Heptahelical terpsichory. Who calls the tune?

The discovery that arrestins can function as ligand-regulated signaling scaffolds has revealed a previously unappreciated level of complexity in G protein-coupled receptor (GPCR) signal transduction. Because arrestin-bound GPCRs are uncoupled from G proteins, arrestin binding can be viewed as switching receptors between two temporally and spatially distinct signaling modes. Recent work has established two factors that underscore this duality of GPCR signaling and suggest it may ultimately have therapeutic significance. The first is that signaling by receptor-arrestin "signalsomes" does not require heterotrimeric G protein activation. The second is that arrestin-dependent signals can be initiated by pathway-specific "biased agonists," creating the potential for drugs that selectively modulate different aspects of GPCR function. Currently, however, little is known about the physiological relevance of G protein-independent signals at the cellular or whole animal levels, and additional work is needed to determine whether arrestin pathway-selective drugs will find clinical application.     

Rhesus macaque copulation calls: Re-evaluating the “honest signal” hypothesis

Male rhesus macaques sometimes give loud calls while thrusting or dismounting during multi-mount copulations.Hauser (1993) has proposed that these calls (1) impose a cost (increased risk of aggression) on calling males, and (2) increase callers' copulation frequencies, supporting the hypothesis that calls function as honest signals (handicaps) that females use to evaluate male quality during mate choice. This hypothesis was re-examined using data collected at Cayo Santiago, Puerto Rico on 40 focal females and their 56 observed copulatory partners. Although attacks by males against copulating pairs were frequent, they were usually directed only against the female of the pair. Males that called were no more likely than silent males to suffer male escalated attack during or immediately following mount series. Male-female dyads in which the male called during copulation were significantly more likely than non-calling dyads to complete the most copulations observed for any given female. Males that called at least once were significantly more likely than non-calling males to complete at least one copulation with a peri-ovulatory female. A log-linear model revealed that male rank and calling were both associated with likelihood of experiencing at least one peri-ovulatory copulation. However, calling was not associated with reception of demonstrated female mate choice behaviors. Controlling for dominance rank, callers did not experience more female proximity maintenance than non-callers. Nor were callers' hip-grasps refused less frequently than non-callers' hip-grasps. These results cast doubt on the hypothesis that rhesus macaque copulation calls are costly, honest indicators of intrinsic male quality. A contrasting alternative hypothesis, that a male's copulatory calls advertise relative immunity from attacks against his copulatory partners, was not supported either. Thus, the function of rhesus macaque copulatory calls remains unknown. The unusually high rate of copulations amongHauser's (1993) subjects may explain the discrepancy in results, but it is unclear how high copulation rates would increase the cost of copulatory calling to males.     

What's in a name? The vervet predator calls and the limits of the Washburnian synthesis

After the Second World War, a renaissance in field primatology took place in the United States under the aegis of the 'new physical anthropology'. Its leader, Sherwood Washburn, envisioned a science uniting studies of hominid fossils with Darwinian population genetics, experimental functional anatomy, and field observation of non-human primates and human hunter-gatherers. Thanks to Washburn's stimulus, his colleague at Berkeley, the bird ethologist Peter Marler, took up the study of the natural communicative behaviour of apes and monkeys. When Marler's first primatological student, Thomas Struhsaker, reported in the mid-1960s that the vervet monkeys of Amboseli, Kenya, give acoustically distinct alarm calls to different predators, and respond to alarm calls as if to the sight of those predators, a debate broke out over whether the vervet calls thus function as names, translating as 'leopard', 'eagle' and 'python'. Washburn and his students argued that no matter what the behavioural evidence, vervet calls could not be predator names, since monkeys had been shown to lack the neuroanatomical basis of naming. This controversy thus reveals, first, the persistence of older patterns of disciplinary allegiance within the new, synthetic physical anthropology; and second, the impotence of adaptationist Darwinism--common to both sides of the debate--as a force for unity.     

