Effects of mining truck traffic on cricket calling activity

Changes in call properties of Boana pulchella (Anura, Hylidae) in response to different noise conditions

The increasing expansion of urban areas leads to the emergence of new noisy environments that can affect animal communication. Calls play a crucial role in the mating displays of anurans, and the negative impact of anthropogenic noise-induced auditory masking has been reported in several species. We investigated the acoustic variation in 96 males (n = 971 calls) of the treefrog Boana pulchella across acoustically undisturbed sites and different noise conditions, associated with urban areas (URBAN) and roads (ROAD), in Central Argentina. We analyzed the effect of anthropogenic noise conditions on 6 temporal (call duration [CD], intercall interval, first and second note duration, internote interval, and call rate) and 3 spectral (dominant frequency of first and second note, frequency difference between them) call properties. The effects of temperature and size on acoustical variables were controlled. We observed differences in all call attributes among the noise conditions, except for intercall interval. Males exposed to URBAN and ROAD exhibited significant changes in CD, dominant frequency of the second note, and frequency difference between them. URBAN males had longest internote interval, while ROAD individuals displayed increased first and second note duration and call rates. Interestingly, ROAD males exhibited immediate changes in call rate in direct response to passing heavy vehicles. Our study emphasizes the impact of anthropogenic noise on the acoustic characteristics of B. pulchella calls. Understanding how animals adapt to noisy environments is crucial in mitigating the adverse effects of urbanization on their communication systems. Future investigations should explore whether the observed call adjustments are effective in avoiding or mitigating the negative consequences of anthropogenic noise on reproductive success.

Pied tamarins change their vocal behavior in response to noise levels in the largest city in the Amazon

Many animal species depend on sound to communicate with conspecifics. However, human-generated (anthropogenic) noise may mask acoustic signals and so disrupt behavior. Animals may use various strategies to circumvent this, including shifts in the timing of vocal activity and changes to the acoustic parameters of their calls. We tested whether pied tamarins (Saguinus bicolor) adjust their vocal behavior in response to city noise. We predicted that both the probability of occurrence and the number of long calls would increase in response to anthropogenic noise and that pied tamarins would temporally shift their vocal activity to avoid noisier periods. At a finer scale, we anticipated that the temporal parameters of tamarin calls (e.g., call duration and syllable repetition rate) would increase with noise amplitude. We collected information on the acoustic environment and the emission of long calls in nine wild pied tamarin groups in Manaus, Brazil. We found that the probability of long-call occurrence increased with higher levels of anthropogenic noise, though the number of long calls did not. The number of long calls was related to the time of day and the distance from home range borders-a proxy for the distance to neighboring groups. Neither long-call occurrence nor call rate was related to noise levels at different times of day. We found that pied tamarins decreased their syllable repetition rate in response to anthropogenic noise. Long calls are important for group cohesion and intergroup communication. Thus, it is possible that the tamarins emit one long call with lower syllable repetition, which might facilitate signal reception. The occurrence and quantity of pied tamarin' long calls, as well as their acoustic proprieties, seem to be governed by anthropogenic noise, time of the day, and social mechanisms such as proximity to neighboring groups.

Crickets in the spotlight: exploring the impact of light on circadian behavior

Crickets serve as a well-established model organism in biological research spanning various fields, such as behavior, physiology, neurobiology, and ecology. Cricket circadian behavior was first reported over a century ago and prompted a wealth of studies delving into their chronobiology. Circadian rhythms have been described in relation to fundamental cricket behaviors, encompassing stridulation and locomotion, but also in hormonal secretion and gene expression. Here we review how changes in illumination patterns and light intensity differentially impact the different cricket behaviors as well as circadian gene expression. We further describe the cricket's circadian pacemaker. Ample anatomical manipulations support the location of a major circadian pacemaker in the cricket optic lobes and another in the central brain, possibly interconnected via signaling of the neuropeptide PDF. The cricket circadian machinery comprises a molecular cascade based on two major transcriptional/translational negative feedback loops, deviating somewhat from the canonical model of Drosophila and emphasizing the significance of exploring alternative models. Finally, the nocturnal nature of crickets has provided a unique avenue for investigating the repercussions of artificial light at night on cricket behavior and ecology, underscoring the critical role played by natural light cycles in synchronizing cricket behaviors and populations, further supporting the use of the cricket model in the study of the effects of light on insects. Some gaps in our knowledge and challenges for future studies are discussed.

Hidden shifts in allometry scaling between sound production and perception in anurans

Background

Animal communication consists of signal production and perception, which are crucial for social interactions. The main form used by anurans is auditory communication, in most cases produced as advertisement calls. Furthermore, sound perception happens mainly through an external tympanic membrane, and plays an important role in social behavior. In this study, we evaluated the influence of body and tympanic membrane sizes on call frequency across the phylogeny of anurans.

Methods

We use data on snout-vent length, tympanic membrane diameter, and dominant frequency of the advertisement call from the literature and from natural history museum collections. We mapped these traits across the anuran phylogeny and tested different models of diversification. Our final dataset includes data on body size, tympanic membrane size, and call dominant frequency of 735 anuran species.

