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John M Terhune - One of the best experts on this subject based on the ideXlab platform.
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through ice communication by weddell seals Leptonychotes Weddellii is possible
Polar Biology, 2017Co-Authors: John M TerhuneAbstract:Based on prior knowledge of the in-air hearing thresholds of seals at the time, Terhune (Polar Biol 27:810–812, 2004) suggested that Weddell seals (Leptonychotes Weddellii) likely could not hear underwater calls, while they were on the ice. However, recent data on phocid hearing thresholds in the air reveal that seals have much lower detection thresholds than previously thought. A re-analysis of the situation using the lower hearing threshold data finds that many of the Weddell seal underwater calls, especially those with high-frequency components, will be audible to seals resting on the ice. Territorial males vocally defending territories under the ice during the breeding season may also be communicating with females on the ice directly above them. This communication may facilitate later mating success of those males.
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weddell seal Leptonychotes Weddellii
Encyclopedia of Marine Mammals (Second Edition), 2009Co-Authors: Jeanette A Thomas, John M TerhuneAbstract:Publisher Summary This chapter focuses on the Weddell seal, which belongs to the family Phocidae, subfamily Monacinae, and tribe Lobodontini. There is a single species within the genus Leptonychotes and the closest relatives are the other Antarctic seals in the tribe Lobodontini, such as crabeater, Lobodon carcinophaga ; leopard, Hydrurga leptonyx ; and Ross seals, Ommatophoca rossii ; and the monk seals in the tribe Monachini such as Caribbean, Mediterranean, and Hawaiian monk seals, Monachus spp. Weddell seals are black with grayish silver streaks, with individual variations. The adult pelt does not have underfur and in pups, the light gray lanugo is longer and thicker than adult hair and is shed by 44 days of age. There is no dramatic sexual dimorphism in body size, males reach 2.5–2.9 m and females are 2.6–3.3 m in length. Weights range from 400 to 500 kg, with pregnant females being the heaviest. At birth, pups weigh 22–29 kg and are about 1.5 m in length. The large brown eyes often have wet circles around them because of no lacrimal duct. A tapetum on the back surface of the retina assists in seeing in low-light levels, especially during the austral winter and deep dives. The external ear is absent; the cochlea is about 10 mm high and forms about two and a half turns. The organ of Corti contains one row of inner and three rows of outer hair cells. The nostrils are oriented vertically and normally are closed but open when the seal needs to respire. There are seven rows of mystacial vibrissae and superciliary whiskers that are smooth, not beaded as in some pinnipeds. The seal has a simple stomach and eats whole fish, heads down first.
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geographic variation of weddell seal Leptonychotes Weddellii airborne mother pup vocalisations
Polar Biology, 2007Co-Authors: Kym Collins, John M TerhuneAbstract:Geographic variation of vocal behaviour may be reflective of genetic, cultural and ecological differences between locations. Such differences have been previously reported in six pinnipeds, including Weddell seals (Leptonychotes Weddellii). This study investigated whether the acoustic characteristics of airborne Weddell seal mother and pup ‘contact’ calls vary geographically between the Vestfold Hills and McMurdo Sound. From each location, 72 mother and 120 pup calls were analysed, with 11 acoustic characteristics measured. MANOVA and Discriminant function analysis (DFA) identified significant differences in several fundamental frequency characteristics. The cross-validated DFA classified greater than 60% of mother and pup vocalisations to the correct location. For novel calls, the probabilities of correctly classifying these percentages by chance are low. Additionally, ordinal logistic regression identified significant differences in the maximum energy distribution of mother and pup vocalisations. For pups, this variation is likely the result of genetic differences between the two populations. Nevertheless, results support suggestions that, when compared with underwater repertoire differences, airborne within-call differences are less efficient at identifying Weddell seal breeding populations.