Do mobbing calls affect the perception of predation risk by forest birds?

We report the results of two field experiments assessing whether exposure to mobbing calls, which usually indicates the presence of a predator, elicits changes in risk perception as measured by the willingness of forest birds to enter or cross gaps in forest cover. In the first experiment, we tested the prediction that wintering black-capped chickadees,Poecile atricapilla , will travel less in open areas to seek food from a feeder during a simulated mobbing event than they will under control conditions. The number of visits to feeders decreased at increasing distances from forest edges (0-10 m) when mobbing calls were played. Mobbing calls increased the overall rate of visits to feeders, but lowered the rate of visits to feeders located at 10 m from forest edges. By contrast, when a stuffed merlin, Falco columbarius, was placed near the feeder, chickadees rarely visited the feeder, regardless of the distance to forest edge. In the second experiment, we tested the prediction that breeding male red-eyed vireos, Vireo olivaceus, would be less attracted to the song of a nearby red-eyed vireo after a playback of a mobbing event than after a ‘neutral’ sound stimulus, especially if they had to cross an open area. Vireos were as willing to enter or cross gaps in forest cover following exposure to mobbing calls, although they responded more frequently to conspecific song under forest cover than across gaps. Our results suggest that forest birds under cover assess the risk of a mobbing situation largely on the basis of the distance to the cause of mobbing. It follows that a trade-off between risk and reward may not occur with mobbing birds, unless mobbing occurs far outside forest cover and/or at very close range (<5 m) to a predator. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Does sociality drive the evolution of communicative complexity? A comparative test with ground-dwelling sciurid alarm calls

While sociality has been hypothesized to drive the evolution of communicative complexity, the relationship remains to be formally tested. We derive a continuous measure of social complexity from demographic data and use this variable to explain variation in alarm repertoire size in ground-dwelling sciurid rodents (marmots, Marmota spp.; prairie dogs, Cynomys spp.; and ground squirrels, Spermophilus spp.). About 40% of the variation in alarm call repertoire size was explained by social complexity in the raw data set. To determine the degree to which this relationship may have been influenced by historical relationships between species, we used five different phylogenetic hypotheses to calculate phylogenetically independent contrasts. Less variation was significantly explained in contrast-based analyses, but a general positive relationship remained. Social complexity explained more variation in alarm call repertoire size in marmots, while sociality explained no variation in repertoire size in prairie dogs and no variation in phylogenetically based analyses of squirrels. In most cases, substantial variation remained unexplained by social complexity. We acknowledge that factors other than social complexity, per se, may contribute to the evolution of alarm call repertoire size in sciurid rodents, and we discuss alternative hypotheses. Our measure of social complexity could be used by other researchers to test explicit evolutionary hypotheses that involve social complexity.     

Maori “bird calls” or “whistles”

This article examines the discourse attendant upon ‘old’ places in contemporary Japan through a case study of a commuter village near Kyoto. It shows how such localities are represented in a national debate about the strength of Japan's ‘vanishing’ tradition, and how local communities mobilize parts of this debate in their dialogue with a variety of collective others about local identity. The guiding axii of this nostalgic discourse are assertions about the typicality of ‘old’ places and their uniqueness. Finally, the article shows how alongside a debate about such communities as repositories of tradition, there is a discussion about their feudal legacy, social control and political conservatism.     

Advertisement calls of Guenther’s frog Hylarana guentheri (Anura: Ranidae) during the breeding season

Acoustic signalling is the most important form of communication in anuran amphibians. Here we recorded and analysed the calls of 18 male Guenther’s frogs (Hylarana guentheri) from the wild during the breeding season. The advertisement calls of H. guentheri were composed of from a single note to five notes, with three-note calls the most recorded. All individuals produced calls around 600 Hz but calls ranged from 470 to 2600 Hz. Comparing the differences between individuals calls, we found within-male coefficients of variation (CV_w) of call intensity, the fundamental frequency, the first formant, the second formant, the third formant and the fourth formant were static (less than 5% variation), whereas those of note duration, call duration, call interval, numbers of pulses and dominant frequency were dynamic (larger than 15% variation). Comparisons of the call characteristics of H. guentheri in this study with other studies from China, Singapore and Vietnam found call characteristics varied greatly between the five different locations.     

