02257nas a2200121 4500008004100000245008500041210006900126520181300195100002402008700002502032700002502057856005302082 2020 eng d00aComparison of methods for rhythm analysis of complex animals’ acoustic signals0 aComparison of methods for rhythm analysis of complex animals aco3 a

Analyzing the rhythm of animals’ acoustic signals is of interest to a growing number of researchers: evolutionary biologists want to disentangle how these structures evolved and what patterns can be found, and ecologists and conservation biologists aim to discriminate cryptic species on the basis of parameters of acoustic signals such as temporal structures. Temporal structures are also relevant for research on vocal production learning, a part of which is for the animal to learn a temporal structure. These structures, in other words, these rhythms, are the topic of this paper. How can they be investigated in a meaningful, comparable and universal way? Several approaches exist. Here we used five methods to compare their suitability and interpretability for different questions and datasets and test how they support the reproducibility of results and bypass biases. Three very different datasets with regards to recording situation, length and context were analyzed: two social vocalizations of Neotropical bats (multisyllabic, medium long isolation calls of Saccopteryx bilineata, and monosyllabic, very short isolation calls of Carollia perspicillata) and click trains of sperm whales, Physeter macrocephalus. Techniques to be compared included Fourier analysis with a newly developed goodness-of-fit value, a generate-and-test approach where data was overlaid with varying artificial beats, and the analysis of inter-onset-intervals and calculations of a normalized Pairwise Variability Index (nPVI). We discuss the advantages and disadvantages of the methods and we also show suggestions on how to best visualize rhythm analysis results. Furthermore, we developed a decision tree that will enable researchers to select a suitable and comparable method on the basis of their data.

1 aBurchardt, Lara, S.1 aKnörnschild, Mirjam1 aGershman, Samuel, J. uhttps://dx.plos.org/10.1371/journal.pcbi.100775502337nas a2200217 4500008004100000245008600041210006900127520164500196653002401841653000901865653002201874653002701896653002001923653001801943100001701961700001601978700002101994700002102015700002102036856006202057 2019 eng d00aDoes bat response to traffic noise support the misleading cue hypothesis?Abstract0 aDoes bat response to traffic noise support the misleading cue hy3 a

The world has become a noisier place due to the increase in urbanization. Noise is generally considered an impediment, altering an animal’s behavior through masking or distraction. But noise can also provide useful information about the environment. For animals that rely on natural environmental noise as an indicator of favorable foraging conditions, increasing levels of anthropogenic noise might mislead informed decision-making. Bats use rain noise, a natural environmental cue, to delay their emergence from the roost, presumably to avoid sensory and metabolic costs associated with foraging in heavy rain. Here we tested the “misleading cue hypothesis,” asking whether traffic noise is mistaken for rain noise by bats. Given the acoustic similarity between rain noise and traffic noise, we predicted that bats would confuse the two. We conducted a playback experiment using rain, traffic, and ambient noise at natural roosts of common big-eared bats (Micronycteris microtis, Phyllostomidae) and recorded bat emergence behavior. In contrast to their response to rain noise, the bats did not delay roost emergence in response to traffic noise. Thus, we found that bats were able to discriminate between traffic noise and rain noise and were not misled by similarity in acoustic parameters in the two noise types, when emerging from their roost. Emerging bats did show more exploration flights during traffic noise than during rain noise, but not during ambient noise, suggesting that they perceive traffic noise as a novel acoustic cue. Our data provide new insights into perception of traffic noise by bats.

10aanthropogenic noise10abats10aevolutionary trap10aMicronycteris microtis10amisleading cues10aTraffic noise1 aGeipel, Inga1 aAmin, Bawan1 aPage, Rachel, A.1 aHalfwerk, Wouter1 aCandolin, Ulrika uhttps://academic.oup.com/beheco/article/30/6/1775/557481105028nas a2200121 4500008004100000245003200041210003000073520469600103100002104799700002204820700002304842856004104865 2014 eng d00aBe loved, be prey, be eaten0 aBe loved be prey be eaten3 a

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.

