Sound production mechanisms have been studied in two delphinid species - the harbour porpoise, Ph... more Sound production mechanisms have been studied in two delphinid species - the harbour porpoise, Phocoena phocoena (L.), and the bottlenosed dolphin, Tursiops truncatus (Montagu). It was found that, in both species, the click sound production was coupled to a considerable pressure increase in the bony nares. The maximum pressure recorded in Phocoena was approximately 54kPa and in Tursiops close to 81 kPa; it was equal in time and amplitude in both nares. The nasal plug muscle was found to be active up to 450 ms prior to and during sound production. Sound production without such activity was not seen. The results suggest that an identical mechanism underlies click production in both species, with, pressurized air being the driving force and the nasal plug muscle having some active regulating function. Probes were inserted into the bony nares of three harbour porpoises, Phocoena phocoena, and one bottlenosed dolphin, Tursiops truncatus, in order to record air pressure variations togethe...
Journal of the Acoustical Society of America, May 1, 2007
The hearing of the bottlenosed dolphins at Kolmrdens Djurpark, Sweden, was examined using a porta... more The hearing of the bottlenosed dolphins at Kolmrdens Djurpark, Sweden, was examined using a portable auditory evoked potential (AEP) system in order to examine the hearing capabilities of dolphins housed in quiet environments with an emphasis on age-related hearing variation. Audiograms were measured on two dolphins and modulation rate transfer functions (MRTF) were also measured on two animals. A complete audiogram (4–200 kHz) was obtained for the oldest dolphin, a 34 year old female named Vicky. Her audiogram showed no evidence of high-frequency hearing loss. Notwithstanding this finding, her click evoked auditory brainstem response (ABR) revealed a marked increase in interpeak latency that could be indicative of an underlying hearing defect. The audiogram obtained from for the male dolphin, a 24 year old named Pichi (measured from 4–107 kHz), demonstrated profound hearing loss at all frequencies. The measured MRTF results indicated typical odontocete following responses to rates exceeding 1000 Hz.
Sound production mechanisms have been studied in two delphinid species-the harbour porpoise, Phoc... more Sound production mechanisms have been studied in two delphinid species-the harbour porpoise, Phocoena phocoena (L.), and the bottlenosed dolphin, Tursiops truncatus (Montagu). It was found that, in both species, the click sound production was coupled to a considerable pressure increase in the bony nares. The maximum pressure recorded in Phocoena was approximately 54kPa and in Tursiops close to 81 kPa; it was equal in time and amplitude in both nares. The nasal plug muscle was found to be active up to 450 ms prior to and during sound production. Sound production without such activity was not seen. The results suggest that an identical mechanism underlies click production in both species, with pressurized air being the driving force and the nasal plug muscle having some active regulating function. Probes were inserted into the bony nares of three harbour porpoises, Phocoena phocoena, and one bottlenosed dolphin, Tursiops truncatus, in order to record air pressure variations together with sound production. Sounds were picked up by a hydrophone manually held to the forehead of the animals. In several of the Phocoena recordings, electromyographic activity in the nasal plug muscle was also recorded.
The present study demonstrates that Asian elephants, Elephas maximus, can successfully be trained... more The present study demonstrates that Asian elephants, Elephas maximus, can successfully be trained to cooperate in an olfactory discrimination test based on a food-rewarded two-alternative instrumental conditioning procedure. The animals learned the basic principle of the test within only 60 trials and readily mastered intramodal stimulus transfer tasks. Further, they were capable of distinguishing between structurally related odor stimuli and remembered the reward value of previously learned odor stimuli after 2, 4, 8, and 16 weeks of recess without any signs of forgetting. The precision and consistency of the elephants' performance in tests of odor discrimination ability and long-term odor memory demonstrate the suitability of this method for assessing olfactory function in this proboscid species. An across-species comparison of several measures of olfactory learning capabilities such as speed of initial task acquisition and ability to master intramodal stimulus transfer tasks shows that Asian elephants are at least as good in their performance as mice, rats, and dogs, and clearly superior to nonhuman primates and fur seals. The results support the notion that Asian elephants may use olfactory cues for social communication and food selection and that the sense of smell may play an important role in the control of their behavior.
