more robust connectivity indices and more effective recommendations for land management.

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

Dispersal success in animals depends in part on their perceptual range, i.e., the distance from which they can acquire information about their environment. We studied how the olfactory perceptual range of a generalist species, the brown garden snail (Cornu aspersum (Müller, 1774)), varied under controlled conditions depending on the context in which stimuli were presented, whether alone or in the presence of another stimulus with opposite properties. Cornu aspersum preferentially orient themselves towards small nettle (Urtica dioica L.) patches, a highly palatable plant, and move away from repulsive plants if these stimuli are placed up to between 20 and 40 cm away from their starting point. A blend of palatable and repulsive plants, tested together, do not significantly influence the orientation of individuals in either direction. Cornu aspersum are thus capable of detecting and evaluating relatively small potential resource patches from a distance, enabling them to limit costly explorations, but this ability is context-dependent. These data could lead to a better understanding of the behaviour of C. aspersum in very heterogeneous landscapes in relation to this species’ ability to colonise a wide range of anthropised and fragmented habitats.

Extending Lévy search theory from one to higher dimensions: Lévy walking favours the blind.

A diverse range of organisms, including T cells, E.coli, honeybees, sharks, turtles, bony fish, jellyfish, wandering albatrosses and even human hunter-gatherers have movement patterns that can be approximated by Lévy walks (LW; sometimes called Lévy flights in the biological and ecological literature). These observations lend support to the 'Lévy flight foraging hypothesis' which asserts that natural selection should have led to adaptations for Lévy flight foraging, because Lévy flights can optimize search efficiencies. The hypothesis stems from a rigorous theory of one-dimensional searching and from simulation data for two-dimensional searching. The potential effectiveness of three-dimensional Lévy searches has not been examined but is central to a proper understanding of marine predators and T cells which have provided the most compelling empirical evidence for LW. Here I extend Lévy search theory from one to three dimensions. The new theory predicts that three-dimensional Lévy searching can be advantageous but only when targets are large compared with the perceptual range of the searchers, i.e. only when foragers are effectively blind and need to come into contact with a target to establish its presence. This may explain why effective blindness is a common factor among three-dimensional Lévy walkers.

Oxygen Uptake At Criterion RPE In Trained And Untrained Females Following Exercise And Memory Anchoring

Exercise and memory anchoring provides a definitive anchoring procedure for linking perceptions of effort to variable intensities of physical exertion. However, it is unclear if relative intensity at a given RPE would remain consistent in individuals of different training status. PURPOSE: The current investigation compared percent of maximal oxygen uptake in recreationally trained (RT) versus untrained (UT) adult females at selected, criterion RPE during maximal, graded, treadmill exercise following exercise and memory anchoring to the Borg 15-category scale. METHODS: The RT (n = 8) group (21.8± 2.0 yrs.) and the UT (n = 3) group (18.0 ± 0.0 yrs.) each received anchoring instructions during a maximal, graded treadmill exercise test at an initial session. The low anchor was assigned a seven and the high anchor was assigned a 19 on the scale. At a second session, memory anchoring instructions were provided prior to a GXT during which RPE was recorded following each stage. Linear regression with RPE as the independent variable and oxygen consumption as the dependent variable was used to calculate percent VO2max for each criterion RPE (7, 9, 11, 13, 15 17, and 19). An independent samples t-test was used to compare percent VO2max between RT and UT at each criterion RPE. RESULTS: As expected, VO2max was higher for the RT than the UT. All other descriptive variables were similar between groups. Relative oxygen uptake at each criterion RPE was also similar. CONCLUSION: Pre-exercise exercise and memory anchoring yielded similar relative VO2 for young adult females independent of training status. It appears that exposure to the high and low anchors during the anchoring procedure is sufficient to guide exercise intensity during a maximal, graded, treadmill exercise test for this population. The current findings further validate Borg’s assumption for the application of a category scale in that the perceptual range may be set equal for all individuals as percent VO2max was similar between young, adult women of varying training status.

