Peer Reviewed Articles
Unsupervised classification of graded animal vocalisations using fuzzy clustering
Abstract
Graded vocal repertoires represent a challenge for bioacoustics. We present an unsupervised classification procedure designed to take gradation into account, based on Mel frequency cepstral coefficients and fuzzy clustering. Cepstral coefficients are well defined for tonal, broadband and pulsed sounds. They compress information about the distribution of energy across frequencies into a limited number of variables. The Mel scale mimics the perception of pitch by mammalian ears. Fuzzy clustering is a soft classification approach. Instead of assigning samples to a single category, it describes their position relative to overlapping clusters and can therefore identify stereotyped and graded vocalisations within a repertoire. We evaluated the performance of this procedure on a set of long-finned pilot whale (Globicephala melas) calls. Fuzzy clustering was much less time-consuming than manual classification (days vs. months), but identified a smaller number of categories (three to six fuzzy clusters compared to 11 human-defined call types). Some fuzzy clusters were similar to sets of human-defined call types, but some call types were spread over several fuzzy clusters. Fuzzy clusters provide new quantitative insight about the gradation of vocal repertoires. We discuss the results and the need to investigate the functions of call gradation in future research.
Authors: Benjamin Benti, Patrick JO Miller, Heike Vester, Florencia Noriega & Charlotte Curé
Published: 7 October 2025
Animal ethnography and a relational approach
to sustainability: methodological challenges and
opportunities in wildlife tourism
Abstract
We adopted a collaborative research approach involving two tourism scholars, a biologist and a photojournalist to discuss ethnography and sustainability from a posthuman ecofeminist perspective. We focused on ethnography as a potentially fruitful methodology for supporting justice in wildlife tourism. We reviewed the literature on more-than-human methodologies, including emerging studies on animal ethnography, critical legitimacy and science issues. Through two open conversations and thematic analysis, drawing on our collective expertise in academia (tourism and biology), business (tourism), the nonprofit sector (animal and environmental protection and conservation), and photojournalism, we developed a stepwise framework for conducting ethnographic studies to foster just wildlife tourism. Our framework emphasises the need to consider animals’ perspectives on wildlife tourism and promote justice by creating connections with our inner selves, coresearchers, animals, sociocultural and natural tourism contexts, and the public (including actual and potential tourists). This framework contributes to more-than-human methodologies, including tourism ethnography, and can support animal ethnographers’ fieldwork practices. It also contributes to advancing approaches to sustainability by emphasising how broad, in-depth thinking about animals in tourism can nurture a suitable mindset for promoting greater justice in wildlife tourism.
Authors:
Giovanna Bertella, Lucia Tomassini, Heike l. Vester & Jo-Anne McArthur
Published: 15 May 2025
Narrating the soundscape of coastal tourism
Abstract
This research letter concerns the soundscape along the Norwegian coastline, but the concepts can be applied to most coastal destinations. We wrote this letter in our roles as scholars of tourism and biology as well as members of a non-profit organisation located in northern Norway that is dedicated to science, conservation and the protection of marine mammals. By contrasting a promotional video with an awareness-raising video, we highlight tourism sector’s missed opportunity to foster sustainability and justice and advocate for inclusive storytelling that considers different voices, stories and soundscapes.
Authors:
Giovanna Bertella & Heike l. Vester
Published: 6 May 2025
A virtual dive into ocean conservation and protection
Abstract
Whale watching provides an opportunity to educate the public about marine conservation and protection, yet it often falls short of this potential and poses an ongoing dilemma as it inherently disturbs the animals. This note discusses Us: The Sea of Sounds, a project that we designed to address challenges by raising awareness about underwater noise pollution and its harmful effects on marine life, especially cetaceans. We adopted immersive and interpretative methods to foster emotional engagement and learning. The project was tested in the form of an interactive exhibition in August 2024 in Bodø, Norway, near prominent whale-watching sites. In this note, we describe the project’s development, the key partners, and the practical implementation of the exhibition. It also reflects on the lessons learned about the possible limited knowledge of the natural environment by residents and the potentials of combining science with art and technology and considers how similar initiatives could promote respectful and responsible marine tourism.
