Search

Abstract: Understanding environmental drivers of species’ behavior is key for successful conservation. Within cetacean research, studies focused on understanding such drivers often consider local conditions (e.g., sea surface temperature), but rarely include large-scale, long-term parameters such as climate indices. Here we make use of long-term passive acoustic monitoring data to examine relationships between eight classes of toothed whales and climate indices, specifically El Niño Southern Oscillation, Pacific Decadal Oscillation, and North Pacific Gyre Oscillation, as well as local surface conditions (temperature, salinity, sea surface height) at two sites in the Hawaiian Archipelago. We find that El Niño Southern Oscillation most influenced cetacean detections at monitored sites. In many cases, detection patterns matched well with combinations of one or more climate indices and surface conditions. Our results highlight the importance of considering climate indices in efforts to understand relationships between marine top predators and environmental conditions.

Successful conservation and management of marine top predators rely on detailed documentation of spatiotemporal behavior. For cetacean species, this information is key to defining stocks, habitat use, and mitigating harmful interactions. Research focused on this goal is employing methodologies such as visual observations, tag data, and passive acoustic monitoring (PAM) data. However, many studies are temporally limited or focus on only one or few species. In this study, we make use of an existing long-term (2009-2019), labeled PAM data set to examine spatiotemporal patterning of at least 10 odontocete (toothed whale) species in the Hawaiian Islands using compositional analyses and modeling techniques. Species composition differs among considered sites, and this difference is robust to seasonal movement patterns. Temporally, hour of day was the most significant predictor of detection across species and sites, followed by season, though patterns differed among species. We describe long-term trends in species detection at one site and note that they are markedly similar for many species. These trends may be related to long-term, underlying oceanographic cycles that will be the focus of future study. We demonstrate the variability of temporal patterns even at relatively close sites, which may imply that wide-ranging models of species presence are missing key fine-scale movement patterns. Documented seasonal differences in detection also highlights the importance of considering season in survey design both regionally and elsewhere. We emphasize the utility of long-term, continuous monitoring in highlighting temporal patterns that may relate to underlying climatic states and help us predict responses to climate change. We conclude that long-term PAM records are a valuable resource for documenting spatiotemporal patterns and can contribute many insights into the lives of top predators, even in highly studied regions such as the Hawaiian Islands.

Passive acoustic monitoring (PAM) has proven a powerful tool for the study of marine mammals, allowing for documentation of biologically relevant factors such as movement patterns or animal behaviors while remaining largely non-invasive and cost effective. From 2008-2019, a set of PAM recordings covering the frequency band of most toothed whale (odontocete) echolocation clicks were collected at sites off the islands of Hawai'i, Kaua'i, and Pearl and Hermes Reef. However, due to the size of this dataset and the complexity of species-level acoustic classification, multi-year, multi-species analyses had not yet been completed. This study shows how a machine learning toolkit can effectively mitigate this problem by detecting and classifying echolocation clicks using a combination of unsupervised clustering methods and human-mediated analyses. Using these methods, it was possible to distill ten unique echolocation click 'types' attributable to regional odontocetes at the genus or species level. In one case, auxiliary sightings and recordings were used to attribute a new click type to the rough-toothed dolphin, Steno bredanensis. Types defined by clustering were then used as input classes in a neural-network based classifier, which was trained, tested, and evaluated on 5-minute binned data segments. Network precision was variable, with lower precision occurring most notably for false killer whales, Pseudorca crassidens, across all sites (35-76%). However, accuracy and recall were high (>96% and >75%, respectively) in all cases except for one type of short-finned pilot whale, Globicephala macrorhynchus, call class at Kaua'i and Pearl and Hermes Reef (recall >66%). These results emphasize the utility of machine learning in analysis of large PAM datasets. The classifier and timeseries developed here will facilitate further analyses of spatiotemporal patterns of included toothed whales. Broader application of these methods may improve the efficiency of global multi-species PAM data processing for echolocation clicks, which is needed as these datasets continue to grow.

