Marine Mammal Science最新文献

The recent rise of ‘omics and other molecular research technologies alongside improved techniques for tissue preservation have broadened the scope of marine mammal research. Collecting biological samples from wild marine mammals is both logistically challenging and expensive. To enhance the power of marine mammal research, great effort has been made in both the field and the laboratory to ensure the scientific integrity of samples from collection through processing, supporting the long-term use of precious samples across a broad range of studies. However, identifying the best methods of sample preservation can be challenging, especially as this technological toolkit continues to evolve and expand. Standardizing best practices could maximize the scientific value of biological samples, foster multi-institutional collaborative efforts across fields, and improve the quality of individual studies by removing potential sources of error from the collection, handling, and preservation processes. With these aims in mind, we summarize relevant literature, share current expert knowledge, and suggest best practices for sample collection and preservation. This manuscript is intended as a reference resource for scientists interested in exploring collaborative studies and preserving samples in a suitable manner for a broad spectrum of analyses, emphasizing support for ‘omics technologies.

Changes in buoyancy of marine mammals can be used to infer environmental changes. In multiple seal species, how “fast” an animal sinks reveals body condition changes through shifts in buoyancy as the ratio between lean and lipid tissue changes. However, quantifying similar at-sea changes in Weddell seals (Leptonychotes weddellii) has remained unexplored. Here, we present a method of inferring buoyancy of Weddell seals by monitoring descent rates from 4-s time-depth data, to reveal in situ insight of their life cycle. We defined a Buoyancy Indicator Segment (BIS) as the descent rate of a dive segment created with the broken-stick method that was systematically filtered to only include characteristic nonstroking and directed travel segments while excluding lung buoyancy biases. We found that BISs predicted body condition changes in Weddell seals, being a function of dive duration, mean depth, and time-of-year. Descent rates quickened with troughs in early April due to postmolt muscle recovery, early July due to winter conditions, and early September possibly due to pregnancy. Each trough was followed by weight gain, with slowing descent rates reaching peaks in late May, early August, and late October. This new approach showed that determining at-sea condition is possible for Weddell seals, deriving a powerful species and environmental monitoring tool.

The common dolphin (Delphinus delphis) is a widely distributed species exhibiting extensive morphological diversity, with previous taxonomies recognizing multiple Delphinus species primarily based on relative beak length. We sequenced mitochondrial genomes of D. delphis morphotypes from multiple regions, calculated mitogenome nucleotide diversity (π = 0.00504), dated Delphinus mitogenome diversification to 1.27 mya, and conducted phylogenetic and population-level analyses focusing on morphotype and geographic origin. We present the first Delphinus sequencing data from Senegal, at the edge of where long- and short-beaked dolphins co-occur in the Atlantic, but only recovering stranded dolphins with long or indeterminate beak lengths. While we detected little genetic structure across most of the North Atlantic, fixation indices demonstrate that Senegalese dolphins are distinct. Geography did not reliably predict phylogeny, with few monophyletic localities, but we do infer a monophyletic group of long-beaked dolphins from California, Peru, and possibly China. However, neither Senegalese long-beaked dolphins nor long-beaked D. d. tropicalis are closely related to Pacific long-beaked dolphins, providing no support for a worldwide long-beaked clade (formerly D. capensis). Our findings reveal a distinctive Senegal Delphinus population and provide a foundation for global genomic analyses to further investigate the evolution of Delphinus morphotypes.

The enlarged size of the aortic bulb is thought to enhance the ability of marine mammals to remain underwater for extended periods. However, a convincing link between aortic bulb size and diving capacity has not been established. Using new and existing data, we examined the relationships between body size, maximum and routine dive duration, and aortic bulb size of pinnipeds. Comparisons among seven species of pinnipeds showed that the diameter of the aortic bulb increases allometrically with body mass (aortic bulb diameter = 0.58 × body mass^0.41). We also found a linear relationship between routine dive duration and relative aortic bulb diameter (routine dive duration = 0.20 × relative aortic bulb diameter − 3.30), but no apparent relationship with maximum dive duration. Our results indicate that relative aortic bulb diameter influences diving capacity, providing further evidence that the aortic bulb is an adaptation to diving. Specifically, the relative diameter of the aortic bulb partially determines how long pinnipeds can routinely remain underwater. This has implications for the ability of different species of marine mammals to adapt to projected environmental changes and effectively forage or evade threats in altered habitats.

Understanding animals' movements is essential to assess habitat use, life-history strategies, and population dynamics. Here, we investigate the movement and behavior patterns of 153 humpback whales in the Southwest Atlantic Ocean (SWA) using data obtained by satellite telemetry between 2003 and 2019 during the species' breeding season (August–December) off the Brazilian coast. Switching state space models were applied to estimate behavior states (bmode) classified as Area Restricted Search (ARS), Transiting (TRANS), or uncertain. Whales were distributed from 4°S to 24°S, and five clusters of ARS behavior were identified along the Brazilian coast. Generalized linear mixed modeling revealed three main results: (1) a transition towards more sinuous behavioral states with increasing latitude; (2) more sinuous movement behavior around new moons; (3) movement behavior was temporally dynamic throughout the breeding season over the years, particularly in 2019. The results then revealed important regions where humpback whales cluster to engage in mating and nursing behaviors, highlighting the influence of spatial location and environmental cycles on their behavior. Estimated movement behavior presented here improves the knowledge about the habitat use and movement patterns of SWA humpback whales in their breeding ground and can be used to mitigate potential human-related impacts.