Sealing the deal - Antarctic fur seals' active hunting tactics to capture small evasive prey revealed by miniature sonar tags.

The ability of predators to adopt hunting tactics that minimise escape reactions from prey is crucial for efficient foraging, and depends on detection capabilities and locomotor performance of both predators and prey. Here, we investigated the efficiency of a small pinniped, the Antarctic fur seal (Arctocephalus gazella) at exploiting their small prey by describing for the first time their fine-scale predator-prey interactions. We compared these with those from another diving predator, the southern elephant seal (Mirounga leonina) that forage on the same prey type.

Foraging habits of Northwest Atlantic hooded seals over the past 30 years: Future habitat suitability under global warming.

The Arctic is a global warming 'hot-spot' that is experiencing rapid increases in air and ocean temperatures and concomitant decreases in sea ice cover. These environmental changes are having major consequences on Arctic ecosystems. All Arctic endemic marine mammals are highly dependent on ice-associated ecosystems for at least part of their life cycle and thus are sensitive to the changes occurring in their habitats.

Composition of cetacean communities worldwide shapes their contribution to ocean nutrient cycling.

Defecation by large whales is known to fertilise oceans with nutrients, stimulating phytoplankton and ecosystem productivity. However, our current understanding of these processes is limited to a few species, nutrients and ecosystems. Here, we investigate the role of cetacean communities in the worldwide biological cycling of two major nutrients and six trace nutrients.

Activity-specific metabolic rates for diving, transiting, and resting at sea can be estimated from time-activity budgets in free-ranging marine mammals.

Time and energy are the two most important currencies in animal bioenergetics. How much time animals spend engaged in different activities with specific energetic costs ultimately defines their likelihood of surviving and successfully reproducing. However, it is extremely difficult to determine the energetic costs of independent activities for free-ranging animals.

Reproductive success is energetically linked to foraging efficiency in Antarctic fur seals.

The efficiency with which individuals extract energy from their environment defines their survival and reproductive success, and thus their selective contribution to the population. Individuals that forage more efficiently (i.e.

Flipper strokes can predict energy expenditure and locomotion costs in free-ranging northern and Antarctic fur seals.

Flipper strokes have been proposed as proxies to estimate the energy expended by marine vertebrates while foraging at sea, but this has never been validated on free-ranging otariids (fur seals and sea lions). Our goal was to investigate how well flipper strokes correlate with energy expenditure in 33 foraging northern and Antarctic fur seals equipped with accelerometers, GPS, and time-depth recorders. We concomitantly measured field metabolic rates with the doubly-labelled water method and derived activity-specific energy expenditures using fine-scale time-activity budgets for each seal.

Frigate birds track atmospheric conditions over months-long transoceanic flights.

Understanding how animals respond to atmospheric conditions across space is critical for understanding the evolution of flight strategies and long-distance migrations. We studied the three-dimensional movements and energetics of great frigate birds (Fregata minor) and showed that they can stay aloft for months during transoceanic flights. To do this, birds track the edge of the doldrums to take advantage of favorable winds and strong convection.

Seasonal influence on the response of the somatotropic axis to nutrient restriction and re-alimentation in captive Steller sea lions (Eumetopias jubatus).

Fluctuations in availability of prey resources can impede acquisition of sufficient energy for maintenance and growth. By investigating the hormonal mechanisms of the somatotropic axis that link nutrition, fat metabolism, and lean tissue accretion, we can assess the physiological impact of decreased nutrient intake on growth. Further, species that undergo seasonal periods of reduced intake as a part of their normal life history may have a differential seasonal response to nutrient restriction.

Energy reallocation during and after periods of nutritional stress in Steller sea lions: low-quality diet reduces capacity for physiological adjustments.

Two groups of female Steller sea lions (groups H and P) were subjected to periods of energy restriction and subsequent refeeding during winter and summer to determine changes in energy partitioning among principal physiological functions and the potential consequences to their fitness. Both sea lion groups consumed high-quality fish (herring) before and after the energy restrictions. During restrictions, group H was fed a lower quantity of herring and group P a caloric equivalent of low-quality fish (pollock).

Changes in glucocorticoids, IGF-I and thyroid hormones as indicators of nutritional stress and subsequent refeeding in Steller sea lions (Eumetopias jubatus).

Physiological responses to changes in energy balance are tightly regulated by the endocrine system through glucocorticoids, IGF-I and thyroid hormones. Changes in these hormones were studied in eight captive female Steller sea lions that experienced changes in food intake, body mass, body composition, and blood metabolites during summer and winter. During a period of energy restriction, one group of sea lions was fed reduced amounts of Pacific herring and another was fed an isocaloric diet of walleye pollock, after which both groups returned to their pre-experimental diets of herring.