Results

The best explanatory model includes body and tympanum size with no interaction term. Although our results show that call frequency is strongly constrained by body and tympanum size, we identify five evolutionary shifts in allometry from that ancestral constraint. We relate these evolutionary shifts to the background noise experienced by populations. Body size is important for myriad ecological interactions and tympanum size is strongly associated with female call frequency preferences. Thus, allometric escape in frog calls might arise through environmental selection such as breeding in fast flowing or soundscape competition, as well as sexual selection linked to tympanum size.

A meta-analysis on the evolution of the Lombard effect reveals that amplitude adjustments are a widespread vertebrate mechanism

Animal communication is central to many animal societies, and effective signal transmission is crucial for individuals to survive and reproduce successfully. One environmental factor that exerts selection pressure on acoustic signals is ambient noise. To maintain signal efficiency, species can adjust signals through phenotypic plasticity or microevolutionary response to natural selection. One of these signal adjustments is the increase in signal amplitude, called the Lombard effect, which has been frequently found in birds and mammals. However, the evolutionary origin of the Lombard effect is largely unresolved. Using a phylogenetically controlled meta-analysis, we show that the Lombard effect is also present in fish and amphibians, and contradictory results in the literature can be explained by differences in signal-to-noise ratios among studies. Our analysis also demonstrates that subcortical processes are sufficient to elicit the Lombard effect and that amplitude adjustments do not require vocal learning. We conclude that the Lombard effect is a widespread mechanism based on phenotypic plasticity in vertebrates for coping with changes in ambient noise levels.

Influence of Anthropogenic Sounds on Insect, Anuran and Bird Acoustic Signals: A Meta-Analysis

Acoustic communication is a way of information exchange between individuals, and it is used by several animal species. Therefore, the detection, recognition and correct understanding of acoustic signals are key factors in effective communication. The priority of acoustic communication is effectiveness rather than perfection, being effective avoids affecting the sound-based communication system of the species. One of the factors that can affect effective communication is the overlap in time and frequency during signal transmission, known as signal masking. One type of sound that can cause masking is anthropogenic noise, which is currently increasing due to urban growth and consequently motorized transportation and machinery. When exposed to anthropogenic noise, animals can use compensatory mechanisms to deal with sound masking, such as the modification of acoustic parameters of their acoustic signal. Here, we performed a meta-analysis investigating whether different taxa have a general tendency for changes in acoustic parameters due to anthropogenic noise, we used taxa and acoustic parameters available in the literature that met the minimum criteria to perform a meta-analysis. We hypothesized that animals exposed to anthropogenic noise use compensation mechanisms, such as changes in dominant, maximum or minimum frequencies, call duration, note duration and call rate to deal with masking. We performed a meta-analysis, which synthesized information from 73 studies comprising 82 species of three taxa: insects, anurans and birds. Our results showed that in the presence of anthropogenic noise, insects did not change the acoustic parameters, while anurans increased call amplitude and birds increased dominant frequency, minimum and maximum frequencies, note duration and amplitude of their songs. The different responses of the groups to anthropogenic noise may be related to their particularities in the production and reception of sound or to the differences in the acoustic parameters considered between the taxa and also the lack of studies in some taxa.

Anthropogenic noise affects insect and arachnid behavior, thus changing interactions within and between species

Urbanization and the by-product pollutants of anthropogenic activity pose unique threats to arthropods by altering their sensory environments. Sounds generated by human activities, like construction and road traffic, can oversaturate or interfere with biotic acoustic cues that regulate important ecological processes, such as trophic interactions and the coordination of mating. Here, we review recent work exploring how anthropogenic noise impacts inter-intra-specific interactions in insects and arachnids. We outline empirical frameworks for future research that integrate three mechanisms by which anthropogenic noise alters behavior through interference with acoustic cues: masking, distraction, and misleading. Additionally, we emphasize the need for experimental designs that more accurately replicate natural soundscapes. We encourage future investigations on the effects of developmental exposure to noise pollution and the impacts of multiple interacting sensory pollutants on insect and arachnid behavior.

Gaps in terrestrial soundscape research: It's time to focus on tropical wildlife

There has been a body of research examining the sounds produced in landscapes. These sounds are commonly defined as soundscapes, however, the term is often used in different contexts. To understand the various meanings attributed to soundscapes, we identified how soundscapes are represented in the scientific literature and identified current knowledge gaps in soundscape research focusing on terrestrial environments. We conducted a quantitative review of published papers with the keyword soundscape available at Web of Science and Scopus databases. A total of 1309 abstracts and a subset of about 5% (N = 68) complete papers and reviews published from 1985 to 2017 were read and analysed, identifying types of sound, types of environment and focal species studied, as well as study regions and climates. By identifying the current focus of research, we also identified gaps and research opportunities. Research was biased towards temperate regions, terrestrial environments, and the impacts on humans in urban areas. Although most of the world's biodiversity is concentrated in tropical wilderness areas, these regions had fewer studies attributed to them. Given the importance of tropical landscapes for biodiversity conservation, we strongly suggest that more research should be undertaken in the tropics, with a particular focus on wildlife in these regions. Furthermore, soundscape research (methods and tools) should increasingly target the anthropogenic impacts on wildlife, including behavioural and physiological changes, alongside the current focus on human-sound interactions and the approach used by bioacoustics methods.