Description: The eastern Atlantic Ocean is considered to provide important breeding and wintering habitats for several migratory cetacean species. The spatio-temporal distributions and migratory behaviors of cetaceans off southern Africa are nevertheless still poorly understood. This study investigated the temporal patterns of acoustic occurrence of baleen whales in a presumed baleen whale breeding area off Namibia using passive acoustic recordings collected between November 2011 and May 2013. Our results show seasonal acoustic presence of humpback whales Megaptera novaeangliae, fin whales Balaenoptera physalus and Antarctic minke whales B. bonaerensis from November to January and from June to August. Their acoustic absence from February to May possibly indicates that most animals migrated to other areas (presumably in higher latitudes) in austral summer to feed. By contrast, Antarctic blue whales B. musculus intermedia were acoustically present throughout the recording period, indicating that part of the population remains at lower latitudes year-round. Our findings support the presumed ecological importance of the oceanic area off Namibia, providing (part of) a suitable cetacean wintering and, possibly, breeding range or migratory corridor. Furthermore, the occurrence of Antarctic blue and minke whales off Namibia, concurrent with their reported acoustic presence in high-latitude feeding areas, adds to growing evidence that baleen whale migration is not obligate but much more dynamic than has long been assumed.

Description: The Protocol on Environmental Protection of the Antarctic Treaty stipulates that the protection of the Antarctic environment and associated ecosystems be fundamentally considered in the planning and conducting of all activities in the Antarctic Treaty area. One of the key pollutants created by human activities in the Antarctic is noise, which is primarily caused by ship traffic (from tourism, fisheries, and research), but also by geophysical research (e.g., seismic surveys) and by research station support activities (including construction). Arguably, amongst the species most vulnerable to noise are marine mammals since they specialize in using sound for communication, navigation and foraging, and therefore have evolved the highest auditory sensitivity among marine organisms. Reported effects of noise on marine mammals in lower-latitude oceans include stress, behavioral changes such as avoidance, auditory masking, hearing threshold shifts, and—in extreme cases—death. Eight mysticete species, 10 odontocete species, and six pinniped species occur south of 60�S (i.e., in the Southern or Antarctic Ocean). For many of these, the Southern Ocean is a key area for foraging and reproduction. Yet, little is known about how these species are affected by noise. We review the current prevalence of anthropogenic noise and the distribution of marine mammals in the Southern Ocean, and the current research gaps that prevent us from accurately assessing noise impacts on Antarctic marine mammals. A questionnaire given to 29 international experts on marine mammals revealed a variety of research needs. Those that received the highest rankings were (1) improved data on abundance and distribution of Antarctic marine mammals, (2) hearing data for Antarctic marine mammals, in particular a mysticete audiogram, and (3) an assessment of the effectiveness of various noise mitigation options. The management need with the highest score was a refinement of noise exposure criteria. Environmental evaluations are a requirement before conducting activities in the Antarctic. Because of a lack of scientific data on impacts, requirements and noise thresholds often vary between countries that conduct these evaluations, leading to different standards across countries. Addressing the identified research needs will help to implement informed and reasonable thresholds for noise production in the Antarctic and help to protect the Antarctic environment.

Description: Detailed information on cetacean distribution is crucial to identify large-scale conservation actions and management decisions. Understanding the ecological drivers behind their spatial patterns in the Southern Ocean is complicated by whales’ mobility and the logistic restrictions in collecting data in polar environments. Species distribution models have become essential tools in ecology and conservation. They relate information on species occurrence with environmental predictors thought to influence its habitat use, to predict its potential distribution and explain environmental drivers of the observed patterns. In this study, we compiled opportunistic presenceonly data for seven whale species in the Southern Ocean from multiple sources. A quality-controlled data set was then used to model species distributions using Maxent software (under the point process modelling framework). Environmental predictors were prepared from multiple in-situ and remotely-sensed sources, based on our experience of the study area and species ecology. We estimated the best combinations of Maxent’s parameters & evaluated model performance on a species-specific spatial block cross-validation to maintain spatial independence between training and testing data. For each species, block size and their spatial allocation into crossvalidation folds was objectively determined according to how much spatial-autocorrelation exists at occurrences. For each of species, we 1) predicted circumpolar potential distribution, 2) determined the most important variables, and 3) showed the relationship between habitat suitability and environmental variables. We believe that our results would be of great importance to explain the habitat preference of species in the Southern Ocean, for the first time for the majority of studied species. However, we argue that these models can only represent a hypothetical, mean state (which actually never becomes manifest) of the potential distribution of the species in space, and hence another set of dynamic models are required to consider the high dynamic environment in the Southern Ocean and the migratory nature of whales.