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vocal individuality of in air weddell seal Leptonychotes Weddellii pup primary calls
Marine Mammal Science, 2006Co-Authors: Kym Collins, John M Terhune, Tracey L Rogers, Kathryn E Wheatley, Robert HarcourtAbstract:As a result of selective pressures faced during lactation, vocal recognition may play a crucial role in maintaining the phocid mother–pup bond during the period of dependence. To investigate this possibility, we examined whether Weddell seal (Leptonychotes Weddellii) pups produce individually distinctive “primary” calls. One temporal, nine fundamental frequency features, and two spectral characteristics were measured. A discriminant function analysis (DFA) of 15 Vestfold Hills pups correctly classified 52% of calls, while the cross-validation procedure classified 29% of calls to the correct pup. A second DFA of 10 known-age McMurdo Sound pups correctly classified 44% of “test” calls. For novel calls, the probabilities of attaining such classification rates by chance are low. The relationship between age and call stereotypy indicated that pups 2 wk and older may be more vocally distinctive. Overall, findings suggest that Weddell seal pup “primary” calls are moderately distinctive and only exhibit sufficient stereotypy to aid maternal recognition by approximately two weeks of age.
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an assessment of the audibility of sound from human transport by breeding weddell seals Leptonychotes Weddellii
Wildlife Research, 2006Co-Authors: Tamara Van Polanen Petel, Mark A. Hindell, John M Terhune, M GieseAbstract:Anthropogenic noise generated through travel in the Antarctic has the potential to affect the region’s wildlife. Weddell seals (Leptonychotes Weddellii) in particular can be exposed to anthropogenic noise because they live under, and breed on, the fast ice on which humans travel. To investigate the potential effects of anthropogenic noise on Weddell seals we developed sound profiles for pedestrian travel, over-snow vehicles, aircraft and watercraft operating at various distances and altitudes from breeding seals. The received 1/3-octave noise levels were then related to an assumed detection threshold for the Weddell seal. We found that most noise levels generated by the pedestrian, quad (4-wheeled, all-terrain vehicle) and Hagglunds (tracked, all-terrain vehicle) were commonly categorised in the inaudible and barely audible range of detection (both in-air and underwater), while noise levels generated by the helicopter, Twin Otter aircraft and Zodiac boat were categorised more commonly in the barely audible and clearly audible range. Experimental underwater recordings of vocal behaviour of Weddell seals exposed to continuous low-amplitude over-snow vehicle noise (i.e. Hagglund operation) were also made. Weddell seals underwater did not alter individual call types in response to low-level Hagglunds noise, but they did decrease their calling rate.
Horst Bornemann - One of the best experts on this subject based on the ideXlab platform.
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Increasing levels and biomagnification of persistent organic pollutants (POPs) in Antarctic biota.
Marine pollution bulletin, 2020Co-Authors: Helmut Goerke, Horst Bornemann, Kurt Weber, Sven Ramdohr, Joachim PlötzAbstract:Representatives of the Antarctic food web (krill, cephalopod, fish, penguin, seal) of the area around Elephant Island and from the Weddell Sea were analysed for the most recalcitrant organochlorine compounds. Due to sorption of the compounds to sinking particles and accumulation in sediments, two benthic fish species (Gobionotothen gibberifrons, Chaenocephalus aceratus) feeding on benthos invertebrates and fish reflected significantly increasing concentrations within a decade (1987-1996), while a benthopelagic species (Champsocephalus gunnari) feeding on krill did not. In the pelagic food chain, lipid normalised concentrations of all compounds increased from Antarctic krill to fish proving that biomagnification of highly lipophilic pollutants (log octanol-water partition coefficient>5) occurs in water-breathing animals. As top predators Weddell and southern elephant seals (Leptonychotes Weddellii, Mirounga leonina) biomagnified the persistent organic pollutants relative to krill 30-160 fold with the exception of hexachlorobenzene, the levels of which were lower than in fish indicating its intense specific elimination.