Authors: Giovanna Bertella, Michal Lovecky, Ellyne Hamran & Heike I. Vester
Published: 17 February 2025
Evidence for discrimination between feeding sounds of familiar fish and unfamiliar mammal‑eating killer whale ecotypes by long‑finned pilot whales
Abstract
Killer whales (KW) may be predators or competitors of other cetaceans. Since their foraging behavior and acoustics differ among populations (‘ecotypes’), we hypothesized that other cetaceans can eavesdrop on KW sounds and adjust their behavior according to the KW ecotype. We performed playback experiments on long-finned pilot whales (Globicephala melas) in Norway using familiar fish-eating KW sounds (fKW) simulating a sympatric population that might compete for foraging areas, unfamiliar mammal-eating KW sounds (mKW) simulating a potential predator threat, and two control sounds. We assessed behavioral responses using animal-borne multi-sensor tags and surface visual observations. Pilot whales barely changed behavior to a broadband noise (CTRL−), whereas they were attracted and exhibited spyhops to fKW, mKW, and to a repeated-tonal upsweep signal (CTRL+). Whales never stopped nor started feeding in response to fKW, whereas they reduced or stopped foraging to mKW and CTRL+. Moreover, pilot whales joined other subgroups in response to fKW and CTRL+, whereas they tightened individual spacing within group and reduced time at surface in response to mKW. Typical active intimidation behavior displayed to fKW might be an antipredator strategy to a known low-risk ecotype or alternatively a way of securing the habitat exploited by a heterospecific sympatric population. Cessation of feeding and more cohesive approach to mKW playbacks might reflect an antipredator behavior towards an unknown KW ecotype of potentially higher risk. We conclude that pilot whales are able to acoustically discriminate between familiar and unfamiliar KW ecotypes, enabling them to adjust their behavior according to the perceived disturbance type.
Authors:
Charlotte Curé· Saana Isojunno· Heike I. Vester· Fleur Visser· Machiel Oudejans· Nicoletta Biassoni· Mathilde Massenet· Lucie Barluet de Beauchesne· Paul J. Wensveen· Lise D. Sivle· Peter L. Tyack·Patrick J. O. Miller
Published: 22 June 2019
Vocal repertoire of long-finned pilot whales (Globicephala melas) in northern Norway
Abstract
The knowledge of the vocal repertoire of pilot whales is very limited. In this paper, the vocal repertoire of long-finned pilot whales recorded during different encounters in the Vestfjord in northern Norway between November 2006 and August 2010 are described. Sounds were analysed using two different methods: (1) an observer-based audio-visual inspection of FFT-derived spectrograms, with which, besides a general variety of clicks, buzzes, nonharmonic sounds, and whistles, 129 different distinct call types and 25 subtypes were distinguished. These call types included pulsed calls and discrete structured whistles varying from simple to highly complex structures composed of several segments and elements. In addition, ultrasonic whistles previously not described for pilot whales were found. In addition to the diversity of single calls, call sequences consisting of repetitions and combinations of specific call types were recorded and (2) a parametric approach that permitted the confirmation of the high variability in pilot whale call structures was developed. It is concluded that the pilot whale vocal repertoire is among the most complex for the mammalian species and the high structural variability, along with call repetitions and combinations, require a closer investigation to judge their importance for vocal communication.
Copyright (2017) Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.
Authors: Heike Vester; Sarah Hallerberg; Marc Timme; Kurt Hammerschmidt
Published: 9 June 2017
Quantifying group specificity of animal vocalizations without specific sender information
Abstract
Recordings of animal vocalization can lack information about sender and context. This is often the case in studies on marine mammals or in the increasing number of automated bioacoustics monitorings. Here, we develop a framework to estimate group specificity without specific sender information. We introduce and apply a bag-of-calls-and-coefficients approach (BOCCA) to study ensembles of cepstral coefficients calculated from vocalization signals recorded from a given animal group. Comparing distributions of such ensembles of coefficients by computing relative entropies reveals group specific differences. Applying the BOCCA to ensembles of calls recorded from group of long-finned pilot whales in northern Norway, we find that differences of vocalizations within social groups of pilot whales (Globicephala melas) are significantly lower than intergroup differences.
Authors: Heike Vester, Kurt Hammerschmidt, Marc Timme, and Sarah Hallerberg
Media coverage:
Spektrum
Nature Physics
Published: 25 February 2016
First record of killer whales (Orcinus orca) feeding on Atlantic salmon (Salmo salar) in northern Norway suggest a multi-prey feeding type
Abstract
Occurrence of killer whales in Norway is linked to the migration of the herring population with most sightings during wintertime. Here we describe the first record of North Atlantic killer whales feeding on Atlantic salmon inside a fjord in northern Norway during summertime, thus adding an important factor in understanding the feeding ecology of North Atlantic killer whales.
