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Goal of Research In the last century, the average global temperature has increased by 0.6ºC and the warming is even greater in some areas such as the Polar Regions. The average atmospheric temperature in Antarctica has increased 0.65ºC just in the last 50 years, with some regions, such as the Antarctic Peninsula, increasing 3.5ºC during that period (IPCC 2001). The warming of the Southern Ocean is showing a smaller, but similar trend with a mid-depth temperature increase of 0.17ºC between the 1950’s and 1980’s (Gille 2002). The continued increase in the global temperature will have an unknown impact on the Southern Ocean ecosystem. Marine mammals are a prominent apex predator in the Southern Ocean and play a major role in the ecosystem. The foraging behavior of marine mammals must be able to accommodate seasonal environmental fluctuations that cause significant variation in prey abundance and location. To understand the foraging strategies utilized by marine mammals it is necessary to have information on the spatial and temporal variation of their environment, in addition to information on how organisms respond to these changes. Such information will allow us to determine how the seals are using oceanographic features to find prey. Furthermore, variations in oceanographic features are coupled with climate driven processes. I will investigate, in southern elephant seals (Mirounga leonina) off the Antarctic Peninsula, the relationship of specific diving behavior and animal movements to oceanographic and bathymetric features, develop and test models of these features’ role in defining habitat use, and predict how these animals might respond to oceanographic variations that are coupled with climate change. Although a three year study may not document changes in foraging behavior associated with global climate change, the data collected can be used to make predictions about how they might respond based on their response to annual variation. Rationale Marine apex predators forage in areas where oceanographic features such as currents, frontal systems, thermal layers, sea mounts and continental shelf breaks help to increase prey availability (Boyd et al. 2001, Field et al. 2001). In the Southern Ocean additional features, such as icebergs, local eddies, and characteristics of the marginal ice zone contribute to predator abundance (Veit et al. 1993, Ichii et al. 1998, Bornemann et al. 2000). All of these features are thought to increase foraging efficiency by physically forcing prey to aggregate (van Franecker 1992, Veit et al. 1993). Our understanding of these associations is limited to population level studies that have found correlations between animal abundance and oceanographic features. The current advances in technology of satellite telemetry, dive recorders, and remote sensing methods, allow us to identify specific diving behavior and relate it to different environmental conditions. This study will use location and diving behavior data, animal derived water column temperature and salinity data, and remotely sensed oceanographic data to expand our understanding of how seals are using oceanographic and bathymetric features. Understanding the link between oceanographic features and foraging behavior is essential if we are going to be able to predict the response of pelagic organisms to global climate change. For example, the warming of the Antarctic Peninsula appears to have resulted in a shift in penguin habitat. Adelie penguins in the northern Antarctic Peninsula are moving south and decreasing in numbers while the Chinstrap penguins are increasing in numbers as they are moving south (Smith et al. 1999). The mechanism of this shift remained a mystery until winter foraging behavior data was collected for the two species. Although there is no difference in foraging behavior between the two species during the summer, during the winter Adelie penguins primarily forage in the winter pack ice while Chinstrap penguins forage in open water (Fraser et al. 1992). The decrease in seasonal pack ice associated with the warming of the peninsula would mean less wintering habitat for the Adelie penguins and may be responsible for the decrease in numbers. In addition to changes in winter pack ice, the climate change has more far-reaching effects such as the increase in summer wind stress in the region of South Shetland and Elephant Islands (US Antarctic Marine Living Resources program - AMLR). Changes in wind stress modifies local currents, eddies, and frontal features that in turn affect the foraging behavior of marine predators that rely on these features to concentrate their prey. Southern elephant seals may be experiencing a shift in habitat use similar to that found in the penguins. In 1983 four elephant