Decoding the ‘zeep’ complex: quantitative analysis of interspecific variation in the nocturnal flight calls of nine wood warbler species (Parulidae spp.)

ABSTRACT

The “zeep” complex consists of nine birds that produce nocturnal flight calls with similar acoustic features. Our inability to distinguish these calls inhibits the acoustic monitoring of these species. We test the hypothesis that flight calls of nine warblers in the “zeep” complex show sufficient acoustic differences to allow differentiation. We investigate divergence in these vocalizations by recording birds held for banding and collecting additional recordings from sound libraries. We used three approaches to compare calls between species: analysis of variance in acoustic properties, discriminant analysis of acoustic properties, and spectrographic cross-correlation. The first approach revealed five species that were different in one or more acoustic properties. The second approach revealed a level of assignment to the correct species (73%) that exceeded levels expected by chance (36%). The third approach revealed calls of seven species to be significantly more similar to conspecific calls than heterospecific calls. Our results suggest the calls of many members of the “zeep” complex exhibit species-specific differences in structure, which may allow differentiation of at least five “zeep” species based on call alone. We advocate for the combined use of these three approaches for the comparison of “zeep” calls in future flight call studies.     

Alarm calls of the Cyprus Wheatear Oenanthe cypriaca—one for nest defence, one for parent–offspring communication?

Alarm calling has been interpreted from the viewpoint of parental investment and nest defence. Calling should increase with an increasing value of the brood to the caller or with increasing vulnerability of the brood. Parental alarm calling might also be viewed from assessment–management with callers using vocalisations to elicit affective responses in others, e.g. in silencing offspring. I examined parental alarm calling in the Cyprus Wheatear (Oenanthe cypriaca) at different developmental stages. The Cyprus Wheatear produces two alarm calls, but one is emitted only during a short period of the year (type II alarm call). The commoner alarm call (type I alarm call), however, is used year-round. Predation was simulated using consistent approach by human observers. The brood cycle was divided into (I) incubation, (II) nestling, (III) early fledging, and (IV) late fledging. Type I calls increased from phases I to III, and decreased afterwards. Type II calls were absent during incubating and occurred during nestling and early fledging stages. As a conclusion, I suggest that the type I alarm call might be used to alert the mate, deter the predator and signal strength of nest defence, while the type II alarm call is addressed to offspring.     

Female answer specificity to male drumming calls in three closely related species of the stonefly genus Zwicknia (Plecoptera: Capniidae)

This study examines the rate of female answers to conspecific versus heterospecific male vibratory calls in three,closely related stonefly species:Zwicknia bifrons,Z.acuta,and Z.rupprechti.In a previous study those three species were recognized on the basis of their distinct male drumming calls along with differences in genital morphology and genetic divergence.During this study no-choice playback experiments using original male call samples from each species were performed,and the answer rate of females to con?specific and heterospecific signal variants was measured.Mixed effect logistic regression models were used to test if male call species identity had a statistically significant effect on female answer probability.Females answered conspecific male calls with significantly higher probability than heterospecific calls in all the three examined species,suggesting that the divergence of vibrational communication can be an important component of the prezygotic isolation between them.Low,but well detectable responsiveness to heterospecific calls was observable between Z.bifrons and Z.acuta,the two species closest to each other regarding mitochondrial genetic divergence and male call pattern similarity.Thus,our results are most congruent with a tight,gradual coevolution of male calls and female preferences.     