Authors: Heike Vester and Kurt Hammerschmidt
Published: 13 February 2013
Research note: “Whale watching in Norway caught between more traditional hunting canons and the lucrative promise of seismic airguns”
Abstract
This research note concerns the role of whale-watching tourism providers in the debate over protection of the marine environment. The case reported is about northern Norwegian whale-watching organizations. Based on the analysis of local newspapers and on the direct experience of one member of our research team, this research note concludes that the whale-watching companies, and more in general the wildlife tourism companies, engage only marginally in the debate. This can be explained referring to the companies’ limited availability of resources and experience in the field, and to the existence of different perspectives relative to the way humans can use and impact the marine environment and its inhabitants.
Authors: Giovanna Bertella and Heike Iris Vester
Published: 1 September 2015
Dietary variation within and between populations of northeast Atlantic killer whales Orcinus orca inferred from δ13C and δ15N analyses
Abstract
Epidermal skin samples from eastern North Atlantic killer whales, Orcinus orca, were analyzed for carbon and nitrogen stable isotope ratios. From those, comparisons within a data set of 17 samples collected from Tysfjord, Norway, in November suggested that diet is relatively specialized during this time period at this location. There were significant differences between a small set of samples from Iceland and those collected from Norway, which had all been assigned to the same population by a previous population genetics study. The results would be consistent with matrilines feeding on either the Norwegian or Icelandic stocks of Atlantic herring (Clupea harengus). There was no significant difference within Icelandic samples between those assigned to the population known to feed upon herring and those assigned to a population hypothesized to follow Atlantic mackerel (Scomber scombrus). The greatest differences were between the epidermal samples analyzed in this study and tooth and bone collagen samples from the North Sea that were analyzed previously, which also showed significantly more variation in isotopic ratios than found for skin samples. These differences could reflect differences in turnover rate, differences in diet-tissue fractionation and discrimination due to the amino acid composition of the different tissues, and/or greater competition promoting dietary variation between groups in the North Sea.
Authors: Andrew D. Foote, Heike Vester, Gísli A. Víkingsson, Jason Newton
Published: 13 June 2012
Call for cooperation to contain damage by Chile’s salmon farms
Abstract
In Chile’s Aysén region, salmon farming is putting severe pressure on fragile marine ecosystems and endangered species. This call urges Chile to adopt a more integrated and collaborative approach between the aquaculture industry and conservation policies — similar to those in other nations — to reduce pollution, protect wildlife, and ensure sustainable coastal development.
Authors: Heike Vester and Marc Timme
Published: 17 June 2010
Southernmost distribution of common Bottlenose dolphins (Tursiops truncatus) in the eastern South Pacific
Abstract
The common bottlenose dolphin (Tursiops truncatus) is a cosmopolitan species that does not range to latitudes greater than 45º in either hemisphere, with a few exceptions. In South American waters, this species is generally distributed in the Atlantic Ocean south to Chubut province (ca. 46º S), while in the eastern South Pacific this species has been recorded in northern and central Chile, with a few records south to 40º S. Here we summarize recent records of common bottlenose dolphins obtained during systematic marine mammal surveys in the Chilean Patagonian and Fuegian channels and fjords (the Los Lagos, Aysén, and Magallanes regions of Chile). These data suggest an extension of the documented range of the species southwards, indicating that bottlenose dolphins may have colonized new areas in the eastern South Pacific or as the result of an increase in survey efforts by scientists in the region.
Authors: Carlos Olavarría, Jorge Acevedo, Heike I. Vester, José Zamorano-Abramson, Francisco A. Viddi, Jorge Gibbons, Emma Newcombe, Juan Capella, A. Rus Hoelzel, Marcelo Flores, Rodrigo Hucke-Gaete & Juan Pablo Torres-Flórez
Published: September 2010
Genetic differentiation within a North Atlantic killer whale ecotype
Abstract
Population genetic structure of North Atlantic killer whale samples was resolved from differences in allele frequencies of 17 microsatellite loci, mtDNA control region haplotype frequencies and for a subset of samples, using complete mitogenome sequences. Three significantly differentiated populations were identified. Differentiation based on microsatellite allele frequencies was greater between the two allopatric populations than between the two pairs of partially sympatric populations. Spatial clustering of individuals within each of these populations overlaps with the distribution of particular prey resources: herring, mackerel and tuna, which each population has been seen predating. Phylogenetic analyses using complete mitogenomes suggested two populations could have resulted from single founding events and subsequent matrilineal expansion. The third population, which was sampled at lower latitudes and lower density, consisted of maternal lineages from three highly divergent clades. Pairwise population differentiation was greater for estimates based on mtDNA control region haplotype frequencies than for estimates based on microsatellite allele frequencies, and there were no mitogenome haplotypes shared among populations. This suggests low or no female migration and that gene flow was primarily male mediated when populations spatially and temporally overlap. These results demonstrate that genetic differentiation can arise through resource specialization in the absence of physical barriers to gene flow.