Comparing permeability of matrix cover types for the marsh rice rat (Oryzomys palustris)

Matrix land cover types differ in permeability to animals moving between habitat patches, and animals may actually move faster across less-suitable areas. Marsh rice rats are wetland specialists whose dispersal crosses upland matrix. Our objectives were to (1) compare matrix permeability for the marsh rice rat among upland cover types, (2) compare permeability within versus outside perceptual range of the wetland, and (3) explore intrinsic and extrinsic features influencing matrix use and permeability. We quantified permeability of grassland, crop field, and forest to the marsh rice rat during 2011–2012, by marking rats in wetlands and estimating the slope of capture rate versus distance (0–95 m) into the matrix. We also compared permeability within (0–15 m) and beyond the perceptual range of rice rats, and tested whether age, sex, time, water depth, rice rat abundance, and vegetation density influenced matrix use and permeability. Permeability was greater for soybean fields than grassland or forest but did not appear to differ within versus beyond rice rats’ perceptual range. Matrix capture rates were higher early in the study and in times and locations with thick ground vegetation and high rice rat abundance in the wetlands. Rice rats captured in the matrix were younger than those in wetland patches. Our findings expand known matrix use by marsh rice rats, and support permeability being high in matrix types dissimilar to suitable habitat. Studying individual movements will help identify mechanisms underlying enhanced permeability in crop fields.

Modulation frequency discrimination with single and multiple channels in cochlear implant users

Temporal envelope cues convey important speech information for cochlear implant (CI) users. Many studies have explored CI users' single-channel temporal envelope processing. However, in clinical CI speech processors, temporal envelope information is processed by multiple channels. Previous studies have shown that amplitude modulation frequency discrimination (AMFD) thresholds are better when temporal envelopes are delivered to multiple rather than single channels. In clinical fitting, current levels on single channels must often be reduced to accommodate multi-channel loudness summation. As such, it is unclear whether the multi-channel advantage in AMFD observed in previous studies was due to coherent envelope information distributed across the cochlea or to greater loudness associated with multi-channel stimulation. In this study, single- and multi-channel AMFD thresholds were measured in CI users. Multi-channel component electrodes were either widely or narrowly spaced to vary the degree of overlap between neural populations. The reference amplitude modulation (AM) frequency was 100 Hz, and coherent modulation was applied to all channels. In Experiment 1, single- and multi-channel AMFD thresholds were measured at similar loudness. In this case, current levels on component channels were higher for single-than for multi-channel AM stimuli, and the modulation depth was approximately 100% of the perceptual dynamic range (i.e., between threshold and maximum acceptable loudness). Results showed no significant difference in AMFD thresholds between similarly loud single- and multi-channel modulated stimuli. In Experiment 2, single- and multi-channel AMFD thresholds were compared at substantially different loudness. In this case, current levels on component channels were the same for single- and multi-channel stimuli (“summation-adjusted” current levels) and the same range of modulation (in dB) was applied to the component channels for both single- and multi-channel testing. With the summation-adjusted current levels, loudness was lower with single than with multiple channels and the AM depth resulted in substantial stimulation below single-channel audibility, thereby reducing the perceptual range of AM. Results showed that AMFD thresholds were significantly better with multiple channels than with any of the single component channels. There was no significant effect of the distribution of electrodes on multi-channel AMFD thresholds. The results suggest that increased loudness due to multi-channel summation may contribute to the multi-channel advantage in AMFD, and that overall loudness may matter more than the distribution of envelope information in the cochlea.

Brief Report: A Hypothetical Construct Based on Limited Data Visual System Recovery After Refractive Surgery

Laser refractive surgery, involving the computer-controlled application of a 193-nm beam of excimer laser "light," is utilized to resculpt the central cornea, thus reducing its apical thickness. On casual inspection, this simple matter of removing or excising a specific amount of central corneal avascular tissue is a smooth, seamless alteration with few apparent secondary issues or sequelae. Normal postoperative recovery is typically gauged by the recovery of high-contrast visual acuity to the same (or better) degree as was previously obtained with a spectacle correction. However, although this is an acceptable means of determining operative success, it is not indicative of the complex challenges imposed upon the neurosensory system. The secondarily imposed strain upon the visual system, regarding the return to its pre-existing visual line-of-sight organization occurs only by bringing multiple adaptations into subtle and seamless play. This process is initiated and completed in a relatively short time period, such that most patients (but not all) are not even marginally aware of the challenges imposed to the visual system. This article is meant to probe those system challenges, serving to highlight this postoperative plasticity, seeking to gain a broader understanding and appreciation of the perceptual range of the visual recovery process.

