The transfer function of a target limits the jitter detection threshold with signals of echolocat... more The transfer function of a target limits the jitter detection threshold with signals of echolocating FM-bats
Echolocating bats hunt prey on the wing under conditions of poor lighting by emission of loud cal... more Echolocating bats hunt prey on the wing under conditions of poor lighting by emission of loud calls and subsequent auditory processing of weak returning echoes. To do so, they need adequate echo-to-noise ratios (ENRs) to detect and distinguish target echoes from masking noise. Early obstacle avoidance experiments report high resilience to masking in free-flying bats, but whether this is due to spectral or spatiotemporal release from masking, advanced auditory signal detection or an increase in call amplitude (Lombard effect) remains unresolved. We hypothesized that bats with no spectral, spatial or temporal release from masking noise, defend a certain ENR via a Lombard effect. We trained four bats (<i>Myotis daubentonii</i>) to approach and land on a target that broadcasted broadband noise at four different levels. An array of seven microphones enabled acoustic localization of the bats and source level estimation of their approach calls. Call duration and peak frequency ...
Echolocating bats listen for weak echoes to navigate and hunt, which makes them prone to masking ... more Echolocating bats listen for weak echoes to navigate and hunt, which makes them prone to masking from background noise and jamming from other bats and prey. Like for electrical fish that display clear spectral jamming avoidance responses (JAR), some studies have reported that bats mitigate the effects of jamming by shifting the spectral contents of their calls, thereby reducing acoustic interference to improve echo-to-noise ratios (ENR). Here we test the hypothesis that FM bats employ a spectral JAR in response to six masking noise-bands ranging from 15-90kHz, by measuring the -3dB endpoints and peak frequency of echolocation calls from five male Daubenton's bats (Myotis daubentonii) during a landing task. The bats were trained to land on a noise generating spherical transducer surrounded by a star-shaped microphone array, allowing for acoustic localization and source parameter quantification of on-axis calls. We show that the bats did not employ spectral JAR as the peak frequen...
dtag audio file for the 12th trial of the afternoon session on 31/10/2012, as well as matlab stru... more dtag audio file for the 12th trial of the afternoon session on 31/10/2012, as well as matlab structures with outputs of click detectors, an echogram and an inter-click interval scatter plot (color-coded with relative apparent output level of the clicks
Track lines of harbour porpoises plotted as distances from loudspeaker (metres) relative to time ... more Track lines of harbour porpoises plotted as distances from loudspeaker (metres) relative to time of exposure (minutes). Vertical red stippled lines indicate period of sound exposure and are therefore absent in the four control trials (trial 1-4). Baseline observations (blue), observations made during sound exposure (red) and observations during recovery (green) of harbour porpoises.
Journal of Experimental Marine Biology and Ecology, 2021
Abstract The rapid increase in the use of unmanned aerial vehicles (UAVs) in wildlife research ha... more Abstract The rapid increase in the use of unmanned aerial vehicles (UAVs) in wildlife research has raised concerns about its potential negative impact on animals. The paucity of studies and the variability of responses of pinnipeds to UAVs prompts the need for species-specific impact assessments. Here we assessed the potential behavioural impact of low altitude UAVs on Weddell seals (Leptonychotes weddellii). This is a preliminary step to envisage the feasibility of replacing and/or complementing traditional ground-based behavioural and morphometric measurements by potentially less invasive UAV aerial images. We flew a small UAV (DJI Mavic 2 zoom fitted with a phocid seal audiogram weighted source level of 84 dB re 20μPa (rms)) over 37 Weddell seals (3 adult males, 12 adult females and 22 mother-pup pairs) during the breeding season at Dumont D'Urville, East Antarctica. For each individual, we assessed the level of reaction during UAV overflights at three altitudes (25, 20 and 15 m) while factoring in pup presence and wind speed. For all altitudes and observations pooled together, Weddell seals predominantly (88%) showed little (vigilant) or no (resting) reactions towards the UAV. Moreover, only 27% of all individuals changed their initial activity during the sampling periods, and mothers rarely ended their nursing bouts (3%). While reactions were low overall, the probability of a stronger reaction occurring increased at lower altitudes, and varied among individuals. Neither the presence of pups nor a change in wind speed appear to influence individuals' response to the UAV significantly. However, on simpler histogram representations of the dataset, we observed the strongest reactions for females (n = 5) with a pup at wind speeds below 5 m.s−1 when ambient noise levels were lowest. While Weddell seals are likely to hear the UAV at 25 to 15 m altitude in low wind speeds, the low-level responses we observed are unlikely to negatively impact their energetic budget and/or reproductive success. Our results suggest a low impact of small UAV overflights of Weddell seals during the breeding season when flying ≥25 m. This allows for collection of high resolution images for behavioural and morphometric studies that can potentially replace more invasive data collection when capturing and handling the animals.
