Computer-animated stimuli to measure motion sensitivity: constraints on signal design in the Jacky dragon

Color in motion: Generating 3-dimensional multispectral models to study dynamic visual signals in animals

Analyzing color and pattern in the context of motion is a central and ongoing challenge in the quantification of animal coloration. Many animal signals are spatially and temporally variable, but traditional methods fail to capture this dynamism because they use stationary animals in fixed positions. To investigate dynamic visual displays and to understand the evolutionary forces that shape dynamic colorful signals, we require cross-disciplinary methods that combine measurements of color, pattern, 3-dimensional (3D) shape, and motion. Here, we outline a workflow for producing digital 3D models with objective color information from museum specimens with diffuse colors. The workflow combines multispectral imaging with photogrammetry to produce digital 3D models that contain calibrated ultraviolet (UV) and human-visible (VIS) color information and incorporate pattern and 3D shape. These “3D multispectral models” can subsequently be animated to incorporate both signaler and receiver movement and analyzed in silico using a variety of receiver-specific visual models. This approach—which can be flexibly integrated with other tools and methods—represents a key first step toward analyzing visual signals in motion. We describe several timely applications of this workflow and next steps for multispectral 3D photogrammetry and animation techniques.

Computerized stimuli for studying oddity effects

Visually hunting predators must overcome the challenges that prey groups present. One such challenge is the confusion effect where an overburdened visual system means predators are unable to successfully target prey. A strategy to overcome confusion is the targeting of distinct, or odd, individuals (the oddity effect). In live prey experiments, manipulation of group member phenotypes can be challenging and prey may differ on more than the single feature one intends to define as odd. The use of highly controllable computerized stimuli to study predator–prey interactions is increasingly popular in the field of behavioral ecology. However, to our knowledge, the validity of computerized stimuli to study the oddity effect has not been established. Predator choice experiments were conducted using naive stickleback predators to ascertain whether the oddity effect could be demonstrated in the absence of live prey. We found evidence for both the oddity effect and preferential targeting of group edges and low-density regions, as would be predicted if predators targeted prey individuals to minimize confusion. The oddity effect was evident at a low threshold, above which dots were no longer perceived as odd and no longer attacked more often than expected by chance. We conclude that computerized stimuli are an improved, practical method for studying oddity effects while further validating the use of similar methods for studying other aspects of visual predation. In addition to higher control of “prey” appearance, the replacement of live prey animals with digital stimuli is ethically beneficial and reusing code improves experimental efficiency.

Male courtship signal modality and female mate preference in the wolf spider Schizocosa ocreata: results of digital multimodal playback studies

Females must be able to perceive and assess male signals, especially when they occur simultaneously with those of other males. Previous studies show female Schizocosa ocreata wolf spiders display receptivity to isolated visual or vibratory courtship signals, but increased receptivity to multimodal courtship. It is unknown whether this is true when females are presented with a choice between simultaneous multimodal and isolated unimodal male courtship. We used digital playback to present females with a choice simulating simultaneous male courtship in different sensory modes without variation in information content: 1) isolated unimodal visual versus vibratory signals; 2) multimodal versus vibratory signals; and 3) multimodal versus visual signals. When choosing between isolated unimodal signals (visual or vibratory), there were no significant differences in orientation latency and number of orientations, approaches or receptive displays directed to either signal. When given a choice between multimodal versus vibratory-only male courtship signals, females were more likely to orient to the multimodal stimulus, and directed significantly more orients, approaches and receptivity behaviors to the multimodal signal. When presented with a choice between multimodal and visual-only signals, there were significantly more orients and approaches to the multimodal signal, but no significant difference in female receptivity. Results suggest that signal modes are redundant and equivalent in terms of qualitative responses, but when combined, multimodal signals quantitatively enhance detection and/or reception. This study confirms the value of testing preference behavior using a choice paradigm, as female preferences may depend on the context (e.g., environmental context and social context) in which they are presented with male signals.