Marine Mammal Science最新文献

Passive acoustic monitoring is a cost-effective means of studying marine mammals that inhabit remote and poorly accessible habitats. Since the 1970s, the mysterious “bio-duck” sound has been reported throughout the Southern Ocean. In 2014, this was attributed to the Antarctic minke whale and has since been retrospectively categorized into different variants of bio-duck calls by multiple studies across a wide geographic range. To date, more than 20 different bio-duck variants have been identified, with intra- and inter-regional variation. Our study presents a bespoke convolutional neural network (CNN) detector trained to identify bio-duck call variants across sites in East Antarctica and Western Australia. The detector achieved high recognition performance across nine geographically distinct datasets, demonstrating strong generalization. Detector performance differed among sites, with the highest performance reported for the Antarctic sites and poorer performance in the Pilbara region of the Australian Northwest Shelf. These differences were explored, comparing the target-signal (bio-duck) levels to ambient noise levels. Variation in performance was likely driven by variable signal-to-noise ratios across testing datasets. This work presents an advancement in the acoustic monitoring of Antarctic minke whales, providing a tool for assessing their acoustic presence across diverse marine soundscapes.

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.