John William Durban

In the eastern North Pacific, common dolphins ( Delphinus delphis bairdii and D. d. delphis ) often form large, energetic aggregations that make characterization of group composition challenging. Here we demonstrate how photogrammetry from drones can be used to precisely estimate total length distributions and infer group composition and reproductive patterns of 2 abundant dolphin subspecies. We obtained precise length measurements of 3519 dolphins from scaled aerial images of 29 groups of common dolphins off southern California (USA) from 2017 to 2021. Groups were assigned to 1 of 3 strata based on subspecies and month sampled: D. d. bairdii (June), D. d. bairdii (October), and D. d. delphis (October). Similarities in overall length distributions were found between all 3 strata, though the length range of D. d. delphis was shifted 0.3 m smaller than D. d. bairdii . Using a hierarchical Bayesian multinomial model, we estimated significantly more variability in length compositions for D. d. bairdii groups sampled in June than within other strata, implying more variable social composition for this stratum. The model-derived estimates of the typical length distributions for each stratum revealed that D. d. delphis had significantly higher proportions of calves, while both D. d. bairdii strata had significantly higher proportions of larger sub-adults, potentially related to calving peaks in the first half of the year for both subspecies. These results provide a better understanding of their basic biology and ecology, and vulnerability to natural and anthropogenic disturbances.

Studies of cetacean diving behavior in multiple locations in different ocean basins allow for an assessment of variability within and among populations. We examine foraging dive behaviors of goose‐beaked whales ( Ziphius cavirostris ) and dense‐beaked whales ( Mesoplodon densirostris ) using data from 132 tagged whales in seven locations in the Pacific and Atlantic Oceans and the Mediterranean Sea. Acoustic recording tags are used to identify foraging dives by the presence of echolocation. For other tag types, foraging dives are identified based on maximum dive depth. Five parameters are used to characterize foraging dives: maximum dive depth, foraging dive duration, dive cycle duration, and the mean and standard deviation of echolocation depths. We find that differences among dives within one tagged individual are typically larger than the differences among individuals or among locations, and that differences among individuals are typically similar in magnitude to differences among locations. Regression is used to estimate the mean and standard deviation of echolocation depths from maximum dive depth for dives without acoustic data. Composite values of foraging dive parameters (and standard deviations) are estimated as the average of all study locations.

As important members of the marine ecosystem, baleen whales are frequently managed and protected, but methodology to assess their health remains limited. Recent technological advances, such as the use of drones, support the non-invasive collection of promising health-associated data, including respiratory exhalant microbiota. Here, we considered five health metrics paired with respiratory exhalant samples to examine the utility of characterizing respiratory microorganisms for health diagnostics of North Atlantic right whales (Eubalaena glacialis), one of the most endangered baleen whale species. In 2016–2024, we used drones to collect 103 exhalant samples from 85 individuals to examine the associated microbiome, using amplicon sequencing methods targeting bacteria and archaea. The health status of sampled whales was characterized using an index of body condition derived from full-body vertical drone images, three qualitative assessments obtained from photo-identification imagery, and an existing health and vital rates model. Using an elastic net penalized regression approach, we demonstrate significant relationships between these health metrics and respiratory-associated microorganisms. Bacterial taxa that significantly contributed to the model for the body condition index differed between the thinnest and most robust males in the dataset. The thin whale harbored taxa belonging to the same genus as mammalian pathogens, Clostridium and Peptoniphilus, whereas the robust whale harbored taxa commonly observed in lipid-rich environments, Sediminispirochaeta and Candidatus Gracilibacteria. These differences warrant further investigation into the mechanisms by which bacteria contribute to whale health. Our findings demonstrate the utility of non-invasive multi-metric health models that include respiratory exhalant microbiota for whale health assessment and management.

Killer whales ( Orcinus orca ) are currently recognized as a single ecologically and morphologically diverse, globally distributed species. Multiple morphotypes or ecotypes have been described, often associated with feeding specialization, and several studies have suggested taxonomic revision to include multiple subspecies or species in the genus. We review the ecological, morphological and genetic data for the well-studied ‘resident’ and Bigg’s (aka ‘transient’) ecotypes in the eastern North Pacific and use quantitative taxonomic guidelines and standards to determine whether the taxonomic status of these killer whale ecotypes should be revised. Our review and new analyses indicate that species-level status is justified in both cases, and we conclude that eastern North Pacific Bigg’s killer whales should be recognized as Orcinus rectipinnus (Cope in Scammon, 1869) and resident killer whales should be recognized as Orcinus ater (Cope in Scammon, 1869).

The sensory mechanisms used by baleen whales (Mysticeti) for locating ephemeral, dense prey patches in vast marine habitats are poorly understood. Baleen whales have a functional olfactory system with paired rather than single blowholes (nares), potentially enabling stereo-olfaction. Dimethyl sulfide (DMS) is an odorous gas emitted by phytoplankton in response to grazing by zooplankton. Some seabirds use DMS to locate prey, but this ability has not been demonstrated in whales. For 14 extant species of baleen whale, nares morphometrics (imagery from unoccupied aerial systems, UAS) was related to published trophic level indices using Bayesian phylogenetic mixed modelling. A significant negative relationship was found between nares width and whale trophic level (β= −0.08, lower 95% CI = −0.13, upper 95% CI = −0.03), corresponding with a 39% increase in nares width from highest to lowest trophic level. Thus, species with nasal morphology best suited to stereo-olfaction are more zooplanktivorous. These findings provide evidence that some baleen whale species may be able to localize odorants e.g. DMS. Our results help direct future behavioural trials of olfaction in baleen whales, by highlighting the most appropriate species to study. This is a research priority, given the potential for DMS-mediated plastic ingestion by whales.