seals gave birth at Palmer Station (Anvers Island, 64º46’S 64º03’W), much further south than their usual sub-Antarctic breeding grounds (Heimark and Heimark 1986). This was the first time elephant seal births were recorded at Palmer Station. It was originally attributed to an unusually warm summer but now a small number of elephant seal regularly give birth at Palmer Station (Fraser, pers comm). Additionally, although some populations of elephant seals are stable or increasing, others, like the Macquarie Island population, have been declining since the 1950’s (Slip and Burton 1999). The influence of oceanographic variation on prey abundance and distribution may be important in these regional differences. Southern elephant seals are one of the top predators in the southern ocean. They spend most of their lives at sea but are tied to land for reproduction and for the annual molt. Elephant seals demonstrate high site fidelity with most seals returning to the same rookery every year and sometimes even the same beach. At Cape Shirreff adult females come ashore to give birth between October and November and depart after approximately one month on the beach. In January and February, after approximately 2 months at sea, females return for the annual molt. Once again, after a month on shore they return to sea for their long foraging trip and will not return until the following breeding season. Previous studies on southern elephant seal females breeding at South Georgia and Macquarie Islands suggest wide coverage of the Southern Ocean, with foraging areas associated with the Antarctic Polar Front, the continental shelf margin or the ice margin (Hindell et al. 1991, Field et al. 2001). Elephant seals travel thousands of kilometers from the rookery and regularly dive to depths over 1000 meters (Slip et al. 1994). For this reason, southern elephant seals are the ideal species for remote sampling of the Southern Ocean. Furthermore, southern elephant seals may be a key species for indicating ecosystem change. During the 1997 - 1998 El Niño northern elephant seals showed low rates of mass gain, long foraging trips, and demonstrated dive behavior that suggested reduced patch residence time and more transit time compared to non-El Niño years. Crocker et al. (in press) suggest that the difficulty in foraging might have been due to alterations in the oceanographic features the seals rely on to concentrate prey or as cues to locate prey. This study will determine what features elephant seals use to find prey and how they deal with changes in these features. I will investigate this by testing the following hypotheses: 1) Elephant seal foraging behavior will be associated with oceanographic features and 2) elephant seals will exhibit variation in diving behavior depending on the water mass. Elephant seals travel long distances between breeding rookeries and feeding sites, and will therefore likely return to oceanic regions where prey are in high abundance due to predictable oceanic processes. I predict that seal foraging behavior will be associated with strong frontal zones that are thought to aggregate prey. This will result in the seals exhibiting variable dive behavior in the different water masses. 3) Variation in the oceanographic features seals use will lead to changes in habitat use and/or decreased foraging success. During the 1997-1998 El Niño, when there was major changes in the structure and function of the North Pacific sub-tropical gyre, northern elephant seals (Mirounga angustirostris) spent significantly less time in foraging patches and more time in transit between the patches and exhibited significantly lower rate of mass gain compared to non-El Niño years (Crocker et al. in press). Approach This study will be conducted at the US AMLR summer field camp at Cape Shirreff, Livingston Island during the 2004-05, 2005-06, 2006-07 seasons. Cape Shirreff is an ideal site for this research because of its location on the Antarctic Peninsula. The Antarctic Peninsula is a long and narrow extension of the Antarctic continent with a strong climatic gradient, making the climate highly variable and particularly sensitive to climate change. The region has also been the site of US AMLR’s long term oceanographic monitoring focusing on krill and apex predator interactions since 1986. I will deploy satellite tags and time-depth recorders on 10 adult female elephant seals at the end of the breeding season. The tags will be recovered approximately 2 months later when seals return for the annual molt and then redeployed on 10 different adult females at the end of the molt. I will recover the tags during the following season when the seals return to breed. The seals will be instrumented with Satellite Relay Data Loggers (SRDLs – Sea Mammal Research Unit) and archival