ITS, OTUs and beyond—fungal hyperdiversity calls for supplementary solutions

Molecular species recognition of fungi emerged years before DNA barcoding ( Seifert 2009 ). While the ideal fungal DNA barcode seems Utopian, two research decades nevertheless highlight the internal transcribed spacer (ITS) as the best available choice ( Seifert 2009 ). Databases providing reliable ITS sequences of known fungi require enormous efforts, but are urgently needed ( Abarenkov et al. 2010a,b ; Begerow et al. 2010 ). Any criticism of such a commitment seems unjustified. However, exclusive focus on the development of ITS reference libraries will delay the progress towards a deeper ecological insight. It is widely acknowledged that ITS fails to recognize species, particularly in some ascomycete lineages ( Balajee et al. 2009 ; Seifert 2009 ). It also appears paradoxical to solely rely on ITS for ecological recognition of fungal species when modern fungal systematics rely on phylogenetic species recognition with concordance of multiple gene genealogies (see Blackwell 2011 ). Considering that at least 98% of the predicted ～5 million fungal species remain undescribed ( Blackwell 2011 ), how will reliance on ITS alone influence the biodiversity estimates and ecological understanding? In this issue, Gazis et al. (2011) elegantly demonstrate through multi‐locus sequence phylogeny analyses that ITS largely underestimates the species diversity of tropical fungal endophytes and even more importantly obscures fundamental ecological and biogeographical patterns. This thorough reflection on species delimitation criteria and their implications for ecological and biogeographical inferences underline that ITS, particularly in hyperdiverse habitats, provides no shortcut to deeper knowledge of fungal ecology.     

Exchange of “signature” calls in captive belugas (Delphinapterus leucas)

Belugas (Delphinapterus leucas) produce echolocation clicks, burst pulses, and whistles. The sounds of 3 captive belugas were recorded using 2 hydrophones at the Port of Nagoya Public Aquarium. There were stable individual differences in the pulse patterning of one type of pulsed sounds (PS1 call), suggesting that belugas use these as “signature” calls. Eighty-eight percent of PS1 calls initiated PS1 calls from other animals within 1 s. PS1 calls repeated by the same individual occurred primarily when other belugas did not respond within 1 s of the first call. Belugas delayed successive PS1 calls when other belugas responded with a PS1 call within 1 s. There was no clear temporal pattern for whistles. It appears that the time limit for responding to calls is 1 s after the initial call. If other individuals do not respond to the PS1 call of a beluga within 1 s, belugas tend to repeat the call and wait for a response. The results of this study suggest that the belugas exchange their individual signatures by using PS1 calls, in a manner similar to that of signature whistles used by bottlenose dolphins.     

Does vocal learning accelerate acoustic diversification? Evolution of contact calls in Neotropical parrots

Learning has been traditionally thought to accelerate the evolutionary change of behavioural traits. We evaluated the evolutionary rate of learned vocalizations and the interplay of morphology and ecology in the evolution of these signals. We examined contact calls of 51 species of Neotropical parrots from the tribe Arini. Parrots are ideal subjects due to their wide range of body sizes and habitats, and their open‐ended vocal learning that allows them to modify their calls throughout life. We estimated the evolutionary rate of acoustic parameters of parrot contact calls and compared them to those of morphological traits and habitat. We also evaluated the effect of body mass, bill length, vegetation density and species interactions on acoustic parameters of contact calls while controlling for phylogeny. Evolutionary rates of acoustic parameters did not differ from those of our predictor variables except for spectral entropy, which had a significantly slower rate of evolution. We found support for correlated evolution of call duration, and fundamental and peak frequencies with body mass, and of fundamental frequency with bill length. The degree of sympatry between species did not have a significant effect on acoustic parameters. Our results suggest that parrot contact calls, which are learned acoustic signals, show evolutionary rates similar to those of morphological traits. This is the first study to our knowledge to provide evidence that change through cultural evolution does not necessarily accelerate the evolutionary rate of traits acquired through life‐long vocal learning.