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.

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.

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.

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.

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We studied the foraging behaviour of lactating female, adult male and juvenile New Zealand (NZ) fur seals to compare and contrast their foraging strategies and assess the degree of spatial separation of their foraging habitats. Adult male fur seals are longer and heavier than lactating females, which are longer and heavier than juveniles. Trip duration was positively correlated with the distance travelled by all age/sex groups. Juveniles conducted longer trips and travelled further from the colony than males. Both juveniles and males conducted longer trips and travelled further than females, which made brief trips because they were provisioning pups. There were no seasonal differences in the behaviour of males, but females and juveniles foraged closer to the colony in summer when they were moulting and females had younger pups. Behavioural differences were recorded between lactating female, male and juvenile seals in the directional bearing from the colony, the distance travelled, the minimum size of the area that was potentially visited and the horizontal swim speed. Intra-specific foraging competition among these age/sex groups was minimal because lactating females typically used continental shelf waters and males utilised deeper waters over the shelf break, adjacent to female foraging grounds. Furthermore, juveniles used pelagic waters, up to 1000 km south of the habitats used by adults. Differences in the habitats used by females, males and juveniles were also apparent in the seafloor gradient, the SST and the surface chl a concentration, with females using regions with the highest chl a concentrations. Results from this study suggest that smaller seals cannot efficiently utilise prey in the same habitats as larger seals because smaller seals do not have the capacity to spend enough time underwater at the greater depths.

We studied the diving behaviour of adult male and lactating female New Zealand fur seals Arctocephalus forsteri to determine inter-sexual differences in their foraging strategies. Adult male fur seals are significantly longer and heavier than lactating females. Lactating females are central place foragers that regularly provision dependent pups, and consequently females conducted shorter duration foraging trips (5.0 ± 3.7 d) compared to the relatively unconstrained adult males (9.0 ± 3.9 d). Male trip durations were not correlated to variables that measured individuals' dive effort. In lactating females, foraging trip duration was significantly, positively correlated to the number of dives h -1 and negatively correlated with the mean dive duration at night. This indicates that females on longer trips invested relatively more time searching for prey patches, which they utilised on relatively short duration dives. Males and females typically dived at night and appeared to utilise both pelagic and benthic habitats. Males dived deeper (max = 380+ m, mean = 52.1 ± 59.3 m) and for longer (max = 14.8 min, mean = 3.6 ± 2.5 min) than females (max = 312 m and 9.3 min, mean = 41.5 ± 26.8 m and 2.7 ± 1.3 min). Inter-sexual foraging competition is likely to be minimal in this species, because females typically utilised continental shelf waters and males foraged in deeper waters over the continental shelf break, beyond female foraging grounds. Inter-sexual differences in fur seal diving behaviour most likely result from sexual dimorphism, which places different physiological constraints on the diving performance of males and females. KEY WORDS: Arctocephalus · Sexual segregation · Foraging ecology · Resource partitioningResale or republication not permitted without written consent of the publisher

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