Habitat heterogeneity is a crucial driver for species distribution across scales. Harbour porpois... more Habitat heterogeneity is a crucial driver for species distribution across scales. Harbour porpoise Phocoena phocoena basin-wide distribution is linked to prey availability, and small-scale (kilometres to tens of kilometres) differences in distribution are prevalent. However, information on porpoise distribution and foraging-behaviour variations on a micro-scale (~100 m to kilometres) is limited. To monitor harbour porpoise distribution and foraging activity on a micro-scale, we deployed passive acoustic dataloggers, logging porpoise acoustic activity at 6 sites in a small, high porpoise-density area in southern Sweden. Data were collected for almost a year, giving detailed time series on porpoise activity. The time series were analysed using dynamic time warping to compare activity patterns between sites. Large differences were found between sites separated by only a few hundred meters, indicating micro-scale spatial preference. Spectral analysis for temporal cyclicity in activity r...
Franciscana dolphins in Babitonga Bay represent the only population of that critically endangered... more Franciscana dolphins in Babitonga Bay represent the only population of that critically endangered species which is confined to an estuary. Surrounded by large cities and harbors, that environment presents intense human activities and potential impacts that may threaten the dolphins. Understanding their habitat use and distribution can inform mitigation of such impacts. Here we used acoustic data from sixty fixed passive acoustic monitoring stations, implemented between June and December 2018. The relationship between the occurrence of franciscanas and environmental variables was investigated with generalized additive mixed models. The selected model presented 51% of explained deviance and included “time of day”, “intensity of presence of Guiana dolphins”, “maximum slope”, and “bottom sediment”, among other less statistically significant variables. A daily distribution pattern was identified, with franciscanas remaining in the areas of greatest occurrence especially in the morning an...
The tag recorded 549 regular click trains, 1056 slow and irregular pulse trains and 255 pulse bur... more The tag recorded 549 regular click trains, 1056 slow and irregular pulse trains and 255 pulse bursts in 70 and 120 kHz band-pass filter bands. Pulse bursts occurred in high intensity aggressive sit ...
A measure proven successful in mitigating harbor porpoise bycatch, is the use of acoustic deterre... more A measure proven successful in mitigating harbor porpoise bycatch, is the use of acoustic deterrents, i.e., pingers. However, most pingers are audible to seals. This may lead to seals associating pinger sounds with easily accessible food, leading to increased depredation, damage, and bycatch. In this study we tested if an experimental pinger, emitting sounds over 30 hr ON/OFF cycles, with low frequency components potentially audible to seals only at close distances, would effectively deter harbor porpoises. The porpoise response was measured by logging echolocation clicks, using C‐POD click detectors, moored at different distances from the pinger. In addition, we calculated the theoretical pinger detection range for seals. Results showed that the pinger had a significant negative effect on the porpoise click activity logged at 0 m and 100 m distance but not at 400 m from the pinger. During pinger ON periods, we found no significant increase in echolocation over consecutive days of t...
It is well-established that the odor of mammalian blood is attractive to top predators such as ti... more It is well-established that the odor of mammalian blood is attractive to top predators such as tigers and wolves and aversive to prey species such as mice and rats. Recent studies have shown that the mammalian blood odor component trans-4,5-epoxy-(E)-2-decenal (TED) elicits corresponding behavioral responses in these two groups of mammals. Here we assess whether a mesopredator, that is, a small-bodied carnivorous mammal that is both predator and prey, is attracted to or repelled by the odor of mammalian blood and TED. To this end, we assessed the behavior of a group of 15 captive meerkats (Suricata suricatta) when presented with wooden logs that were impregnated either with horse blood or with TED, and compared it to their behavior toward a fruity odor (iso-pentyl acetate) and a near-odorless solvent (diethyl phthalate). We found that the meerkats displayed significantly more interactions with the odorized wooden logs such as sniffing and pawing when these were impregnated with the two prey-associated odors compared to the two non-prey-associated odors. Most importantly, no significant difference was found in the number of interactions with the wooden logs impregnated with horse blood and TED, respectively. These results demonstrate that meerkats, despite being small-bodied mesopredators, are clearly attracted to the odor of mammalian blood. Further, the results suggest that a single blood odor component can be as efficient as the odor of real blood in eliciting behavioral responses in this herpestid mammal, similar to previous findings in feline and canine top predators.
