Marine Mammal Science最新文献

The influence of habitat degradation on the trophic interactions of marine predators remains poorly understood. We investigated the foraging ecology of resident common bottlenose dolphins (Tursiops truncatus) in Biscayne Bay, Florida, which has experienced extensive seagrass loss since 2010. Using stable isotope analysis (δ¹³C and δ¹⁵N) of dolphin skin tissue and Bayesian mixing models (“SIBER” and “MixSIAR” packages in R), we compared foraging habitat and prey preferences of two dolphin communities exposed to differing levels of anthropogenic impact. The mixing models indicate that foraging habitats and food sources are significantly different between communities. Dolphins from the northern community, situated in a highly urbanized area with severe habitat degradation, primarily relied on pelagic prey, while dolphins from the southern community, where habitat degradation is less severe, primarily foraged on seagrass-associated prey. The drivers of spatial differences in foraging habitat preferences and diets are unclear but could reflect the availability and predictability of food sources in pelagic vs. seagrass-associated habitats in Biscayne Bay. Despite these challenges, the dietary plasticity demonstrated by both communities suggests a potential adaptive response to habitat decline. However, dolphins from the northern community may face higher risks due to their proximity to intense anthropogenic activity.

Rorquals and sperm whales are top predators of complex open ocean food webs and, although mesopelagic fish and cephalopods are predated upon by these cetaceans, the contribution of these prey groups to the whales' diet is not fully understood. Here, we aimed to better describe the consumption of mesopelagic prey by identifying targeted species at mid-latitudes. We analyzed the prey availability and predator preferences by comparing the vertical distribution and abundance of fish and cephalopod species in the water column with the prey items found in fecal samples through DNA metabarcoding. We found that rorquals consumed mesopelagic fish that perform diel vertical migrations (DVMs), such as myctophids. These species were found at depths that matched the deep foraging behavior during daytime (0–200 m) and shallow foraging behavior during night (0–50 m), confirming that rorquals rely on the DVM to feed. Also, although a high diversity of cephalopods was found across the water column, the fecal content of sperm whales was mainly composed of Histioteuthis bonnellii, which was abundant between 600 and 1200 m and matches the diving patterns described for this species. Here, we present a comprehensive analysis of the diets of rorquals and sperm whales, expanding our understanding of open ocean trophic ecology to promote effective cetacean conservation.

The common bottlenose dolphin (CBD) inhabits the waters surrounding the Kuroshio Current in the western North Pacific. Understanding its population structure is critical for effective conservation and management. However, the tracking durations of fin-mounted Advanced Research and Global Observation Satellite tags in a previous study were limited to 48 days, restricting insights. This study aimed to improve the understanding of the habitat range of CBDs by extended tracking periods. Between 2020 and 2024, tags were deployed on 14 CBDs off Kii Peninsula facing the Kuroshio waters. Tagged dolphins were tracked for up to 103 days. Most dolphins remained in the coastal waters along the Kuroshio Current, while some moved into the East China Sea or along the Southwest Islands. The movement patterns showed flexibility, with CBDs shifting directions, likely influenced by oceanographic conditions, such as water currents. State-space models fitted with the tracking data showed that the Kuroshio coastal waters were the primary habitat for CBDs. The study also found that some dolphins migrated across the Kuroshio Current to other areas. These results highlight the dynamic nature of CBD habitat use and the importance of long-term tracking to fully understand their migration and population structure for successful conservation efforts.

Skin lesions are valuable indicators of individual and population health in cetaceans. To understand the occurrence of skin and mucosal lesions among dolphins inhabiting South Australian waters, this study employs opportunistic sampling of deceased dolphins during 2021–2024. A total of 52 dolphins, comprising 23 Indo-Pacific bottlenose dolphins (Tursiops aduncus) and 29 common dolphins (Delphinus delphis), underwent thorough macroscopic, microscopic, and ancillary diagnostics of identified lesions. Thirty-three individuals displayed 115 skin and 12 mucosal lesions. The most common skin lesion sites were the head (23%–34%), peduncle (25%–26%), and lateral surfaces (17%–19%). A negative association was found between body condition and the number of infectious skin lesions in T. aduncus. Tattoo Skin Disease was identified in 13% of D. delphis skin lesions and 29% of T. aduncus skin lesions. Additional etiologies of skin lesions included bacteria (including Erysipelothrix rhusiopathiae, Mycobacterium marinum, Vibrio spp.), protozoa, physiological, and trauma-related (propeller strike and shark bite). Opportunistic bacterial ulcerative dermatitis occurred predominantly in dolphins from the Adelaide Dolphin Sanctuary. Novel findings include the identification of herpesvirus in oral/genital papillomas, cutaneous lesions from an erysipelas-infected animal, and M. marinum skin abscessation, not previously reported in free-ranging Australian cetaceans. This study complements live-animal observational studies and provides diagnostic insight into dolphin skin lesions, supporting their use as population and ecosystem health indicators.

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.