dive recorders (Wildlife Computers). The SRDLs collect, summarize, and transmit data on the animal’s behavior (location, dive depth, and dive duration) and environment (temperature, salinity, and light) via the ARGOS satellite system. This allows for near real-time tracking and accurate geopositioning. The archival dive recorders must be recovered to obtain the data. These tags measure dive behavior (dive depth, dive duration), environmental temperature, light, and pressure at high resolution. For tag deployment and recovery, seals will be immobilized with an intramuscular injection of Telezol and anesthesia will be maintained with intravenous injections of Ketaset. The female will be weighed using a hand winch and scale suspended from a metal tripod. Body composition will be determined by blubber depth measurements with a portable ultrasound scanner and morphometrics. The SRDLs will be attached to the top of the head with 5 minute marine epoxy with the antenna angled forward so that it will be out of the water when the seal surfaces. The archival dive recorders will similarly be attached to the pelage on the dorsal midline between the shoulders. The tags will be retrieved when the seal returns and the epoxy mount will be left to fall off during the molt. The tag data will be integrated with remotely sensed, in situ, and model derived oceanographic data using a live access server hosted by the Pacific Fisheries Environmental Laboratory. This system allows animal tracks to be visualized along with bathymetry, weekly sea surface temperatures, chlorophyll observations, sea surface height and surface wind vectors. The live access server allows us to extract data in a variety of formats that are easily imported into data analysis programs. I will use the animal derived temperature and salinity data to place behavior in the context of water masses by defining habitat types using hierarchical agglomerative cluster analysis on the temperature and salinity profiles. Each dive's combined temperature and salinity profile can then be assigned to a cluster that will be examined for a relationship to known water types in the Southern Ocean. I will then examine the diving behavior in the different clusters. Elephant seals exhibit a number of distinct recurring dive profiles that have been associated with diving, foraging, and food processing (Crocker et al. 1994, 1997, in press; Le Boeuf et al. 1992, 1993, 2000; Slip et al. 1994; Hindell et al. 1991). Using logistic regression I will look for features associated with different dive profiles. This analysis was used successfully on temperature-depth data from 22 female northern elephant seals (Crocker et al. 2003). They were able to assign 82 ± 9% of dives from each individual into clusters representing thermally defined water types. Additionally there were highly significant changes in diving behavior parameters between water types. This approach should be much improved by the inclusion of salinity data. Habitat usage will be modeled based on individual seal utilization. Animals show preference for a habitat when it uses an area more than would be expected on the basis of relative availability of the habitat. Because seals are central place foragers this approach is complicated by the relative accessibility of habitat from haulout sites. I will model the relative accessibility of habitat mechanistically based on distance from the haulout, speed of movement, and the observed distribution of trip durations (Aarts et al. 2003). I will then use a Generalized Additive model approach to relate the spatial utilization of the seals to the environmental variables defining the habitats. These data will be used to investigate foraging behavior and see how the seals change their behavior to deal with seasonal and annual variation. Significance This study will provide information on the foraging behavior of one of the Southern Oceans prominent apex predators. Global warming will likely affect oceanographic features such as currents, eddies, and ice edge characteristics. This three-year study will most likely not demonstrate affects of global warming on elephant seals but it can provide data that can be used as a baseline in the future. With the information obtained from this study on the mechanisms seals are using to find prey, I will be able to model what affects global warming will have on this species. In addition to providing habitat for many animals, the Southern Ocean plays an important role in global climate. Oceans absorb about half the heat from the sun with the top 3 meters holding more heat than the entire atmosphere. Ocean currents then carry the heat away from the warmer tropics towards the polar regions. Recent studies have found that temperature data collected in the Southern Ocean is better at predicting rainfall in Australia than the Southern Oscillation Index (CSIRO Marine Research). Currently many resources are being devoted to developing models on the Southern Ocean’s role in global climate change. The temperature and salinity profiles collected by the seals will be collecting data in regions and seasons that are unlikely to be sampled in more traditional ways. I will share these data with oceanographers who are working on creating models to predict the effect of global climate change. Literature cited Aarts, G., J. Matthiopoulos, B. McConnell, and M. Fedak. 