The ability of dolphins to produce pulse sounds with a bandwidth of up to 150 kHz, has been inten... more The ability of dolphins to produce pulse sounds with a bandwidth of up to 150 kHz, has been intensively studied with focus on their sonar capabilities, i.e. the detection, ranging and discrimination of objects of various shapes, textures and material. The sonar pulses have been found to be directional, with a -3db beam width of about 10 degrees in both the vertical and the horizontal plane, and with the beam axis ea. 5 degrees above that of the rostrum. Pulse sounds also frequently occur in social situations (Paper I), but studies of these sounds traditionally have been limited to their audio band, omni-directional components. Hypothesising that social pulse sounds in bottlenose dolphins (Tursiops truncatus) also were directional, early recordings within this study were done across a net barrier, in a narrow channel connecting two pools, to increase the probability to record such sounds with a fixed hydrophone. These recordings confirmed the presence of ultrasonic frequencies in pulse sounds emitted in aggressive interactions, where the interacting animals were oriented face-to-face on either side of the net barrier. There were also indications that they were directional (Paper I). These sounds also had a pronounced energy peak 1 sec), labelled "Machine-gun" sound, occurred frequently in the initial phase of the aggressive interactions. While emitting this sound, the animal kept its rostrum, and possibly the sound beam axis aimed at the agonist, suggesting that it was deliberately used to expose the opponent to powerful broadband pulse sounds, probably to provoke a fight (Paper III).To avoid the restrictions on the behaviour imposed on the dolphins by the net barrier setup, an acoustic tag system was developed (Paper II). The tag was attached to the receiving dolphin instead of the transmitter, and made it possible to study the use of the directionality of the pulse sounds in social contexts, while the interacting dolphins were fully free-swimming. The tag, based on click detectors, recorded the envelope of pulses within two narrow band pass frequency filters, centred on 70kHz and 120kHz, respectively (Paper II). The tag recordings verified the presence of energy within both filter frequency bands in social pulse sounds, in particular in aggressive interactions (Paper III). This thesis suggests that thedirectionality of such pulse sounds is used intentionally to address social signals to a specific individual, or group of individuals. The relatively loud omni-directional audio band component will facilitate for nearby conspecifics to monitor the progress of the interaction. It will also make the signal clearly audible to the opponents throughout an interaction, even if they may be tumbling around, being unable to keep the sound beam axis aimed at the other. Similar pulse bursts were recorded in association with what was interpreted as play-fight, between subadults and juveniles (Paper IV). However, unlike the real aggressive bursts, these bursts had a trailing FM whistle, and this combined signal is suggested to be an appeasement signal, analogous with the laugh and giggle observed in apes. It is supposed to prevent play-fights from escalating into physical and potentially dangerous real fights. It was never recorded in true aggressive interactions among adults.There were individual differences between the animals in amount of received directional pulse sounds while carrying the tag (Paper III). The socially most active of the females, having an intermediate position in the dominance hierarchy, received significantly more directional pulse sounds than the other, socially less active, but higher ranked female. The breeding male received the least number of pulse sounds. This lends support to the presence of "echolocation manners", as suggested by Johnson and Norris (1994), making it socially unacceptable to aiming the sonar beam towards conspecifics unless the intention is to conveying a social message.Dolphins lack the facial plasticity playing a dominant role in the social life of many terrestrial mammals, e.g. primates, canids and felids. This directional signal modality is used to express internal emotions and can be addressed to selected individuals, further stressed by a direct glare. Dolphins completely lack such a facial plasticity but most likely not the need for expressing emotions. This thesis suggests that in dolphins the facial expressions may have been replaced bydirectional pulse sounds. The facial expressions in e.g., wolves, is supposed to be the result of a mixture of dominance/aggression vs. submission/fear emotions. We propose that the pulse sounds, seen in the aggressive interactions, reflect a similar mix of feelings. Obvious parameters in such a graded social signal system are pulse repetition rate, amplitude, duration and power spectrum. To study this further a broadband acoustic tag, preferably attached to several animals simultaneously, is required.
