Marine Mammal Science最新文献

Goose-beaked whale (Ziphius cavirostris), a cosmopolitan odontocete, is commonly found in the Mediterranean Sea. This study, the first to examine the stomach contents of the goose-beaked whale in the Aegean Sea and Levantine Basin, reveals key aspects of its diet. The stomach contents of one whale from Seferihisar, Türkiye, in 2016, and five from a mass stranding on Cyprus in February 2023 were analyzed. A total of 1,448 lower beaks from 16 cephalopod species were identified, with six species—Octopoteuthis sicula, Ancistrocheirus lesueurii, Histioteuthis reversa, Chtenopteryx sicula, Chiroteuthis veranii, and Todarodes sagittatus—comprising the primary diet. Four species—Loligo forbesii, Pyroteuthis margaritifera, Pterygioteuthis giardi, and Brachioteuthis riisei—were recorded for the first time in goose-beaked whale stomachs. Their prey preference is generally pelagic cephalopods, though benthic or demersal species are occasionally eaten. The high species diversity and the presence of species not found in other studies may be due to differences in cephalopod fauna characterized by seabed and other oceanographic features of the eastern Mediterranean. The Mediterranean population is genetically divided into western and eastern subpopulations, and their diets appear to differ.

Humpback whales have the most diverse diet of all rorquals. Their ability to use different prey depending on local availability makes them a promising indicator species for ecosystem dynamics. During five summer–fall seasons in 2017–2021, regular observations of humpback whale feeding aggregations were conducted as part of multi-year cetacean monitoring in Senyavin Strait, on the eastern Chukotka Peninsula. The study included assessing the trophic level of the whales using stable isotope analysis, as well as collateral observations of feeding behavior, spatial distribution, and surface activity records. We found that the spatial distribution, daytime activity patterns, and trophic levels of the whales differed significantly between 2017 and 2018–2021. These differences, combined with some additional observations of whale feeding activity, suggest that the whales fed on fish, most likely polar cod, in 2017 and switched to preferentially krill in later years. We suggest that our observations in 2017 coincided with a sporadic schooling event of polar cod. We show that a single humpback whale population can abruptly change its feeding habits and switch from one prey type to another under optimal conditions. The high degree of behavioral plasticity may be one of the keys to the evolutionary success of this species.

European Union (EU) legislation requires Member States to monitor the environmental status of European maritime waters and the conservation status of protected species including cetaceans, to assess the impact of anthropogenic activities and the effectiveness of management and conservation actions. Year-round shipboard surveys were conducted between 2007 and 2012 in Madeira archipelago coastal waters, realizing 8713 km of track line (10–24 replicates of each block surveyed) in sea conditions of Beaufort ≤ 4, to study the distribution and abundance of cetaceans. Abundance was estimated using design-based distance sampling methods, whereas distribution was modeled using generalized additive models. Twelve species were recorded, and mean abundance in the study area was estimated for common bottlenose dolphin (623; CV = 0.212), Atlantic-spotted dolphin (985; CV = 0.292), common dolphin (546; CV = 0.280), short-finned pilot whale (120; CV = 0.324), Ziphiidae (31; CV = 0.342), and Balaenopteridae (19; CV = 0.296). These first-surface point estimates of mean abundance and model-predicted distribution for these taxa in Madeira waters provide baseline values for future assessment of their status for the EU Habitats Directive and Marine Framework Strategy Directive. They are also the basis for the creation of a Site of Community Interest for the bottlenose dolphin and an important contribution for the spatial management of whale-watching activities in Madeira.

Sea otters (Enhydra lutris) exhibit morphological and physiological adaptations supporting a mass-specific resting metabolic rate (RMR) 2.9-fold higher than predicted for terrestrial mammals of similar size. Their elevated metabolism results primarily from thermogenic mitochondrial proton leak to compensate for heat loss in the marine environment because of their high surface-area-to-volume ratio, combined with their reliance on fur insulation rather than blubber. Key respiratory adaptations include an enlarged lung volume, 3.5-fold greater than predicted allometrically, and a proportionately elevated tidal volume, enabling efficient oxygen uptake and carbon dioxide elimination. Complementary cardiovascular adaptations include a heart mass 1.3-fold greater than the allometric prediction, a correspondingly elevated stroke volume, normal heart rate, increased hemoglobin concentration, and enhanced arterial oxygen content. Together, these adaptations result in an elevated cardiac output and enhanced convective oxygen transport to support the elevated RMR. These multi-level adaptations, present even in young animals, likely evolved under selective pressures favoring thermogenesis over increased insulation by blubber, representing a convergent evolutionary strategy consistent with the principle of symmorphosis, similar to terrestrial athletic mammals adapted for sustained aerobic performance rather than energy conservation. Additional benefits of enlarged lungs, such as enhanced buoyancy and pulmonary oxygen stores, may also have contributed to their evolution.