@inbook {57555, title = {Be loved, be prey, be eaten}, year = {2014}, abstract = {

Animal communication is one of the most fundamental of all social behaviors. It modulates interactions among neighbors and strangers, siblings and parents, and individuals and their prospective mates. One of the most fundamental functions of communication is to enhance the sender\’s conspicuousness, to cause the sender to stand out against the background so it can be detected by the receiver. This is a challenge for signals that function over long distances, such as those that function in territorial advertisement and mate attraction, because signal intensity and fidelity decrease with distance from the sender. At longer distances a signal is less likely to be above the receiver\’s threshold for detection and recognition, and it is also more likely to be masked by noise as the intensity of noise at the receiver is independent of its distance from the sender.

Another type of noise is generated by conspecifics signaling in the same channel. We may perceive a chorus of frogs or insects as a melodious, even co- operative unit. But to members of the chorus the calls of their neighbors are every bit as deleterious to their own call\’s ability to be detected as is environ- mental noise. There is also \“noise\” within the perceptual systems of the receiver that ameliorates signal detection. One example is habituation. Upon continual exposure to a signal, an animal will tend to ignore it, and some of the animal\’s neurons will cease to fire. Another type of perceptual noise is incremental forgetting of a signal once it is perceived. Some signals are more\ memorable than others, surviving longer in the receiver\’s memory. The importance of conspecific noise and perceptual noise is usually less appreciated in animal communication studies than is environmental noise.

Selection often will favor senders to produce communication signals that stand out against these three types of background noise. Conspicuousness is accomplished in a variety of ways. In the acoustic domain animals can use fre- quency bands that contain less noise; they can call longer, at a faster rate, or at a higher amplitude; they can call during periods when others are silent; and they can produce calls that are more complex. Visual signals can stand out more against background when their spectral properties and spatial patterns differ from those in the background, when colors are brighter and patterns are more complex, and when motion patterns associated with the signal, such as push-up displays in lizards, are different than the pattern of background movement, such as vegetation being blow in the wind (e.g., Fleishman, 1992). Increasing signal complexity in both the acoustic and visual domains can to some extent remedy the receiver habituating to and forgetting a signal. There is less known about how chemical, tactile, and electrical signals can enhance contrast with the background.

In a survey of preferences for sexual signals, Michael Ryan and Anne Keddy-Hector (1992) showed that across modalities prospective mates tended to prefer sexual signals that were greater in magnitude: longer and louder, faster and brighter, more complex and with more background contrast. Although there were numerous cases in which prospective mates preferred signals that were near the population mean, there were few cases in which there was a preference for signals of lesser magnitude. A simple rule of thumb for sexual signals is that more is better. Selection for signal efficacy, however, creates a dilemma for the sender: the curse of unintended receivers. In general, each signal has evolved under selection to communi- cate with a specific intended receiver. In the case of sexual advertisement sig- nals, the intended receivers are prospective mates, usually female conspecifics. Other receivers can also detect and respond to signals even if there was no selection on the sender to communicate with them. We refer to these receivers as eavesdroppers or unintended receivers. It is important to note that the terms intended and unintended should not imply intention- ality but instead refer to hypotheses about the selection forces that favored the evolution of these signals. With few exceptions, senders and receivers do not communicate in a private channel. The world is populated by unin- tended receivers, eavesdroppers who are attendant to the signals of senders, often to the demise of senders. In this chapter we explore the tension that exists in sexual communication systems between being conspicuous to\ potential mates and attracting eavesdroppers, between being loved, being prey, and being eaten.

}, author = {Rachel A. Page and Michael J. Ryan and Ximena E. Bernal} } @article {53397, title = {Cognitive constraints on optimal foraging in frog-eating bats}, journal = {Animal Behaviour}, volume = {143}, year = {2018}, month = {Jan-09-2018}, pages = {43 - 50}, abstract = {

Animals are expected to optimize energy intake when choosing between different foraging options. A common explanation for deviations from optimal economic decisions is that there is an imperfect relationship between physical reality and an animal\&$\#$39;s perceptual processes, which can constrain assessment of profitability. One such phenomenon that is apparently ubiquitous across taxa is proportional processing, where a perceived change in a stimulus is proportional to the change in stimulus magnitude. In this study, we investigated whether proportional processing explains how frog-eating bats, Trachops cirrhosus, discriminate between patches of frog choruses that vary in their number of calling frogs. To test this, we created artificial choruses consisting of one to six calling frogs. In the flight cage, we then tested the preference of bats (N = 17) with every pairwise combination of chorus size. We found that while bats generally preferred larger choruses, preferences for larger choruses were better explained by the relative, not absolute, differences in chorus sizes. This indicates that T. cirrhosus is perceptually limited in its ability to discriminate between choruses of varying size as the choruses increase in size. Foragers are likely to be less choosy when choosing among larger patches.

}, keywords = {Decision making, foraging, frog-eating bat, patch choice, proportional processing, t{\'u}ngara frog}, issn = {00033472}, doi = {10.1016/j.anbehav.2018.07.007}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0003347218302227https://api.elsevier.com/content/article/PII:S0003347218302227?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0003347218302227?httpAccept=text/plain}, author = {Hemingway, Claire T. and Michael J. Ryan and Rachel A. Page} } @article {52575, title = {Interactions between complex multisensory signal components result in unexpected mate choice responses}, journal = {Animal Behaviour}, volume = {134}, year = {2017}, month = {Jan-12-2017}, pages = {239 - 247}, abstract = {

Multimodal (multisensory) signalling is common in many species and often facilitates communication. How receivers integrate individual signal components of multisensory displays, especially with regard to variance in signal complexity, has received relatively little attention. In nature, male t\úngara frogs, Physalaemus pustulosus, produce multisensory courtship signals by vocalizing and presenting their inflating and deflating vocal sac as a visual cue. Males can produce a simple call (whine only) or a complex call (whine \þ one or more chucks). In a series of two-choice experiments, we tested female preferences for variation in acoustic call complexity and amplitude (unimodal signals). We then tested preferences for the same calls when a dynamic robotic frog was added to one call, generating a multi- modal stimulus. Females preferred a complex call to a simple call; when both calls contained at least one chuck, additional numbers of chucks did not further increase attractiveness. When calls contained zero or one chuck, the visual stimulus of the robofrog increased call attractiveness. When calls contained multiple chucks, however, the visual component failed to enhance call attractiveness. Females also preferred higher amplitude calls and the addition of the visual component to a lower amplitude call did not alter this preference. At relatively small amplitude differences, however, the visual signal increased overall discrimination between the calls. These results indicate that the visual signal component does not provide simple enhancement of call attractiveness. Instead, females integrate multisensory components in a nonlinear fashion. The resulting perception and behavioural response to complex signals probably evolved in response to animals that communicate in noisy environments.

}, keywords = {anurans, mate choice, multimodal signalling, nonlinear interactions, sexual selection, signal weighting, t{\'u}ngara frog, vocal sac}, issn = {00033472}, doi = {10.1016/j.anbehav.2016.07.005}, url = {http://linkinghub.elsevier.com/retrieve/pii/S000334721630121X}, author = {Stange, Nicole and Rachel A. Page and Michael J. Ryan and Taylor, Ryan C.} }