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A review of data on abundance, trends in abundance, habitat utilisation and diet for Southern Ocean ice-breeding seals
2020Co-Authors: Colin Southwell, Horst Bornemann, Marthán N Bester, Michael F Cameron, Jeffrey L. Laake, John L. Bengtson, Peter L. Boveng, A. Schytte-blix, Jaume Forcada, Erling S. NordøyAbstract:The development of models of marine ecosystems in the Southern Ocean is becoming increasingly important as a means of understanding and managing impacts such as exploitation and climate change. Collating data from disparate sources, and understanding biases or uncertainties inherent in those data, are important first steps for improving ecosystem models. This review focuses on seals that breed in ice habitats of the Southern Ocean (i.e. the crabeater seal, Lobodon carcinophaga; Ross seal, Ommatophoca rossii; leopard seal, Hydrurga leptonyx; and Weddell seal, Leptonychotes Weddellii). Data on populations (abundance and trends in abundance), distribution and habitat use (movement, key habitat and environmental features) and foraging (diet) are summarised, and potential biases and uncertainties inherent in those data are identified and discussed. Spatial and temporal gaps in knowledge of the populations, habitats and diet of each species are also identified.
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foraging behaviour of weddell seals Leptonychotes Weddellii in connection to oceanographic conditions in the southern weddell sea
Progress in Oceanography, 2019Co-Authors: Dominik Nachtsheim, Marthán N Bester, Svenja Ryan, Michael Schroder, Laura Jensen, Christiaan W C Oosthuizen, Wilhelm Hagen, Horst BornemannAbstract:The region of the Filchner Outflow System (FOS) in the southeastern Weddell Sea is characterized by intensive and complex interactions of different water masses. Dense Ice Shelf Water (ISW) emerging from beneath the ice shelf cavities on the continental shelf, meets Modified Warm Deep Water (MWDW) originating from the Antarctic Circumpolar Current at the sill of the Filchner Trough. These hydrographic features convert the FOS into an oceanographic key region, which may also show enhanced biological productivity and corresponding aggregations of marine top predators. In this context, six adult Weddell seals (Leptonychotes Weddellii) were instrumented with CTD-combined satellite relay data loggers in austral summer 2014. By means of these long-term data loggers we aimed at investigating the influence of environmental conditions on the seals’ foraging behaviour throughout seasons, focussing on the local oceanographic features. Weddell seals performed pelagic and demersal dives, mainly on the continental shelf, where they presumably exploited the abundant bentho-pelagic fish fauna. Diurnal and seasonal variations in light availability affected foraging activities. MWDW was associated with increased foraging effort. However, we observed differences in movements and habitat use between two different groups of Weddell seals. Seals tagged in the pack ice of the FOS focussed their foraging activities to the western and, partly, eastern flank of the Filchner Trough, which coincides with inflow pathways of MWDW. In contrast, Weddell seals tagged on the coastal fast ice exhibited typical central-place foraging and utilized resources close to their colony. High foraging effort in MWDW and high utilization of areas associated with an inflow of MWDW raise questions on the underlying biological features. This emphasizes the importance of further interdisciplinary ecological investigations in the near future, as the FOS may soon be impacted by predicted climatic changes.
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winter foraging hotspots and habitat use of weddell seals Leptonychotes Weddellii at the filchner outflow system southern weddell sea
EPIC3XXXIV SCAR Biennial Meetings & 2016 Open Science Conference Kuala Lumpur Malaysia 2016-08-20-2016-08-30, 2016Co-Authors: Dominik Nachtsheim, Marthán N Bester, Svenja Ryan, Michael Schroder, Laura Jensen, Christiaan W C Oosthuizen, Horst BornemannAbstract:The region of the Filchner Outflow System (FOS) in the southeastern Weddell Sea is characterized by intensive and complex interactions of different water masses. These hydrographic features convert the FOS in an oceanographic hotspot, which may also show enhanced biological productivity and corresponding aggregations of marine top predators. In this context, six adult Weddell seals (Leptonychotes Weddellii) were instrumented with CTD- combined satellite-relay dive loggers during austral summer 2014 to investigate the influence of environmental conditions on the seals’ foraging behaviour over winter and identify potential foraging hotspots in the FOS. Weddell seals preferred foraging in shallow areas of the continental shelf (< 700 m), where they presumably exploited the abundant bentho-pelagic fish fauna during both pelagic and demersal dives. Diurnal and seasonal variations in light availability also affected foraging activities. Furthermore, Eastern Shelf Water and modified Warm Deep Water were associated with increased hunting time and foraging effort. Moreover, two areas in the FOS were emphasized as potential foraging hotspots characterized by long residence times suggesting enhanced prey availability. However, the underlying biological principles contributing to these foraging hotspots still remain unclear. This highlights the importance of further ecological investigations as the FOS is already threatened by predicted climatic changes.
