Marine Mammal Science最新文献

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.

Monitoring changes to animals' physiological states in managed settings is critical in modern animal welfare assessment. Under human care, marine mammals can be conditioned for voluntary biological sample collection, reducing effects of handling stress on physiological state, thus better reflecting normal physiology. This study validated the use of salivary cortisol in bottlenose dolphins as an alternative to blood cortisol for evaluating acute adrenal response to a controlled physiological stressor. Time-matched blood and saliva were collected from nine bottlenose dolphins before, during, and after out-of-water annual vaccination, and analyzed by enzyme-immunoassay. Significant short-term peaks in cortisol occurred similarly in both blood and saliva occurred during vaccination, validating detection of a marked adrenal response. We also measured diurnal variation in salivary cortisol over daylight periods in 12 dolphins over 15 days. Salivary cortisol exhibited a detectable diurnal rhythm in males only, with peaks occurring at first sampling and declining throughout the day. Both intra- and interindividual differences in mean salivary cortisol levels were detected, highlighting the need to establish normal baseline parameters at an individual level for welfare assessment. This sampling approach demonstrated the potential for voluntary serial saliva sampling in animal care facilities as a welfare monitoring tool.

The Australian fur seal ( Arctocephalus pusillus doriferus , AUFS) population, currently less than 47% of its pre-harvest size, represents the largest resident marine predator biomass in south-eastern Australia. This region, characterized by low marine productivity and rapid warming, is home to Kanowna Island, the third-largest AUFS colony. Territorial male AUFS, due to size sexual dimorphism, exert a greater influence on trophic dynamics than their conspecifics and serve as indicators of ecosystem health through their body condition index (BCI). Over a 12-year period (2009–2021), BCI data from 547 adult males revealed a significant decline, suggesting deteriorating nutritional conditions. Lower BCI was associated with warmer sea surface temperatures (current-year), higher spring Chlorophyll-a concentrations in southern Tasmanian waters (1-year lag), and stronger Bonney Upwelling westerly winds (2-year lag). Additionally, negative correlations emerged with the Indian Ocean Dipole (current- and 2-year lags), while positive correlations were linked to the Southern Annular Mode and Southern Oscillation Index (1-year and 2-year lags). These findings indicate that climate variability and warming may further impact AUFS male body condition, posing risks to broader demographic parameters and population stability. Long-term monitoring is essential to evaluate ongoing nutritional stress and potential population-level consequences under future climate scenarios.