Annemarie Surlykke

Bio: Annemarie Surlykke is an academic researcher from University of Southern Denmark. The author has contributed to research in topics: Human echolocation & Courtship. The author has an hindex of 43, co-authored 97 publications receiving 5058 citations. Previous affiliations of Annemarie Surlykke include University of Copenhagen & Odense University.

Echolocation behavior of big brown bats, Eptesicus fuscus, in the field and the laboratory.

Abstract: Echolocation signals were recorded from big brown bats, Eptesicus fuscus, flying in the field and the laboratory. In open field areas the interpulse intervals (IPI) of search signals were either around 134 ms or twice that value, 270 ms. At long IPI's the signals were of long duration (14 to 18-20 ms), narrow bandwidth, and low frequency, sweeping down to a minimum frequency (Fmin) of 22-25 kHz. At short IPI's the signals were shorter (6-13 ms), of higher frequency, and broader bandwidth. In wooded areas only short (6-11 ms) relatively broadband search signals were emitted at a higher rate (avg. IPI= 122 ms) with higher Fmin (27-30 kHz). In the laboratory the IPI was even shorter (88 ms), the duration was 3-5 ms, and the Fmin 30- 35 kHz, resembling approach phase signals of field recordings. Excluding terminal phase signals, all signals from all areas showed a negative correlation between signal duration and Fmin, i.e., the shorter the signal, the higher was Fmin. This correlation was reversed in the terminal phase of insect capture sequences, where Fmin decreased with decreasing signal duration. Overall, the signals recorded in the field were longer, with longer IPI's and greater variability in bandwidth than signals recorded in the laboratory.

How Some Insects Detect and Avoid Being Eaten by Bats: Tactics and Countertactics of Prey and Predator

Abstract: S insects have evolved audition and evasive behaviors in response to selective pressure from bats, and other insects were preadapted to detecting ultrasonic signals. Some bats have evolved in turn, improving the range or resolution of sonar signals and serendipitously making them less detectable by insects. In other words, there is a kind of evolutionary escalation going on between bats and insects. Our aim with this review is to present the complex interactions between echolocating bats and insects with bat-detecting ears and show how these interactions may be advantageous for predator or prey. To document our examples, we cite mostly newer studies and reviews in which the reader can find references to original works. Insects occupied all terrestrial habitats at least 300 million years ago, long before bats appeared in the Eocene, about 50 million years ago. Ears have appeared independently 19 times in the class Insecta. In the period before bats, ears and complex acoustical behaviors appeared independently in at least seven orders of insects (Hoy et al. 1989, Robert et al. 1992, Yager 1999). Antibat tactics, which must have appeared in insects since the Eocene, are now known in members of four orders: Lepidoptera (moths and nocturnal butterflies), Orthoptera (crickets), Dictyoptera (praying mantids), and Neuroptera (green lacewings), and possibly also in the Diptera (flies) and Coleoptera (beetles). Insect tympanal organs, or ears, consist basically of an external, thin membrane (the tympanum) and associated internal air sacs, or tracheae. The auditory (sensory) cells attach to the tympanum or to an internal membrane (Yager 1999). Tympanal organs of most modern tympanate insects respond to a wide band of frequencies extending well into the ultrasonic range (above 20 kHz),as was probably true for preEocene tympanate insects as well. Tympanate insects are physically small animals that can produce high-frequency sounds more efficiently; hence, high frequencies are used by many insects for acoustical communication between conspecifics. Consequently, many sonorous insects were preadapted to the evolution of bats (Hoy 1992). According to one possible scenario, a vast larder of nocturnal, flying insects awaited exploitation, and a flying mammal, the microchiropteran bat, was one successful exploiter. Echolocation, or biosonar, was a prerequisite for success in darkness, and even the first nocturnal bats probably used it (see Hoy 1992). Most of the nearly 700 microchiropteran bat species eat insects that they detect using biosonar (Schnitzler and Kalko 2001). However, bat biosonar has two major disadvantages: attenuation and forewarning. The frequencies used by echolocating bats range generally from 20 kHz to 100 kHz, with some outliers using frequen-

Sperm whale clicks: Directionality and source level revisited

Abstract: In sperm whales (Physeter catodon L. 1758) the nose is vastly hypertrophied, accounting for about one-third of the length or weight of an adult male. Norris and Harvey [in Animal Orientation and Navigation, NASA SP-262 (1972), pp. 397–417] ascribed a sound-generating function to this organ complex. A sound generator weighing upward of 10 tons and with a cross-section of 1 m is expected to generate high-intensity, directional sounds. This prediction from the Norris and Harvey theory is not supported by published data for sperm whale clicks (source levels of 180 dB re 1 μPa and little, if any, directionality). Either the theory is not borne out or the data is not representative for the capabilities of the sound-generating mechanism. To increase the amount of relevant data, a five-hydrophone array, suspended from three platforms separated by 1 km and linked by radio, was deployed at the slope of the continental shelf off Andenes, Norway, in the summers of 1997 and 1998. With this system, source levels up to 223 dB re 1 μPa peRMS were recorded. Also, source level differences of 35 dB for the same click at different directions were seen, which are interpreted as evidence for high directionality. This implicates sonar as a possible function of the clicks. Thus, previously published properties of sperm whale clicks underestimate the capabilities of the sound generator and therefore cannot falsify the Norris and Harvey theory.