Seeing, adapting to, and reproducing the appearance of nature.

The perception of color in nature is a complex multidimensional phenomenon. The vast range and high dimensionality of the light stimulus in a natural scene is reduced in range and dimension by the human visual system. The color experience is reduced to the appearance attributes of brightness, lightness, colorfulness, chroma, saturation, and hue from spectral energy distributions in the scene, while the vast range of light levels present in the world is reduced to a more manageable perceptual range through local adaptation. These processes set the stage for our efforts to capture, process, and reproduce the colors of nature as well as make artistic interpretations of them. This paper reviews the challenges involved in accurately capturing and reproducing optical phenomena observed in nature.

How fish might adjust their acoustic communication in anthropogenic noise: a response to comments on Radford et al.

We are grateful for the thoughtful and supportive commentaries (Brumm 2014Candolin 2014; Kunc 2014; Wong 2014; ) written about our recent review of how fish might potentially adjust their acoustic communication in response to anthropogenic (man-made) noise (Radford et al. 2014). A clear consensus among the commen-tators and ourselves is the need for more studies directly investigat-ing this issue. Here, we emphasize 3 reasons why such research is important.First, Brumm (2014) rightly points out that we need to estab-lish the extent of the potential problem caused by anthropogenic noise because many fish species tend to communicate acoustically over only very short distances (often <1 m). This is clearly a much smaller perceptual range than that of even the low-amplitude close calls common in many social birds and mammals (Palombit et al. 1999Radford and Ridley 2008; ) and certainly than that of louder songs and alarm calls (Bradbury and Vehrencamp 2011). As Wong (2014) mentions, though, sound transmits much further and at higher amplitudes in water than in air, so the area of potential impact arising from an anthropogenic noise source may be greater than on land. The uncertainty about the likelihood of an effect is why it is crucial to obtain actual measurements of signal-to-noise ratios in natural conditions and within the usual communication ranges of fishes (Brumm 2014).The second reason for further research, not unrelated to the first point, is that many fishes use multicomponent signaling; determining the relative importance of the acoustic compo-nent relates directly to the likely impact of anthropogenic noise (Brumm 2014Candolin 2014; ). One possibility is that there is redundancy in the signaling process: the same information could be conveyed to receivers through other sensory modalities (e.g., visual, electrical, or chemical), as well as acoustically (Brumm 2014). If so, then the loss of the acoustic element of the display would not necessarily have a detrimental effect on the message conveyed. On the other hand, signals in different sensory modali-ties could be complementary, either providing related but different pieces of information or being used at different stages in the sig-naling process (Candolin 2014Wong 2014; ). In such cases, loss of the acoustic component could result in changes in the information received and thus changes in responses; for instance, assessment of individual quality could be affected, leading to less selective mate choice (Heuschele et al. 2009Candolin 2014; ). In all prob-ability, the effects of anthropogenic noise will be species specific and so further work, rather than extrapolations from existing knowledge, is required.A third reason for investigating the responses of fish to anthro-pogenic noise is their potential as model organisms. Ultimately, what is needed are detailed studies assessing fitness consequences (Morley et al. 2014); in the case of acoustic communication, changes by signalers could be costly and there could be direct or indirect effects on survival and reproductive success (Read et al. 2014). The majority of work conducted on how anthropogenic noise affects aquatic organisms has been on marine mammals, but for obvious reasons determining fitness consequences in such long-lived animals is difficult. Fish, and indeed invertebrates (see Wale et al. 2013a2013b, ; Nedelec et al. 2014 for recent evidence of impacts of noise), are currently understudied relative to their abundance and importance (Morley et al. 2014Kunc 2014; ; Radford et al. 2014). However, species in these taxonomic groups provide more scope than marine mammals for direct assessments of fitness consequences due to their generally smaller sizes, shorter life spans, and the potential for experimental manipulation.We therefore need new studies, ideally involving field experi-ments with data collected from free-ranging animals. Captive-based work, offering carefully controlled conditions and the possibility of detailed observations, can provide a valuable step-ping stone in determining the potential for noise to have an impact (e.g., Bruintjes and Radford 2013Simpson et al. 2014; ; Voellmy et al. 2014). However, what is vital moving forward is research conducted close to real noise sources that allows a full range of natural behaviors in environmentally realistic condi-tions to be determined. This undoubtedly presents a logistical challenge, but we hope our review and the associated commen-taries will stimulate and inspire researchers to find innovative approaches and thus advance our understanding of how anthro-pogenic noise can impact fish in general and their acoustic com-munication in particular.