Authors: Andrew D. Foote, Julia Vilstrup, Renaud de Stephanis, Philippe Verborgh, Sandra C. Abel Nielsen, Morten Rasmussen, Robert J. Reid, Kelly M. Robertson, Lars Kleivane, Nils Øien, Tiu Similä, Heike Vester, Gísli A. Vikingsson,Robert Deaville, Emer Rogan, Eske Willerslev, M. Thomas P. Gilbertand Stuart B. Piertney
Published: 11 December 2010
Click sounds produced by cod (Gadus morhua)
Abstract
Conspicuous sonic click sounds were recorded in the presence of cod (Gadus morhua), together with either harp seals (Pagophilus groenlandicus), hooded seals (Cystophora cristata) or a human diver in a pool. Similar sounds were never recorded in the presence of salmon (Salmo salar) together with either seal species, or from either seal or fish species when kept separately in the pool. It is concluded that cod was the source of these sounds and that the clicks were produced only when cod were approached by a swimming predatorlike body. The analyzed click sounds (n = 377) had the following characteristics (overall averages +/- S.D.): peak frequency = 5.95 +/- 2.22 kHz; peak-to-peak duration = 0.70 +/- 0.45 ms; sound pressure level (received level) = 153.2 +/- 7.0 dB re 1 microPa at 1 m. At present the mechanism and purpose of these clicks is not known. However, the circumstances under which they were recorded and some observations on the behavior of the seals both suggest that the clicks could have a predator startling function.
Authors: Vester, H.I., Folkow, L.P. and A.S. Blix
Published: 30 January 2004
Theses
PhD thesis:
“Vocal repertoire of two matrilineal social whale species:
Long-finned Pilot whales (Globicephala melas) and Killer whales (Orcinus orca) in northern Norway”, Heike Vester
2017 University of Goettingen, Germany
“Revealing structure in vocalisations of parrots and social whales”
Noriega Romero Vargas, Maria Florencia
2018 University of Goettingen, Germany
Master & Bachelor thesis:
Master of Science Thesis “Applied Computer Science” 15.10.2015
Towards Automated Photo Identification of Killer Whales
by Burooj Ghani,
Department of Computational Neuroscience, Third Institute of Physics – Biophysics,
Georg-August-Universität Göttingen, Max Planck Institute for Dynamics and Self-Organization, Göttingen.
“Distribution of cetaceans in Vestfjorden, Norway, and possible impacts of seismic surveys”
Master thesis by Felipe Matos, Faculty of Biosciences and Aquaculture, University of Nordland
May 2015
“Distribution and vocal behavior of Atlantic white-sided dolphins (Lagenorhynchus acutus) in northern Norway”.
Master thesis by Ellyne Hamran, Faculty of Biosciences and Aquaculture, University of Nordland 2014.
Photo-Identification of Salmon Eating Killer Whales (Orcinus orca) in Norway (2012).Kristin Reehaug Jacobsen from the University of Nordland in Bodø has completed her bachelor thesis 15.6.2012
Investigating Specific Groups of Killer Whales (Orcinus orca) Through Photo Identification in Norway (2012). Ellyne Dudkowski from the University of Nordland in Bodø has completed her bachelor thesis 15.6.2012 Dudkowski_Bachelors_Thesis_on_Killer_Whales_3
2008 Master project by Silke Nielebock from the University of Oldenburg in Germany. Her thesis was completed 2008 and can be downloaded in German: okotourismus-in-norwegen-touristenprofil-des-okotourismusbetriebs-ocean-sounds-auf-den-lofoten
2008 article by Silke Nielebock AK Norden “Okoturismus in Norwegen”
2008 Philosophy student Martin Lee Miller spent some time with us in 2007 to study the north, the whales and the visitors. He completed his thesis: “Symphony of Silence” at the University of Oslo.
Posters & conferences & technical reports:
“The Vocal Behavior and Distribution of the Atlantic White-sided Dolphins (Lagenorhynchus acutus) in Northern Norway,” poster presentation at the European Cetacean Society, 23rd – 25th March 2015 in St. Julian’s, Malta.