How animals extract information from their surroundings to guide motor patterns is central to the... more How animals extract information from their surroundings to guide motor patterns is central to their survival. Here, we use echo-recording tags to show how wild hunting bats adjust their sensory strategies to their prey and natural environment. When searching, bats maximize the chances of detecting small prey by using large sensory volumes. During prey pursuit, they trade spatial for temporal information by reducing sensory volumes while increasing update rate and redundancy of their sensory scenes. These adjustments lead to very weak prey echoes that bats protect from interference by segregating prey sensory streams from the background using a combination of fast-acting sensory and motor strategies. Counterintuitively, these weak sensory scenes allow bats to be efficient hunters close to background clutter broadening the niches available to hunt for insects.
Philosophical Transactions of the Royal Society B: Biological Sciences
The thermal biology of ectotherms is often used to infer species' responses to changes in tem... more The thermal biology of ectotherms is often used to infer species' responses to changes in temperature. It is often proposed that temperate species are more cold-tolerant, less heat-tolerant, more plastic, have broader thermal performance curves (TPCs) and lower optimal temperatures when compared to tropical species. However, relatively little empirical work has provided support for this using large interspecific studies. In the present study, we measure thermal tolerance limits and thermal performance in 22 species of Drosophila that developed under common conditions. Specifically, we measure thermal tolerance (CT min and CT max ) as well as the fitness components viability, developmental speed and fecundity at seven temperatures to construct TPCs for each of these species. For 10 of the species, we also measure thermal tolerance and thermal performance following developmental acclimation to three additional temperatures. Using these data, we test several fundamental hypotheses ...
The Journal of the Acoustical Society of America, 2018
Sperm whales generate multi-pulsed clicks for echolocation and communication with an inter-pulse ... more Sperm whales generate multi-pulsed clicks for echolocation and communication with an inter-pulse interval (IPI) determined by the size of their hypertrophied sound producing nose. The IPI has therefore been used to estimate body size and distinguish between individuals, and it has been hypothesized that conspecifics may use IPIs to recognize each other. However, the degree to which IPIs vary within individuals has not explicitly been tested, and therefore the inherent precision of this measure and its applicability for size estimation for researchers and sperm whales alike remain unknown. Here, the variability in IPI from both animal-borne Dtags and far-field recordings from echolocating and communicating sperm whales is quantified. Three different automatic methods (envelope, cepstrum, and cross-correlation) are tested and it is found that the envelope approach results in the least dispersion. Furthermore, it is shown that neither growth, depth, nor recording aspect fully explains ...
The high blood-O affinity of the bar-headed goose () is an integral component of the biochemical ... more The high blood-O affinity of the bar-headed goose () is an integral component of the biochemical and physiological adaptations that allow this hypoxia-tolerant species to undertake migratory flights over the Himalayas. The high blood-O affinity of this species was originally attributed to a single amino acid substitution of the major hemoglobin (Hb) isoform, HbA, which was thought to destabilize the low-affinity T state, thereby shifting the T-R allosteric equilibrium towards the high-affinity R state. Surprisingly, this mechanistic hypothesis has never been addressed using native proteins purified from blood. Here, we report a detailed analysis of O equilibria and kinetics of native major HbA and minor HbD isoforms from bar-headed goose and greylag goose (), a strictly lowland species, to identify and characterize the mechanistic basis for the adaptive change in Hb function. We find that HbA and HbD of bar-headed goose have consistently higher O affinities than those of the greylag...
The Journal of the Acoustical Society of America, 2018
The Australian snubfin dolphin (Orcaella heinsohni) is endemic to Australian waters, yet little i... more The Australian snubfin dolphin (Orcaella heinsohni) is endemic to Australian waters, yet little is known about its abundance and habitat use. To investigate the feasibility of Passive Acoustic Monitoring for snubfin dolphins, biosonar clicks were recorded in Cygnet Bay, Australia, using a four-element hydrophone array. Clicks had a mean source level of 200 ± 5 dB re 1 μPa pp, transmission directivity index of 24 dB, mean centroid frequency of 98 ± 9 kHz, and a root-mean-square bandwidth of 31 ± 3 kHz. Such properties lend themselves to passive acoustic monitoring, but are comparable to similarly-sized delphinids, thus requiring additional cues to discriminate between snubfins and sympatric species.