Description: To date, the majority of studies investigating marine mammal distribution and behavior take a single-species perspective, which is often driven by the logistic difficulties of collecting appropriate data at sea. Passive acoustic monitoring tools, provided these exhibit sufficient bandwidth, have the potential to provide insights into community structure as devices operate autonomously simultaneously collecting data on baleen, pinniped and toothed whale acoustic presence. Data can provide information on local species diversity, residency times and patterns in species co-occurrence. Using multi-year passive acoustic data from 6 sites in the Weddell Sea, Atlantic sector of the Southern Ocean, we here explore how local marine mammal community compositions develop over time. We show that the effective number of species exhibited little variation over time, reflecting that species remain in Antarctic waters throughout austral winter. Community composition showed almost complete seasonal overturn, recognizing that species replace each other throughout the year. For all 6 sites, community dissimilarity increased with increasing temporal distance reflecting temporal trends in community composition beyond seasonality. Several species exhibited significant positive or negative co-occurrence patters over time, suggesting predator-prey relationships, competition for prey species as well as acoustic interference between co-occurring species. These seasonal associations were consistent across and between all oceanic sites, but partly inversed at the Western Antarctic Peninsula recording site. This study shows that the application of biodiversity metrics to PAM data can foster insights to the timing of behaviors and community composition, which can boost the interpretation of responses in the light of ongoing environmental changes.

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schall, E., Di Iorio, L., Berchok, C., Filun, D., Bedrinana-Romano, L., Buchan, S. J., Van Opzeeland, I., Sears, R., & Hucke-Gaete, R. Visual and passive acoustic observations of blue whale trios from two distinct populations. Marine Mammal Science, (2019): 1-10, doi:10.1111/mms.12643.

Description: Blue whale populations from both hemispheres are thought to undertake annual migrations between high latitude feeding grounds and low latitude breeding grounds (Mackintosh, 1966). For individuals of some populations these predetermined movements to and from wintering areas where calving occurs have been confirmed through photo‐identification, satellite‐tracking, and passive acoustic monitoring (Burtenshaw et al., 2004; Mate, Lagerquist, & Calambokidis, 1999; Sears & Perrin, 2002; Stafford, Nieukirk, & Fox, 1999a). However, for many blue whale populations no clear migratory behavior has been reported and locations of respective breeding grounds remain unclear (e.g., Hucke‐Gaete, Osman, Moreno, Findlay, & Ljungblad, 2004; Samaran et al., 2013; Stafford, Chapp, Bohnenstiel, & Tolstoy, 2011; Thomisch et al., 2016). On feeding grounds in the Gulf of St. Lawrence and along the coast of California, blue whales have been observed to form female–male pairs during summer, which can remain stable up to over several weeks, with the number of pairs increasing towards the end of summer (Sears & Perrin, 2002; Calambokidis, unpublished data;1 RS, unpublished data). These pairs are sometimes joined by a second male, forming a blue whale trio, which often is observed to engage in surface active behaviors lasting several minutes (Sears & Perrin, 2002; RS, unpublished data). The formation of blue whale trios is probably related to reproductive competition between male escorts and female choice (RS, unpublished data). Blue whale males produce population‐specific songs likely functioning as reproductive advertisement (Edds‐Walton, 1997; Oleson et al. 2007a; Stafford, Fox, & Clark, 1998). Several studies have reported song year‐round in low‐, mid‐, and high‐latitude waters, frequently with high song production rates during summer on the feeding grounds (e.g., Barlow et al., 2018; Buchan, Stafford, & Hucke‐Gaete, 2015; Samaran, Adam, & Guinett, 2010; Širović et al., 2004; Stafford, Nieukirk, & Fox, 1999b; Thomisch et al., 2016). Therefore, breeding activities in blue whales may be more opportunistic, i.e., not restricted to the breeding season or to a specific habitat.