Phenotypic variation in oronasal perception and the relative effects of PROP and Thermal Taster Status

Individual variation in taste perception has long been investigated, particular in relation to PROP taster status (PTS). Recently, a new marker has been identified, Thermal Taster Status (TTS), whereby individuals are categorised as thermal tasters (TTs) or thermal non-tasters (TnTs) based on their ability to perceive taste solely from temperature stimulation. The aim of this study was to investigate the incidence of thermal tasters and relative effects of PTS and TTS on oronasal sensitivity across the whole perceptual range. Both detection thresholds (ASTM E679) and intensity measures at suprathreshold level (rated on gLMS) for stimuli from a range of modalities were determined from up to 124 subjects pre-screened for their PTS and TTS. For the detection threshold tests stimuli included tastants (sucrose, NaCl, caffeine), trigeminal stimuli (N-ethyl-2-isopropyl-5-methylcyclohexanecarboxamide (WS3) and capsaicin), and aromas (ethyl butyrate and isoamyl acetate). Tastants (sucrose, NaCl, citric acid and caffeine) plus capsaicin as a trigeminal stimulus were evaluated at suprathreshold level. No significant differences were found within either PTS or TTS groups at detection threshold level, with one exception; TTs had a lower threshold for sucrose (p<0.05). At supra-threshold level, PROP supertasters (pSTs) and medium tasters (pMTs) rated stimuli higher than non-tasters, and a consistent trend was observed that TTs rated stimuli higher than TnTs, although only ratings for temperature (warm and cold) reached significance. Global analyses applied across each modality, showed that in general TTs rated gustatory and trigeminal modalities significantly higher than TnTs, whilst this was not the case for olfactory stimuli, indicating that the mechanism for increased perception for TTs may be located in the oral cavity. PTS and TTS were shown to be independent phenotypes, but interestingly, ANOVA revealed significant interactions between TTS and PTS across the three modalities. Most notably, within pMTs, TTs rated stimuli intensity higher than TnTs, while the opposite trend was observed for pSTs. The intensity advantage gained by thermal tasters appears to be more apparent for pMTs than the already highly sensitive pSTs.

Simple individual‐based models effectively represent Afrotropical forest bird movement in complex landscapes

Summary Reliable estimates of dispersal rates between habitat patches (i.e. functional connectivity) are critical for predicting long‐term effects of habitat fragmentation on population persistence. Connectivity measures are frequently derived from least cost path or graph‐based approaches, despite the fact that these methods make biologically unrealistic assumptions. Individual‐based models (IBMs) have been proposed as an alternative as they allow modelling movement behaviour in response to landscape resistance. However, IBMs typically require excessive data to be useful for management. Here, we test the extent to which an IBM requiring only an uncomplicated set of movement rules [the ‘stochastic movement simulator’ (SMS)] can predict animal movement behaviour in real‐world landscapes. Movement behaviour of two forest birds, the Cabanis's greenbul Phyllastrephus cabanisi (a forest specialist) and the white‐starred robin Pogonocichla stellata (a habitat generalist), across an Afrotropical matrix was simulated using SMS. Predictions from SMS were evaluated against a set of detailed movement paths collected by radiotracking homing individuals. SMS was capable of generating credible predictions of bird movement, although simulations were sensitive to the cost values and the movement rules specified. Model performance was generally highest when movement was simulated across low‐contrasting cost surfaces and when virtual individuals were assigned low directional persistence and limited perceptual range. SMS better predicted movements of the habitat specialist than the habitat generalist, which highlights its potential to model functional connectivity when species movements are affected by the matrix. Synthesis and applications. Modelling the dispersal process with greater biological realism is likely to be critical for improving our predictive capability regarding functional connectivity and population persistence. For more realistic models to be widely applied, it is vital that their application is not overly complicated or data demanding. Here, we show that given relatively basic understanding of a species' dispersal ecology, the stochastic movement simulator represents a promising tool for estimating connectivity, which can help improve the design of functional ecological networks aimed at successful species conservation.

