Marine Mammal Science最新文献

We compiled, collated, and annotated 1033 dugong records for the Indonesian archipelago for the period 2010–2022. The database comprises 337 incidental reports documented via various media sources and 696 cases based on publications and gray literature. Four of six apparent dugong hotspot areas were clustered around small archipelagos of the Banda Sea. Two others were clustered roughly 1000 km away around archipelagos at the opposite end of the Java Sea. Both Indonesian hotspot clusters were adjacent to recognized dugong hotspots located outside Indonesian waters. Notwithstanding known seagrass-dependency, documented dugong records were not significantly correlated with seagrass abundance. Seagrass was most prevalent around small sparsely populated offshore archipelagos, where riverine freshwater and sedimentation were also less. Notwithstanding seagrass presence along the west coast of Sumatra, the area had limited connectivity to other dugong hotspots and was largely devoid of dugong records. Dugong size–structure data were bimodal and dominated by larger animals, suggesting either recent immigration or recent local decline in reproductive success. Most documented mortality records were on the north-west side of the Java Sea and mainly due to entanglement bycatch. Citizen science, gray literature, and social media data have clear added value but the need for more quantitative, standardized, and reliable data are emphasized.

Wildlife health assessments offer critical insights in applied ecological research, but their interpretation is often limited by missing complementary data. There is heightened need for such data for European harbor seals (Phoca vitulina vitulina) given their recent population decline. We investigated trends in and hematological markers of health and survival of pre- and post- weaned harbor seal pups using a 10-year rehabilitation database (n = 2428), and established hematological reference ranges from clinically healthy pups at release (age 3–12 months; n = 260). Hematological parameters at admission were related to pup age class and diagnoses. Specifically, values for parasitic pneumonia—the predominant diagnosis at admission for post-weaned pups—fell outside reference ranges for some parameters. Both body mass and hematological parameters at admission were related to the probability of surviving to release. Parameters associated with survival differed with age class but included those closely related to immune function, parasitic burden, anemia, and dehydration. Trends in admission numbers and body mass were mostly driven by changes in stranding protocols; however, there was an indication of emerging trends associated with population decline. These findings provide hematological markers to assess health and survival of both stranded and free-living harbor seal pups.

Foraging behavior is a key driver of ecological and evolutionary processes. Individual specialization can influence the behavioral flexibility of populations in response to environmental change, making it crucial to account for individual variation. While biologging has significantly advanced our understanding of individual specializations, its limitations in sample size and ethical concerns related to animal handling highlight the need for alternative approaches. We present a complementary, non-invasive method using relative vibrissae length (RVL) measured from images as a morphological proxy for foraging strategy in Galápagos sea lions (Zalophus wollebaeki). In this species, RVL differs significantly between strategies: benthic foragers have shorter vibrissae due to abrasion compared to pelagic foragers. Our method proved highly reliable, demonstrating strong intra- and inter-observer repeatability, as well as within-season consistency. Moreover, RVL remained stable across multiple years, indicating long-term persistence in individual foraging specialization. Vibrissae length exemplifies how behavioral specializations can shape morphological traits within an individual's lifetime, offering a novel approach to study ecological polymorphisms. Integrating RVL assessments with existing tracking methods can improve our ability to investigate foraging specializations at the population level and bridge the gap between high-resolution data and broader-scale ecological monitoring, providing a scalable tool for studying foraging strategies in pinnipeds.

Cetacean skin microbiome samples are traditionally collected by swabbing the skin of captured animals or using skin tissue from remote biopsies. The effects of different sampling methods are not well understood, and factors such as swab type and storage methods may affect the microbiome. The objective of this study was to determine if samples collected by swabbing biopsied skin from bottlenose dolphins yield sufficient microbial DNA for gene sequencing, while testing if commonly used sampling and storage methods affect the skin microbiome. Skin swab samples were collected during remote biopsy surveys with either a nylon flocked swab and flash frozen with liquid nitrogen or with a cotton swab and stored in RNAlater. Sequencing of the V3–V4 region of the 16S rRNA gene revealed swabs from dolphin skin biopsies yielded sufficient DNA to characterize the microbiome. We found no significant difference between the two sampling and storage methods tested, suggesting that studies using different techniques may be comparable. This work also demonstrates a novel technique to collect samples for interpretation of the skin microbiome of free-ranging animals. Benefits of this method are that it can be done without capture and preserves valuable and typically scarce biopsy skin samples for other analyses.

Baleen plates have been widely used to investigate the life cycle of mysticetes using a variety of chemical markers. Among these, stable isotope analysis (SIA) has been consistently applied to investigate their migratory movements and shifts in diet. However, the location of the baleen segment reflecting the most recently incorporated stable isotopes, corresponding to the whale's most contemporary habitat and diet composition, remains unclear and hampers the correct interpretation of the results. In this study, we analyzed δ¹⁵N, δ¹³C, and δ³⁴S values along the baleen plate of a pregnant fin whale (Balaenoptera physalus) and its fetus to identify the baleen segment/s that were simultaneously deposited in both individuals. Our approach was based on the premise that the fetal baleen had been synthesized soon before sampling and therefore reflected contemporary habitat and diet signals of the pregnant whale. To allow comparison, the results were corrected for fetal–mother discrimination (F-MD) factors (i.e., the isotopic differences between fetal and maternal tissues). Fetal δ¹⁵N and δ¹³C values aligned most closely with maternal baleen segments located 2–4 cm below the gingiva line, indicating that they had likely been deposited simultaneously with fetal baleen formation and therefore reflect the pregnant whale's most recent diet and habitat use. Conversely, fetal δ³⁴S values did not consistently align with any maternal baleen segments, probably due to dissimilar incorporation rates and/or differences in tissue discrimination factors. Our results highlight the importance of extracting baleen from its base, below the gingival line, to correctly assign the timing of deposition of the various baleen segments and ensure accurate interpretation in chronological studies using intrinsic markers on baleen plates.