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Hydrographic influences on the summer dive behaviour of Weddell seals (Leptonychotes Weddellii) in Atka Bay, Antarctica
Polar Biology, 2013Co-Authors: Trevor Mcintyre, L. Stansfield, Horst Bornemann, Joachim Plötz, Marthán N BesterAbstract:In order to gain insights into species-level behavioural responses to the physical environment, it is necessary to obtain information from various populations and at all times of year. We analysed the influences of physical environmental parameters on the mid-summer dive behaviour of Weddell seals (Leptonychotes Weddellii) from a little-known population at Atka Bay, Antarctica. Dive depth distributions followed a typical bimodal pattern also exhibited by seals from other populations and seals targeted both shallow water layers of
Joachim Plötz - One of the best experts on this subject based on the ideXlab platform.
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Increasing levels and biomagnification of persistent organic pollutants (POPs) in Antarctic biota.
Marine pollution bulletin, 2020Co-Authors: Helmut Goerke, Horst Bornemann, Kurt Weber, Sven Ramdohr, Joachim PlötzAbstract:Representatives of the Antarctic food web (krill, cephalopod, fish, penguin, seal) of the area around Elephant Island and from the Weddell Sea were analysed for the most recalcitrant organochlorine compounds. Due to sorption of the compounds to sinking particles and accumulation in sediments, two benthic fish species (Gobionotothen gibberifrons, Chaenocephalus aceratus) feeding on benthos invertebrates and fish reflected significantly increasing concentrations within a decade (1987-1996), while a benthopelagic species (Champsocephalus gunnari) feeding on krill did not. In the pelagic food chain, lipid normalised concentrations of all compounds increased from Antarctic krill to fish proving that biomagnification of highly lipophilic pollutants (log octanol-water partition coefficient>5) occurs in water-breathing animals. As top predators Weddell and southern elephant seals (Leptonychotes Weddellii, Mirounga leonina) biomagnified the persistent organic pollutants relative to krill 30-160 fold with the exception of hexachlorobenzene, the levels of which were lower than in fish indicating its intense specific elimination.
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Hydrographic influences on the summer dive behaviour of Weddell seals (Leptonychotes Weddellii) in Atka Bay, Antarctica
Polar Biology, 2013Co-Authors: Trevor Mcintyre, L. Stansfield, Horst Bornemann, Joachim Plötz, Marthán N BesterAbstract:In order to gain insights into species-level behavioural responses to the physical environment, it is necessary to obtain information from various populations and at all times of year. We analysed the influences of physical environmental parameters on the mid-summer dive behaviour of Weddell seals (Leptonychotes Weddellii) from a little-known population at Atka Bay, Antarctica. Dive depth distributions followed a typical bimodal pattern also exhibited by seals from other populations and seals targeted both shallow water layers of
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hydrographic influences on the summer dive behaviour of weddell seals Leptonychotes Weddellii in atka bay antarctica
Polar Biology, 2013Co-Authors: Trevor Mcintyre, L. Stansfield, Horst Bornemann, Joachim Plötz, Marthán N BesterAbstract:In order to gain insights into species-level behavioural responses to the physical environment, it is necessary to obtain information from various populations and at all times of year. We analysed the influences of physical environmental parameters on the mid-summer dive behaviour of Weddell seals (Leptonychotes Weddellii) from a little-known population at Atka Bay, Antarctica. Dive depth distributions followed a typical bimodal pattern also exhibited by seals from other populations and seals targeted both shallow water layers of <50 m and depths near the seafloor. Increased stratification of temperature layers within the water column resulted in increased forage efforts by the seals through relatively high numbers of dives to the seafloor, as well as forage effort associated with shallow dives. We interpret these behavioural responses to be due to increased water temperature stratification resulting in the concentration of prey species in particular depth layers.
