Article

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: 5.29). 05/2007; 274(1612):905-12. DOI: 10.1098/rspb.2006.0200
Source: PubMed

ABSTRACT 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. Áreas ripárias são muitas vezes consideradas locais necessários para o forrageio por morcegos insetívoros por causa da alta disponibilidade de insetos e facilidade de movimento e recepção da ecolocalização na floresta. No entanto, os efeitos da obstrução da vegetação e disponibilidade de insetos sobre a atividade de morcegos não têm sido comparados entre as áreas ripárias e não ripárias. Nós usamos gravadores autônomos de ultrassom para avaliar os efeitos da estrutura da vegetação, massa e composição da assembleia de insetos sobre a atividade do morcego insetívoro aéreo Pteronotus parnellii ao longo do canal central de riachos e áreas não ripárias em uma floresta tropical na Amazônia central brasileira. Nós quantificamos a obstrução da vegetação usando fotografias horizontais da floresta, capturamos os insetos noturnos com armadilhas luminosas e gravamos a atividade dos morcegos durante 110 noites (1.320 h) em 22 pontos de amostragem. Pteronotus parnellii foi mais ativo em locais com vegetação arbustiva densa, que foram mais comuns longe das zonas ripárias. A atividade dos morcegos foi relacionada com a disponibilidade de insetos (massa e composição), independente do tipo de habitat. A capacidade de detectar insetos sobre a vegetação e evitar obstáculos não deve restringir a atividade de P. parnellii em locais obstruídos. Isto sugere que a massa e a composição de espécies de insetos tiveram forte influência sobre o uso do habitat do que a obstrução da vegetação. Pteronotus parnellii provavelmente seleciona lugares obstruídos como locais de alimentação devido à disponibilidade de presas de maior qualidade.
    Journal of Mammalogy 07/2015; DOI:10.1093/jmammal/gyv108 · 2.23 Impact Factor
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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.
    Journal of Applied Ecology 07/2014; DOI:10.1111/1365-2664.12303 · 4.75 Impact Factor
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    • "Convergent evolution of social behavior in particular, where similar behavior has evolved due to similar selective pressures and not phylogenetic relatedness, can provide replication of behavior so that mechanisms of behavioral variation can be tested. Although convergent evolution is traditionally studied in terms of morphological traits (McGhee, 2011; Rosenblum, 2006; Taylor and McPhail, 2000), there are numerous examples of behavioral convergence , including maternal care strategies in mammals (Fisher et al., 2002), web making in Hawaiian spiders (Blackledge and Gillespie, 2004), echolocation call structure in bats (Jones and Holderied, 2007), and display behavior in Caribbean Anolis lizards (Johnson et al., 2010; Ord et al., 2013). Although studying convergent evolution of a trait as potentially complex and dynamic as 'behavior' is challenging, the replication of such an integrated trait in fact makes it ideal for tests of how proximate mechanisms that regulate behavior evolve. "
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    ABSTRACT: Variation in aggression among species can be due to a number of proximate and ultimate factors, leading to patterns of divergent and convergent evolution of behavior among even closely related species. Caribbean Anolis lizards are well known for their convergence in microhabitat use and morphology, but they also display marked convergence in social behavior and patterns of aggression. We studied 18 Anolis species across six ecomorphs on four different Caribbean islands to test four main hypotheses. We hypothesized that species differences in aggression would be due to species differences in circulating testosterone (T), a steroid hormone implicated in numerous studies across vertebrate taxa as a primary determinant of social behavior; more aggressive species were expected to have higher baseline concentrations of T and corticosterone. We further hypothesized that low-T species would increase T and corticosterone levels during a social challenge. Within three of the four island assemblages studied we found differences in T levels among species within an island that differ in aggression, but in the opposite pattern than predicted: more aggressive species had lower baseline T than the least aggressive species. The fourth island, Puerto Rico, showed the pattern of baseline T levels among species we predicted. There were no patterns of corticosterone levels among species or ecomorphs. One of the two species tested increased T in response to a social challenge, but neither species elevated corticosterone. Our results suggest that it is possible for similarities in aggression among closely related species to evolve via different proximate mechanisms.
    Hormones and Behavior 04/2014; 65(4). DOI:10.1016/j.yhbeh.2014.03.006 · 4.51 Impact Factor
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