Sabre D. Mahaffy

While coastal delphinid sociality has been extensively investigated across the globe, little is known about the social structure of odontocetes in the open ocean. The rough‐toothed dolphin ( Steno bredanensis ) is a globally distributed oceanic dolphin occurring in tropical and warm‐temperate waters. Around the main Hawaiian Islands, two demographically distinct populations have been identified: one off Kauaʻi and Niʻihau, the other off Hawaiʻi Island. We investigated differences in network structure and association patterns between these populations using photo‐identification data collected from 2002–2020. Social network analysis revealed that the Kauaʻi–Niʻihau population was more subdivided into distinct social clusters (i.e., had higher modularity: 0.58 vs. 0.47) and less densely interconnected (i.e., lower network density: 0.07 vs. 0.12) than the Hawaiʻi Island population. Mean association strength within clusters was higher off Hawaiʻi Island (0.31) than off Kauaʻi–Niʻihau (0.22). Social connections off Hawaiʻi Island also relied more strongly on a smaller number of individuals that linked clusters together. We suggest that differences in population density and habitat extent may contribute to differences in social network structure. Although low re‐sighting rates limited our ability to characterize either population comprehensively, applying identical methods allowed us to identify relative differences in network structure between them.

Compared to their well‐studied coastal temperate counterparts, killer whales ( Orcinus orca ) in tropical‐subtropical and oceanic areas are under‐documented. We used sighting, photo‐identification, and acoustic data of killer whales in the central tropical Pacific (CTP), collected from multiple platforms between 2002 and 2023, to assess their temporal and spatial distribution, group dynamics and behavior, movements, pigmentation and dorsal fin morphology, and vocalizations. Killer whales were rarely encountered but occur year‐round in the CTP, primarily in waters deeper than 1000 m. Photo‐identification of 113 individuals included multi‐year resightings of individuals off the main Hawaiian Islands but found no matches to eastern tropical Pacific catalogs. CTP killer whales share characteristics with other tropical‐subtropical killer whale populations including pigmentation and morphology, small group sizes (range: 1–12, Mdn = 5), and diverse prey choices (e.g., other cetaceans, bony fishes, and sharks). Acoustic recordings, collected during shipboard sightings, were dominated by echolocation clicks and high‐frequency modulated whistles and provide the first detailed characterization of CTP killer whale vocalizations. This is the most expansive study of CTP killer whales to date, and it underscores the importance of continued collaboration between research groups and the local community in order to better understand rarely sighted species.

Spatial and social behaviours in animals are intertwined, yet the causal direction of this feedback—and how it varies across scales—remains largely unresolved. Using long-term data from false killer whales ( Pseudorca crassidens ) in the main Hawaiian Islands, we developed and applied a scale-explicit analytical framework to test how social reliance and resource ephemerality govern top-down versus bottom-up processes linking movement and sociality. Movements, association networks, genetic relatedness, and isotopic niches reveal that strong social bonds drive bottom-up emergence of short-term intra-group movements, while ephemeral and likely island-associated prey landscapes impose top-down constraints on inter-group dynamics across scales. These complementary processes generate persistent, fine-scale fidelity within some groups and relatively well-differentiated feeding niches among them. Our findings highlight a general mechanism by which life-history strategies and environmental stochasticity jointly determine the scale and direction of feedback between space use and sociality—shaping population structure and connectivity in mobile social predators.

Epigenetic aging models hold great promise for enhancing many aspects of wildlife research and management. However, their utility is limited by the need to train models using known‐aged animals, which are rare among wildlife species. We present a novel approach to developing methylation‐based age prediction models that enables us to train models using samples from individuals whose chronological age is estimated with uncertainty based on photo‐identification catalogue data. Our approach incorporates this uncertainty into model training by representing the age of each individual with a probability distribution rather than a point estimate. We similarly represent the methylation profiles of individuals as binomial distributions and produce a distribution of predicted age for each sample that reflects the uncertainty in both its age and methylation profile. We compared age models trained using a wide range of parameterisations, training data sets and analytical methods to determine how well they predicted the catalogue‐based age estimates. The resulting model has a median absolute error of 1.70 years, outperforming many published clocks trained with known‐age samples. This approach significantly expands the range of species for which accurate methylation‐based age models can be developed, particularly those of conservation concern where known‐age samples are limited. By producing distributions of predicted age, it also enables researchers to accurately communicate the uncertainty in their age estimates to subsequent data users.

Age is important for studying population dynamics, but it is difficult to obtain reasonably accurate age estimates and associated uncertainty of free‐ranging individuals, especially for cetaceans. We developed a protocol for deriving probabilistic age estimates using information commonly curated in marine mammal photo‐identification catalogs and applied the approach to 81 biopsy‐sampled and genetically sexed false killer whales ( Pseudorca crassidens ) from the endangered main Hawaiian Islands insular population. The protocol integrates qualitative evidence into a quantitative framework for deriving age estimates and plausible age ranges. Confidence ratings reflecting the strength of available evidence were developed to account for uncertainty. Estimates were then translated to statistical distributions to depict probabilistic age estimates that can be used in further analyses. Age estimates ranged from 3 to 40 years (minimum: 1–33; maximum: 5–65) and were strongly influenced by the estimated age when first seen and length of sighting history. Sensitivity analyses show that population‐level age distribution estimates are robust to age class misclassifications and lack of auxiliary information, including sex. This protocol may provide a guide for aging individuals of some species from photo‐identification catalogs and for which other aging methods from biological samples are not yet feasible or available.

Cookiecutter sharks (Isistius spp.) are small pelagic squaloid sharks found throughout tropical and sub-tropical waters that are known to feed opportunistically on a range of prey, including animals much larger than themselves. Short-finned pilot whales (Globicephala macrorhynchus) are resident to Hawaiʻi Island and are often observed with fresh and healed cookiecutter shark bites. In this study, cookiecutter bites were used to infer the spatiotemporal patterns of the foraging behaviour of sharks on pilot whales off the Hawaiian Islands (21°N, 158°W to 18.5°N, 154.5°W). A photo-identification catalogue of 399 resident short-finned pilot whales (representing 5,859 identifications of known individuals from 365 encounters from 2003 to 2012), were used to infer the prevalence and seasonal variation in shark presence. The mean proportion of the pilot whale’s body visible for documenting shark bites was 22.2% (SD ± 10.0). A total of 9,281fresh, healed, and scarred bite marks were documented on 396 of 399 whales (99.2%). Bites were most frequently documented on the head (32.9% of all bites), followed by the lateral sides (29.8%) and peduncle (26.1%), while the dorsal fin had the lowest percentage of bites (11.2%). The presence of fresh bites varied with ordinal date, with peaks in April, July and mid-October and were also negatively correlated with sea surface temperature. There was also a peak in fresh bites in the transition between crescent and quarter lunar phases. These results provide further evidence that cookiecutter sharks in Hawaiʻi may perform seasonal migrations or dietary shifts.

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.