1 aPage, Rachel, A.1 aRyan, Michael, J.1 aBernal, Ximena, E. uhttps://bio.acousti.ca/id/node/5755502274nas a2200241 4500008004100000022001400041245009400055210006900149260001600218300001500234520143200249653000901681653002001690653001301710653002101723653001001744653000901754100001701763700002401780700002101804700002101825856018601846 2019 eng d a0022-094900aNoise as an informational cue for decision-making: the sound of rain delays bat emergence0 aNoise as an informational cue for decisionmaking the sound of ra cSep-01-2020 ajeb.1920053 a

Background noise can have strong negative consequences on animals, reducing individual fitness by masking communication signals, impeding prey detection and increasing predation risk. While the negative impacts of noise across taxa have been well documented, the use of noise as an informational cue, providing animals with reliable information on environmental conditions has been less well studied. In the tropical rainforest, downpours can be intense and frequent. Strong rainfall may impede efficient orientation and foraging for bats that need echolocation to both navigate and detect prey, and can result in higher flight costs due to increased metabolic rates. Using playback experiments at natural roosts we tested whether two bat species, differing in their hunting strategies and foraging habitats, use rain noise as a cue to delay emergence from their roosts. We found that both species significantly delayed their emergence time during rain noise playbacks compared to silence and ambient noise controls. We conclude that bats can use background noise, here the acoustic component of rainfall, as a reliable informational cue to make informed decisions, here about whether to initiate foraging trips or remain in the shelter of their roosts. Our findings suggest that environmental background noise can sometimes be beneficial to animals, in particular in situations where other sensory cues may be absent.

10abats10adecision-making10aforaging10ainformation cues10aNoise10arain1 aGeipel, Inga1 aSmeekes, Marcus, J.1 aHalfwerk, Wouter1 aPage, Rachel, A. uhttp://jeb.biologists.org/lookup/doi/10.1242/jeb.192005https://syndication.highwire.org/content/doi/10.1242/jeb.192005https://syndication.highwire.org/content/doi/10.1242/jeb.19200502209nas a2200241 4500008004100000022001300041245006600054210006500120260001600185300001200201490000800213520132800221653002001549653001301569653002001582653001701602653002801619653001801647100002601665700002201691700002101713856023301734 2018 eng d a0003347200aCognitive constraints on optimal foraging in frog-eating bats0 aCognitive constraints on optimal foraging in frogeating bats cJan-09-2018 a43 - 500 v1433 a

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'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.

10aDecision making10aforaging10afrog-eating bat10apatch choice10aproportional processing10atúngara frog1 aHemingway, Claire, T.1 aRyan, Michael, J.1 aPage, Rachel, A. uhttps://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/plain03094nas a2200397 4500008004100000022001300041245005700054210005700111260001600168520180000184653000801984653002301992653001702015653001302032653000802045653002102053653001502074653001702089100002202106700002202128700001802150700001902168700001602187700002502203700003402228700002402262700002302286700001602309700001802325700002602343700002602369700002602395700002502421700001702446856023302463 2018 eng d a0960982200aResource Ephemerality Drives Social Foraging in Bats0 aResource Ephemerality Drives Social Foraging in Bats cJan-11-20183 a

