Michael Fedak | University of St Andrews (original) (raw)

Papers by Michael Fedak

American Journal of Physiology-Legacy Content, 1976

During the antarctic winter emperor penguins (Aptenodytes forsteri) spend up to four mo fasting w... more During the antarctic winter emperor penguins (Aptenodytes forsteri) spend up to four mo fasting while they breed at rookeries 80 km or more from the sea, huddling close together in the cold. This breeding cycle makes exceptional demands on their energy reserves, and we therefore studied their thermoregulation and locomotion. Rates of metabolism were measured in five birds (mean body mass, 23.37 kg) at ambient temperatures ranging from 25 to -47 degrees C. Between 20 and -10 degrees C the metabolic rate (standard metabolic rate (SMR)) remained neraly constant, about 42.9 W. Below -10 degrees C metabolic rate increased lineraly with decreasing ambient temperature and at -47 degrees C it was 70% above the SMR. Mean thermal conductance below -10 degrees C was 1.57 W m-2 degrees C-1. Metabolic rate during treadmill walking increased linearly with increasing speed. Our data suggest that walking 200 km (from the sea to the rookery and back) requires less than 15% of the energy reserves of ...

Journal of Applied Physiology, 1990

The body composition of living gray seals (Halichoerus grypus) can be accurately predicted from a... more The body composition of living gray seals (Halichoerus grypus) can be accurately predicted from a two-step model that involves measurement of total body water (TBW) by 2H or 3H dilution and application of predictive relationships between body components and TBW that were derived empirically by slaughter chemical analysis. TBW was overestimated by both 2HHO and 3HHO dilution; mean overestimates were 2.8 +/- 0.9% (SE) with 2H and 4.0 +/- 0.6% with 3H. The relationships for prediction of total body fat (TBF), protein (TBP), gross energy (TBGE), and ash (TBA) were as follows: %TBF = 105.1 - 1.47 (%TBW); %TBP = 0.42 (%TBW) - 4.75; TBGE (MJ) = 40.8 (mass in kg) - 48.5 (TBW in kg) - 0.4; and TBA (kg) = 0.1 - 0.008 (mass in kg) + 0.05 (TBW in kg). These relationships are applicable to gray seals of both sexes over a wide range of age and body conditions, and they predict the body composition of gray seals more accurately than the predictive equations derived from ringed seals (Pusa hispida)...

Veterinary Record, 1988

A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be... more A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be a reliable and reasonably safe immobilisation agent for field work on grey and southern elephant seals. It was better than previously reported drugs used either singly or in combination.

Veterinary Record, 1988

A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be... more A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be a reliable and reasonably safe immobilisation agent for field work on grey and southern elephant seals. It was better than previously reported drugs used either singly or in combination.

Journal of Applied Physiology, 1981

A simple one-step procedure that eliminates the need to calibrate the O2 analyzer or measure the ... more A simple one-step procedure that eliminates the need to calibrate the O2 analyzer or measure the flow past the animal is described for calibrating an open-flow respirometry system. The technique is particularly useful for situations of high ambient humidity and for large or active animals where a mask is employed to capture expired gases. A measured N2 flow is used to calibrate the system. The equations describing the technique are given, and the accuracy of the method is discussed in detail. The errors associated with the technique are compared with those of more conventional procedures and are usually smaller.

The Journal of Applied Ecology, 1989

... (a) R2 Male 9 May 84-13 Aug 84 1 0 63 0-26 RIO Male 18 Jun 85-11 Aug 85 3 0 86 0 37 ... 2. Di... more ... (a) R2 Male 9 May 84-13 Aug 84 1 0 63 0-26 RIO Male 18 Jun 85-11 Aug 85 3 0 86 0 37 ... 2. Diurnal variation in the activity of four male common seals in May, June and July: (a) R2, (b) RIO, (c) R 1I and (d) R25; (El) absent from, (E) diving within or (-) hauled out within study area. ...