During the past 25 years, Fjord&Baelt (F&B) in Denmark has kept harbour porpoises (Phocoena phoco... more During the past 25 years, Fjord&Baelt (F&B) in Denmark has kept harbour porpoises (Phocoena phocoena) for research and education. Some animals were bycaught in static fishing gear and then brought to the center under a special permit, and some were born at the facility. At F&B, the harbour porpoises are trained several times every day for research projects, public presentations for visitors, and educational programs for schools. They are also provided with enrichment activities in addition to the enclosure's natural and dynamic habitat. The center's research on animal behaviour, reproductive and diving physiology, outreach, and bioacoustics have resulted in more than 60 scientific publications, involving scientists from research institutions in Denmark and abroad. There is a close collaboration between F&B and the adjacent Marine Biological Research Center (MRC) of the University of Southern Denmark (SDU), also established in 1997.
This study presents a first approach to determine a suckling bout criterion interval (BCI) by app... more This study presents a first approach to determine a suckling bout criterion interval (BCI) by applying a log e frequency analysis to a dataset of Tursiops truncatus neonate feeding frequencies. The data were gathered by continuous observation on four calves 15-24 hr a day for the first 14 days postpartum. The study was conducted at the dolphinarium of the Kolma˚rden Wild Animal Park, Kolma˚rden, Sweden. Based on a total of 3,752 individual suckling intervals, a BCI of 107.7 sec was established. The relevance of this finding is discussed. Zoo Biol 22:477-488, 2003.
Your article is protected by copyright and all rights are held exclusively by Springer Science +B... more Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media Dordrecht. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
The Journal of the Acoustical Society of America, 2014
ABSTRACT SAMBAH (Static Acoustic Monitoring of the Baltic Sea Harbor Porpoise) is an EU LIFE + -f... more ABSTRACT SAMBAH (Static Acoustic Monitoring of the Baltic Sea Harbor Porpoise) is an EU LIFE + -funded project with the primary goal of estimating the abundance and distribution of the critically endangered Baltic Sea harbor porpoise. From May 2011 to April 2013, project members in all EU countries around the Baltic Sea undertook a static acoustic survey using 304 porpoise detectors distributed in a randomly positioned systematic grid in waters 5–80 m deep. In the recorded data, click trains originating from porpoises have been identified automatically using an algorithm developed specifically for Baltic conditions. To determine the click train C-POD detection function, a series of experiments have been carried out, including acoustic tracking of wild free ranging porpoises using hydrophone arrays in an area with moored C-PODs and playbacks of porpoise-like signals at SAMBAH C-PODs during various hydrological conditions. Porpoise abundance has been estimated by counting the number of individuals detected in short time interval windows (snapshots), and then accounting for false positive detections, probability of animals being silent, and probability of detection of non-silent animals within a specified maximum range. We describe the method in detail, and how the auxiliary experiments have enabled us to estimate the required quantities.
Environmental and ecological factors can trigger changes in the acoustic repertoire of cetaceans.... more Environmental and ecological factors can trigger changes in the acoustic repertoire of cetaceans. This study documents the first use of a well-established passive acoustic monitoring device (C-POD) to analyze echolocation sounds and behavior of franciscana dolphins in different habitats: estuary [Babitonga Bay (BB)] and open sea [Itapirubá Beach (IB)]. A total of 10 924 click trains were recorded in BB and 6 093 in IB. An inter-click interval < 10 ms (so called "feeding buzzes") was used as a proxy for foraging activity. The main difference in the acoustic parameters between the two habitats was related to the frequency spectrum, with higher maximum and lower modal and minimum click frequencies in BB, and a train frequency range of 17 kHz, against 10 kHz in IB. Also, the click emission rate (clicks/s) was almost 20% higher in BB. Both studied habitats showed a high proportion of feeding buzzes (BB = 68%; IB = 58%), but with a higher probability of occurrence in BB (p < 0.001) and at night (p < 0.001) in both habitats. The C-PODs showed great potential to monitor occurrence, bioacoustics parameters, and echolocation behavior of franciscana dolphins. Longer-term temporal and spatial monitoring are necessary for elucidating several issues raised in this study.