Observations of animals feeding in aggregations are often interpreted as events of social foraging, but it can be difficult to determine whether the animals arrived at the foraging sites after collective search [1, 2, 3, 4] or whether they found the sites by following a leader [5, 6] or even independently, aggregating as an artifact of food availability [7, 8]. Distinguishing between these explanations is important, because functionally, they might have very different consequences. In the first case, the animals could benefit from the presence of conspecifics, whereas in the second and third, they often suffer from increased competition [3, 9, 10, 11, 12, 13]. Using novel miniature sensors, we recorded GPS tracks and audio of five species of bats, monitoring their movement and interactions with conspecifics, which could be inferred from the audio recordings. We examined the hypothesis that food distribution plays a key role in determining social foraging patterns [14, 15, 16]. Specifically, this hypothesis predicts that searching for an ephemeral resource (whose distribution in time or space is hard to predict) is more likely to favor social foraging [10, 13, 14, 15] than searching for a predictable resource. The movement and social interactions differed between bats foraging on ephemeral versus predictable resources. Ephemeral species changed foraging sites and showed large temporal variation nightly. They aggregated with conspecifics as was supported by playback experiments and computer simulations. In contrast, predictable species were never observed near conspecifics and showed high spatial fidelity to the same foraging sites over multiple nights. Our results suggest that resource (un)predictability influences the costs and benefits of social foraging.

10abat10abehavioral ecology10aecholocation10aforaging10aGPS10amovement ecology10anavigation10asociobiology1 aEgert-Berg, Katya1 aHurme, Edward, R.1 aGreif, Stefan1 aGoldstein, Aya1 aHarten, Lee1 aM., Luis, Gerardo He1 aFlores-Martínez, José, Juan1 aValdés, Andrea, T.1 aJohnston, Dave, S.1 aEitan, Ofri1 aBorissov, Ivo1 aShipley, Jeremy, Ryan1 aMedellin, Rodrigo, A.1 aWilkinson, Gerald, S.1 aGoerlitz, Holger, R.1 aYovel, Yossi uhttps://linkinghub.elsevier.com/retrieve/pii/S0960982218312909https://api.elsevier.com/content/article/PII:S0960982218312909?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0960982218312909?httpAccept=text/plain03035nas a2200289 4500008004100000245010500041210006900146260001600215300001400231490000700245520213200252653002302384653000902407653002402416653002002440653002502460100002502485700002502510700002602535700002202561700001802583700002602601700002402627700001802651700002302669856005302692 2014 eng d00aTrophic niche flexibility in Glossophaga soricina: how a nectar seeker sneaks an insect snack0 aTrophic niche flexibility in iGlossophaga soricinai how a nectar cJan-06-2014 a632 - 6410 v283 a

Omnivory enables animals to fill more than one trophic niche, providing access to a wider variety of food resources with potentially higher nutrient value, particularly when resources become scarce. Animals can achieve omnivory using different strategies, for example opportunistic foraging, or switching between multiple trophic niches.

The Neotropical bat Glossophaga soricina (Pallas, 1766) is a common and widespread species known for nectar feeding, but it also eats fruit and insects. Approaching stationary objects (flowers and fruits) or moving objects (insects) poses different sensory tasks and should require different echolocation behaviours. Here we tested the contrasting hypothesis that G. soricina can approach both stationary and moving objects using the same echolocation behaviour, thus feeding at different trophic levels by a single sensory mechanism.

Using DNA barcoding, we demonstrate that G. soricina eats beetles (Coleoptera), flies (Diptera) and noctuid moths with bat-detecting ears. Laboratory observations show that G. soricina actively hunts for prey so insect consumption does not appear to be opportunistic. After capture, individuals consumed prey while perched and manipulated them with jaw, thumb, wrist and wing movements, but food handling was longer and chewing rate slower than in obligate insectivores.

In contrast to most insectivorous bats, the echolocation calls of G. soricina are of high frequency and low intensity, and G. soricina did not produce feeding buzzes when approaching insects. An acoustic model of detection distances shows that its low-intensity calls fail to trigger the auditory neurons of eared moths, allowing G. soricina to overcome auditory prey defences.

Individuals achieved niche flexibility using a unique but generalist behavioural approach rather than employing two different specialist methods. Our findings provide a novel insight into the functional mechanisms of insect capture in G. soricina and highlight the importance of considering niche flexibility in classifying trophic links in ecological communities.