Description: ES thanks Prof. Dr. Per J. Palsbøll for the supervision of the initial Master research project, the Marco Polo fund, and the University Groningen for covering travel expenses. We thank the Melimoyu Ecosystem Research Institute, SNP Patagonia Sur, and the company Teledyne Reson for partially funding the acoustic data collection in southern Chile. RHG is thankful to WWF‐Germany/Chile for partially funding fieldwork through grants to Centro Ballena Azul. CLB thanks the team of the Mingan Island Cetacean Study for their logistical support of boats and lodging, access to the North Atlantic blue whale database, and field assistance; Yvon Bélanger for opening his home to her and RS's field crews; for financial support from the National Science Foundation (Graduate Fellowship), National Defense Industrial Association, American Museum of Natural History (Lerner Gray Fund for Marine Research Grant), Penn State Applied Research Laboratory, and private donors Jeff and Lynn Kraus; and graduate advisors at Penn State University David L. Bradley, Thomas B. Gabrielson, and Diana McCammon. LDI thanks the Croisières du Grand Héron and Center Mériscope for allowing and supporting fieldwork, the Animal Behavior Department of the University of Zurich (Switzerland), the Bioacoustics Research Program at Cornell University (USA) and Prof. M. Manser and C. W. Clark for supervising LDI's Ph.D. The work was supported by grants to LDI for her PhD from the Forschungskommission der Universität Zürich, Züricher Tierschutz, Basler Stiftung für Biologische Forschung, SCNAT, Zangger‐Weber‐Stiftung, SSVA. SJB thanks the Center for Oceanographic Research COPAS Sur‐Austral, CONICYT PIA PFB31, the Office of Naval Research Global (awards N62909‐16‐2214 and N00014‐17‐2606), and a grant to the Centro de Estudios Avanzados en Zonas Áridas from Programa Regional CONICYT R16A10003 for support during manuscript writing. We would like to thank the field crews (F. Viddi, J. Ruiz, A. Carpentier, M. Lessard, A. Liebschner, C. Ramp, S. Angel, K. Aucrenaz, T. Doniol‐Valcroze, J. LeBreus, B. Kot, and J. Puschock) for their immense commitment to blue whale research.

Description: Acoustic metrics (AM) assist our interpretation of acoustic environments by aggregating a complex signal into a unique number. Numerous AM have been developed for terrestrial ecosystems, with applications ranging from rapid biodiversity assessments to characterizing habitat quality. However, there has been comparatively little research aimed at understanding how these metrics perform to characterize the acoustic features of marine habitats and their relation with ecosystem biodiversity. Our objectives were to 1) assess whether AM are able to capture the spectral and temporal differences between two distinct Antarctic marine acoustic environment types (i.e., pelagic vs. on-shelf), 2) evaluate the performance of a combination of AM compared to the signal full frequency spectrum to characterize marine mammals acoustic assemblages (i.e., species richness–SR–and species identity) and 3) estimate the contribution of SR to the local marine acoustic heterogeneity measured by single AM. We used 23 different AM to develop a supervised machine learning approach to discriminate between acoustic environments. AM performance was similar to the full spectrum, achieving correct classifications for SR levels of 58% and 92% for pelagic and on-shelf sites respectively and 〉 88% for species identities. Our analyses show that a combination of AM is a promising approach to characterize marine acoustic communities. It allows an intuitive ecological interpretation of passive acoustic data, which in the light of ongoing environmental changes, supports the holistic approach needed to detect and understand trends in species diversity, acoustic communities and underwater habitat quality