Marine Mammal Science最新文献

Cognition is an animal's real-time adaptation system for responding to change. Rapid environmental change, often anthropogenic, is expanding the range and severity of challenges confronting wild animals. Effective conservation requires a multifaceted approach that includes animals' capacities. Large-brained, long-lived animals such as marine mammals often have extensive capability to adaptively modify their behavior due to their cognition, which comprises the mechanisms of information acquisition, processing, and flexible action. Consequently, current behavior need not be a final predictor of future behavior for these animals. This flexibility provides an underutilized and under examined point of leverage for humans interested in improving life outcomes for wild animals. In this team-written, interdisciplinary paper, we argue that application of cognitive approaches may facilitate many conservation efforts directed toward marine mammals. Starting with a workshop on this topic at the 24th Biennial Conference on the Biology of Marine Mammals, scientists representing a wide range of disciplinary expertise addressed eight different conservation concerns for six marine mammal species and provided potential cognitive explanations of and interventions aimed at related behavior. Our treatment highlights the value of integrated laboratory and field research, and the importance of tight lines of communication between scientists and conservation managers.

Eastern North Pacific gray whales (Eschrichtius robustus) rely on energy obtained from Arctic feeding grounds to complete their 15,000–20,000 km annual round-trip migration between feeding and breeding areas. However, quantitative estimates of their food requirements remain scarce. Using an age-structured bioenergetics model incorporating life cycle stages and migration timings, we estimated daily energy needs across life stages. We found females need to supply nursing calves with 24–35 L of milk per day for 9–10 months. After weaning, juveniles require ~400 kg per day of Arctic amphipods (~5.6% of body weight), while the largest adults need a minimum of ~1000 kg per day (~5.4%) during the 154-day summer foraging period. In contrast, pregnant females need 1600–1900 kg of prey per day (~9%–10%) to support fetal growth and store sufficient energy to produce milk while fasting and traveling northbound after calving in Mexico. Upon returning to their Arctic feeding grounds, lactating females require 1300–1600 kg of prey per day (7.9%–8.6%) for another 3.6 months to support the high costs of milk production. These estimates provide a quantitative framework for assessing how changes in Arctic prey availability can affect gray whale health, fitness, reproductive success, and population trends.

Pygmy killer whales (Feresa attenuata) are a poorly studied, globally-distributed species found in pelagic waters and around oceanic islands. They are naturally rare, making them difficult to study. Reports indicate that they are highly vulnerable to artisanal fisheries bycatch in some areas. To investigate the global genetic structure of these animals, we sequenced a 671 bp section of the mitochondrial control region of 89 globally distributed samples. Overall haplotypic diversity is h = 0.94 ± 0.020, while nucleotide diversity is π = 0.0088 ± 0.0035. We found statistically significant genetic differentiation between all pairs of strata (F_ST from 0.115 to 0.381, Φ_ST from −0.01 to 0.876) and evidence of phylogeographic structure. The most striking result is the deep divergence between samples from the Sulu Sea (n = 3), which are separated from all other pygmy killer whale haplotypes by four transitions and one indel. The net nucleotide divergence between the Sulu Sea haplotypes and all others (d_A = 0.013) is higher than that between many recognized cetacean subspecies and tenfold higher than that between the Pacific and western North Atlantic samples. A Bayesian phylogenetic tree indicates that the divergence between the Sulu Sea and the rest of the samples is comparable to that between other sister species from the same subfamily, suggesting the presence of an unrecognized pygmy killer whale taxon. Further study, including more extensive sampling, is needed in order to better understand and conserve the genetic diversity of this poorly-understood species.