Sound production mechanisms have been studied in two delphinid species - the harbour porpoise, Ph... more Sound production mechanisms have been studied in two delphinid species - the harbour porpoise, Phocoena phocoena (L.), and the bottlenosed dolphin, Tursiops truncatus (Montagu). It was found that, in both species, the click sound production was coupled to a considerable pressure increase in the bony nares. The maximum pressure recorded in Phocoena was approximately 54kPa and in Tursiops close to 81 kPa; it was equal in time and amplitude in both nares. The nasal plug muscle was found to be active up to 450 ms prior to and during sound production. Sound production without such activity was not seen. The results suggest that an identical mechanism underlies click production in both species, with, pressurized air being the driving force and the nasal plug muscle having some active regulating function. Probes were inserted into the bony nares of three harbour porpoises, Phocoena phocoena, and one bottlenosed dolphin, Tursiops truncatus, in order to record air pressure variations togethe...
Journal of the Acoustical Society of America, May 1, 2007
The hearing of the bottlenosed dolphins at Kolmrdens Djurpark, Sweden, was examined using a porta... more The hearing of the bottlenosed dolphins at Kolmrdens Djurpark, Sweden, was examined using a portable auditory evoked potential (AEP) system in order to examine the hearing capabilities of dolphins housed in quiet environments with an emphasis on age-related hearing variation. Audiograms were measured on two dolphins and modulation rate transfer functions (MRTF) were also measured on two animals. A complete audiogram (4–200 kHz) was obtained for the oldest dolphin, a 34 year old female named Vicky. Her audiogram showed no evidence of high-frequency hearing loss. Notwithstanding this finding, her click evoked auditory brainstem response (ABR) revealed a marked increase in interpeak latency that could be indicative of an underlying hearing defect. The audiogram obtained from for the male dolphin, a 24 year old named Pichi (measured from 4–107 kHz), demonstrated profound hearing loss at all frequencies. The measured MRTF results indicated typical odontocete following responses to rates exceeding 1000 Hz.
Sound production mechanisms have been studied in two delphinid species-the harbour porpoise, Phoc... more Sound production mechanisms have been studied in two delphinid species-the harbour porpoise, Phocoena phocoena (L.), and the bottlenosed dolphin, Tursiops truncatus (Montagu). It was found that, in both species, the click sound production was coupled to a considerable pressure increase in the bony nares. The maximum pressure recorded in Phocoena was approximately 54kPa and in Tursiops close to 81 kPa; it was equal in time and amplitude in both nares. The nasal plug muscle was found to be active up to 450 ms prior to and during sound production. Sound production without such activity was not seen. The results suggest that an identical mechanism underlies click production in both species, with pressurized air being the driving force and the nasal plug muscle having some active regulating function. Probes were inserted into the bony nares of three harbour porpoises, Phocoena phocoena, and one bottlenosed dolphin, Tursiops truncatus, in order to record air pressure variations together with sound production. Sounds were picked up by a hydrophone manually held to the forehead of the animals. In several of the Phocoena recordings, electromyographic activity in the nasal plug muscle was also recorded.
The present study demonstrates that Asian elephants, Elephas maximus, can successfully be trained... more The present study demonstrates that Asian elephants, Elephas maximus, can successfully be trained to cooperate in an olfactory discrimination test based on a food-rewarded two-alternative instrumental conditioning procedure. The animals learned the basic principle of the test within only 60 trials and readily mastered intramodal stimulus transfer tasks. Further, they were capable of distinguishing between structurally related odor stimuli and remembered the reward value of previously learned odor stimuli after 2, 4, 8, and 16 weeks of recess without any signs of forgetting. The precision and consistency of the elephants' performance in tests of odor discrimination ability and long-term odor memory demonstrate the suitability of this method for assessing olfactory function in this proboscid species. An across-species comparison of several measures of olfactory learning capabilities such as speed of initial task acquisition and ability to master intramodal stimulus transfer tasks shows that Asian elephants are at least as good in their performance as mice, rats, and dogs, and clearly superior to nonhuman primates and fur seals. The results support the notion that Asian elephants may use olfactory cues for social communication and food selection and that the sense of smell may play an important role in the control of their behavior.