The Journal of Visualization and Computer Animation, 1996

Canadian Journal of Zoology, 1992

In the austral summers of 1986 and 1988–1989, 51 southern elephant seals (Mirounga leonina) at Hu... more In the austral summers of 1986 and 1988–1989, 51 southern elephant seals (Mirounga leonina) at Husvik, South Georgia (54°10′S; 36°43′W), were stomach lavaged after chemical immobilization. Only cephalopod remains were retrieved, including 1070 lower beaks that were identified and measured. In total these were estimated to represent a wet weight of 187.8 kg. Fourteen species of squid from 11 families and 2 species of octopod from 1 family were present. The most important species overall were the squids Psychroteuthis glacialis in terms of numerical abundance (33.7%) and Moroteuthis knipovitchi in terms of estimated biomass (31.2%). The remaining biomass was mainly comprised of the five large muscular squids, Kondakovia longimana (24.0%), P. glacialis (15.4%), Martialia hyadesi (11.2%), Alluroteuthis antarcticus (10.8%), and Gonatus antarcticus (3.6%). Larger seals of both sexes fed on a wider variety of cephalopod species than smaller seals, with large males taking the greatest diver...

Biological Conservation, 2005

We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a ... more We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identiWcation and satellite telemetry to investigate trends in grey seal abundance, site Wdelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the Southwest British Isles during their annual cycle. Nine out of 16 seals Wtted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean D 49.8 seals) and a lower abundance during the breeding season (mean D 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3-1), and was close to 1:1 during the summer. Inter-annual site Wdelity outside the breeding season was very high, varying from 70% to 95% of identiWed seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.

Annual Review of Physiology, 1982

This series of four papers investigates the link between the energetics and the mechanics of terr... more This series of four papers investigates the link between the energetics and the mechanics of terrestrial locomotion. Two experimental variables are used throughout the study: speed and body size. Mass-specific metabolic rates of running animals can be varied by about tenfold using either variable. This first paper considers metabolic energy consumed during terrestrial locomotion. New data relating rate of oxygen consumption and speed are reported for: eight species of wild and domestic artiodactyls; seven species of carnivores; four species of primates; and one species of rodent. These are combined with previously published data to formulate a new allometric equation relating mass-specific rates of oxygen consumed (^o,/Af(,) during locomotion at a constant speed to speed and body mass (based on data from 62 avian and mammalian species): V 0 JM h = 0-533 M b-°-* u .v a +0-300 M 6-o-»oa where fy) t /M b has the units ml O t s-1 kg" 1 ; M b is in kg; and v is in m s" 1. This equation can be expressed in terms of mass-specific rates of energy consumption (j^metab/^ft) using the energetic equivalent of 1 ml 0 8 = 20-1 J because the contribution of anaerobic glycolysis was negligible: metab/M. = IO 7 M 6-°-»«.» a + 6-O 3 M ft-»-»»» where E metab /M b has the units watts/kg. This new relationship applies equally well to bipeds and quadrupeds and differs little from the allometric equation reported 12 years ago by Taylor, Schmid-Nielsen & Raab (1970). Ninety per cent of the values calculated from this general equation for the diverse assortment of avian and mammalian species included in this regression fall within 25 % of the observed values at the middle of the speed range where measurements were made. This agreement is impressive when one considers that mass-specific rates of oxygen consumption differed by more than 1400% over this size range of animals.

Due to the low accessibility of the region, most of the seasonally ice-covered Southern Ocean rem... more Due to the low accessibility of the region, most of the seasonally ice-covered Southern Ocean remains unobserved during winter. Here we show that southern elephant seals (Mirounga leonina), equipped with oceanographic sensors, can measure winter hydrography with unprecedented temporal and spatial resolution. Seals provided a 30-fold increase in hydrographic profiles from the sea ice zone, allowing the major fronts to be mapped south of 60° S. Sea-ice formation rates in the East Antarctic sector were estimated ...

