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1. 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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2. A new species of terrestrial foam-nesting frog of the Adenomera simonstuarti complex (Anura, Leptodactylidae) from white-sand forests of central Amazonia, Brazil

   https://doi.org/10.3897/zse.100.110133  

   Martins, Bryan da_Cunha; Tamanini_Mônico, Alexander; Mendonça, C; Dantas, Silionamã_P; Souza, Jesus_R D; Hanken, James; Lima, Albertina P; Ferrão, Miquéias (March 2024, Zoosystematics and Evolution)

   By using integrative taxonomy, we describe a new species of terrestrial foam-nesting frog of the genus Adenomera from white-sand forests of the Rio Negro Sustainable Development Reserve, Central Amazonia, Brazil. Within the A. andreae clade, the new species belongs to the A. simonstuarti complex where it is sister to the lineage from the lower Juruá River. The new species is assigned to the genus Adenomera by having adult SVL smaller than 34.1 mm, by its lack of fringing and webbing between toes and by the absence of spines on the thumb of adult males. It differs from other Adenomera by the following combination of characters: antebrachial tubercle absent; toe tips flattened or slightly flattened, with visible expansions; nearly solid, dark-coloured stripe on underside of forearm; single-note advertisement call; notes formed by 11–21 incomplete pulses; call duration varying between 100 and 199 ms; fundamental frequency 1,765–2,239 Hz; dominant frequency 3,448–4,349 Hz; and endotrophic tadpoles with spiracle present and labial teeth absent. Over the last decade, we have inventoried many permanent sampling modules in ombrophilous forests in the Manaus Region and in the Purus-Madeira interfluve, but the new species was found only in the white-sand forest from West Negro-Solimões Interfluve. Adenomera sp. nov. may be endemic to, or at least a specialist in, this environment. 

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3. Three new species of the Synapturanus rabus complex (Microhylidae: Otophryninae) in Colombia with a review of the genus Synapturanus.

   Osorno, Mariela; Gutiérrez, Laura; Lynch, John; Keefee, Rachel; Caicedo, José; Chan, Kan; Tonini, João; de_Sá, Rafael O (March 2023, Zootaxa)

   Vences, Miguel (Ed.)

   The Neotropical microhylid genus Synapturanus was represented by only three species for almost five decades and remains poorly known. Recently two new species were described from the Eastern Guyana Shield, one from Peru, and one from Brazil. We describe three new species related to the S. rabus species complex with known distribution only in western Amazonia, Colombia. The S. rabus complex consists of the smallest species in the genus; one of the new species is slightly larger than S. rabus and we describe its full osteology; the other two new species are smaller than S. rabus. Wealso described the call and larvae of one of the new species. We provide an updated diagnosis and review the available molecular and phenotypic data for the genus. 

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4. Glucocorticoid-Mediated Changes in Male Green Treefrog Vocalizations Alter Attractiveness to Females

   https://doi.org/10.1093/icb/icab053  

   Leary, Christopher J; Crocker-Buta, Sarah; Holloway, Ashli; Kennedy, Joseph G (May 2021, Integrative and Comparative Biology)

   Synopsis Adrenal glucocorticoids (GCs) are increasingly recognized as important modulators of male courtship signals, suggesting that circulating levels of these steroids can play a central role in sexual selection. However, few studies have examined whether GC-mediated effects on male sexual signals actually impact mate choice by females. Here, we examine how corticosterone (CORT)-mediated changes in the vocalizations of male green treefrogs, Dryophytes cinereus, influence attractiveness to females. In this species, agonistic acoustic signaling between rival males competing for mates increases circulating CORT levels in contest losers. Acute elevations in CORT, in turn, decrease the duration of male advertisement calls and increase the latency between successive calls, resulting in a net reduction in vocal effort (the amount of signaling per unit time) that occurs independently of changes in circulating androgens. Based on known preferences for acoustic features in D. cinereus, and other anuran species, the direction of CORT-mediated effects on temporal call characteristics is expected to compromise attractiveness to females, but whether they are of sufficient magnitude to impact female mate choice decisions is unclear. To examine whether CORT-mediated effects on male advertisement calls reduce attractiveness to females, we broadcast vocalizations in dual speaker playback experiments approximating the mean and 1 SD above and below the mean call duration and vocal effort values (the two primary vocal features impacted by elevated CORT) of males with low and high CORT levels. Results revealed strong preferences by females for the calls characteristic of males with low CORT in tests using the approximate mean and 1 SD above the mean call duration and vocal effort values, but females did not show a preference for calls of males with low CORT in trials using call values approximating 1 SD below the mean. Overall, females preferred males with signal traits predictive of low CORT, however this effect was nonlinear with attenuated preferences when signal alternatives differed only marginally indicating a possible thresholding effect. Specifically, females appeared to discriminate between males with low versus high CORT based primarily on differences in call rates associated with CORT-mediated changes in call duration and vocal effort. Our results highlight that changes in circulating CORT during male–male vocal interactions can decrease attractiveness to females, suggesting that circulating levels of CORT can play a critical role in both intra- and intersexual selection. 

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5. 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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