Ellyne Hamran (1), Heike Vester (1, 2), Jarle Tryti Nordeide (1)
(1) University of Nordland, Faculty of Biosciences and Aquaculture, 8049 Bodø, Norway; (2) Ocean Sounds, 8312 Henningsvær, Norway
The Atlantic white-sided dolphins (Lagenorhynchus acutus) are migratory dolphins and their vocal behavior and distribution are understudied in Norway. Vessel based surveys were conducted in order to determine the vocal behavior and occurrence in the Vestfjorden in northern Norway. Hydrophone recordings were used to describe the vocal behavior of clicks, whistles, calls, buzzes and to determine the presence or absence of stereotyped whistles. Clicks (98-99%) were the most abundant sound produced and whistles (65.4%-76.0% excluding clicks) were equally abundant second to clicks. Stereotyped whistles were also observed (e.g. 11-20 kHz, length 853 msec). The relationship of vocal behavior and activity resulted in a dependence on activity: foraging, socializing, milling, and traveling. Sound production increased during socializing and calls were observed most commonly during traveling (32.4%) and least common during foraging (18.8%). Buzzes varied (0-14.0%) and were absent during milling. Photo-ID and sightings were used for tracking and a total of 72 yearly sightings were observed including 55 photo-ID individuals of which 29 individuals were re-sighted again. Two of the 15 re-sighted individuals were observed on 6 occasions with gaps no greater than two years. Many sightings of Atlantic white-sided dolphins including the re-sightings of photo-ID individuals indicate a stronger presence of Atlantic white-sided dolphins than previously reported in the Vestfjorden in northern Norway.
North Atlantic Killer Whale workshop 2012 in Galway, Ireland: NKW-abstract-book
Report_on_further_comparisons_of_Morgan_acoustic_repertoire_Vester_Samarra_2011
Vester, H.I., L.P. Folkow and A. Schytte Blix, 2001. “Underwater vocalisation of captive hooded and harp seals during live fish hunting.”Proc. Soc.Mar.Mamm.Conf. in Vancouver, November 2001.
Vester, H.I., L.P. Folkow and A. Schytte Blix, 2001. “Click sounds produced by cod (Gadus morhua) – a possible anti-predator behaviour?” Proc. ICA conference in Rome, September 2001.
Vester, H., 2007. “Whale watching and ecotourism – a field study from Northern Norway”Proc. of the Global Ecotourism Conference 2007 in Oslo.
Other publications
“Whales and Seascapes of Lofoten”, mulit media DVD, H.Vester & G. Reichtert, 2010.
“Marine Mammals and Fish of Vesteraalen and Lofoten”, H. Vester, Audio CD in cooperation with Gruenrekorder.de, 2009.
Whale Watching Guidelines
WW_Feasibility_Survey_Report_Lofoten_2013-12_26
Guidelines by H. Vester & R. Eriksson, Ocean Sounds & WWF Norway, 2007:
With our 5 years research experience and the help of the WWF Norway, we created a leaflet with new whale watching guidelines. Whale watching in Norway is totally unregulated and there is a need of regulating the boat traffic and human activities around the whales. Whales and whale watching boats are often disturbed by the presence of many boats or boats that drive irresponsible. Please use our guidelines, distribute them and if you go on whale watching tours in Norway, show them to your skipper and guide and ask them to follow it.
wwf_oceansounds_whalewatching-guidelines_2008_small
wwf_oceansounds_hvalsafari-retningslinjer_2008_small
PRESENTATIONS
Heike Vester, Invited speaker at the Whale Watching workshop, University in Tromsø, Norway. 25th of December 2014.
“Complex communication of social whales” Vester, Heike, Marc Timme and Sarah Hallerberg 27-29 of June 2012, Berlin. Max Planck –Chile research Seminar.
“Marine Wildlife of Lofoten”, invited speaker at the “Today´s diagnose and preservation of the Cantabric Sea and The North of Europe” Pakea Bizkaia Conference 22nd January 2011, Maritime Museum in Bilbao, Spain.
“Whale and Dolphin communication in Vestfjorden, northern Norway”, speaker at the Aquadyne Technology Awareness Seminar 29th – 30th September 2010 in Oslo
“Who says what in the Vestfjord – whale communication”, public lecture at the University of Nordland, northern Norway, 07.10.2009.
“Ocean Sounds and Scientific Tourism”, public lecture organised by the Center for Research in Patagonian Ecosystems (CIEP) in Coyhaique, Patagonia, Chile, 24.03.2009.
“Benefits and risks of whale watching – a case study of northern Norway” Workshop on scientific tourism organised by Center for Research in Patagonian Ecosystems (CIEP)in Coyhaique, Patagonia, Chile, 22 -29 of April 2008. (http://ciep.cl/blog/)
“Whale watching and ecotourism – a field study from Northern Norway”. Speaker at the Global Ecotourism Conference in Oslo, 15th of May 2007.
Participating at the UNEP/GRID workshop: “Linking tourism and conservation” in Arendal in Norway 12-13 May 2007.