Journal of Zoology, 1992

Three types of Argos satellite transmitter were attached to grey seals (Halichoerus grypus) at Do... more Three types of Argos satellite transmitter were attached to grey seals (Halichoerus grypus) at Donna Nook (South Humberside, UK) between 1985 and 1989 in order to investigate their movements. With the first two transmitters (A and B) the entire package was attached to ...

Journal of Applied Ecology, 1999

1. Grey seals Halichoerus grypus Fab. are large, numerous marine top predators. Fears concerning ... more 1. Grey seals Halichoerus grypus Fab. are large, numerous marine top predators. Fears concerning competition with ®sheries have prompted calls for control measures. However, little is known about the areas where grey seals forage or the distances they may travel. 2. The movements of 14 grey seals caught at the Farnes in northeast England (12) and Abertay in eastern Scotland (2) between August 1991 and July 1993 were investigated using Argos Satellite Relay Data Loggers (SRDLs). A total of 1461 seal days of location and behavioural data (mean 104´3 days per seal) covered all months of the year except February and March. 3. The seal movements were on two geographical scales: long and distant travel (up to 2100 km away); and local, repeated trips from the Farnes, Abertay and other haul-out sites to discrete oshore areas. 4. Long distance travel included visits to Orkney, Shetland, the Faroes, and far oshore into the Eastern Atlantic and the North Sea. During travel the seals moved at speeds of between 75 and 100 km day ±1 (0´87 and 1´16 m s ±1). Most of the time, long distance travel was directed to known haul-out sites. The large distances travelled indicate that grey seals that haul out at the Farnes are not ecologically isolated from those at Orkney, Shetland and the Faroes. 5. In 88% of trips to sea, individual seals returned to the same haul-out site from which they departed. The durations of these trips were short (mean 2´33 days) and their destinations at sea were often localized areas characterized by a gravel/sand seabed sediment. This is the preferred burrowing habitat of sandeels, an important part of grey seal diet. This, and the fact that dives in these areas were primarily to the seabed, leads us to conclude that these were foraging areas. The limited extents of return-trips from a haul-out site (mean 39´8 km) suggest that the direct impact of seal predation may be greater on ®sheries within this coastal zone, especially those near seal haul-out sites, rather than on ®sheries further oshore. 6. An average of 43% of all the seals' time was spent within 10 km of a haul-out site, although localized foraging areas were identi®ed considerably further oshore. Proximity to a haul-out may provide safety from predation. Alternatively, these periods may be used for rest or social interaction, or we may be underestimating foraging activity near haul-out sites. 7. We suggest that the movement patterns observed in this study may persist through time and across the grey seals which haul-out at the Farnes. We also suggest that a study such as this could be combined with diet studies and haul-out censuses to map foraging intensity. Such information is an essential component of seal±®shery interaction models, upon which management decisions should be based.

Proceedings of the National Academy of Sciences, 2007

Responses by marine top predators to environmental variability have previously been almost imposs... more Responses by marine top predators to environmental variability have previously been almost impossible to observe directly. By using animal-mounted instruments simultaneously recording movements, diving behavior, and in situ oceanographic properties, we studied the behavioral and physiological responses of southern elephant seals to spatial environmental variability throughout their circumpolar range. Improved body condition of seals in the Atlantic sector was associated with Circumpolar Deep Water upwelling regions within the Antarctic Circumpolar Current, whereas High-Salinity Shelf Waters or temperature/salinity gradients under winter pack ice were important in the Indian and Pacific sectors. Energetic consequences of these variations could help explain recently observed population trends, showing the usefulness of this approach in examining the sensitivity of top predators to global and regional-scale climate variability.

Journal of experimental biology, 2004

The energetic cost of diving in marine mammals is a difficult value to derive given the problems ... more The energetic cost of diving in marine mammals is a difficult value to derive given the problems of assessing metabolic rate for an animal at sea. Nevertheless, it is fundamental to our understanding of the foraging strategies of air-breathers exploiting underwater food sources. We ...