Prediction of peak oxygen uptake from differentiated ratings of perceived exertion during wheelchair propulsion in trained wheelchair sportspersons

To assess the validity of predicting peak oxygen uptake (VO(2peak)) from differentiated ratings of perceived exertion (RPE) obtained during submaximal wheelchair propulsion. Three subgroups of elite male wheelchair athletes [nine tetraplegics (TETRA), nine paraplegics (PARA), eight athletes without spinal cord injury (NON-SCI)] performed an incremental speed exercise test followed by graded exercise to exhaustion (VO(2peak) test). Oxygen uptake (VO₂), heart rate (HR) and differentiated RPE (Central RPE(C), Peripheral RPE(P) and Overall RPE(O)) were obtained for each stage. The regression lines for the perceptual ranges 9-15 on the Borg 6-20 scale ratings were performed to predict VO(2peak). There were no significant within-group mean differences between measured VO(2peak) (mean 1.50 ± 0.39, 2.74 ± 0.48, 3.75 ± 0.33 L min(-1) for TETRA, PARA and NON-SCI, respectively) and predicted VO(2peak) determined using HR or differentiated RPEs for any group (P > 0.05). However, the coefficients of variation (CV %) between measured and predicted VO(2peak) using HR showed high variability for all groups (14.3, 15.9 and 9.7%, respectively). The typical error ranged from 0.14 to 0.68 L min(-1) and the CV % between measured and predicted VO(2peak) using differentiated RPE was ≤11.1% for TETRA, ≤7.5% for PARA and ≤20.2% for NON-SCI. Results suggest that differentiated RPE may be used cautiously for TETRA and PARA athletes when predicting VO(2peak) across the perceptual range of 9-15. However, predicting VO(2peak) is not recommended for the NON-SCI athletes due to the large CV %s (16.8, 20.2 and 18.0%; RPE(C), RPE(P) and RPE(O), respectively).

Bright moonlight triggers natal dispersal departures

Upon leaving their natal area, dispersers are confronted with unknown terrains. Species-specific perceptual ranges (i.e. the maximum distance from which an individual can perceive landscape features) play a crucial role in spatial movement decisions during such wanderings. In nocturnal animals that rely on vision, perceptual range is dramatically enhanced during moonlight, compared to moonless conditions. This increase of the perceptual range is an overlooked element that may be responsible for the successful crossing of unfamiliar areas during dispersal. The information gathered from 143 radio-tagged eagle owl Bubo bubo juveniles in Spain, Finland and Switzerland shows that, although the decision to initiate dispersal is mainly an endogenous phenomenon determined by the attainment of a given age (∼6 months), dispersers leave their birthplace primarily under the best light conditions at night, i.e. when most of the lunar disc is illuminated. This sheds new light into the mechanisms that may trigger dispersal from parental territory.

Individual traits as drivers of spatial dispersal and infestation patterns in a host–bark beetle system

