Walrus Research Active
The USGS Alaska Science Center conducts long-term research on the Pacific walrus to provide scientific information to Department of Interior management agencies and Alaska Native co-management partners. In addition, the USGS Pacific walrus research program collaborates with the U.S. Fish and Wildlife Service (USFWS) and the State of Alaska’s Department of Fish and Game and Alaska Native co-management partners to deliver scientific products that advance knowledge of walrus ecology and the importance of walrus in northern ecosystems. Because addressing population-level questions requires collaboration between U.S. and Russian scientists, many USGS studies have relied on Russian partnership.
Return to Ecosystems >> Marine Ecosystems
Population dynamics
Department of Interior partner agencies require information on Pacific walrus survival, reproduction, population abundance, and population trend to inform management decisions and address statutory responsibilities. US and Russian partners conducted aerial surveys in 1975, 1976, 1980, 1985, and 1990 to estimate population abundance. In 2006, USGS collaborated with US Fish and Wildlife Service (USFWS) and Russian partners to estimate population abundance from an offshore aerial survey that accounted for the proportion of walruses that were in-water and therefore unavailable to be counted, and was the first to rigorously account for uncertainty in the population abundance estimate. Because these offshore survey efforts resulted in large uncertainty in the estimated population size, development began on alternative abundance estimation methods. The USFWS has led an effort, with USGS support, to estimate Pacific walrus population abundance using genetic mark-recapture methods. USGS efforts developing methods to determine sex and age of walruses from remotely collected biopsies support this effort. USGS developed methods to estimate regional population size at a large coastal haulout and has refined these methods through use of unoccupied aerial systems (UAS or survey drones) through support of the USGS National Uncrewed Systems Office to estimate the regional walrus abundance in the U.S. Chukchi Sea autumn waters during 2018 and 2019.
Age structure surveys provide information on population demographics required by USFWS statutory responsibilities under the Marine Mammal Protection Act (MMPA). In the 1950’s, F.H. Fay pioneered methods for collecting walrus sex and age structure data by observing facial and tusk characteristics. These methods were applied to collect age structure data on offshore surveys from 1981-1999 with Department of the Interior support. The State of Alaska’s Department of Fish and Game evaluated these methods and found them to provide invaluable information on population demographics.
USGS developed integrated population models that estimated Pacific walrus survival, reproduction, and population trend. These models used all available age structure and population survey data to estimate population parameters required by the MMPA. These models found the age structure data to strongly influence estimated population trends, prompting USGS and FWS with support from the Alaska Department of Fish and Game to collect additional age structure data during 2013 - 2017. USGS is pursuing further age structure data collection beginning in 2023. Development of integrated population models has allowed USGS and collaborators to evaluate threats posed to the Pacific walrus population from climate related changes in the Arctic. For example, an increase in deaths of young walruses resulting from disturbances at large coastal haulouts can affect population trend.
Seasonal distribution and habitat use
Pacific walruses primarily consume invertebrates that live in bottom sediments of the shallow continental shelf waters that extend across the Bering and Chukchi seas. In response to the understanding that sea ice loss causes walruses to change their movement and foraging behavior in ways that may affect survival and reproduction, USGS has developed minimally invasive methods to track walruses with small satellite-linked tags and has collected behavior and movement data from walruses across the Bering and Chukchi seas in support of numerous studies. These studies include correcting aerial survey estimates for walruses in-water and therefore unavailable to be counted; understanding how walruses move within their habitat relative to sea ice movement in the northern Bering Sea; identifying how they move relative to sea ice and benthic biomass distributions in the Bering, and Chukchi Seas; and understanding how their resting and foraging efforts change when summer sea ice disappears. The tracking data have also revealed walrus foraging areas within the Chukchi Sea and contributed to a broader understanding of marine mammal seasonal distributions in the Pacific Arctic. The tracking data are currently being analyzed to better understand how Pacific walruses utilize the largest coastal haulout in northwestern Alaska.
