High-Pitched Notes during Vocal Contests Signal Genetic Diversity in Ocellated Antbirds

University of Sussex, United Kingdom
PLoS ONE (Impact Factor: 3.23). 12/2009; 4(12):e8137. DOI: 10.1371/journal.pone.0008137
Source: PubMed


Animals use honest signals to assess the quality of competitors during aggressive interactions. Current theory predicts that honest signals should be costly to produce and thus reveal some aspects of the phenotypic or genetic quality of the sender. In songbirds, research indicates that biomechanical constraints make the production of some acoustic features costly. Furthermore, recent studies have found that vocal features are related to genetic diversity. We linked these two lines of research by evaluating if constrained acoustic features reveal male genetic diversity during aggressive interactions in ocellated antbirds (Phaenostictus mcleannani). We recorded the aggressive vocalizations of radiotagged males at La Selva Biological Station in Costa Rica, and found significant variation in the highest frequency produced among individuals. Moreover, we detected a negative relationship between the frequency of the highest pitched note and vocalization duration, suggesting that high pitched notes might constrain the duration of vocalizations through biomechanical and/or energetic limitations. When we experimentally exposed wild radiotagged males to simulated acoustic challenges, the birds increased the pitch of their vocalization. We also found that individuals with higher genetic diversity (as measured by zygosity across 9 microsatellite loci) produced notes of higher pitch during aggressive interactions. Overall, our results suggest that the ability to produce high pitched notes is an honest indicator of male genetic diversity in male-male aggressive interactions.

Full-text preview

Available from: PubMed Central
    • "Little Spotted Kiwi have lower genetic diversity than Brown Kiwi and all other species of kiwi (Ramstad et al. 2010), and this may be reflected in their lower vocal diversity. Genetic diversity is related to song diversity or structure in birds at an individual level (Marshall et al. 2003;Seddon et al. 2004;Pfaff et al. 2007;Araya-Ajoy et al. 2009; McDonald and Wright 2011) and also at a population level (Robin et al. 2011). Is it therefore feasible that a relation between genetic and call diversity exists at the species level in kiwi, providing at least a partial explanation for the differences in vocal diversity between LSK and Brown Kiwi? "
    [Show abstract] [Hide abstract]
    ABSTRACT: The ability to identify individuals by call is particularly important for monitoring cryptic or nocturnal species. It provides key benefits in conservation management, such as allowing correction of biases in censuses and monitoring individual survival. Call surveys are a key tool in conservation of kiwi (Apterygidae), yet individuality of calls has previously been assessed in just one of the five species, the Brown Kiwi (formerly North Island Brown Kiwi, Apteryx mantelli). We have made the first test of whether Little Spotted Kiwi (Apteryx owenii; LSK) can be individually identified by call. Three classification methods (discriminant function analysis, support vector machines and statistical classifiers) were used to assign identity from either call or syllable variables. Using syllables, classification was significantly better than expected by chance for both males and females. Individual LSK can therefore be identified acoustically, suggesting that vocalisations may be used for conspecific identification. Classifier performance was worse using call variables, with no better than chance assignment for females and low accuracy for males. Significant differences in classification ability between the sexes support the hypothesis that the function of calls of male and female LSK differ. Furthermore, identification by call was much less reliable in LSK than in the more genetically diverse Brown Kiwi. This indicates that call diversity may be related to genetic diversity in kiwi, which, if confirmed, could provide a powerful conservation tool for rapid assessment of genetic differences among populations of these threatened species.
    No preview · Article · Jan 2014 · The Emu: official organ of the Australasian Ornithologists' Union
  • Source
    • "Importantly, these quivers associated with sound production provide a stimulus that can be detected by both the inner ear and mechanosensory lateral line system, but how this information might be differentially used by the female remains unknown. Since many of the acoustic characteristics associated with sound production are energetically expensive, they likely function as honest signals used during mate choice, as demonstrated in other vertebrate and invertebrate taxa [80], [81], [82]. However, it is also likely that other non-intended receivers, both males and females, in the vicinity of a courting male can eavesdrop on the sounds and use it to gain social, spawning, or feeding opportunities. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Sexual reproduction in all animals depends on effective communication between signalers and receivers. Many fish species, especially the African cichlids, are well known for their bright coloration and the importance of visual signaling during courtship and mate choice, but little is known about what role acoustic communication plays during mating and how it contributes to sexual selection in this phenotypically diverse group of vertebrates. Here we examined acoustic communication during reproduction in the social cichlid fish, Astatotilapia burtoni. We characterized the sounds and associated behaviors produced by dominant males during courtship, tested for differences in hearing ability associated with female reproductive state and male social status, and then tested the hypothesis that female mate preference is influenced by male sound production. We show that dominant males produce intentional courtship sounds in close proximity to females, and that sounds are spectrally similar to their hearing abilities. Females were 2-5-fold more sensitive to low frequency sounds in the spectral range of male courtship sounds when they were sexually-receptive compared to during the mouthbrooding parental phase. Hearing thresholds were also negatively correlated with circulating sex-steroid levels in females but positively correlated in males, suggesting a potential role for steroids in reproductive-state auditory plasticity. Behavioral experiments showed that receptive females preferred to affiliate with males that were associated with playback of courtship sounds compared to noise controls, indicating that acoustic information is likely important for female mate choice. These data show for the first time in a Tanganyikan cichlid that acoustic communication is important during reproduction as part of a multimodal signaling repertoire, and that perception of auditory information changes depending on the animal's internal physiological state. Our results highlight the importance of examining non-visual sensory modalities as potential substrates for sexual selection contributing to the incredible phenotypic diversity of African cichlid fishes.
    Full-text · Article · May 2012 · PLoS ONE
  • Source
    • "Nevertheless, this hypothesis remains interesting as a potential general explanation for why species where the body size hypothesis does not apply use HAF as a sexual signal because available evidence for birds suggests that higher frequencies may generally be more demanding (Lambrechts 1996; Christie et al. 2004; Araya-Ajoy et al. 2009; Cardoso 2010; but see also Nelson 2000). This asymmetry toward HAF being more demanding rests on indirect evidence (comparisons of aspects of performance across the frequency range), and more work on this would be useful. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The behavioral literature contains inconsistent results on the function of sound frequency (pitch) across species, offering an unexplored opportunity to investigate evolutionary diversification of communication systems. I review those results for birds, where about half the studied species use lower than average frequency (LAF) as a relevant sexual signal, and the remaining species use higher than average frequency (HAF) for the same functions. This variation appears nonrandom with respect to putative causal factors, suggesting that advertising body size determines which species use LAF as a sexual signal. I evaluate different hypotheses to explain why the remaining species use HAF instead. Integrating tests of alternative hypotheses on focal species will be required to demonstrate the causes for this divergence in communication systems.
    Preview · Article · Mar 2012 · Behavioral Ecology
Show more