Adult male, female and juvenile New Zealand and Australian fur seals Arctocephalus forsteri and A. pusillus doriferus regularly return to colonies, creating the potential for intra-and inter-specific foraging competition in nearby waters. We hypothesise that the fur seals in this study utilise different prey, thereby reducing competition and facilitating coexistence. We analysed scats and regurgitates from adult male, female and juvenile New Zealand fur seals and adult male Australian fur seals and compared prey remains found in the samples. Most prey consumed by adult male and female fur seals occur over the continental shelf or shelf break, less than 200 km from Cape Gantheaume. Adult female fur seals utilised proportionally more low-energy prey such as large squid and medium-sized fish. The adult female diet reflected that of a generalist predator, dictated by prey abundance and their dependant pups' fasting abilities. In contrast, adult male New Zealand and Australian fur seals consumed proportionally more energy-rich prey such as large fish or birds, most likely because they could more efficiently access and/or handle such prey. Juvenile fur seals primarily consumed small fish that occur in pelagic waters, south of the shelf break, suggesting juveniles cannot efficiently utilise prey where adult fur seals forage. The age and sex groups in this study employ dramatically different strategies to maximise their survival and reproductive success and consequently the prey that they utilise reflect their different physiological constraints and metabolic requirements.

Blue whales Balaenoptera musculus aggregate to feed in a regional upwelling system during November-May between the Great Australian Bight (GAB) and Bass Strait. We analysed sightings from aerial surveys over 6 upwelling seasons (2001-02 to 2006-07) to assess within-season patterns of blue whale habitat selection, distribution, and relative abundance. Habitat variables were modelled using a general linear model (GLM) that ranked sea surface temperature (SST) and sea surface chlorophyll (SSC) of equal importance, followed by depth, distance to shore, SSC gradient, distance to shelf break, and SST gradient. Further discrimination by hierarchical partitioning indicated that SST accounted for 84.4% of variation in blue whale presence explained by the model, and that probability of sightings increased with increasing SST. The large study area was resolved into 3 zones showing diversity of habitat from the shallow narrow shelf and associated surface upwelling of the central zone, to the relatively deep upper slope waters, broad shelf and variable upwelling of the western zone, and the intermediate features of the eastern zone. Density kernel estimation showed a trend in distribution from the west during November-December, spreading south-eastward along the shelf throughout the central and eastern zones during January-April, with the central zone most consistently utilised. Encounter rates in central and eastern zones peaked in February, coinciding with peak upwelling intensity and primary productivity. Blue whales avoided inshore upwelling centres, selecting SST ~1°C cooler than remotely sensed ambient SST. Whales selected significantly higher SSC in the central and eastern zones than the western zone, where relative abundance was extremely variable. Most animals departed from the feeding ground by late April.

The extent of increasing anthropogenic impacts on large marine vertebrates partly depends on the animals' movement patterns. Effective conservation requires identification of the key drivers of movement including intrinsic properties and extrinsic constraints associated with the dynamic nature of the environments the animals inhabit. However, the relative importance of intrinsic versus extrinsic factors remains elusive. We analyze a global dataset of ∼2.8 million locations from >2,600 tracked individuals across 50 marine vertebrates evolutionarily separated by millions of years and using different locomotion modes (fly, swim, walk/paddle). Strikingly, movement patterns show a remarkable convergence, being strongly conserved across species and independent of body length and mass, despite these traits ranging over 10 orders of magnitude among the species studied. This represents a fundamental difference between marine and terrestrial vertebrates not previously identified, likely linked to the reduced costs of locomotion in water. Movement patterns were primarily explained by the interaction between species-specific traits and the habitat(s) they move through, resulting in complex movement patterns when moving close to coasts compared with more predictable patterns when moving in open oceans. This distinct difference may be associated with greater complexity within coastal microhabitats, highlighting a critical role of preferred habitat in shaping marine vertebrate global movements. Efforts to develop understanding of the characteristics of vertebrate movement should consider the habitat(s) through which they move to identify how movement patterns will alter with forecasted severe ocean changes, such as reduced Arctic sea ice cover, sea level rise, and declining oxygen content.

Establishing the diets of marine generalist consumers is difficult, with most studies limited to the use of morphological methods for prey identification. Such analyses rely on the preservation of diagnostic hard parts, which can limit taxonomic resolution and introduce biases. DNA-based analyses provide a method to assess the diets of marine species, potentially overcoming many of the limitations introduced by other techniques. This study compared the effectiveness of morphological and DNA-based analysis for determining the diet of a free-ranging generalist predator, the arrow squid (Nototodarus gouldi). A combined approach was more effective than using either of the methods in isolation. Nineteen unique prey taxa were identified, of which six were found by both methods, 10 were only detected using DNA and three were only identified using morphological methods. Morphological techniques only found 50% of the total number of identifiable prey taxa, whereas DNA-based techniques found 84%. This study highlights the benefits of using a combination of techniques to detect and identify prey of generalist marine consumers.