Acoustic harassment devices (AHD) or 'seal scarers' are used extensively, not only to det... more Acoustic harassment devices (AHD) or 'seal scarers' are used extensively, not only to deter seals from fisheries, but also as mitigation tools to deter marine mammals from potentially harmful sound sources, such as offshore pile driving. To test the effectiveness of AHDs, we conducted two studies with similar experimental set-ups on two key species: harbour porpoises and harbour seals. We exposed animals to 500 ms tone bursts at 12 kHz simulating that of an AHD (Lofitech), but with reduced output levels (source peak-to-peak level of 165 dB re 1 µPa). Animals were localized with a theodolite before, during and after sound exposures. In total, 12 sound exposures were conducted to porpoises and 13 exposures to seals. Porpoises were found to exhibit avoidance reactions out to ranges of 525 m from the sound source. Contrary to this, seal observations increased during sound exposure within 100 m of the loudspeaker. We thereby demonstrate that porpoises and seals respond very diffe...
To improve conservation strategies for threatened sea turtles more knowledge on their ecology, be... more To improve conservation strategies for threatened sea turtles more knowledge on their ecology, behavior, and how they cope with severe and changing weather conditions is needed. Satellite and animal motion datalogging tags were used to study the inter-nesting behavior of two female loggerhead turtles in the Gulf of Mexico, which regularly has hurricanes and tropical storms during nesting season. We contrast the behavioral patterns and swimming energetics of two turtles, the first tracked in calm weather and a second tracked before, during, and after a tropical storm. Turtle #1 was highly active and swam at the surface or submerged 95% of the time during the entire inter-nesting period with high estimated specific oxygen consumption rate (0.95 ml min(-1) kg(-0.83)). Turtle #2 was inactive for most of the first nine days of the inter-nesting period where she rested at the bottom (80% of the time) with low estimated oxygen consumption (0.62 ml min(-1) kg(-0.83)). Midway through the int...
The transfer function of a target limits the jitter detection threshold with signals of echolocat... more The transfer function of a target limits the jitter detection threshold with signals of echolocating FM-bats
Echolocating bats hunt prey on the wing under conditions of poor lighting by emission of loud cal... more Echolocating bats hunt prey on the wing under conditions of poor lighting by emission of loud calls and subsequent auditory processing of weak returning echoes. To do so, they need adequate echo-to-noise ratios (ENRs) to detect and distinguish target echoes from masking noise. Early obstacle avoidance experiments report high resilience to masking in free-flying bats, but whether this is due to spectral or spatiotemporal release from masking, advanced auditory signal detection or an increase in call amplitude (Lombard effect) remains unresolved. We hypothesized that bats with no spectral, spatial or temporal release from masking noise, defend a certain ENR via a Lombard effect. We trained four bats (<i>Myotis daubentonii</i>) to approach and land on a target that broadcasted broadband noise at four different levels. An array of seven microphones enabled acoustic localization of the bats and source level estimation of their approach calls. Call duration and peak frequency ...
Echolocating bats listen for weak echoes to navigate and hunt, which makes them prone to masking ... more Echolocating bats listen for weak echoes to navigate and hunt, which makes them prone to masking from background noise and jamming from other bats and prey. Like for electrical fish that display clear spectral jamming avoidance responses (JAR), some studies have reported that bats mitigate the effects of jamming by shifting the spectral contents of their calls, thereby reducing acoustic interference to improve echo-to-noise ratios (ENR). Here we test the hypothesis that FM bats employ a spectral JAR in response to six masking noise-bands ranging from 15-90kHz, by measuring the -3dB endpoints and peak frequency of echolocation calls from five male Daubenton's bats (Myotis daubentonii) during a landing task. The bats were trained to land on a noise generating spherical transducer surrounded by a star-shaped microphone array, allowing for acoustic localization and source parameter quantification of on-axis calls. We show that the bats did not employ spectral JAR as the peak frequen...
dtag audio file for the 12th trial of the afternoon session on 31/10/2012, as well as matlab stru... more dtag audio file for the 12th trial of the afternoon session on 31/10/2012, as well as matlab structures with outputs of click detectors, an echogram and an inter-click interval scatter plot (color-coded with relative apparent output level of the clicks
Track lines of harbour porpoises plotted as distances from loudspeaker (metres) relative to time ... more Track lines of harbour porpoises plotted as distances from loudspeaker (metres) relative to time of exposure (minutes). Vertical red stippled lines indicate period of sound exposure and are therefore absent in the four control trials (trial 1-4). Baseline observations (blue), observations made during sound exposure (red) and observations during recovery (green) of harbour porpoises.