2003. Modelling habitat preference in seals. 15th Biannual Conference on the Biology of Marine Mammals abstracts. Greensborro, North Carolina. Bornemann, H., M. Kreyscher, S. Ramdohr, T. Martin, A. Carlini, L. Sellmann and J. Plötz. 2000. Southern elephant seal movements and Antarctic sea ice. Antarctic Science 12: 315. Boyd, I.L., E.J. Hawker, M.A. Brandon and I.J. Staniland. 2001. Measurement of ocean temperatures using instruments carried by Antarctic fur seals. Journal of Marine Systems 27: 277-288. Crocker, D.E., D.P. Costa, G.W. Boehlert and B.J. LeBoeuf. 2003. Ocean thermal structure and foraging behavior in female northern elephant seals. 15th Biannual Conference on the Biology of Marine Mammals abstracts. Greensborro, North Carolina. Crocker, D.E., D.P. Costa, B.J. LeBoeuf, P.M. Webb and D.S. Houser (in press). Impact of El Niño on the foraging behavior of female northern elephant seals. Marine Ecology Progress Series. Crocker, D.E., B.J. LeBoeuf and D.P. Costa. 1997. Drift diving in female northern elephant seals: implications for food processing. Canadian Journal of Zoology 75: 27-39. Crocker, D.E., B.J. LeBoeuf, Y. Naito, T. Asaga and D.P. Costa. 1994. Swim speed and dive function in a female northern elephant seal. In: Elephant seals: population biology, ecology, behavior, and physiology, B.J. LeBoeuf and R.M. Laws, eds. University of California Press, Berkeley, CA. pp. 328-342. Field, I., M.A. Hindell, D.J. Slip and K. Michael. 2001. Foraging strategies of southern elephant seals (Mirounga leonina) in relation to frontal zones and water masses. Antarctic Science 13: 371-379. Fraser, W.R., W. Trivelpiece, D.G. Ainley and S.G. Trivelpiece. 1992. Increases in Antarctic penguin populations: reduced competition with whales or a loss of sea ice due to environmental warming? Polar Biology 11: 525-531. Gille, S.T. 2002. Warming of the Southern Ocean Since the 1950’s. Science 295:1275-1277. Heimark, R. J., and G.M. Heimark. 1986. Southern Elephant Seal Mirounga leonina Pupping at Palmer Station Antarctica. Journal of Mammalogy 67: 189-190. Hindell, M.A., D.J. Slip and H.R. Burton. 1991. The diving behavior of adult male and female southern elephant seals, Mirounga leonina. Australian Journal of Zoology 39: 595619. Ichii, T., K. Katayama, N. Obitsu, H. Ishii and M. Naganobu. 1998. Occurrence of Antarctic krill (Euphausia superba) concentrations in the vicinity of the South Shetland Islands: relationship to environmental parameters. Deep Sea Research 45: 1235-1262. Intergovernmental Panel on Climate Change. 2001. Technical Summary. LeBoeuf, B.J., D.E. Crocker, S.B. Blackwell, P.A. Morris and P.A. Thorson. 1993. Sex differences in diving and foraging behavior of northern elephant seals. Symposium of the Zoological Society of London. 66: 149-178. LeBoeuf, B.J., D.E. Crocker, D.P. Costa, S.B. Blackwell, P.M. Webb and D.S. Houser. 2000. Foraging ecology of northern elephant seals. Ecological Monographs 70: 353-382. LeBoeuf, B.J., Y. Naito, T. Asaga, D. Crocker and D.P. Costa. 1992. Swim speed in a female northern elephant seal:Metabolic and foraging implications. Canadian Journal of Zoology 70: 786-795. Slip, D.J. and H.R. Burton. 1999. Population status and seasonal haulout patterns of the southern elephant seal (Mirounga leonine) at Heard Island. Antarctic Science 11: 38-47. Slip, D.J., M.A. Hindell and H.R. Burton. 1994. Diving behavior of southern elephant seals from Macquarie Island: An Overview. In: Elephant seals: population biology, ecology, behavior, and physiology, B.J. LeBoeuf and R.M. Laws, eds. University of California Press, Berkeley, CA, pp 253-270 Smith, R.C., D. Ainley, K. Baker, E. Domack, S. Emslie, B. Fraser, J. Kennett, A Leventer, E. Mosley-Thompson, S. Stammerjohn and M. Vernet. 1999. Marine ecosystem sensitivity to climate change. BioScience 49: 393-404. van Franecker, J. A. 1992. Top predators as indicators for ecosystem events in the confluence zone and the marginal ice zone of the Weddell and Scotia seas, Antarctica, November 1988-January 1989. Polar Biology 12: 93. Veit, R.R., E.D. Silverman and I. Everson. 1993. Aggregation patterns of pelagic predators and their principal prey, Antarctic krill, near South Georgia. Journal of Animal Ecology 62: 551-564.