Background: To tag large marine vertebrates, without the need to catch them, avoiding using barbs for tag retention, and precisely controlling tag location, the remote Tag Attachment Device on a pole (TADpole) was developed. This allows single-pin tags (Finmount, Wildlife Computers) to be attached to the dorsal fins of free-swimming large marine vertebrates. Results: TADpole comprises a pole-mounted holster that carries a tag. It uses compressed air, and a micro-controller, to rapidly insert a stainless-steel pin through a corrodible metal retaining ring in the first tag attachment wing, the animal's dorsal fin, and then a press fit Delrin retaining ring in the tag wing on the other side of the fin. Tagging only occurs when the trailing edge of the dorsal fin touches a trigger bar in the holster, ensuring optimal pin placement. It was developed using fins from cadavers, then trialed on briefly restrained coastal dolphins that could be followed in successive days and weeks, and then on free-swimming animals in the field. The latter showed very short touch/response intervals and highlighted the need for several iterative revisions of the pneumatic system. This resulted in reducing the total time from triggering to tag application to ~ 20 ms. Subsequent efforts expanded the TADpole's applicability to sharks. One free-swimming Atlantic spotted dolphin, two white sharks, and one whale shark were then tagged using the TADpole. Conclusions: Being able to tag free-swimming dolphins and sharks remotely and precisely with satellite-linked telemetry devices may contribute to solving conservation challenges. Sharks were easier to tag than dolphins. Dolphin touch-to-response times were 28 ms or less. Delphinid skin has unique polymodal axon bundles that project into the epidermis, perhaps a factor in their uniquely fast response, which is 10 × faster than humans. Their primary reaction to tagging is to abduct the flippers and roll the fin out of the TADpole holster. This device has the potential to deliver high-quality tag data from large vertebrates with dorsal fins without the stress and logistics associated with catch-and-release, and without the trauma of tags that use barbs for retention. It also collects a dorsal fin biopsy core. [ABSTRACT FROM AUTHOR]

Natural populations that are rare, cryptic or inaccessible provide a monumental challenge to monitoring, as adequate data are extremely difficult to collect. Surveys often encompass only a small portion of a population's range due to difficult terrain or inclement weather, especially for populations with extensive ranges. Thus, to maximise encounters, sampling efforts may be largely opportunistic or biased to accessible areas. The resulting sparse and spatially biased data may be difficult to model, standardise across years and incorporate into an assessment or management framework. However, in many monitoring programs, there are usually multiple threads of data that, though each may have its own limitations, can be synthesised to reveal important ecological processes.Here, we demonstrate a simple technique to incorporate two additional streams of data on the same population, telemetry and survey effort data, into capture‐recapture analyses to address spatiotemporal sampling bias using simulated data. Utilisation distributions (UDs) computed from telemetry data are overlaid with UDs of survey efforts, providing an 'effort by animal space use' overlap covariate for modelling detection in a Jolly–Seber open population model.Using simulated data, we found that our method resulted in more accurate and precise estimates of abundance than traditional capture‐recapture models. We then applied this method to a 16 year photo‐identification capture‐recapture dataset (n = 143 individuals) along with telemetry data (n = 44 satellite tag deployments) collected from the endangered population of false killer whales resident to the main Hawaiian Islands.Incorporating space use and effort into this analysis improved precision of abundance estimates relative to previous modelling endeavours. [ABSTRACT FROM AUTHOR]

This article discusses the recommendation to rename the species Ziphius cavirostris, commonly known as Cuvier's beaked whale, to the goose-beaked whale. The authors argue that the current name perpetuates harm due to Georges Cuvier's involvement in scientific racism and misogyny. They highlight Cuvier's role in creating and disseminating scientific racism, as well as his exploitation of Saartjie Baartman, a Khoisan woman. The authors call for the marine mammal science community to discontinue the use of Cuvier's name and to reconsider all eponymous names of marine mammal species, in order to create a more inclusive and respectful field. [Extracted from the article]

Endangered Southern Resident killer whales (Orcinus orca) are fish‐eaters that preferentially prey on adult Chinook salmon (Oncorhynchus tshawytscha). Despite being salmon specialists, individuals from all three killer whale pods (J, K, L) have been observed harassing and killing porpoises (family Phocoenidae) without consuming them. Retrospectively, we identified and analyzed 78 episodes of Southern Resident killer whales harassing porpoises between 1962 and 2020, of which 28 resulted in the porpoise's death ("phocoenacide"). Fifty‐six episodes involved harbor porpoise (Phocoena phocoena), 13 involved Dall's porpoise (Phocoenoides dalli), and the porpoise species was unreported for nine episodes. Southern Resident killer whales often targeted young porpoises that were similar in size to adult Chinook salmon. Both sexes participated in porpoise harassment. Juveniles engaged in the behavior the most; however, their rates of engagement were not found to differ significantly from most other age classes. The behavior was passed through generations and social groupings, as it was first observed in L pod and spread to the other two pods. Killer whales are highly complex animals known to exhibit social learning and cultural transmission of learned behaviors, but the reason(s) for this behavior is unknown. Hypotheses include the social and developmental benefits of play, hunting practice, or displaced epimeletic behavior. [ABSTRACT FROM AUTHOR]