Habitat heterogeneity is a crucial driver for species distribution across scales. Harbour porpois... more Habitat heterogeneity is a crucial driver for species distribution across scales. Harbour porpoise Phocoena phocoena basin-wide distribution is linked to prey availability, and small-scale (kilometres to tens of kilometres) differences in distribution are prevalent. However, information on porpoise distribution and foraging-behaviour variations on a micro-scale (~100 m to kilometres) is limited. To monitor harbour porpoise distribution and foraging activity on a micro-scale, we deployed passive acoustic dataloggers, logging porpoise acoustic activity at 6 sites in a small, high porpoise-density area in southern Sweden. Data were collected for almost a year, giving detailed time series on porpoise activity. The time series were analysed using dynamic time warping to compare activity patterns between sites. Large differences were found between sites separated by only a few hundred meters, indicating micro-scale spatial preference. Spectral analysis for temporal cyclicity in activity r...
Franciscana dolphins in Babitonga Bay represent the only population of that critically endangered... more Franciscana dolphins in Babitonga Bay represent the only population of that critically endangered species which is confined to an estuary. Surrounded by large cities and harbors, that environment presents intense human activities and potential impacts that may threaten the dolphins. Understanding their habitat use and distribution can inform mitigation of such impacts. Here we used acoustic data from sixty fixed passive acoustic monitoring stations, implemented between June and December 2018. The relationship between the occurrence of franciscanas and environmental variables was investigated with generalized additive mixed models. The selected model presented 51% of explained deviance and included “time of day”, “intensity of presence of Guiana dolphins”, “maximum slope”, and “bottom sediment”, among other less statistically significant variables. A daily distribution pattern was identified, with franciscanas remaining in the areas of greatest occurrence especially in the morning an...
The tag recorded 549 regular click trains, 1056 slow and irregular pulse trains and 255 pulse bur... more The tag recorded 549 regular click trains, 1056 slow and irregular pulse trains and 255 pulse bursts in 70 and 120 kHz band-pass filter bands. Pulse bursts occurred in high intensity aggressive sit ...
A measure proven successful in mitigating harbor porpoise bycatch, is the use of acoustic deterre... more A measure proven successful in mitigating harbor porpoise bycatch, is the use of acoustic deterrents, i.e., pingers. However, most pingers are audible to seals. This may lead to seals associating pinger sounds with easily accessible food, leading to increased depredation, damage, and bycatch. In this study we tested if an experimental pinger, emitting sounds over 30 hr ON/OFF cycles, with low frequency components potentially audible to seals only at close distances, would effectively deter harbor porpoises. The porpoise response was measured by logging echolocation clicks, using C‐POD click detectors, moored at different distances from the pinger. In addition, we calculated the theoretical pinger detection range for seals. Results showed that the pinger had a significant negative effect on the porpoise click activity logged at 0 m and 100 m distance but not at 400 m from the pinger. During pinger ON periods, we found no significant increase in echolocation over consecutive days of t...
It is well-established that the odor of mammalian blood is attractive to top predators such as ti... more It is well-established that the odor of mammalian blood is attractive to top predators such as tigers and wolves and aversive to prey species such as mice and rats. Recent studies have shown that the mammalian blood odor component trans-4,5-epoxy-(E)-2-decenal (TED) elicits corresponding behavioral responses in these two groups of mammals. Here we assess whether a mesopredator, that is, a small-bodied carnivorous mammal that is both predator and prey, is attracted to or repelled by the odor of mammalian blood and TED. To this end, we assessed the behavior of a group of 15 captive meerkats (Suricata suricatta) when presented with wooden logs that were impregnated either with horse blood or with TED, and compared it to their behavior toward a fruity odor (iso-pentyl acetate) and a near-odorless solvent (diethyl phthalate). We found that the meerkats displayed significantly more interactions with the odorized wooden logs such as sniffing and pawing when these were impregnated with the two prey-associated odors compared to the two non-prey-associated odors. Most importantly, no significant difference was found in the number of interactions with the wooden logs impregnated with horse blood and TED, respectively. These results demonstrate that meerkats, despite being small-bodied mesopredators, are clearly attracted to the odor of mammalian blood. Further, the results suggest that a single blood odor component can be as efficient as the odor of real blood in eliciting behavioral responses in this herpestid mammal, similar to previous findings in feline and canine top predators.