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Seal-mounted cameras detect invertebrate fauna on underside of Antarctic ice shelf
Marine Ecology Progress Series, 2006Co-Authors: Yuuki Y Watanabe, Horst Bornemann, Joachim Plötz, Katsufumi Sato, Yasuhiko Naito, Nikolai Liebsch, Nobuyuki MiyazakiAbstract:While modern sampling techniques, such as autonomous underwater vehicles, are increasing our knowledge of the fauna beneath Antarctic sea ice of only a few meters in depth, greater sampling difficulties mean that little is known about the marine life underneath Antarctic ice shelves over 100 m thick. In this study, we present underwater images showing the underside of an Antarctic ice shelf covered by aggregated invertebrate communities, most likely cnidarians and isopods. These images, taken at an average depth of 145 m, were obtained with a digital still camera system attached to Weddell seals Leptonychotes Weddellii foraging just beneath the ice shelf. Our observations indicate that, similar to the sea floor, ice shelves serve as an important habitat for a remarkable amount of marine invertebrate fauna in Antarctica.
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light and scanning electron microscopical study on antarctophthirus ogmorhini lice from the antarctic seal Leptonychotes Weddellii
Parasitology Research, 2002Co-Authors: Birgit Mehlhorn, Heinz Mehlhorn, Joachim PlötzAbstract:Adult lice (Antarctophthirus ogmorhini) from the Weddell seal Leptonychotes Weddellii were investigated by means of light and scanning electron microscopy. We established that this species is characterized by several morphological peculiarities which enable it to survive the low temperatures of the Antarctic sea and the body depression which occurs during the deep (450 m) and long diving periods of the seals. The main peculiarities are: (1) the cuticle of the ventral and lateral surfaces is much thinner than that of the dorsal surface, (2) the body has numerous stiff spines which are covered by a thick layer of the seal's sebum that closely surrounds the body of the louse, (3) the whole body is covered by a close layer of leaf-like scales which are apparently able to trap air bubbles and thus to provide a small zone of air close to the surface of the cuticle.
Robert Harcourt - One of the best experts on this subject based on the ideXlab platform.
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paternity analysis shows experience not age enhances mating success in an aquatically mating pinniped the weddell seal Leptonychotes Weddellii
Behavioral Ecology and Sociobiology, 2007Co-Authors: Robert Harcourt, M.f: Cameron, J J Kingston, Joseph R Waas, Mark A. HindellAbstract:For polygynous mammals with no paternal care, the number of offspring sired is often the sole measure of male reproductive success. The potential for polygyny is highest when resources or other environmental factors such as restricted breeding sites force females to aggregate. In these circumstances, males compete intensely for females and mating success may vary greatly among males, further intensifying selection for those traits that confer an advantage in reproduction. Hence, determinants of male success in competition for females are likely to be under strong sexual selection. Paternity analysis was used in conjunction with measures of age, site fidelity, and behavior during the breeding season to assess variance in male breeding success in Weddell seals (Leptonychotes Weddellii) breeding at Turtle Rock, McMurdo Sound (77.727S, 166.85E) between 1997 and 2000. Paternity could be assigned to 177 pups at relaxed or 80% confidence level or 111 pups at strict or 95% confidence levels. Weddell seals at Turtle Rock show a modest degree of polygyny with the greatest number of pups sired by any individual male in a single season equalling 5 or ∼10% of the pups born. Over four consecutive years, most (89.2%) males sired at least one pup. In a generalized linear model (GLM), age and the age first seen at the study site as an adult were unrelated to mating success, but adult experience, either site-specific or elsewhere in McMurdo Sound, over the reproductive life span of males explained nearly 40% of variance in total mating success with 80% confidence and 24% of variance at 95% confidence. While learning where females are likely to be may enhance male reproductive success, aquatic mating reduces the ability of males to monopolize females, and thereby increases equity in mating success.
