84 research outputs found
Using acoustic monitoring to reveal nearly year‐round presence of humpback whales (Megaptera novaeangliae) in the waters of southern Iceland
No full textIcelandic waters are a crucial feeding ground for North Atlantic humpback whales, yet their occurrence in these subarctic waters remains underexplored. This study examined seasonal and diel patterns in humpback whale occurrence off the Vestmannaeyjar archipelago, southern Iceland, from June 2018 to May 2019, using automated acoustic detections from bottom-moored hydrophones. Vocalizations were manually categorized into social calls, song fragments, or songs. Further classification identified seven social sound types and 25 unique song units. Humpback whales were detected on 126 out of 329 recording days and were present in nearly all months except April and May. Social calls were most common in summer and fall, while song fragments and songs were prevalent in winter. No diel singing pattern was observed. These findings suggest southern Iceland serves as a vital habitat for humpback whales, acting as a feeding ground in summer and a migration stopover or overwintering site in winter. The study underscores the potential of acoustic monitoring to uncover important habitats year-round, especially when field observations are scarce, and emphasizes the need for ongoing monitoring of habitat use. Continued acoustic monitoring could provide further insights into the whales' behavioral patterns and preferences, essential for their conservation
Functional design and use of acoustic signals produced by killer whales (Orcinus orca)
No full textThis study aimed to investigate possible functions of the sounds produced by
herring-eating killer whales in the Northeast Atlantic.
In this study, I investigated the whistle repertoire of killer whales, which had
previously only been studied in British Columbia, where it appeared to be restricted to
the audible range. However, I show that high frequency whistles (> 17 kHz) were
detected in Northeast Atlantic populations but not in Northeast Pacific populations.
These results indicated substantial intraspecific variation in whistle production in
killer whales. Little variation was observed in high frequency whistles recorded from
three different sites in the Northeast Atlantic, suggesting this signal has a similar
function across locations.
The estimated active space of high frequency whistles and burst-pulse calls
suggested that these are short-range signals used for within-group communication.
Source levels of burst-pulse calls were lower than what was previously described in
British Columbia, which possibly reflected the fact that these sounds do not need to
propagate far because distances between group members are generally short. Calls,
high frequency whistles and herding calls produced at different depths did not appear
to suffer effects due to increased pressure, such as changing frequency or duration
characteristics.
Feeding appeared to take place below 10 m of depth, as suggested by the
localisation of depth of production of feeding-related sounds. These depths were
consistent with those at which tailslaps were produced in Dtags attached to individual
whales. Feeding periods were characterised by deep diving, increased sound
production and highly non-directional movement. These findings suggested that killer
whales in a herring spawning ground use a feeding strategy different from carousel
feeding used in herring overwintering grounds.
These findings showed that Northeast Atlantic killer whales have a different sound
repertoire to other populations, and suggested that they may employ different feeding
strategies depending on prey behaviour
Killer whale tossing a salmon in the air.
No full textObserved in Vestmannaeyjar (S Iceland) on 15 July 2015 (photograph by F. Samarra).</p
Social associations, relatedness and population genetic structure of killer whales (Orcinus orca) in Iceland
No full textIn killer whales, fish- versus mammal-eating ecological differences are regarded as key ecological drivers of sociality, but the potential influence of specific target prey characteristics remains unclear. This thesis aimed to study the social patterns and dynamics of Icelandic killer whales feeding upon herring, a schooling prey that undergoes frequent changes in distribution and school size.
I used a multi-disciplinary approach combining photo-identification and genetic data to understand the sociality, role of kinship and genetic differentiation within the population. Individuals sighted in summer-spawning and overwintering herring grounds during at least five separate days (N = 198) were considered associated if photographed within 20 seconds of each other. Photo-identified individuals were genotyped (N = 61) for 22 microsatellites and mitochondrial DNA control region (611 bp). The population had weak but non-random associations, fission-fusion dynamics at the individual level and seasonal patterns of preferred associations. The society was significantly structured but not hierarchically. Social clusters were highly diverse and, whilst kinship was correlated with association, it was not a prerequisite for social membership. Indeed, some cluster members had different mitochondrial haplotypes, representing separate maternal lineages. Individuals with different observed movement patterns were genetically distinct, but associated with each other. No sex-biased dispersal or inbreeding was detected.
