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Understanding how closely related, sympatric species distribute themselves relative to their environment is critical to understanding ecosystem structure and function and predicting effects of environmental variation. The Antarctic Peninsula supports high densities of krill and krill consumers; however, the region is warming rapidly, with unknown consequences. Humpback whales Megaptera novaeangliae and Antarctic minke whales Balaenoptera bonaerensis are the largest krill consumers here, yet key data gaps remain about their distribution, behavior, and interactions and how these will be impacted by changing conditions. Using satellite telemetry and novel spatial point-process modeling techniques, we quantified habitat use of each species relative to dynamic environmental variables and determined overlap in core habitat areas during summer months when sea ice is at a minimum. We found that humpback whales ranged broadly over continental shelf waters, utilizing nearshore bays, while minke whales restricted their movements to sheltered bays and areas where ice is present. This presents a scenario where minke whale core habitat overlaps substantially with the broader home ranges of humpback whales. While there is no indication that prey is limiting in this ecosystem, increased overlap between these species may arise as climate-driven changes that affect the extent, timing, and duration of seasonal sea ice decrease the amount of preferred foraging habitat for minke whales while concurrently increasing it for humpback whales. Our results provide the first quantitative assessment of behaviorally based habitat use and sympatry between these 2 krill consumers and offers insight into the potential effects of a rapidly changing environment on the structure and function of a polar ecosystem.

During the winter months, from June to September, humpback whales Megaptera novaeangliae breed and calve in the waters of the Great Barrier Reef (GBR) after migrating north from Antarctic waters. Clearly defined wintering areas for breeding and calving comparable to those identified in other parts of the world have not yet been identified for humpback whales in the GBR Marine Park (GBRMP), mainly because of its large size, which prohibits broad-scale surveys. To identify important wintering areas in the GBRMP, we developed a predictive spatial habitat model using the Maxent modelling method and presence-only sighting data from nondedicated aerial surveys. The model was further validated using a small independent satellite tag data set of 12 whales migrating north into the GBR. The model identified restricted ranges in water depth (30 to 58 m, highest probability 49 m) and sea surface temperature (21 to 23°C, highest probability 21.8°C) and identified 2 core areas of higher probability of whale occurrence in the GBRMP, which correspond well with the movements of satellite tagged whales. We propose that one of the identified core areas is a potentially important wintering area for humpback whales and the other a migration route. With an estimated increase in port and coastal development and shipping activity in the GBRMP and a rapidly increasing population of whales recovering from whaling off the east Australian coast, the rate of human interactions with whales is likely to increase. Identifying important areas for breeding and calving is essential for the future management of human interactions with breeding humpback whales.

Flexibility in foraging behaviour and diet are characteristics of many penguin species. While these 2 aspects of foraging ecology are presumably tightly coupled, the connection between them is rarely examined directly. Using time-depth recorders and satellite telemetry we documented the foraging behaviour of 43 chick-rearing macaroni penguins Eudyptes chrysolophus at Heard Island. We also compared these behavioural data with prey recovered from the stomach contents of each tracked bird. During guard stage, foraging trips were significantly shorter (average duration = 23 ± 18 h, range = 47 ± 40 km) compared to creche stage (average duration = 115 ± 112 h, range = 169 ± 102 km). Creche stage trips also included significantly more shallow dives that appear to be related to travel (39% of dives

The Australian sea lion is a listed threatened species under Australian Commonwealth legislation, based on limited population size and the likelihood of further declines in population abundance. Incidental mortality of this species in the west coast rock lobster fishery was identified as a key threat to the distinct sub-population of about 700 ind. on the west coast of Australia. Reports of incidental mortalities in this fishery from a variety of fishery-dependent sources suggested that a minimum of 4 to 5 mortalities occur every fishing season. All reported captures were in shallow waters (

Southern Ocean waters are highly productive and contain important food resources for many indigenous predators, including humans. Management of these resources has fallen under the regulation of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), which has identified a suite of predators as indicator species for monitoring ecosystem fluctuations, including crabeater seals. For crabeater seals to fulfil this role, however, they must respond predictably to fluctuations in krill distribution and abundance. Here, we investigated the validity of using the diving behaviour of this species as an indicator of krill distribution and abun- dance. We used behavioural data collected from 23 crabeater seals fitted with satellite-linked time- depth recorders off eastern Antarctica to quantify habitat use as a function of the amount of time they spent within geographic regions with varying environmental characteristics. This was then linked with diving behaviour in those regions. By integrating geographic location and diving parameters, we demonstrated that habitat use and foraging behaviour within eastern Antarctic waters fluctuated in response to seasonal and spatial environmental variability. Our attempts to use oceanographic variables to develop models of crabeater seal habitat use and behaviour demonstrated real limitations in inferring behaviour from a simple set of environmental factors, but we identified ocean depth and the proximity to the ice edge as factors influencing seasonal habitat use and diving behaviour. Whilst our understanding of the influences driving crabeater seal distribution has improved as a result of telemetry studies, it would appear premature to infer cross-species patterns in distribution and abun- dance with krill given the low predictive power of models derived in the present study. Furthermore, the dynamic and regionally variable use of pelagic habitat by this widely abundant Antarctic preda- tor has important implications for the estimation of crabeater seal biomass.