Data from: The return to water in ancestral Xenopus was accompanied by a novel mechanism for producing and shaping vocal signals

Listeners locate potential mates using species-specific vocal signals. As tetrapods transitioned from water to land, lungs replaced gills, allowing expiration to drive sound production. Some frogs then returned to water. Here we explore how air-driven sound production changed upon re-entry to preserve essential acoustic information on species identity in the secondarily aquatic frog genus Xenopus. We filmed movements of cartilage and muscles during evoked sound production in isolated larynges. Results refute the current theory for Xenopus vocalization, cavitation, and favor instead sound production by mechanical excitation of laryngeal resonance modes following rapid separation of laryngeal arytenoid discs. Resulting frequency resonance modes (dyads) are intrinsic to the larynx rather than due to neuromuscular control. Dyads are a distinctive acoustic signature. While their component frequencies overlap across species, their ratio is shared within each Xenopus clade providing information on species identity that could facilitate both conspecific localization and ancient species divergence.Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter)

Biomechanics and control of vocalization in a non-songbird

The neuromuscular control of vocalization in birds requires complicated and precisely coordinated motor control of the vocal organ (i.e. the syrinx), the respiratory system and upper vocal tract. The biomechanics of the syrinx is very complex and not well understood. In this paper, we aim to unravel the contribution of different control parameters in the coo of the ring dove (Streptopelia risoria) at the syrinx level. We designed and implemented a quantitative biomechanical syrinx model that is driven by physiological control parameters and includes a muscle model. Our simple nonlinear model reproduces the coo, including the inspiratory note, with remarkable accuracy and suggests that harmonic content of song can be controlled by the geometry and rest position of the syrinx. Furthermore, by systematically switching off the control parameters, we demonstrate how they affect amplitude and frequency modulations and generate new experimentally testable hypotheses. Our model suggests that independent control of amplitude and frequency seems not to be possible with the simple syringeal morphology of the ring dove. We speculate that songbirds evolved a syrinx design that uncouples the control of different sound parameters and allows for independent control. This evolutionary key innovation provides an additional explanation for the rapid diversification and speciation of the songbirds

Walking the line: search behavior and foraging success in ant species

Finding food is one of the most important tasks an animal faces. Although the impact of behavior and morphology on individual foraging success is well characterized, an understanding of the extent of interspecific differences in these traits as well as their influence on resource competition is lacking. Temperate ant communities represent an ideal opportunity for examining how search behavior and morphology affect a species' ability to find food first because ant species demonstrate both a wide range of foraging patterns and intense interspecific competition for food resources. For 10 species across 2 communities, species-specific speed and turning rate were quantified by filming their foraging behavior in nature; we also measured the ratio of leg length to body length of their foragers. Food discovery ability was determined by observing which species found baits first when they were present in the immediate environment. Our results show that foraging patterns are species specific, suggesting that search behavior is an important component of niche separation in ant communities. We also suggest that ant species maximize discovery success at the community level using both behavioral and morphological mechanisms. Good discoverers moved in straighter lines, thereby possibly increasing their chances of finding food, and had longer legs relative to their body size, increasing their efficiency of movement. Copyright 2011, Oxford University Press.