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vocal individuality of in air weddell seal Leptonychotes Weddellii pup primary calls
Marine Mammal Science, 2006Co-Authors: Kym Collins, John M Terhune, Tracey L Rogers, Kathryn E Wheatley, Robert HarcourtAbstract:As a result of selective pressures faced during lactation, vocal recognition may play a crucial role in maintaining the phocid mother–pup bond during the period of dependence. To investigate this possibility, we examined whether Weddell seal (Leptonychotes Weddellii) pups produce individually distinctive “primary” calls. One temporal, nine fundamental frequency features, and two spectral characteristics were measured. A discriminant function analysis (DFA) of 15 Vestfold Hills pups correctly classified 52% of calls, while the cross-validation procedure classified 29% of calls to the correct pup. A second DFA of 10 known-age McMurdo Sound pups correctly classified 44% of “test” calls. For novel calls, the probabilities of attaining such classification rates by chance are low. The relationship between age and call stereotypy indicated that pups 2 wk and older may be more vocally distinctive. Overall, findings suggest that Weddell seal pup “primary” calls are moderately distinctive and only exhibit sufficient stereotypy to aid maternal recognition by approximately two weeks of age.
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individual variation of in air female pup contact calls in weddell seals Leptonychotes Weddellii
Behaviour, 2005Co-Authors: Kym Collins, John M Terhune, Tracey L Rogers, Kathryn E Wheatley, Paul D Mcgreevy, Robert HarcourtAbstract:Vocal recognition may function as a critical factor in maintaining the phocid mother-pup bond during lactation. For vocal recognition to function, the caller must produce individually distinct calls that are recognised by their intended recipient. Mother-pup vocal recognition has been studied extensively in colonial otariids and appears to be characteristic of this family. Although less numerous, empirical studies of phocid species have revealed a range of recognition abilities. This study investigated whether Weddell seal (Leptonychotes Weddellii) females produce individually distinct 'pup contact' calls that function during natural pair reunions. Fifteen calls from each of nine females recorded in the Vestfold Hills, Antarctica were analysed. One temporal, nine fundamental frequency and five spectral characteristics were measured. Results of the cross-validated Discriminant Function Analysis revealed that mothers produce individually distinct calls with 56% of calls assigned to the correct individual. The probability of achieving this level of discrimination on novel data by chance alone is highly improbable. Analysis of eight mother-pup reunions recorded near McMurdo Sound, Antarctica further demonstrated that these 'pup contact' calls function during natural pair reunions. Behavioural analysis also revealed that pups were chiefly responsible for establishing and maintaining close contact throughout the reunion process. Our study therefore demonstrates that Weddell seal females produce calls with sufficient stereotypy to allow pups to identify them during pair reunions, providing evidence of a functioning mother-pup vocal recognition system.
Dominik Nachtsheim - One of the best experts on this subject based on the ideXlab platform.
