The Evolution of Language

Global increases in environmental noise levels – arising from expansion of human populations, transportation networks, and resource extraction – have catalysed a recent surge of research into the effects of noise on wildlife. Synthesising a coherent understanding of the biological consequences of noise from this literature is challenging. Taxonomic groups vary in auditory capabilities. A wide range of noise sources and exposure levels occur, and many kinds of biological responses have been observed, ranging from individual behaviours to changes in ecological communities. Also, noise is one of several environmental effects generated by human activities, so researchers must contend with potentially confounding explanations for biological responses. Nonetheless, it is clear that noise presents diverse threats to species and ecosystems and salient patterns are emerging to help inform future natural resource-management decisions. We conducted a systematic and standardised review of the scientific literature published from 1990 to 2013 on the effects of anthropogenic noise on wildlife, including both terrestrial and aquatic studies. Research to date has concentrated predominantly on European and North American species that rely on vocal communication, with approximately two-thirds of the data set focussing on songbirds and marine mammals. The majority of studies documented effects from noise, including altered vocal behaviour to mitigate masking, reduced abundance in noisy habitats, changes in vigilance and foraging behaviour, and impacts on individual fitness and the structure of ecological communities. This literature survey shows that terrestrial wildlife responses begin at noise levels of approximately 40 dBA, and 20% of papers documented impacts below 50 dBA. Our analysis highlights the utility of existing scientific information concerning the effects of anthropogenic noise on wildlife for predicting potential outcomes of noise exposure and implementing meaningful mitigation measures. Future research directions that would support more comprehensive predictions regarding the magnitude and severity of noise impacts include: broadening taxonomic and geographical scope, exploring interacting stressors, conducting larger-scale studies, testing mitigation approaches, standardising reporting of acoustic metrics, and assessing the biological response to noise-source removal or mitigation. The broad volume of existing information concerning the effects of anthropogenic noise on wildlife offers a valuable resource to assist scientists, industry, and natural-resource managers in predicting potential outcomes of noise exposure.

https://www.wildliferesearch.co.uk/Wildlife_Research/Publications_files/A%20synthesis%20of%20two%20decades%20of%20research%20documenting%20the%20effects%20of%20noise%20on%20wildlife%20Shannon.pdf

A synthesis of two decades of research documenting the effects of noise on wildlife

Behavioural adjustments for a life in the city

Vocalizations of anuran amphibians have received much attention in studies of behavioral ecology and physiology, but also provide informative characters for identifying and delimiting species. We here review the terminology and variation of frog calls from a perspective of integrative taxonomy, and provide hands-on protocols for recording, analyzing, comparing, interpreting and describing these sounds. Our focus is on advertisement calls, which serve as premating isolation mechanisms and, therefore, convey important taxonomic information. We provide recommendations for terminology of frog vocalizations, with call, note and pulse being the fundamental subunits to be used in descriptions and comparisons. However, due to the complexity and diversity of these signals, an unequivocal application of the terms call and note can be challenging. We therefore provide two coherent concepts that either follow a note-centered approach (defining uninterrupted units of sound as notes, and their entirety as call) or a call-centered approach (defining uninterrupted units as call whenever they are separated by long silent intervals) in terminology. Based on surveys of literature, we show that numerous call traits can be highly variable within and between individuals of one species. Despite idiosyncrasies of species and higher taxa, the duration of calls or notes, pulse rate within notes, and number of pulses per note appear to be more static within individuals and somewhat less affected by temperature. Therefore, these variables might often be preferable as taxonomic characters over call rate or note rate, which are heavily influenced by various factors. Dominant frequency is also comparatively static and only weakly affected by temperature, but depends strongly on body size. As with other taxonomic characters, strong call divergence is typically indicative of species-level differences, whereas call similarities of two populations are no evidence for them being conspecific. Taxonomic conclusions can especially be drawn when the general advertisement call structure of two candidate species is radically different and qualitative call differences are thus observed. On the other hand, quantitative differences in call traits might substantially vary within and among conspecific populations, and require careful evaluation and analysis. We provide guidelines for the taxonomic interpretation of advertisement call differences in sympatric and allopatric situations, and emphasize the need for an integrative use of multiple datasets (bio-acoustics, morphology, genetics), particularly for allopatric scenarios. We show that small-sized frogs often emit calls with frequency components in the ultrasound spectrum, although it is unlikely that these high frequencies are of biological relevance for the majority of them, and we illustrate that detection of upper harmonics depends also on recording distance because higher frequencies are attenuated more strongly. Bioacoustics remains a prime approach in integrative taxonomy of anurans if uncertainty due to possible intraspecific variation and technical artifacts is adequately considered and acknowledged.