Journal of Experimental Marine Biology and Ecology, 2021
Abstract The rapid increase in the use of unmanned aerial vehicles (UAVs) in wildlife research ha... more Abstract The rapid increase in the use of unmanned aerial vehicles (UAVs) in wildlife research has raised concerns about its potential negative impact on animals. The paucity of studies and the variability of responses of pinnipeds to UAVs prompts the need for species-specific impact assessments. Here we assessed the potential behavioural impact of low altitude UAVs on Weddell seals (Leptonychotes weddellii). This is a preliminary step to envisage the feasibility of replacing and/or complementing traditional ground-based behavioural and morphometric measurements by potentially less invasive UAV aerial images. We flew a small UAV (DJI Mavic 2 zoom fitted with a phocid seal audiogram weighted source level of 84 dB re 20μPa (rms)) over 37 Weddell seals (3 adult males, 12 adult females and 22 mother-pup pairs) during the breeding season at Dumont D'Urville, East Antarctica. For each individual, we assessed the level of reaction during UAV overflights at three altitudes (25, 20 and 15 m) while factoring in pup presence and wind speed. For all altitudes and observations pooled together, Weddell seals predominantly (88%) showed little (vigilant) or no (resting) reactions towards the UAV. Moreover, only 27% of all individuals changed their initial activity during the sampling periods, and mothers rarely ended their nursing bouts (3%). While reactions were low overall, the probability of a stronger reaction occurring increased at lower altitudes, and varied among individuals. Neither the presence of pups nor a change in wind speed appear to influence individuals' response to the UAV significantly. However, on simpler histogram representations of the dataset, we observed the strongest reactions for females (n = 5) with a pup at wind speeds below 5 m.s−1 when ambient noise levels were lowest. While Weddell seals are likely to hear the UAV at 25 to 15 m altitude in low wind speeds, the low-level responses we observed are unlikely to negatively impact their energetic budget and/or reproductive success. Our results suggest a low impact of small UAV overflights of Weddell seals during the breeding season when flying ≥25 m. This allows for collection of high resolution images for behavioural and morphometric studies that can potentially replace more invasive data collection when capturing and handling the animals.
How animals extract information from their surroundings to guide motor patterns is central to the... more How animals extract information from their surroundings to guide motor patterns is central to their survival. Here, we use echo-recording tags to show how wild hunting bats adjust their sensory strategies to their prey and natural environment. When searching, bats maximize the chances of detecting small prey by using large sensory volumes. During prey pursuit, they trade spatial for temporal information by reducing sensory volumes while increasing update rate and redundancy of their sensory scenes. These adjustments lead to very weak prey echoes that bats protect from interference by segregating prey sensory streams from the background using a combination of fast-acting sensory and motor strategies. Counterintuitively, these weak sensory scenes allow bats to be efficient hunters close to background clutter broadening the niches available to hunt for insects.
Philosophical Transactions of the Royal Society B: Biological Sciences
The thermal biology of ectotherms is often used to infer species' responses to changes in tem... more The thermal biology of ectotherms is often used to infer species' responses to changes in temperature. It is often proposed that temperate species are more cold-tolerant, less heat-tolerant, more plastic, have broader thermal performance curves (TPCs) and lower optimal temperatures when compared to tropical species. However, relatively little empirical work has provided support for this using large interspecific studies. In the present study, we measure thermal tolerance limits and thermal performance in 22 species of Drosophila that developed under common conditions. Specifically, we measure thermal tolerance (CT min and CT max ) as well as the fitness components viability, developmental speed and fecundity at seven temperatures to construct TPCs for each of these species. For 10 of the species, we also measure thermal tolerance and thermal performance following developmental acclimation to three additional temperatures. Using these data, we test several fundamental hypotheses ...