American Journal of Physiology-Legacy Content, 1976

During the antarctic winter emperor penguins (Aptenodytes forsteri) spend up to four mo fasting w... more During the antarctic winter emperor penguins (Aptenodytes forsteri) spend up to four mo fasting while they breed at rookeries 80 km or more from the sea, huddling close together in the cold. This breeding cycle makes exceptional demands on their energy reserves, and we therefore studied their thermoregulation and locomotion. Rates of metabolism were measured in five birds (mean body mass, 23.37 kg) at ambient temperatures ranging from 25 to -47 degrees C. Between 20 and -10 degrees C the metabolic rate (standard metabolic rate (SMR)) remained neraly constant, about 42.9 W. Below -10 degrees C metabolic rate increased lineraly with decreasing ambient temperature and at -47 degrees C it was 70% above the SMR. Mean thermal conductance below -10 degrees C was 1.57 W m-2 degrees C-1. Metabolic rate during treadmill walking increased linearly with increasing speed. Our data suggest that walking 200 km (from the sea to the rookery and back) requires less than 15% of the energy reserves of ...

Journal of Applied Physiology, 1990

The body composition of living gray seals (Halichoerus grypus) can be accurately predicted from a... more The body composition of living gray seals (Halichoerus grypus) can be accurately predicted from a two-step model that involves measurement of total body water (TBW) by 2H or 3H dilution and application of predictive relationships between body components and TBW that were derived empirically by slaughter chemical analysis. TBW was overestimated by both 2HHO and 3HHO dilution; mean overestimates were 2.8 +/- 0.9% (SE) with 2H and 4.0 +/- 0.6% with 3H. The relationships for prediction of total body fat (TBF), protein (TBP), gross energy (TBGE), and ash (TBA) were as follows: %TBF = 105.1 - 1.47 (%TBW); %TBP = 0.42 (%TBW) - 4.75; TBGE (MJ) = 40.8 (mass in kg) - 48.5 (TBW in kg) - 0.4; and TBA (kg) = 0.1 - 0.008 (mass in kg) + 0.05 (TBW in kg). These relationships are applicable to gray seals of both sexes over a wide range of age and body conditions, and they predict the body composition of gray seals more accurately than the predictive equations derived from ringed seals (Pusa hispida)...

Veterinary Record, 1988

A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be... more A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be a reliable and reasonably safe immobilisation agent for field work on grey and southern elephant seals. It was better than previously reported drugs used either singly or in combination.

Veterinary Record, 1988

A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be... more A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be a reliable and reasonably safe immobilisation agent for field work on grey and southern elephant seals. It was better than previously reported drugs used either singly or in combination.

Journal of Applied Physiology, 1981

A simple one-step procedure that eliminates the need to calibrate the O2 analyzer or measure the ... more A simple one-step procedure that eliminates the need to calibrate the O2 analyzer or measure the flow past the animal is described for calibrating an open-flow respirometry system. The technique is particularly useful for situations of high ambient humidity and for large or active animals where a mask is employed to capture expired gases. A measured N2 flow is used to calibrate the system. The equations describing the technique are given, and the accuracy of the method is discussed in detail. The errors associated with the technique are compared with those of more conventional procedures and are usually smaller.

The Journal of Applied Ecology, 1989

... (a) R2 Male 9 May 84-13 Aug 84 1 0 63 0-26 RIO Male 18 Jun 85-11 Aug 85 3 0 86 0 37 ... 2. Di... more ... (a) R2 Male 9 May 84-13 Aug 84 1 0 63 0-26 RIO Male 18 Jun 85-11 Aug 85 3 0 86 0 37 ... 2. Diurnal variation in the activity of four male common seals in May, June and July: (a) R2, (b) RIO, (c) R 1I and (d) R25; (El) absent from, (E) diving within or (-) hauled out within study area. ...