Here we update U.S. West Coast Biologically Important Areas (BIAs) that were published in 2015 using new data and approaches. Additionally, BIAs were delineated for two species that were not delineated in the 2015 BIAs: fin whales and Southern Resident killer whales (SRKW). While harbor porpoise BIAs remained the same, substantial changes were made for other species including identifying both larger overall areas (parent BIAs) and smaller core areas (child BIAs). For blue, fin, and humpback whales we identified, delineated, and scored BIAs using the overlap between the distribution and relative density from three data sources, leveraging the strengths and weaknesses of these approaches: 1) habitat density models based on Southwest Fisheries Science Center (SWFSC) line-transect data from systematic ship surveys conducted through 2018, 2) satellite tag data from deployments conducted by three research groups, and 3) sightings of feeding behavior from non-systematic effort mostly associated with small-boat surveys for photo-identification conducted by Cascadia Research Collective. While the previous BIAs were based solely on a more subjective assignment from only the small boat sightings, here we incorporate the other two data sources and use a more rigorous, quantitative approach to identify higher density areas and integrate the data types. This resulted in larger, better-supported, objective BIAs compared to the previous effort. Our methods are also more consistent with the delineation of BIAs in other regions. For SRKWs, the parent BIA was based on a modification of the Critical Habitat boundaries defined by the National Oceanographic and Atmospheric Administration (NOAA) and the Department of Fisheries and Oceans (DFO) Canada; a core BIA highlighting areas of intensified use was identified using both NOAA's Critical Habitat and kernel density analyses of satellite tag data. Gray whale BIAs were re-evaluated for the migratory corridor of Eastern North Pacific gray whales, for Pacific Coast Feeding Group feeding areas, and for gray whales that feed regularly in Puget Sound. [ABSTRACT FROM AUTHOR]

Small, island-associated populations of cetaceans have evolved around numerous oceanic islands, likely due to habitat discontinuities between nearshore and offshore waters. However, little is known about the ecology and structure of cetacean populations around the Mariana Islands, a remote archipelago in the western Pacific Ocean. We present sighting, photo-identification, and genetic data collected during twelve years of surveys around these islands that reveal the existence of a small, island-associated population of bottlenose dolphins. Nearly half of the photo-identified individuals were encountered in more than one year. Both haplotypic and nuclear genetic diversity among sampled individuals was low (haplotypic diversity = 0.701, nuclear heterozygosity = 0.658), suggesting low abundance. We used mark-recapture analysis of photo-identification data to estimate yearly abundance in the southern portion of the population's range from 2011 to 2018. Each abundance estimate was less than 54 individuals, with each upper 95% confidence interval below 100. Additional survey effort is necessary to generate a full population abundance estimate. We found extensive introgression of Fraser's dolphin DNA into both the mitochondrial and nuclear genomes of the population, suggesting at least two hybridization events more than two generations in the past. The Mariana Islands are used extensively by the U.S. military for land and sea training operations. Thus, this unique bottlenose dolphin population likely faces high exposure to multiple threats. [ABSTRACT FROM AUTHOR]

Context: Funding agencies are often unlikely to fund research on rarely-encountered species and limited time is usually spent with such species when they are not the focus of research. Thus, knowledge of these species often lags behind their encounter rates. Aims: To gain information on rarely-encountered odontocetes in Hawai'i while simultaneously studying common ones. Methods: During a long-term small-boat based study, we prioritised time spent with rarely-encountered species, collecting photos and biopsy samples, and satellite tagging. Sample sizes were augmented with photo contributions from members of the public and other researchers, and genetic samples from stranded animals and other researchers. Results from genetic and tag data analyses were interpreted in the context of social network placement and re-sighting histories. Key results: Pygmy killer whales (Feresa attenuata) represented <2% of odontocete sightings, and sighting rates varied by depth and among islands. Photo-identification shows that 318 of 443 identified individuals are linked by association in the main component of the social network. Movements among islands were limited, with individuals off O'ahu and Hawai'i exhibiting high site fidelity, although resident groups from each island share a common mitochondrial haplotype. Three groups involved in mass strandings in two different years were not linked to the main component of the social network, and did not share mitochondrial haplotypes with known resident groups. Conclusions: The approach of prioritising rarely-encountered species for additional sampling is an effective way of learning more about poorly-known species. Implications: Such an approach may be critical for filling data gaps for populations potentially at risk from human activities. Rarely-encountered species of odontocetes often get little research attention or funding to study them. We describe an approach to maximise information from these species while undertaking studies of more common ones, and illustrate this approach with information on pygmy killer whales, a poorly-known and rarely-encountered delphinid in Hawai'i. This article belongs to the Collection Marine Mammals in the Pacific. [ABSTRACT FROM AUTHOR]