Bat echolocation calls: adaptation and convergent evolution. Proc R Soc Lond B Biol Sci

School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 05/2007; 274(1612):905-12. DOI: 10.1098/rspb.2006.0200
Source: PubMed


Bat echolocation calls provide remarkable examples of 'good design' through evolution by natural selection. Theory developed from acoustics and sonar engineering permits a strong predictive basis for understanding echolocation performance. Call features, such as frequency, bandwidth, duration and pulse interval are all related to ecological niche. Recent technological breakthroughs have aided our understanding of adaptive aspects of call design in free-living bats. Stereo videogrammetry, laser scanning of habitat features and acoustic flight path tracking permit reconstruction of the flight paths of echolocating bats relative to obstacles and prey in nature. These methods show that echolocation calls are among the most intense airborne vocalizations produced by animals. Acoustic tracking has clarified how and why bats vary call structure in relation to flight speed. Bats using broadband echolocation calls adjust call design in a range-dependent manner so that nearby obstacles are localized accurately. Recent phylogenetic analyses based on gene sequences show that particular types of echolocation signals have evolved independently in several lineages of bats. Call design is often influenced more by perceptual challenges imposed by the environment than by phylogeny, and provides excellent examples of convergent evolution. Now that whole genome sequences of bats are imminent, understanding the functional genomics of echolocation will become a major challenge.

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    • "The risk of collision and the difficulty of achieving aerial maneuvers reduce flight efficiency in cluttered areas (Norberg and Rayner 1987; Schnitzler and Kalko 2001). Furthermore, dense vegetation may interfere with the detection of potential prey (Kusch et al. 2004; Jones and Holderied 2007; Rainho et al. 2010). Structural complexity of vegetation may influence bat foraging as they may avoid navigating in cluttered sites (Sleep and Brigham 2003; Ober and Hayes 2008; Jung et al. 2012). "
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    ABSTRACT: Riparian areas often are assumed to be necessary sites for foraging by insectivorous bats because of high insect availability and ease of movement and echolocation in the forest. However, effects of vegetation clutter and insect availability on bat activity have not been compared between riparian and nonriparian areas. We used autonomous recorders to evaluate the effects of vegetation structure, insect mass, and assemblage composition on the activity of the aerial insectivorous bat Pteronotus parnellii along stream channels and nonriparian areas in a tropical rainforest in central Brazilian Amazonia. We quantified vegetation clutter using horizontal photographs, captured nocturnal insects with light traps, and recorded bat activity for 110 nights (1,320 h) in 22 sampling plots. Pteronotus parnellii was more active in sites with dense understory vegetation, which were more common away from riparian zones. Bat activity was related to insect availability (mass and composition), independent of the habitat type. Ability to detect insects on vegetation and avoid obstacles should not restrict the activity of P. parnellii in cluttered sites. This suggests that mass and species composition of insects had stronger influences on habitat use than did vegetation clutter. Pteronotus parnellii probably selects cluttered places as feeding sites due to the availability of higher quality prey.
    Full-text · Article · Jul 2015 · Journal of Mammalogy
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    • "Although research across many disciplines (e.g. [12], [49]) has greatly advanced our understanding of the echolocation system of bats it is still not proven that the high-frequency echolocation calls of R. mehelyi are truly deviating from their ecologically optimal peak frequency. Our current findings suggest that this could indeed be the case and will stimulate future studies to fully investigate this hypothesis. "
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    ABSTRACT: Animals employ an array of signals (i.e. visual, acoustic, olfactory) for communication. Natural selection favours signals, receptors, and signalling behaviour that optimise the received signal relative to background noise. When the signal is used for more than one function, antagonisms amongst the different signalling functions may constrain the optimisation of the signal for any one function. Sexual selection through mate choice can strongly modify the effects of natural selection on signalling systems ultimately causing maladaptive signals to evolve. Echolocating bats represent a fascinating group in which to study the evolution of signalling systems as unlike bird songs or frog calls, echolocation has a dual role in foraging and communication. The function of bat echolocation is to generate echoes that the calling bat uses for orientation and food detection with call characteristics being directly related to the exploitation of particular ecological niches. Therefore, it is commonly assumed that echolocation has been shaped by ecology via natural selection. Here we demonstrate for the first time using a novel combined behavioural, ecological and genetic approach that in a bat species, Rhinolophus mehelyi : (1) echolocation peak frequency is an honest signal of body size; (2) females preferentially select males with high frequency calls during the mating season; (3) high frequency males sire more off-spring, providing evidence that echolocation calls may play a role in female mate choice. Our data refute the sole role of ecology in the evolution of echolocation and highlight the antagonistic interplay between natural and sexual selection in shaping acoustic signals.
    Full-text · Article · Jul 2014 · PLoS ONE
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    • "In contrast to territorial and mating calls of birds and anurans that have undergone selection to communicate the species of the caller, echolocation calls of bats have been selected primarily to enable foraging in darkness. Accordingly, bat species occupying similar foraging niches often produce similar calls (Siemers, Kalko & Schnitzler 2001; Jones & Holderied 2007). Furthermore, in contrast to the stereotypical calls of many bird and anuran species, bats exhibit considerable plasticity in their echolocation and adjust their calls to suit their navigational task (Kalko & Schnitzler 1993; Berger-Tal et al. 2008). "
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    ABSTRACT: 1. Acoustic surveys have become a common survey method for bats and other vocal taxa. Previous work shows that bat echolocation may be misidentified, but common analytic meth-ods, such as occupancy models, assume that misidentifications do not occur. Unless rare, such misidentifications could lead to incorrect inferences with significant management implications. 2. We fit a false-positive occupancy model to data from paired bat detector and mist-net sur-veys to estimate probability of presence when survey data may include false positives. We compared estimated occupancy and detection rates to those obtained from a standard occu-pancy model. We also derived a formula to estimate the probability that bats were present at a site given its detection history. As an example, we analysed survey data for little brown bats Myotis lucifugus from 135 sites in Washington and Oregon, USA. 3. We estimated that at an unoccupied site, acoustic surveys had a 14% chance per night of producing spurious M. lucifugus detections. Estimated detection rates were higher and occu-pancy rates were lower under the false-positive model, relative to a standard occupancy model. Un-modelled false positives also affected inferences about occupancy at individual sites. For example, probability of occupancy at individual sites with acoustic detections but no captures ranged from 2% to 100% under the false-positive occupancy model, but was always 100% under a standard occupancy model. 4. Synthesis and applications. Our results suggest that false positives sufficient to affect infer-ences may be common in acoustic surveys for bats. We demonstrate an approach that can estimate occupancy, regardless of the false-positive rate, when acoustic surveys are paired with capture surveys. Applications of this approach include monitoring the spread of White-Nose Syndrome, estimating the impact of climate change and informing conservation listing decisions. We calculate a site-specific probability of occupancy, conditional on survey results, which could inform local permitting decisions, such as for wind energy projects. More gener-ally, the magnitude of false positives suggests that false-positive occupancy models can improve accuracy in research and monitoring of bats and provide wildlife managers with more reliable information.
    Full-text · Article · Jul 2014 · Journal of Applied Ecology
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