The Journal of the Acoustical Society of America, 2018
Sperm whales generate multi-pulsed clicks for echolocation and communication with an inter-pulse ... more Sperm whales generate multi-pulsed clicks for echolocation and communication with an inter-pulse interval (IPI) determined by the size of their hypertrophied sound producing nose. The IPI has therefore been used to estimate body size and distinguish between individuals, and it has been hypothesized that conspecifics may use IPIs to recognize each other. However, the degree to which IPIs vary within individuals has not explicitly been tested, and therefore the inherent precision of this measure and its applicability for size estimation for researchers and sperm whales alike remain unknown. Here, the variability in IPI from both animal-borne Dtags and far-field recordings from echolocating and communicating sperm whales is quantified. Three different automatic methods (envelope, cepstrum, and cross-correlation) are tested and it is found that the envelope approach results in the least dispersion. Furthermore, it is shown that neither growth, depth, nor recording aspect fully explains ...
The high blood-O affinity of the bar-headed goose () is an integral component of the biochemical ... more The high blood-O affinity of the bar-headed goose () is an integral component of the biochemical and physiological adaptations that allow this hypoxia-tolerant species to undertake migratory flights over the Himalayas. The high blood-O affinity of this species was originally attributed to a single amino acid substitution of the major hemoglobin (Hb) isoform, HbA, which was thought to destabilize the low-affinity T state, thereby shifting the T-R allosteric equilibrium towards the high-affinity R state. Surprisingly, this mechanistic hypothesis has never been addressed using native proteins purified from blood. Here, we report a detailed analysis of O equilibria and kinetics of native major HbA and minor HbD isoforms from bar-headed goose and greylag goose (), a strictly lowland species, to identify and characterize the mechanistic basis for the adaptive change in Hb function. We find that HbA and HbD of bar-headed goose have consistently higher O affinities than those of the greylag...
The Journal of the Acoustical Society of America, 2018
The Australian snubfin dolphin (Orcaella heinsohni) is endemic to Australian waters, yet little i... more The Australian snubfin dolphin (Orcaella heinsohni) is endemic to Australian waters, yet little is known about its abundance and habitat use. To investigate the feasibility of Passive Acoustic Monitoring for snubfin dolphins, biosonar clicks were recorded in Cygnet Bay, Australia, using a four-element hydrophone array. Clicks had a mean source level of 200 ± 5 dB re 1 μPa pp, transmission directivity index of 24 dB, mean centroid frequency of 98 ± 9 kHz, and a root-mean-square bandwidth of 31 ± 3 kHz. Such properties lend themselves to passive acoustic monitoring, but are comparable to similarly-sized delphinids, thus requiring additional cues to discriminate between snubfins and sympatric species.
Acoustic harassment devices (AHD) or 'seal scarers' are used extensively, not only to det... more Acoustic harassment devices (AHD) or 'seal scarers' are used extensively, not only to deter seals from fisheries, but also as mitigation tools to deter marine mammals from potentially harmful sound sources, such as offshore pile driving. To test the effectiveness of AHDs, we conducted two studies with similar experimental set-ups on two key species: harbour porpoises and harbour seals. We exposed animals to 500 ms tone bursts at 12 kHz simulating that of an AHD (Lofitech), but with reduced output levels (source peak-to-peak level of 165 dB re 1 µPa). Animals were localized with a theodolite before, during and after sound exposures. In total, 12 sound exposures were conducted to porpoises and 13 exposures to seals. Porpoises were found to exhibit avoidance reactions out to ranges of 525 m from the sound source. Contrary to this, seal observations increased during sound exposure within 100 m of the loudspeaker. We thereby demonstrate that porpoises and seals respond very diffe...
To improve conservation strategies for threatened sea turtles more knowledge on their ecology, be... more To improve conservation strategies for threatened sea turtles more knowledge on their ecology, behavior, and how they cope with severe and changing weather conditions is needed. Satellite and animal motion datalogging tags were used to study the inter-nesting behavior of two female loggerhead turtles in the Gulf of Mexico, which regularly has hurricanes and tropical storms during nesting season. We contrast the behavioral patterns and swimming energetics of two turtles, the first tracked in calm weather and a second tracked before, during, and after a tropical storm. Turtle #1 was highly active and swam at the surface or submerged 95% of the time during the entire inter-nesting period with high estimated specific oxygen consumption rate (0.95 ml min(-1) kg(-0.83)). Turtle #2 was inactive for most of the first nine days of the inter-nesting period where she rested at the bottom (80% of the time) with low estimated oxygen consumption (0.62 ml min(-1) kg(-0.83)). Midway through the int...
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Papers by Kristian Beedholm