/pdf/the-use-of-bioacoustics-in-anuran-taxonomy-theory-1cy4oo38d8.pdf

The use of bioacoustics in anuran taxonomy: theory, terminology, methods and recommendations for best practice

On the occasion of the centenary of the discovery of the Lombard effect, we review the literature on noise-dependent regulation of vocal amplitude in humans and other animals The article addresses the scientific and the biological history of the Lombard effect: first, it sketches the evolution of the study of the Lombard effect, and second it reflects on the biological evolution of the effect itself By comparing the findings from anurans, birds and mammals, we try to trace back the phylogenetic origins of this basic vocal mechanism for acoustic communication in noise The current evidence suggests two alternative parsimonious hypotheses: either the Lombard effect is the outcome of a convergent evolution in birds and mammals or it may be a synapomorphy of all amniotes If the latter is true, then the Lombard effect would have evolved to maintain vocal communication in the presence of noise more than 300 million years ago

The evolution of the Lombard effect: 100 years of psychoacoustic research

http://donaldkroodsma.com/wp-content/uploads/2014/01/Podos-et-al.-On-doing-good-science.pdf

On the relationship between, and measurement of, amplitude and frequency in birdsong

When animals live in cities, they have to adjust their behaviour and life histories to novel environments. Noise pollution puts a severe constraint on vocal communication by interfering with the detection of acoustic signals. Recent studies show that city birds sing higher-frequency songs than their conspecifics in non-urban habitats. This has been interpreted as an adaptation to counteract masking by traffic noise. However, this notion is debated, for the observed frequency shifts seem to be less efficient at mitigating noise than singing louder, and it has been suggested that city birds might use particularly high-frequency song elements because they can be produced at higher amplitudes. Here, we present the first phonetogram for a songbird, which shows that frequency and amplitude are strongly positively correlated in the common blackbird (Turdus merula), a successful urban colonizer. Moreover, city blackbirds preferentially sang higher-frequency elements that can be produced at higher intensities and, at the same time, happen to be less masked in low-frequency traffic noise.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2012.2798

Bird song and anthropogenic noise: vocal constraints may explain why birds sing higher-frequency songs in cities

In order to achieve the goal of understanding the neurobiology of birdsong, it is necessary to understand the peripheral mechanisms by which song is produced. This paper reviews recent advances in the understanding of syringeal and respiratory motor control and how birds utilize these systems to create their species-typical sounds. Songbirds have a relatively homogeneous duplex vocal organ in which sound is generated by oscillation of a pair of thickened labia on either side of the syrinx. Multiple pairs of syringeal muscles provide flexible, independent control of sound frequency and amplitude, and each side of the syrinx exhibits a degree of acoustic specialization. This is in contrast to many non-songbirds, including vocal learners such as parrots, which have fewer syringeal muscles and use syringeal membranes to generate sound. In doves, at least, these membranes generate a harmonic signal in which the fundamental frequency is regulated by respiratory pressure in the air sac surrounding the syrinx and the overtones are filtered out by the vocal tract. The songs of adult songbirds are generally accompanied by precisely coordinated respiratory and syringeal motor patterns that, despite their relative stereotypy, are modulated in real time by somatosensory feedback. Comparative studies indicate songbirds have evolved species-specific motor patterns that utilize the two sides of the syrinx in specific ways and enhance the particular acoustic effects characterizing the species song. A vocal mimic tutored with heterospecific song uses the same motor pattern as the tutor species when he accurately copies the song, suggesting that physical or physiological constraints on sound production have had a prominent role in the evolution of species-specific motor patterns. An understanding of the relationship between the central processing and peripheral performance of song motor programs is essential for an understanding of the development, function, and evolution of these complex vocal signals.

Sue Anne Zollinger

Papers

The evolution of the Lombard effect: 100 years of psychoacoustic research

On the relationship between, and measurement of, amplitude and frequency in birdsong

Bird song and anthropogenic noise: vocal constraints may explain why birds sing higher-frequency songs in cities

Producing Song: The Vocal Apparatus

The Lombard effect.