The Journal of Visualization and Computer Animation, 1996

Canadian Journal of Zoology, 1992

In the austral summers of 1986 and 1988–1989, 51 southern elephant seals (Mirounga leonina) at Hu... more In the austral summers of 1986 and 1988–1989, 51 southern elephant seals (Mirounga leonina) at Husvik, South Georgia (54°10′S; 36°43′W), were stomach lavaged after chemical immobilization. Only cephalopod remains were retrieved, including 1070 lower beaks that were identified and measured. In total these were estimated to represent a wet weight of 187.8 kg. Fourteen species of squid from 11 families and 2 species of octopod from 1 family were present. The most important species overall were the squids Psychroteuthis glacialis in terms of numerical abundance (33.7%) and Moroteuthis knipovitchi in terms of estimated biomass (31.2%). The remaining biomass was mainly comprised of the five large muscular squids, Kondakovia longimana (24.0%), P. glacialis (15.4%), Martialia hyadesi (11.2%), Alluroteuthis antarcticus (10.8%), and Gonatus antarcticus (3.6%). Larger seals of both sexes fed on a wider variety of cephalopod species than smaller seals, with large males taking the greatest diver...

Biological Conservation, 2005

We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a ... more We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identiWcation and satellite telemetry to investigate trends in grey seal abundance, site Wdelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the Southwest British Isles during their annual cycle. Nine out of 16 seals Wtted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean D 49.8 seals) and a lower abundance during the breeding season (mean D 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3-1), and was close to 1:1 during the summer. Inter-annual site Wdelity outside the breeding season was very high, varying from 70% to 95% of identiWed seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.

Annual Review of Physiology, 1982

This series of four papers investigates the link between the energetics and the mechanics of terr... more This series of four papers investigates the link between the energetics and the mechanics of terrestrial locomotion. Two experimental variables are used throughout the study: speed and body size. Mass-specific metabolic rates of running animals can be varied by about tenfold using either variable. This first paper considers metabolic energy consumed during terrestrial locomotion. New data relating rate of oxygen consumption and speed are reported for: eight species of wild and domestic artiodactyls; seven species of carnivores; four species of primates; and one species of rodent. These are combined with previously published data to formulate a new allometric equation relating mass-specific rates of oxygen consumed (^o,/Af(,) during locomotion at a constant speed to speed and body mass (based on data from 62 avian and mammalian species): V 0 JM h = 0-533 M b-°-* u .v a +0-300 M 6-o-»oa where fy) t /M b has the units ml O t s-1 kg" 1 ; M b is in kg; and v is in m s" 1. This equation can be expressed in terms of mass-specific rates of energy consumption (j^metab/^ft) using the energetic equivalent of 1 ml 0 8 = 20-1 J because the contribution of anaerobic glycolysis was negligible: metab/M. = IO 7 M 6-°-»«.» a + 6-O 3 M ft-»-»»» where E metab /M b has the units watts/kg. This new relationship applies equally well to bipeds and quadrupeds and differs little from the allometric equation reported 12 years ago by Taylor, Schmid-Nielsen & Raab (1970). Ninety per cent of the values calculated from this general equation for the diverse assortment of avian and mammalian species included in this regression fall within 25 % of the observed values at the middle of the speed range where measurements were made. This agreement is impressive when one considers that mass-specific rates of oxygen consumption differed by more than 1400% over this size range of animals.

Due to the low accessibility of the region, most of the seasonally ice-covered Southern Ocean rem... more Due to the low accessibility of the region, most of the seasonally ice-covered Southern Ocean remains unobserved during winter. Here we show that southern elephant seals (Mirounga leonina), equipped with oceanographic sensors, can measure winter hydrography with unprecedented temporal and spatial resolution. Seals provided a 30-fold increase in hydrographic profiles from the sea ice zone, allowing the major fronts to be mapped south of 60° S. Sea-ice formation rates in the East Antarctic sector were estimated ...

