Arginine vasotocin (AVT) is the nonmammalian homologue of arginine vasopressin (AVP), and like vasopressin serves as an important modulator of social behavior in addition to its peripheral functions related to osmoregulation, reproductive physiology, and stress hormone release. In amphibians and reptiles the neuroanatomical organization of brain AVT cells and fibers broadly resembles that seen in mammals and other taxa. Both parvocellular and magnocellular AVT-containing neurons are present in multiple populations located mainly in the basal forebrain from the accumbens-amygdala area to the preoptic area and hypothalamus, from which originate widespread fiber connections spanning the brain with a particularly heavy innervation of areas associated with social behavior and decision making. As for mammalian AVP, AVT is present in greater amounts in males in many brain areas and its presence varies seasonally, with hormonal state, and in males with differing social status. AVT’s social influence is also conserved across herpetological taxa, with significant effects on social signaling and aggression, and, based on the very small number of studies investigating more complex social behaviors in amphibians and reptiles, AVT may also modulate parental care and social bonding when it is present in these vertebrates. Within this conserved pattern, however, both AVT anatomy and social behavior effects vary significantly across species. Accounting for this diversity represents a challenge to understanding the mechanisms by which AVT exerts its behavioral effects, as well are a potential tool for discerning the structure-function relationships underlying AVT’s many effects on behavior.

Urbanisation can affect mating opportunities and thereby alter inter‐ and intra‐sexual selection pressures on sexual traits. Biotic and abiotic urban conditions can influence an individual's success in pre‐ and post‐copulatory mating, for example through impacts on mate attraction and mate preference, fertilisation success, resource competition or rival interactions. Divergent sexual selection pressures can lead to differences in behavioural, physiological, morphological or life‐history traits between urban and non‐urban populations, ultimately driving adaptation and speciation. Most studies on urban sexual selection and mating interactions report differences between urban and non‐urban populations or correlations between sexual traits and factors associated with increased urbanisation, such as pollution, food availability and risk of predation and parasitism. Here we review the literature on sexual selection and sexual traits in relation to urbanisation or urban‐associated conditions. We provide an extensive list of abiotic and biotic factors that can influence processes involved in mating interactions, such as signal production and transmission, mate choice and mating opportunities. We discuss all relevant data through the lens of two, non‐mutually exclusive theories on sexual selection, namely indicator and sensory models. Where possible, we indicate whether these models provide the same or different predictions regarding urban‐adapted sexual signals and describe different experimental designs that can be useful for the different models as well as to investigate the drivers of sexual selection. We argue that we lack a good understanding of: (i) the factors driving urban sexual selection; (ii) whether reported changes in traits result in adaptive benefits; and (iii) whether these changes reflect a short‐term ecological, or long‐term evolutionary response. We highlight that urbanisation provides a unique opportunity to study the process and outcomes of sexual selection, but that this requires a highly integrative approach combining experimental and observational work.

Animals show a rich diversity of signals and displays. Among the many selective forces driving the evolution of communication signals, one widely recognized factor is the structure of the environment where animals communicate. In particular, animals communicating by sounds often emit acoustic signals from specific locations, such as high up in the air, from the ground or in the water. The properties of these different display sites may impose different constraints on sound production, and therefore drive signal evolution. Here, we used comparative phylogenetic analyses to assess the relationship between calling site (aquatic versus nonaquatic), body size and call dominant frequency of 160 frog species from the families Ranidae, Leptodactylidae and Hylidae. We found that the frequency of frogs calling from the water was lower than that of species calling outside of the water, a trend that was consistent across the three families studied. Furthermore, phylogenetic path analysis revealed that call site had both direct and indirect effects on call frequency. Indirect effects were mediated by call site influencing male body size, which in turn was negatively associated with call frequency. Our results suggest that properties of display sites can drive signal evolution, most likely not only through morphological constraints imposed on the sound production mechanism, but also through changes in body size, highlighting the relevance of the interplay between morphological adaptation and signal evolution. Changes in display site may therefore have important evolutionary consequences, as it may influence sexual selection processes and ultimately may even promote speciation.

Wind, a major source of environmental noise, forces invertebrates that communicate with plant-borne vibrations to adjust their signaling when communicating in windy conditions. However, the strategies that animals use to reduce the impact of wind noise on communication are not well studied. We investigated the effects of wind on the production of tremulatory signals in the neotropical katydid Copiphora brevirostris. First, we recorded katydid signaling activity and natural wind variation in the field. Additionally, we exposed katydid couples during their most active signaling time period to artificial wind of different levels, and we recorded the number of tremulations produced by the males. We found that wind levels are at their lowest between 2:00 and 5:00 in the morning, which coincides with peak signaling period for male katydids. Furthermore, we found that males produce significantly fewer tremulations when exposed to wind rather than acoustic noise or silence. Wind velocity significantly affected the number of tremulations produced during the wind treatment, with fewer tremulations produced with higher wind velocities. Our results show that katydids can time their vibratory signaling both in the short- and long-term to favorable sensory conditions, either through behavioral flexibility in response to short-term fluctuations in wind or as a result of an evolutionary process in response to predictable periods of low-wind conditions. Significance statement: Animal communication can be hampered by noise across all sensory modalities. Most research on the effects of noise and the strategies to cope with it has focused on animals that use airborne sounds to communicate. However, although hundreds of thousands of invertebrates communicate with vibrational signals, we know very little about how noise affects this form of communication. For animals that rely on substrate-borne vibrations, wind represents the major source of environmental noise. Wind velocity levels can be predictable at a long-term scale (hours) but rather unpredictable at a short time scale (seconds). Both scales of variation are important for communication. Using a combination of field observations and lab experiments, we investigated the strategies used by a neotropical katydid Copiphora brevirostris to cope with vibrational noise induced by wind. Our results demonstrate that C. brevirostris times its signals at the long- and short-term range. Katydids signaled more at the times at night when wind velocity was lowest. Moreover, when exposed to wind gusts during their peak time of activity, katydids signaled more during the wind-free gaps.

Signal detection is a fundamental requirement for any communicative interaction. Acoustic signals, however, experience amplitude losses during their transmission through the environment, reducing their detection range. Displaying from sites that increase the amplitude of the sound produced, such as cavities or some reflective surfaces, can improve the detectability of signals by distant receivers. We measured the effect of leaf calling sites on the calls of an arboreal (Hyalinobatrachium fleischmanni) and a leaf-litter specialist (Silverstoneia flotator) frog species. We collected the leaves where males of both species were observed calling, and conducted playback experiments to measure their effect on the amplitude of frog calls. Overall, the leaves used by H. fleischmanni and S. flotator were of similar dimensions, and amplified the calls of each species by about 5.0 and 2.5 dB, respectively. The degree of call amplification was unrelated to leaf dimensions or the position of the frogs on the leaves, but explained by the different frequency content of the calls of each species. We suggest that amplification of frogs calls by leaves could represent either a benefit or impose costs for arboreal and terrestrial species, which may depend on the spatial location of intended and unintended receivers.