The ability of dolphins to produce pulse sounds with a bandwidth of up to 150 kHz, has been inten... more The ability of dolphins to produce pulse sounds with a bandwidth of up to 150 kHz, has been intensively studied with focus on their sonar capabilities, i.e. the detection, ranging and discrimination of objects of various shapes, textures and material. The sonar pulses have been found to be directional, with a -3db beam width of about 10 degrees in both the vertical and the horizontal plane, and with the beam axis ea. 5 degrees above that of the rostrum. Pulse sounds also frequently occur in social situations (Paper I), but studies of these sounds traditionally have been limited to their audio band, omni-directional components. Hypothesising that social pulse sounds in bottlenose dolphins (Tursiops truncatus) also were directional, early recordings within this study were done across a net barrier, in a narrow channel connecting two pools, to increase the probability to record such sounds with a fixed hydrophone. These recordings confirmed the presence of ultrasonic frequencies in pulse sounds emitted in aggressive interactions, where the interacting animals were oriented face-to-face on either side of the net barrier. There were also indications that they were directional (Paper I). These sounds also had a pronounced energy peak 1 sec), labelled "Machine-gun" sound, occurred frequently in the initial phase of the aggressive interactions. While emitting this sound, the animal kept its rostrum, and possibly the sound beam axis aimed at the agonist, suggesting that it was deliberately used to expose the opponent to powerful broadband pulse sounds, probably to provoke a fight (Paper III).To avoid the restrictions on the behaviour imposed on the dolphins by the net barrier setup, an acoustic tag system was developed (Paper II). The tag was attached to the receiving dolphin instead of the transmitter, and made it possible to study the use of the directionality of the pulse sounds in social contexts, while the interacting dolphins were fully free-swimming. The tag, based on click detectors, recorded the envelope of pulses within two narrow band pass frequency filters, centred on 70kHz and 120kHz, respectively (Paper II). The tag recordings verified the presence of energy within both filter frequency bands in social pulse sounds, in particular in aggressive interactions (Paper III). This thesis suggests that thedirectionality of such pulse sounds is used intentionally to address social signals to a specific individual, or group of individuals. The relatively loud omni-directional audio band component will facilitate for nearby conspecifics to monitor the progress of the interaction. It will also make the signal clearly audible to the opponents throughout an interaction, even if they may be tumbling around, being unable to keep the sound beam axis aimed at the other. Similar pulse bursts were recorded in association with what was interpreted as play-fight, between subadults and juveniles (Paper IV). However, unlike the real aggressive bursts, these bursts had a trailing FM whistle, and this combined signal is suggested to be an appeasement signal, analogous with the laugh and giggle observed in apes. It is supposed to prevent play-fights from escalating into physical and potentially dangerous real fights. It was never recorded in true aggressive interactions among adults.There were individual differences between the animals in amount of received directional pulse sounds while carrying the tag (Paper III). The socially most active of the females, having an intermediate position in the dominance hierarchy, received significantly more directional pulse sounds than the other, socially less active, but higher ranked female. The breeding male received the least number of pulse sounds. This lends support to the presence of "echolocation manners", as suggested by Johnson and Norris (1994), making it socially unacceptable to aiming the sonar beam towards conspecifics unless the intention is to conveying a social message.Dolphins lack the facial plasticity playing a dominant role in the social life of many terrestrial mammals, e.g. primates, canids and felids. This directional signal modality is used to express internal emotions and can be addressed to selected individuals, further stressed by a direct glare. Dolphins completely lack such a facial plasticity but most likely not the need for expressing emotions. This thesis suggests that in dolphins the facial expressions may have been replaced bydirectional pulse sounds. The facial expressions in e.g., wolves, is supposed to be the result of a mixture of dominance/aggression vs. submission/fear emotions. We propose that the pulse sounds, seen in the aggressive interactions, reflect a similar mix of feelings. Obvious parameters in such a graded social signal system are pulse repetition rate, amplitude, duration and power spectrum. To study this further a broadband acoustic tag, preferably attached to several animals simultaneously, is required.