Echolocating Bats Cry Out Loud to Detect Their Prey

Abstract: Echolocating bats have successfully exploited a broad range of habitats and prey. Much research has demonstrated how time-frequency structure of echolocation calls of different species is adapted to acoustic constraints of habitats and foraging behaviors. However, the intensity of bat calls has been largely neglected although intensity is a key factor determining echolocation range and interactions with other bats and prey. Differences in detection range, in turn, are thought to constitute a mechanism promoting resource partitioning among bats, which might be particularly important for the species-rich bat assemblages in the tropics. Here we present data on emitted intensities for 11 species from 5 families of insectivorous bats from Panama hunting in open or background cluttered space or over water. We recorded all bats in their natural habitat in the field using a multi-microphone array coupled with photographic methods to assess the bats' position in space to estimate emitted call intensities. All species emitted intense search signals. Output intensity was reduced when closing in on background by 4–7 dB per halving of distance. Source levels of open space and edge space foragers (Emballonuridae, Mormoopidae, Molossidae, and Vespertilionidae) ranged between 122–134 dB SPL. The two Noctilionidae species hunting over water emitted the loudest signals recorded so far for any bat with average source levels of ca. 137 dB SPL and maximum levels above 140 dB SPL. In spite of this ten-fold variation in emitted intensity, estimates indicated, surprisingly, that detection distances for prey varied far less; bats emitting the highest intensities also emitted the highest frequencies, which are severely attenuated in air. Thus, our results suggest that bats within a local assemblage compensate for frequency dependent attenuation by adjusting the emitted intensity to achieve comparable detection distances for prey across species. We conclude that for bats with similar hunting habits, prey detection range represents a unifying constraint on the emitted intensity largely independent of call shape, body size, and close phylogenetic relationships.

Auditory scene analysis by echolocation in bats

Abstract: Echolocating bats transmit ultrasonic vocalizations and use information contained in the reflected sounds to analyze the auditory scene. Auditory scene analysis, a phenomenon that applies broadly to all hearing vertebrates, involves the grouping and segregation of sounds to perceptually organize information about auditory objects. The perceptual organization of sound is influenced by the spectral and temporal characteristics of acoustic signals. In the case of the echolocating bat, its active control over the timing, duration, intensity, and bandwidth of sonar transmissions directly impacts its perception of the auditory objects that comprise the scene. Here, data are presented from perceptual experiments, laboratory insect capture studies, and field recordings of sonar behavior of different bat species, to illustrate principles of importance to auditory scene analysis by echolocation in bats. In the perceptual experiments, FM bats (Eptesicus fuscus) learned to discriminate between systematic and random d...

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The Analysis of Time Series: An Introduction

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Auditory Scene Analysis

Abstract: Auditory scene analysis (ASA) is defined and the problem of partitioning the time-varying spectrum resulting from mixtures of individual acoustic signals is described Some basic facts about ASA are presented These include causes and effects of auditory organization (sequential, simultaneous, and the old-plus-new heuristic) Processes employing different cues collaborate and compete in determining the final organization of the mixture These processes take advantage of regularities in the mixture that give clues about how to parse it There are general regularities that apply to most types of sound, as well as regularities in particular types of sound The general ones are hypothesized to be used by innate processes, and the ones specific to restricted environments to be used by learned processes in humans and possibly by innate ones in animals The use of brain recordings and the study of nonhuman animals is discussed

The Senses Considered As Perceptual Systems

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From spatial orientation to food acquisition in echolocating bats

Abstract: Field research on echolocation behavior in bats has emphasized studies of food acquisition, and the adaptive value of sonar signal design as been considered largely in the context of foraging. However, echolocation tasks related to spatial orientation also differ among bats and are relevant to understanding signal structure. Here, we argue that the evolution of echolocation in bats is characterized by two key innovations: first, the evolution of echolocation for spatial orientation and, second, a later transition for prey acquisition. This conceptual framework calls for a new view on field data from bats orienting and foraging in different types of habitats. According to the ecological constraints in which foraging bats operate, four distinct functional groups or guilds can be defined. Within each group, signal design and echolocation behavior are rather similar.