Tree-killing bark beetle species such as Ips sp. and Dendroctonus sp. are considered one of the most severe biotic hazards affecting forests at the global scale. Although spatio-temporal patterns of dispersal and infestations have been widely observed and statistically analyzed profound knowledge about the host–bark beetle interactions that evoke these patterns is scarce. We developed an individual-based and spatially explicit model – the Infestation Pattern Simulation (IPS) model – to elucidate how individual traits affect system-level dispersal and infestation patterns. IPS simulates processes including dispersal, host selection, aggregation, and finally colonization, or rejection by host defence on a local scale. Host–bark beetle interactions are implemented highly dynamically, i.e. individual adaptive behavior takes into account space- and time-dependent variations in traits. Simulations consider one dispersal wave starting from a single source located in a virtual stand. Finally, the effects of both bark beetle- and host tree-specific parameters on emerging system patterns were quantified using a one-factor-at-a-time sensitivity analysis approach. As system-level response variables we used (i) percentage of successful beetles, (ii) number of infestations, and (iii) maximum infestation distance to source. Among bark beetle-specific parameters those affecting host recognition (e.g. perceptual range, energetic level) and attack synchrony (e.g. source size, time lag between flight cohorts) were revealed to be highly sensitive with regard to all three response variables. In addition, the host tree's resistance and spatial distribution is also shown to be decisive for infestation occurrence. The model provides a conceptual framework linking individual behavior to system-level patterns. Thus it represents a powerful tool – complementing lab- and field-based approaches – which may contribute to our understanding of the complex spatio-temporal processes that govern host–bark beetle dynamics.

Body size and spatial scales in avian response to landscapes: a meta‐analysis

Response of species to their environment is dependent on the scales that individuals interact with landscapes. Several life‐history traits have been suggested to influence scales of response to landscapes, but little empirical work has addressed this issue, limiting our ability to predict the relevant scale(s) at which species respond to their environment. Body size is frequently hypothesized to be relevant for predicting the effects of landscape structure on species given correlations between body size and various measures of mobility or perceptual range, yet evidence of this relationship remains equivocal. We conducted a meta‐analysis of 22 studies to address the question of whether body size is related to the characteristic scale at which bird species respond to landscape structure. On the basis of correlation coefficients and linear mixed models, we show that body size is positively related to the characteristic scale of response to landscapes. The strength of this relationship is less than body size – dispersal allometries, suggesting that response to landscapes may be influenced, in part, by factors other than dispersal (e.g. territory size). However, the strength of the observed body size – scale relationship may have been affected by several factors, including limitations in the range of body sizes and landscape extents tested. Our findings suggest that life‐history traits mediate aspects of the scales at which species respond to the landscape and contribute to developing a more predictive framework for investigating scalar relationships in nature.

Psychometric properties associated with perceived vocal roughness using a matching task

A psychophysical matching paradigm has been used to better quantify voice quality under laboratory conditions. The goals of this study were to establish which of two candidate comparison stimuli would best ensure that the range of perceived vocal roughness could be adequately bracketed using a matching task and to provide a general solution to the problem of estimating vocal roughness. Psychometric functions for roughness matching indicated that a speech-like sawtooth-plus-noise complex (20 dB signal-to-noise ratio) amplitude modulated by a sinusoidal function raised to the 4th power yielded a comparison stimulus with a perceptual dynamic range well suited for roughness matching.

Multi-scale Inference of Interaction Rules in Animal Groups Using Bayesian Model Selection

Inference of interaction rules of animals moving in groups usually relies on an analysis of large scale system behaviour. Models are tuned through repeated simulation until they match the observed behaviour. More recent work has used the fine scale motions of animals to validate and fit the rules of interaction of animals in groups. Here, we use a Bayesian methodology to compare a variety of models to the collective motion of glass prawns (Paratya australiensis). We show that these exhibit a stereotypical ‘phase transition’, whereby an increase in density leads to the onset of collective motion in one direction. We fit models to this data, which range from: a mean-field model where all prawns interact globally; to a spatial Markovian model where prawns are self-propelled particles influenced only by the current positions and directions of their neighbours; up to non-Markovian models where prawns have ‘memory’ of previous interactions, integrating their experiences over time when deciding to change behaviour. We show that the mean-field model fits the large scale behaviour of the system, but does not capture the observed locality of interactions. Traditional self-propelled particle models fail to capture the fine scale dynamics of the system. The most sophisticated model, the non-Markovian model, provides a good match to the data at both the fine scale and in terms of reproducing global dynamics, while maintaining a biologically plausible perceptual range. We conclude that prawns’ movements are influenced by not just the current direction of nearby conspecifics, but also those encountered in the recent past. Given the simplicity of prawns as a study system our research suggests that self-propelled particle models of collective motion should, if they are to be realistic at multiple biological scales, include memory of previous interactions and other non-Markovian effects.