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1. Can you hear/see me? Multisensory integration of signals does not always facilitate mate choice

   https://doi.org/10.1093/beheco/arac061  

   Coss, Derek A; Ryan, Michael J; Page, Rachel A; Hunter, Kimberly L; Taylor, Ryan C (June 2022, Behavioral Ecology)

   Candolin, Ulrika (Ed.)

   Abstract Females of many species choose mates using multiple sensory modalities. Multimodal noise may arise, however, in dense aggregations of animals communicating via multiple sensory modalities. Some evidence suggests multimodal signals may not always improve receiver decision-making performance. When sensory systems process input from multimodal signal sources, multimodal noise may arise and potentially complicate decision-making due to the demands on cognitive integration tasks. We tested female túngara frog, Physalaemus (=Engystomops) pustulosus, responses to male mating signals in noise from multiple sensory modalities (acoustic and visual). Noise treatments were partitioned into three categories: acoustic, visual, and multimodal. We used natural calls from conspecifics and heterospecifics for acoustic noise. Robotic frogs were employed as either visual signal components (synchronous vocal sac inflation with call) or visual noise (asynchronous vocal sac inflation with call). Females expressed a preference for the typically more attractive call in the presence of unimodal noise. However, during multimodal signal and noise treatments (robofrogs employed with background noise), females failed to express a preference for the typically attractive call in the presence of conspecific chorus noise. We found that social context and temporal synchrony of multimodal signaling components are important for multimodal communication. Our results demonstrate that multimodal signals have the potential to increase the complexity of the sensory scene and reduce the efficacy of female decision making. 

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2. Multisensory integration facilitates perceptual restoration of an interrupted call in a species of frog

   https://doi.org/10.1093/beheco/arac053  

   Zhu, Bicheng; Yang, Yue; Zhou, Ya; Deng, Ke; Wang, Tongliang; Wang, Jichao; Tang, Yezhong; Ryan, Michael J; Cui, Jianguo (June 2022, Behavioral Ecology)

   Jennions, Michael D (Ed.)

   Abstract Communication signals by both human and non-human animals are often interrupted in nature. One advantage of multimodal cues is to maintain the salience of interrupted signals. We studied a frog that naturally can have silent gaps within its call. Using video/audio-playbacks, we presented females with interrupted mating calls with or without a simultaneous dynamic (i.e., inflating and deflating) vocal sac and tested whether multisensory cues (noise and/or dynamic vocal sac) inserted into the gap can compensate an interrupted call. We found that neither inserting white noise into the silent gap of an interrupted call nor displaying the dynamic vocal sac in that same gap restored the attraction of the call equivalent to that of a complete call. Simultaneously presenting a dynamic vocal sac along with noise in the gap, however, compensated the interrupted call, making it as attractive as a complete call. Our results demonstrate that the dynamic visual sac compensates for noise interference. Such novel multisensory integration suggests that multimodal cues can provide insurance against imperfect sender coding in a noisy environment, and the communication benefits to the receiver from multisensory integration may be an important selective force favoring multimodal signal evolution. 

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3. Covariation among multimodal components in the túngara frog’s courtship display.

   https://doi.org/doi:10.1242/jeb.241661  

   James, L.S.; Halfwerk, W.; Hunter, K.L.; Page, R.A.; Taylor, R.C.; Wilson, P.S.; Ryan, M.J. (January 2021, Journal of experimental biology)

   null (Ed.)

   Communication systems often include a variety of components, including those that span modalities, which may facilitate detection and decision-making. For example, female tungara frogs and fringe-lipped bats generally rely on acoustic mating signals to find male tungara frogs in a mating or foraging context, respectively. However, two additional cues (vocal sac inflation and water ripples) can enhance detection and choice behavior. To date, we do not know the natural variation and covariation of these three components. To address this, we made detailed recordings of calling males, including call amplitude, vocal sac volume and water ripple height, in 54 frogs (2430 calls). We found that all three measures correlated, with the strongest association between the vocal sac volume and call amplitude. We also found that multimodal models predicted the mass of calling males better than unimodal models. These results demonstrate how multimodal components of a communication system relate to each other and provide an important foundation for future studies on how receivers integrate and compare complex displays. 

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4. On the function of a female-like signal type in the vibrational repertoire of Enchenopa male treehoppers (Hemiptera: Membracidae)

   https://doi.org/10.1093/jeb/voad010  

   Escalante, Ignacio; Kellner, Jerald_R; Desjonquères, Camille; Noffsinger, Gianna_M; Cirino, Lauren_A; Rodríguez, Ariel_N; DeLong, Sage_A; Rodríguez, Rafael_L (December 2023, Journal of Evolutionary Biology)

   Abstract Animals often mimic the behaviours or signals of conspecifics of the opposite sex while courting. We explored the potential functions of a novel female-like signal type in the courtship displays of male Enchenopa treehoppers. In these plant-feeding insects, males produce plant-borne vibrational advertisement signals, to which females respond with their own duetting signals. Males also produce a signal type that resembles the female duetting responses. We experimentally tested whether this signal modifies the behaviour of receivers. First, we tested whether the female-like signal would increase the likelihood of a female response. However, females were as likely to respond to playbacks with or without them. Second, we tested whether the female-like signal would inhibit competing males, but males were as likely to produce displays after playbacks with or without them. Hence, we found no evidence that this signal has an adaptive function, despite its presence in the courtship display, where sexual selection affects signal features. Given these findings, we also explored whether the behavioural and morphological factors of the males were associated with the production of the female-like signal. Males that produced this signal had higher signalling effort (longer and more frequent signals) than males that did not produce it, despite being in worse body condition. Lastly, most males were consistent over time in producing the female-like signal or not. These findings suggest that condition-dependent or motivational factors explain the presence of the female-like signal. Alternatively, this signal might not bear an adaptive function, and it could be a way for males to warm up or practice signalling, or even be a by-product of how signals are transmitted through the plant. We suggest further work that might explain our puzzling finding that a signal in the reproductive context might not have an adaptive function. 

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5. Chemical cues in the mating behavior of a highly polygynous bird

   https://doi.org/10.1007/s00265-024-03477-0  

   Rivers, Pearl R; DuVal, Emily H (June 2024, Behavioral Ecology and Sociobiology)

   Visual and auditory signals are well-established components of avian courtship, but the role of chemical signaling remains poorly understood, particularly in mating systems with elaborate courtship displays. To test how chemical cues influence mating behavior we conducted two experiments in the lance-tailed manakin (Chiroxiphia lanceolata). First, in a field experiment, we tested the response of free-living males and females to manipulation of chemical cues at male display perches by cleaning the perches with ethanol or a dry cloth (control) and quantified a potential chemical signaling behavior (bill-wiping) in response to experimental manipulation. During bouts of dance perch maintenance and displays with a female present (i.e., activity relevant to female mate choice) males increased bill-wiping behavior during initial ethanol treatment periods. We also detected carryover effects of the ethanol treatment; in later treatment periods males bill-wiped more when the prior treatment was ethanol. The likelihood of a female either revisiting a display area or copulating with a male was unrelated to experimental treatment. Next, in captive trials, we assessed female preference for olfactory cues from males that differed in their genetic diversity, a trait previously identified as relevant to female mate choice. In contrast to similar trials in other bird species, females showed no clear preference. Together, these results provide some evidence for chemical signaling by males at display perches, but it remains unclear what information chemical cues convey. 

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