During the past 25 years, Fjord&Baelt (F&B) in Denmark has kept harbour porpoises (Phocoena phoco... more During the past 25 years, Fjord&Baelt (F&B) in Denmark has kept harbour porpoises (Phocoena phocoena) for research and education. Some animals were bycaught in static fishing gear and then brought to the center under a special permit, and some were born at the facility. At F&B, the harbour porpoises are trained several times every day for research projects, public presentations for visitors, and educational programs for schools. They are also provided with enrichment activities in addition to the enclosure's natural and dynamic habitat. The center's research on animal behaviour, reproductive and diving physiology, outreach, and bioacoustics have resulted in more than 60 scientific publications, involving scientists from research institutions in Denmark and abroad. There is a close collaboration between F&B and the adjacent Marine Biological Research Center (MRC) of the University of Southern Denmark (SDU), also established in 1997.
This study presents a first approach to determine a suckling bout criterion interval (BCI) by app... more This study presents a first approach to determine a suckling bout criterion interval (BCI) by applying a log e frequency analysis to a dataset of Tursiops truncatus neonate feeding frequencies. The data were gathered by continuous observation on four calves 15-24 hr a day for the first 14 days postpartum. The study was conducted at the dolphinarium of the Kolma˚rden Wild Animal Park, Kolma˚rden, Sweden. Based on a total of 3,752 individual suckling intervals, a BCI of 107.7 sec was established. The relevance of this finding is discussed. Zoo Biol 22:477-488, 2003.
Your article is protected by copyright and all rights are held exclusively by Springer Science +B... more Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media Dordrecht. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
The Journal of the Acoustical Society of America, 2014
ABSTRACT SAMBAH (Static Acoustic Monitoring of the Baltic Sea Harbor Porpoise) is an EU LIFE + -f... more ABSTRACT SAMBAH (Static Acoustic Monitoring of the Baltic Sea Harbor Porpoise) is an EU LIFE + -funded project with the primary goal of estimating the abundance and distribution of the critically endangered Baltic Sea harbor porpoise. From May 2011 to April 2013, project members in all EU countries around the Baltic Sea undertook a static acoustic survey using 304 porpoise detectors distributed in a randomly positioned systematic grid in waters 5–80 m deep. In the recorded data, click trains originating from porpoises have been identified automatically using an algorithm developed specifically for Baltic conditions. To determine the click train C-POD detection function, a series of experiments have been carried out, including acoustic tracking of wild free ranging porpoises using hydrophone arrays in an area with moored C-PODs and playbacks of porpoise-like signals at SAMBAH C-PODs during various hydrological conditions. Porpoise abundance has been estimated by counting the number of individuals detected in short time interval windows (snapshots), and then accounting for false positive detections, probability of animals being silent, and probability of detection of non-silent animals within a specified maximum range. We describe the method in detail, and how the auxiliary experiments have enabled us to estimate the required quantities.
Environmental and ecological factors can trigger changes in the acoustic repertoire of cetaceans.... more Environmental and ecological factors can trigger changes in the acoustic repertoire of cetaceans. This study documents the first use of a well-established passive acoustic monitoring device (C-POD) to analyze echolocation sounds and behavior of franciscana dolphins in different habitats: estuary [Babitonga Bay (BB)] and open sea [Itapirubá Beach (IB)]. A total of 10 924 click trains were recorded in BB and 6 093 in IB. An inter-click interval < 10 ms (so called "feeding buzzes") was used as a proxy for foraging activity. The main difference in the acoustic parameters between the two habitats was related to the frequency spectrum, with higher maximum and lower modal and minimum click frequencies in BB, and a train frequency range of 17 kHz, against 10 kHz in IB. Also, the click emission rate (clicks/s) was almost 20% higher in BB. Both studied habitats showed a high proportion of feeding buzzes (BB = 68%; IB = 58%), but with a higher probability of occurrence in BB (p < 0.001) and at night (p < 0.001) in both habitats. The C-PODs showed great potential to monitor occurrence, bioacoustics parameters, and echolocation behavior of franciscana dolphins. Longer-term temporal and spatial monitoring are necessary for elucidating several issues raised in this study.
Uploads
Papers by Mats Amundin