Journal of Zoology, 1992

Three types of Argos satellite transmitter were attached to grey seals (Halichoerus grypus) at Do... more Three types of Argos satellite transmitter were attached to grey seals (Halichoerus grypus) at Donna Nook (South Humberside, UK) between 1985 and 1989 in order to investigate their movements. With the first two transmitters (A and B) the entire package was attached to ...

Journal of Applied Ecology, 1999

1. Grey seals Halichoerus grypus Fab. are large, numerous marine top predators. Fears concerning ... more 1. Grey seals Halichoerus grypus Fab. are large, numerous marine top predators. Fears concerning competition with ®sheries have prompted calls for control measures. However, little is known about the areas where grey seals forage or the distances they may travel. 2. The movements of 14 grey seals caught at the Farnes in northeast England (12) and Abertay in eastern Scotland (2) between August 1991 and July 1993 were investigated using Argos Satellite Relay Data Loggers (SRDLs). A total of 1461 seal days of location and behavioural data (mean 104´3 days per seal) covered all months of the year except February and March. 3. The seal movements were on two geographical scales: long and distant travel (up to 2100 km away); and local, repeated trips from the Farnes, Abertay and other haul-out sites to discrete oshore areas. 4. Long distance travel included visits to Orkney, Shetland, the Faroes, and far oshore into the Eastern Atlantic and the North Sea. During travel the seals moved at speeds of between 75 and 100 km day ±1 (0´87 and 1´16 m s ±1). Most of the time, long distance travel was directed to known haul-out sites. The large distances travelled indicate that grey seals that haul out at the Farnes are not ecologically isolated from those at Orkney, Shetland and the Faroes. 5. In 88% of trips to sea, individual seals returned to the same haul-out site from which they departed. The durations of these trips were short (mean 2´33 days) and their destinations at sea were often localized areas characterized by a gravel/sand seabed sediment. This is the preferred burrowing habitat of sandeels, an important part of grey seal diet. This, and the fact that dives in these areas were primarily to the seabed, leads us to conclude that these were foraging areas. The limited extents of return-trips from a haul-out site (mean 39´8 km) suggest that the direct impact of seal predation may be greater on ®sheries within this coastal zone, especially those near seal haul-out sites, rather than on ®sheries further oshore. 6. An average of 43% of all the seals' time was spent within 10 km of a haul-out site, although localized foraging areas were identi®ed considerably further oshore. Proximity to a haul-out may provide safety from predation. Alternatively, these periods may be used for rest or social interaction, or we may be underestimating foraging activity near haul-out sites. 7. We suggest that the movement patterns observed in this study may persist through time and across the grey seals which haul-out at the Farnes. We also suggest that a study such as this could be combined with diet studies and haul-out censuses to map foraging intensity. Such information is an essential component of seal±®shery interaction models, upon which management decisions should be based.

Proceedings of the National Academy of Sciences, 2007

Responses by marine top predators to environmental variability have previously been almost imposs... more Responses by marine top predators to environmental variability have previously been almost impossible to observe directly. By using animal-mounted instruments simultaneously recording movements, diving behavior, and in situ oceanographic properties, we studied the behavioral and physiological responses of southern elephant seals to spatial environmental variability throughout their circumpolar range. Improved body condition of seals in the Atlantic sector was associated with Circumpolar Deep Water upwelling regions within the Antarctic Circumpolar Current, whereas High-Salinity Shelf Waters or temperature/salinity gradients under winter pack ice were important in the Indian and Pacific sectors. Energetic consequences of these variations could help explain recently observed population trends, showing the usefulness of this approach in examining the sensitivity of top predators to global and regional-scale climate variability.

Journal of experimental biology, 2004

The energetic cost of diving in marine mammals is a difficult value to derive given the problems ... more The energetic cost of diving in marine mammals is a difficult value to derive given the problems of assessing metabolic rate for an animal at sea. Nevertheless, it is fundamental to our understanding of the foraging strategies of air-breathers exploiting underwater food sources. We ...