10aacoustic modelling10abats10amolecular scatology10apredator–prey10astealth echolocation1 aClare, Elizabeth, L.1 aGoerlitz, Holger, R.1 aDrapeau, Violaine, A.1 aAdams, Amanda, M.1 aNagel, Juliet1 aDumont, Elizabeth, R.1 aHebert, Paul, D. N.1 aFenton, Brock1 aKonarzewski, Marek uhttp://doi.wiley.com/10.1111/fec.2014.28.issue-302214nas a2200229 4500008004100000022001400041245008800055210006900143260001600212300001600228490000800244520146400252653002101716653001801737653001201755653002501767653001901792100002101811700001501832700001701847856012001864 2008 eng d a0022-094900aComparing passive and active hearing: spectral analysis of transient sounds in bats0 aComparing passive and active hearing spectral analysis of transi cMar-06-2009 a1850 - 18580 v2113 a

n vision, colour constancy allows the evaluation of the colour of objects independent of the spectral composition of a light source. In the auditory system, comparable mechanisms have been described that allows the evaluation of the spectral shape of sounds independent of the spectral composition of ambient background sounds. For echolocating bats, the evaluation of spectral shape is vitally important both for the analysis of external sounds and the analysis of the echoes of self-generated sonar emissions. Here, we investigated how the echolocating bat Phyllostomus discolor evaluates the spectral shape of transient sounds both in passive hearing and in echolocation as a specialized mode of active hearing. Bats were trained to classify transients of different spectral shape as low- or highpass. We then assessed how the spectral shape of an ambient background noise influenced the spontaneous classification of the transients. In the passive-hearing condition, the bats spontaneously changed their classification boundary depending on the spectral shape of the background. In the echo-acoustic condition, the classification boundary did not change although the background- and spectral-shape manipulations were identical in the two conditions. These data show that auditory processing differs between passive and active hearing: echolocation represents an independent mode of active hearing with its own rules of auditory spectral analysis.

10abackground noise10acall analysis10ahearing10aperceptual constancy10aspectral shape1 aGoerlitz, H., R.1 aHubner, M.1 aWiegrebe, L. uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.017715https://syndication.highwire.org/content/doi/10.1242/jeb.01771501987nas a2200157 4500008004100000245010400041210006900145260001600214490000600230520146900236100001701705700002501722700001801747700001901765856004501784 2016 eng d00aLinking the sender to the receiver: vocal adjustments by bats to maintain signal detection in noise0 aLinking the sender to the receiver vocal adjustments by bats to  cJan-11-20160 v53 a

Short-term adjustments of signal characteristics allow animals to maintain reliable communication in noise. Noise-dependent vocal plasticity often involves simultaneous changes in multiple parameters. Here, we quanti ed for the  rst time the relative contributions of signal amplitude, duration,
and redundancy for improving signal detectability in noise. To this end, we used a combination of behavioural experiments on pale spear-nosed bats (Phyllostomus discolor) and signal detection models. In response to increasing noise levels, all bats raised the amplitude of their echolocation calls by 1.8–7.9 dB (the Lombard e ect). Bats also increased signal duration by 13%–85%, corresponding to an increase in detectability of 1.0–5.3 dB. Finally, in some noise conditions, bats increased signal redundancy by producing more call groups. Assuming optimal cognitive integration, this could result in a further detectability improvement by up to 4 dB. Our data show that while the main improvement in signal detectability was due to the Lombard e ect, increasing signal duration and redundancy can also contribute markedly to improving signal detectability. Overall, our  ndings demonstrate that
the observed adjustments of signal parameters in noise are matched to how these parameters are processed in the receiver’s sensory system, thereby facilitating signal transmission in  uctuating environments.

1 aLuo, Jinhong1 aGoerlitz, Holger, R.1 aBrumm, Henrik1 aWiegrebe, Lutz uhttp://www.nature.com/articles/srep18556