Climate change is affecting a wide range of global systems, with polar ecosystems experiencing the most rapid change. Although climate impacts affect lower-trophic-level and short-lived species most directly, it is less clear how long-lived and mobile species will respond to rapid polar warming because they may have the short-term ability to accommodate ecological disruptions while adapting to new conditions. We found that the population dynamics of an iconic and highly mobile polar-associated species are tightly coupled to Arctic prey availability and access to feeding areas. When low prey biomass coincided with high ice cover, gray whales experienced major mortality events, each reducing the population by 15 to 25%. This suggests that even mobile, long-lived species are sensitive to dynamic and changing conditions as the Arctic warms.

Despite their enormous size, whales make their living as voracious predators. To catch their much smaller, more maneuverable prey, they have developed several unique locomotor strategies that require high energetic input, high mechanical power output and a surprising degree of agility. To better understand how body size affects maneuverability at the largest scale, we used bio-logging data, aerial photogrammetry and a high-throughput approach to quantify the maneuvering performance of seven species of free-swimming baleen whale. We found that as body size increases, absolute maneuvering performance decreases: larger whales use lower accelerations and perform slower pitch-changes, rolls and turns than smaller species. We also found that baleen whales exhibit positive allometry of maneuvering performance: relative to their body size, larger whales use higher accelerations, and perform faster pitch-changes, rolls and certain types of turns than smaller species. However, not all maneuvers were impacted by body size in the same way, and we found that larger whales behaviorally adjust for their decreased agility by using turns that they can perform more effectively. The positive allometry of maneuvering performance suggests that large whales have compensated for their increased body size by evolving more effective control surfaces and by preferentially selecting maneuvers that play to their strengths.

Recovering small, endangered populations is challenging, especially if the drivers of declines are not well understood. While infrequent births and deaths may be important to the outlook of endangered populations, small sample sizes confound studies seeking the mechanisms underlying demographic fluctuations. Individual metrics of health, such as nutritive condition, can provide a rich data source on population status and may translate into population trends. We examined interannual changes in body condition metrics of endangered Southern Resident killer whales (SRKW) collected using helicopters and remotely operated drones. We imaged and measured the condition of the majority of all three social pods (J, K, and L) in each of seven years between 2008 and 2019. We used Bayesian multi‐state transition models to identify relationships between body condition changes and both tributary‐specific and area‐based indices of Chinook salmon abundance, and K‐fold cross‐validation to compare the predictive power of candidate salmon covariates. We found that Fraser River (tributary‐specific) and Salish Sea (area‐based) Chinook salmon abundances had the greatest predictive power for J Pod body condition changes, as well as the strongest relationships between any salmon covariates and SRKW condition across pods. Puget Sound (tributary‐specific) Chinook salmon abundance had the greatest predictive power for L Pod body condition changes, but a weaker relationship than Fraser River or Salish Sea abundance had with J Pod body condition. The best‐fit model for K Pod included no Chinook covariates. In addition, we found elevated mortality probabilities in SRKW exhibiting poor body condition (reflecting depleted fat reserves), 2–3 times higher than whales in more robust condition. Collectively, these findings demonstrate that (1) fluctuations in SRKW body condition can in some cases be linked to Chinook salmon abundance; (2) the three SRKW pods appear to have distinct patterns of body condition fluctuations, suggesting different foraging patterns; and (3) aerial photogrammetry is a useful early‐warning system that can identify SRKW at higher risk of mortality in the near future.

The Antarctic Peninsula (AP) is rapidly warming and empirical data on abundance trends of marine organisms are required to understand the impact of these physical changes, and interacting anthropogenic impacts, on the ecosystem. Recent estimates inferred increasing abundance of Type A killer whales at the top of this food chain, and here we provide new data on the abundance of Type B1 and B2 killer whales using photographic mark‐recaptures collected during austral summers from 2008/2009 to 2017/2018. Both ecotypes were regularly photographed around the AP coastline, particularly off the west side, and individuals of both showed site fidelity across years. B1s had a higher re‐identification rate (58% photographed in multiple years, range: 1–7 years) compared to B2s (31%, 1–4 years). We fit mark‐recapture models that allowed temporary emigration beyond the study area, to effectively monitor the size of wide‐ranging populations and documented contrasting trends for B1s and B2s. A smaller population size (~102) of B1s was estimated to use the area, with a declining trend in abundance (−4.7% per year) and reduced apparent survival in recent years. In contrast, a much larger population size (~740) of B2s was estimated to be generally stable in abundance and apparent survival over the past decade.

Evidence indicates that Antarctic minke whales (AMWs) in the Ross Sea affect the foraging behaviour, especially diet, of sympatric Adélie penguins (ADPEs) by, we hypothesize, influencing the availability of prey they have in common, mainly crystal krill. To further investigate this interaction, we undertook a study in McMurdo Sound during 2012–2013 and 2014–2015 using telemetry and biologging of whales and penguins, shore-based observations and quantification of the preyscape. The 3D distribution and density of prey were assessed using a remotely operated vehicle deployed along and to the interior of the fast-ice edge where AMWs and ADPEs focused their foraging. Acoustic surveys of prey and foraging behaviour of predators indicate that prey remained abundant under the fast ice, becoming successively available to air-breathing predators only as the fast ice retreated. Over both seasons, the ADPE diet included less krill and more Antarctic silverfish once AMWs became abundant, but the penguins' foraging behaviour (i.e. time spent foraging, dive depth, distance from colony) did not change. In addition, over time, krill abundance decreased in the upper water column near the ice edge, consistent with the hypothesis (and previously gathered information) that AMW and ADPE foraging contributed to an alteration of prey availability.