Marine Mammal Science最新文献

In 2024, an expedition was conducted off northwestern Baja California, México, to find and identify the beaked whale species that produced the BW43 echolocation pulse previously recorded in this area and elsewhere in the North Pacific. There were five Mesoplodon sightings and 21 BW43 acoustic detections on both a towed array and drifting pole buoy recorders over the course of the survey. Three of the sightings had concurrent acoustic detections, and a biopsy sample and environmental DNA were also collected from one of the sightings. The genetic identification confirms that the Mesoplodon sighted and acoustically recorded was the ginkgo-toothed beaked whale (Mesoplodon ginkgodens), and the co-occurrence of these sightings with the BW43 acoustic detections definitively links the species and its echolocation pulse. This is the first time that genetically confirmed ginkgo-toothed beaked whales have been observed at sea and definitively linked to the BW43 pulse. This paper details the encounters, acoustic behavior, genetics, coloration, and external morphology of this species, including a comprehensive review of its distribution using historical sightings, strandings, and acoustic detection data from the North Pacific Ocean.

Harbor seals (Phoca vitulina) are one of the most important apex-predators in the Wadden Sea. However, baseline information on their distribution and behavior is still sparse and geographically restricted. Passive acoustic monitoring (PAM) of their underwater sounds can provide information about their fine-scaled distribution and habitat use. This study is the first to analyze underwater vocal behavior of harbor seals in the Wadden Sea, exploring temporal patterns and characteristics of vocalizations. Passive acoustic data from the Dutch Wadden Sea were collected east of Lauwersoog during the breeding season in July 2021 and south of the island of Vlieland in September 2022. We describe and document four acoustically distinct harbor seal call types based on spectro-temporal call characteristics. Results showed a significantly higher vocal activity for two out of the four call types during the breeding season and clear differences in the dial distribution of calls. The results of this study provide a basis for PAM-based monitoring of harbor seal activity and a potential fundament for AI-based call detection algorithms. The increasing evidence for the importance of underwater sound for aquatic habitat quality and suitability emphasizes the need to acoustically map critical habitats and document the natural sounds of living organisms.

North Pacific humpback whales (Megaptera novaeangliae) have recovered rapidly following their depletion by commercial whaling. Diet studies are necessary to assess food web implications of their recovery. This study investigates the diet composition of humpback whales foraging in the northern Strait of Georgia, British Columbia, Canada, an area experiencing a recent return of humpback whales. Humpback whale skin samples (n = 108), juvenile herring (n = 202), adult herring (n = 23), euphausiids (n = 63), and amphipods (n = 6) were collected in the summer months of 2022 and 2023 and analyzed for carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes. Applying these isotope data, the Bayesian mixing model MixSIAR was used to estimate the contribution of each prey type to humpback whale diet. We found that, during the summer months, humpback whales primarily consumed euphausiids (85.3%, range: 76.4%–94.0%) and juvenile herring (10.2%, range: 0.8%–21.0%), with minimal contributions from adult herring and amphipods. Diet composition was consistent across months and years. These findings provide critical insights into humpback whale foraging ecology, informing conservation efforts for both predator and prey species in the region.

In Atlantic bottlenose dolphins, prior work has suggested that whistle vocalizations often have been observed to co-occur with one bubble type, the bubble stream. However, vocal correlates have not been identified for another type of bubble, the bubble burst. While watching research session recordings, we serendipitously observed an absence of dolphin vocalization during bubble bursts. We formally investigated this in two studies by examining bubble bursts produced by 11 dolphins participating in various tasks with an exploratory study (n = 553) and a preregistered, confirmatory study (n = 150). In both studies, we compare the amplitude during the production of the bubble burst to the 2 s prior to its production, and the presence/absence of different vocal types. Amplitude during the bubble burst was significantly quieter than the 2 s prior, and there were significant reductions in all vocal types, especially among whistles and burst-pulses, in both studies. Physiological evidence supports this phenomenon, since dolphin vocal production depends on pneumatic pressure in the nasal system, which may be relieved when the bubble burst is produced. However, testing in acoustically isolated conditions is necessary to confirm our observations. Aspects of the bubble burst itself, and its vocal suppression, may serve communicative purposes in dolphins.

Monitoring the body condition of animals offers insights into their energetic needs, prey consumption, and vulnerability to environmental pressures. Southern hemisphere humpback whales ( Megaptera novaeangliae ) depend on Antarctic krill for their annual energy requirements. Drone-based photogrammetry was used to assess the energetic cost of migration and reproduction for breeding stock G humpback whales. Body measurements of 103 adult whales (2017–2019) were used to estimate body condition in Colombia (breeding ground) and the Western Antarctic Peninsula (feeding ground) and seasonal change was predicted. Humpback whales reached their peak body condition between early March and late May, and their lowest between late August and early December. The change in body condition was converted into losses of blubber volume, mass, lipid, energy, and ultimately the biomass of krill required to cover migration. On average, an adult humpback whale lost 36 percentage points of its body condition over the migration, equivalent to 12 m³ or 11,000 kg of blubber tissue, 5000 kg of lipid, 196,000,000 kJ or 57,000 kg of Antarctic krill. By linking migration and reproductive energy costs to krill biomass, our findings provide critical ecological context for understanding how environmental changes such as krill population fluctuations could impact whale populations.

Southern right whales ( Eubalaena australis ) have shown population recovery since protection from commercial whaling and are considered a flagship species for successful conservation management. However, recovery remains incomplete, with recent evidence suggesting slowed growth and variability in reproductive success. This project used 30 years of count data in Australia (1992–2022) to investigate long-term trends in relative abundance at three key reproductive areas in South Australia. Varied rates of increase were observed, while recovery trends have moderated at the major aggregation area of Head of Bight (3.34%/year, 95% CI: 2.24, 4.44); higher growth rates were observed at Fowlers Bay, where recolonization has occurred (15.29%/year, 95% CI: 7.54, 24.33). Results support that recovery trends for the Australian population are dynamic and variable across decades. Drivers of variability may include saturation of certain areas, reoccupation of suitable habitats, spatio-temporal disturbance, and changes to factors driving migration, including body condition, prey availability, and climate change. Decadal shifts in relative abundance indicate an expanding habitat range, highlighting the importance of suitable habitat and connective migration corridors, which are increasingly important during critical life stages. Adaptive conservation management and effective threat mitigation are essential to secure recovery of this threatened species in Australia.