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foraging behaviour of weddell seals Leptonychotes Weddellii in connection to oceanographic conditions in the southern weddell sea
Progress in Oceanography, 2019Co-Authors: Dominik Nachtsheim, Marthán N Bester, Svenja Ryan, Michael Schroder, Laura Jensen, Christiaan W C Oosthuizen, Wilhelm Hagen, Horst BornemannAbstract:The region of the Filchner Outflow System (FOS) in the southeastern Weddell Sea is characterized by intensive and complex interactions of different water masses. Dense Ice Shelf Water (ISW) emerging from beneath the ice shelf cavities on the continental shelf, meets Modified Warm Deep Water (MWDW) originating from the Antarctic Circumpolar Current at the sill of the Filchner Trough. These hydrographic features convert the FOS into an oceanographic key region, which may also show enhanced biological productivity and corresponding aggregations of marine top predators. In this context, six adult Weddell seals (Leptonychotes Weddellii) were instrumented with CTD-combined satellite relay data loggers in austral summer 2014. By means of these long-term data loggers we aimed at investigating the influence of environmental conditions on the seals’ foraging behaviour throughout seasons, focussing on the local oceanographic features. Weddell seals performed pelagic and demersal dives, mainly on the continental shelf, where they presumably exploited the abundant bentho-pelagic fish fauna. Diurnal and seasonal variations in light availability affected foraging activities. MWDW was associated with increased foraging effort. However, we observed differences in movements and habitat use between two different groups of Weddell seals. Seals tagged in the pack ice of the FOS focussed their foraging activities to the western and, partly, eastern flank of the Filchner Trough, which coincides with inflow pathways of MWDW. In contrast, Weddell seals tagged on the coastal fast ice exhibited typical central-place foraging and utilized resources close to their colony. High foraging effort in MWDW and high utilization of areas associated with an inflow of MWDW raise questions on the underlying biological features. This emphasizes the importance of further interdisciplinary ecological investigations in the near future, as the FOS may soon be impacted by predicted climatic changes.
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winter foraging hotspots and habitat use of weddell seals Leptonychotes Weddellii at the filchner outflow system southern weddell sea
EPIC3XXXIV SCAR Biennial Meetings & 2016 Open Science Conference Kuala Lumpur Malaysia 2016-08-20-2016-08-30, 2016Co-Authors: Dominik Nachtsheim, Marthán N Bester, Svenja Ryan, Michael Schroder, Laura Jensen, Christiaan W C Oosthuizen, Horst BornemannAbstract:The region of the Filchner Outflow System (FOS) in the southeastern Weddell Sea is characterized by intensive and complex interactions of different water masses. These hydrographic features convert the FOS in an oceanographic hotspot, which may also show enhanced biological productivity and corresponding aggregations of marine top predators. In this context, six adult Weddell seals (Leptonychotes Weddellii) were instrumented with CTD- combined satellite-relay dive loggers during austral summer 2014 to investigate the influence of environmental conditions on the seals’ foraging behaviour over winter and identify potential foraging hotspots in the FOS. Weddell seals preferred foraging in shallow areas of the continental shelf (< 700 m), where they presumably exploited the abundant bentho-pelagic fish fauna during both pelagic and demersal dives. Diurnal and seasonal variations in light availability also affected foraging activities. Furthermore, Eastern Shelf Water and modified Warm Deep Water were associated with increased hunting time and foraging effort. Moreover, two areas in the FOS were emphasized as potential foraging hotspots characterized by long residence times suggesting enhanced prey availability. However, the underlying biological principles contributing to these foraging hotspots still remain unclear. This highlights the importance of further ecological investigations as the FOS is already threatened by predicted climatic changes.
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winter foraging hotspots of weddell seals Leptonychotes Weddellii in the southern weddell sea
EPIC360 p., 2016Co-Authors: Dominik NachtsheimAbstract:The region of the Filchner Outflow System (FOS) in the southeastern Weddell Sea is characterized by intensive and complex interactions of different water masses. These hydrographic features convert the FOS in an oceanographic hotspot, which may also show enhanced biological productivity and corresponding aggregations of marine top predators. In this context, six adult Weddell seals (Leptonychotes Weddellii) were instrumented with CTD- combined satellite-relay dive loggers during austral summer 2014 to investigate the influence of environmental conditions on the seals’ foraging behaviour over winter and identify potential foraging hotspots in the FOS. Weddell seals preferred foraging in shallow areas of the continental shelf (< 700 m), where they presumably exploited the abundant bentho-pelagic fish fauna during both pelagic and demersal dives. Diurnal and seasonal variations in light availability also affected foraging activities. Furthermore, Eastern Shelf Water and modified Warm Deep Water were associated with increased hunting time and foraging effort. Moreover, two areas in the FOS were emphasized as potential foraging hotspots characterized by long residence times suggesting enhanced prey availability. However, the underlying biological principles contributing to these foraging hotspots still remain unclear. This highlights the importance of further ecological investigations as the FOS is already threatened by predicted climatic changes.