This study revealed that the Icelandic population has a multilevel society without clear hierarchical tiers or nested coherent social units, different from the well-studied salmon- (‘residents’) and seal-eating populations in the Northeast Pacific. In the Icelandic population kinship drives social structure less strongly than in residents. These findings suggest effective foraging on schooling herring in seasonal grounds promotes the formation of flexible social groupings which can include non-kin. Killer whale sociality may be strongly influenced by local ecological context, such as the characteristics of the specific target prey (e.g., predictability, biomass, and density) and subsequent foraging strategies of the population
Climate change and cetacean health : impacts and future directions
No full textAcknowledgments We would like to thank Dr Jo Kershaw for paper recommendations and insightful comments. We would also like to thank two anonymous reviewers for very helpful feedback on the manuscript that helped improve it.Peer reviewe
Low-frequency signals produced by Northeast Atlantic killer whales (Orcinus orca)
No full textKiller whale acoustic behavior has been extensively investigated, however most studies have focused on pulsed calls and whistles. This study reports the production of low-frequency signals by killer whales at frequencies below 300 Hz. Recordings of killer whales were made in Iceland and Norway when whales were observed feeding on herring, and no other cetacean species were nearby. Low-frequency sounds were identified in Iceland and ranged in duration between 0.14 and 2.77 seconds and in frequency between 50 and 270 Hz, well below the previously reported lower limit for killer whale tonal sounds of 500 Hz. LFS appeared to be produced close in time to tail slaps, indicative of feeding attempts, suggesting that these sounds may be related to a feeding context. However, their precise function is unknown and they could be the by-product of a non-vocal behavior, rather than a vocal signal deliberately produced by the whales. Although killer whales in Norway exhibit similar feeding behavior, this sound was not detected in recordings from Norway. This study suggests that, like other delphinids, killer whales also produce low-frequency sounds but further studies will be required to understand whether similar sounds exist in other killer whale populations
Gannets are not attracted to fishing vessels in Iceland-potential influence of a discard ban and food availability
No full textBLC was supported by a NERC GW4+ Doctoral Training Partnership studentship from the Natural Environment Research Council [NE/L002434/1]. We thank Ólafur Torfason, Niall Tierney, and Rachel Stroud for fieldwork assistance in Skrúður, and Mamma-Rósa for food and housing in Vestmannaeyjar. We thank the Hellisey hunting club for the use of cabin and assistance with boat trips to Hellisey. We thank Filipa Samarra, Miguel Neves, Gary Haskins, and team members in the Icelandic Orca Project for boat trips to Hellisey. We thank Lucy Hawkes, David Pascall, Alice Williams, Richard Phillips, Brendan Godley and all reviewers for constructive comments on the manuscript. The GPS tracking data are available through the BirdLife International Seabird Tracking Database (http://www.seabirdtracking.org).Peer reviewe
Kinematic and static GNSS experiments with gLAB and RTKLIB using Argonaut and Ublox mass market receivers
No full textThe Global Navigation Satelite System, GNSS is a constellation of satellites orbiting around the Earth and transmitting signals that contain ranging codes and navigation data, allowing the user to compute its position and providing a continuous 3D location and timing. With the prediction of over 1.2 billion devices that will use GNSS and a revenue of 54.9 billion Euros just in Europe in 2025, it has become a keystone for Europe and Worlds development in fields so important such as transportation, research, meteorology, agriculture and search and rescue among others. For those reasons is so important to keep improving GNSS techniques such as kinematic and static data processing and develop robust and powerful software. On this master thesis, it has been analysed the navigation results with two of the most advanced GNSS data processing tools that there are available nowadays, the GNSS-Lab tool suite, gLAB developed by the group of Astronomy and GEomatics gAGE in collaboration with the European Space Agency, ESA, and the Real Time Kinematics LIBrary, RTKLIB, developed by the Tokyo University of marine science and technology, with data captured with two mass market GNSS receivers, the Argonaut and the Ublox EVK 7. In the first chapter, it has been explained some guidelines to understand the GNSS and explain what it is and how it works with some examples and then, the mathematical explanation of each kind of GNSS signal used in this master thesis. In the second chapter, it has been analyzed the two main programs used for processing and analyzing GNSS data captured in the experiment, the gLAB, and the RTKLIB. On the third part, it has been explained how the data was captured in the different environments that the data had to face, and also, how the antennas were placed to do the experiment in kinematic and static data acquisition. On the fourth section, it can be seen the methodology used by the author of this master thesis to be able to process and get the results, if the reader deserves to reproduce them, are explained on the fourth part. In the fifth chapter, it can be seen the results, first, it is going to be explained which were the main problems that faced the author when performing the data capture whether static or kinematic and then the navigation results on gLAB data tool and the navigations solutions of the RTKLIB data tool. In the last chapter, it can be seen the conclusions that draw the author of the master thesis after evaluating the results and some future work that could be done
Caller sex and orientation influence spectral characteristics of “two-voice” stereotyped calls produced by free-ranging killer whales
No full textAuthor Posting. © Acoustical Society of America, 2007. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 121 (2007): 3932-3937, doi:10.1121/1.2722056.This study investigates how particular received spectral characteristics of stereotyped calls of sexually dimorphic adult killer whales may be influenced by caller sex, orientation, and range. Calls were ascribed to individuals during natural behavior using a towed beamforming array. The fundamental frequency of both high-frequency and low-frequency components did not differ consistently by sex. The ratio of peak energy within the fundamental of the high-frequency component relative to summed peak energy in the first two low-frequency component harmonics, and the number of modulation bands off the high-frequency component, were significantly greater when whales were oriented towards the array, while range and adult sex had little effect. In contrast, the ratio of peak energy in the first versus second harmonics of the low-frequency component was greater in calls produced by adult females than adult males, while orientation and range had little effect. The dispersion of energy across harmonics has been shown to relate to body size or sex in terrestrial species, but pressure effects during diving are thought to make such a signal unreliable in diving animals. The observed spectral differences by signaler sex and orientation suggest that these types of information may be transmitted acoustically by freely diving killer whales.Funding was provided by WHOI’s
Rinehart Coastal Research Center and Ocean Ventures Fund,
and a Royal Society USA/Canada fellowship to PJOM
- …