The mating and sociosexual (nonconceptive) behaviors of narrow-ridged finless porpoises (Neophocaena asiaeorientalis) have been extensively studied in captivity. However, such behaviors may differ significantly from those that have developed in wild populations. Drone videos captured the behaviors of wild finless porpoises including a total of 60 copulatory attempts and 76 sociosexual and 103 nursing behavioral events from April 2022 to December 2023 during boat and land-based surveys in the northern Aki Nada region of the Seto Inland Sea, Japan. The majority of copulatory attempts were initiated by adults in groups (61.7%). Receivers evaded 65% of copulatory attempts, while 35% were accepted. Sociosexual behaviors observed included body-to-body rubbing, copulation attempts on nonadults, and homosexual interactions. Most sociosexual events involved the receivers accepting the actions rather than evading them. Despite occasional observations of independently swimming and solitary calves, mother–calf pairs were seen predominantly in the infant position (51.4% of the time), suggesting extensive maternal care in wild conditions. These observations illustrate the variability of sexual behaviors in wild finless porpoises, with most being solitary except for reproduction and individuals living in groups.

There is a pressing need to build population-specific acoustic classifiers for killer whales (Orcinus orca) in the Salish Sea. However, building datasets that result in generalizable models is challenging due to diverse killer whale repertoires and confounding signals such as humpback whale calls and environmental noise. In this work we focus on building biologically informed training datasets with expert guided call type balancing and measure its effects on detection and classification performance. Neural network models were created using the BirdNET framework and were trained to recognize Southern Resident (SRKW) and West Coast Transient (TKW) killer whales, alongside humpback whales and background noise. Models were trained on nine systematically constructed datasets (12,000 samples each) that varied the percentage of call type labeled replacements (0%, 10%, 30%) per killer whale population while holding humpback and background annotations constant. Models were evaluated on 20% of the available training data (holdout) and a novel dataset from a different recording setup and location. Performance was assessed with precision–recall, area under the precision-recall curve, mean average precision, and Matthews Correlation Coefficient to measure misclassification. For both killer whale classes, performance on the in-sample data was high with AUC values above 0.873 but degraded when applied to data collected from a different hydrophone system. Detection and classification accuracy for SRKW was consistently high, while the ability of the models to generalize performance to out-of-distribution data was strongly dependent on call type balancing. Model generalization was sensitive to how call type labeled data were incorporated into the training datasets, with different inclusion strategies producing distinct generalization behaviors across populations. These results demonstrate the value of incorporating domain knowledge when training bioacoustics neural networks and highlight the need for publicly available call type catalogs across populations.

Telomeres, repetitive nucleotide sequences at chromosome ends, shorten with oxidative damage and cell replication, and are increasingly used as biomarkers of stress and physiological state. Despite this potential, telomere length (TL) in marine mammals has been measured using Southern blot hybridization in only a few cases, often from different tissue types, limiting interspecific comparisons. This study provides the first standardized TL dataset for leukocytes from blood samples of 42 captive individuals representing 12 species (six cetaceans and six pinnipeds), analyzed with the same Southern blot protocol. Additionally, plasma reactive oxygen metabolites (d-ROMs), biological antioxidant potential (BAP), and proportion of lymphocytes among leukocytes—potentially influencing TL—were measured. Species-mean TLs ranged from 12.1 to 13.9 kb. Bayesian models revealed no statistically meaningful differences in TL, d-ROMs, BAP, or lymphocyte proportion between cetaceans and pinnipeds. At the individual level, TL showed no significant association with d-ROMs, BAP, or lymphocyte proportion, but a weak negative association with age. Because all animals were captive, future research incorporating wild individuals will be essential to clarify species- or taxon-specific physiological baselines. This study fills a methodological gap by providing the first multi-species, standardized reference for TL and oxidative stress markers in marine mammals from the blood cell type.

Pedigrees can provide important data for abundance estimation by providing a means to infer the presence of individuals that might otherwise not be detected. Such information may be particularly important for endangered species, where the addition or removal of just a few individuals can make the difference between population growth and decline. Here, we use gametic mark-recapture methods to incorporate pedigree information into male abundance estimates for the endangered North Atlantic right whale (Eubalaena glacialis)—a species for which there is conflicting information: some data suggest that almost all individuals have been identified by photo-identification efforts and are therefore accounted for, whereas other data suggest that a substantial number of individuals may not be identified and are therefore “missing” from abundance estimates. Our pedigree analyses did not infer a large number of North Atlantic right whales that were unaccounted for in the photo-identification data, suggesting that the photo-identification catalog is representative of the species as a whole and that abundance estimates based on those data are accurate.