Recorded Talk: Pacific Walruses: Responding to Change? Strait Science, April 2023
Monitoring large coastal haulouts
Walruses haul out of the water and rest between foraging bouts. They rest on sea ice when it is available but use land when waters are ice free. The Chukchi Sea continental shelf has been ice-free during most summers since 2007, and the seasonal duration of ice-free conditions will increase in the decades ahead. When walruses gather in large numbers to rest on shore at locations that are termed “haulouts”, they are at risk from large mortality events resulting from disturbances that cause stampedes. They are also at increased risk from any vessel spill events because walrus distributions are so densely concentrated at and around coastal haulouts. To reduce these risks, managers require an understanding of the distribution and occurrence of large coastal haulouts. USGS has partnered with the USFWS and a Russian collaborator to document the occurrence and distribution of Pacific walrus haulouts. USGS is supporting a revision of the Pacific Walrus Haulout Database in collaboration with USFWS.
USGS has developed methods to monitor walruses resting on shore through use of Earth observing satellite imagery. USGS is supporting local management of haulouts by providing satellite imagery analysis to local managers during the haulout season. USGS has worked with Russian partners to extend these methods at haulout sites with complex substrates and terrain and plans to continue this work at Alaskan study sites with State of Alaska, FWS and academic partners. To support that effort, the USGS Advanced Research Computing center is using trail camera ground-truth imagery collected by partner agencies to teach deep neural networks to recognize walruses so they can more rapidly detect walruses remotely. USGS is also collaborating to automate interpretation of the walrus haulouts apparent in optical Earth observing imagery so that information can be transferred to management partners in real-time, and USGS has supported harmonization of aerial survey imagery collection efforts conducted in the U.S. and Russia so that haulout monitoring studies and results may be unified range-wide.
Consequences of shifting prey base and increased energetic demands
The loss of sea ice has caused shifts in walrus space use, is forecasted to increase the energetic demands for lactating walruses and may cause changes to walrus prey. By coupling walrus behavior models with an understanding of the energy demands throughout the reproductive life of female walruses, USGS evaluated the energetic consequences of forecasted sea ice loss over the next century. This study found that continued sea ice loss will increase walrus energetic demands, but there was uncertainty about the impact increased energetic demands might have on body condition and how that may affect reproduction rates. To understand how the walrus population may respond to the increased energetic demands, USGS is evaluating methods to monitor possible changes in walrus reproductive success over time as environmental conditions change. Using information collected by Native Alaskan communities in the Bering Strait region, from captive walruses in zoos and aquaria, and from aerial imagery from drones at coastal haulouts, USGS is investigating different methods to monitor walrus body condition and how variation in body condition may affect female reproductive success.
In support of this study USGS has (1) collaborated to determine how to reliably measure fat stores from harvested walruses; (2) evaluated the condition and composition of walrus fat stores; (3) collaborated to evaluate energetic costs for resting walruses across the range of reproductive conditions and across juvenile age-classes; (4) collaborated to evaluate energetic cost of swimming, diving, and resting in water; and (5) explored the development of diving capabilities in young walruses. Finally, the loss of sea ice may cause changes to walrus prey and understanding the consequences of a shift in the prey base requires methods to understand walrus diet. So, USGS developed non-invasive methods to monitor walrus diet.
Potential effects of increased vessel traffic
Arctic marine mammals have historically had low exposure to vessel traffic and noise, but sea ice loss has increased accessibility of Arctic waters to vessels. Thus, Arctic vessel traffic is expected to increase, yet its effect on walruses is unknown. Vessel exposure has the potential to change walrus population dynamics by altering how much time walruses use to rest, travel, and forage. Such changes may require walruses to consume more calories or reduce their energy stores which are needed to support growth, reproduction, and maintenance. The USGS conducted an initial study of effects of vessel exposure on Pacific walrus behavior in the Chukchi Sea using data from satellite-tagged walruses (collected by USGS, Russian collaborators, and the State of Alaska’s Department of Fish and Game) and vessel locations. Foraging walruses were no more likely to stop foraging and start traveling when they were within 17 km of vessels than when they were greater than 17 km from vessels. Due to the small number of walruses exposed to vessels at close distances, this study did not determine at what distance vessel exposure affects walrus behaviors; however, it provided an upper bound on the distance at which the vessels encountered may disturb foraging walruses. Furthermore, USGS developed extensive analytical methods that will help detect the effect of vessel exposure on walrus behavior when sufficient walrus tracking data are available with improved resolution. USGS also supported a study to evaluate walrus in-air hearing range.
Stock Definition
The Marine Mammal Protection Act requires an understanding of whether there are distinct stocks within the Pacific walrus sub-species. Pacific walruses range across the shallow waters of the continental shelf that extends between Alaska and the Russian Far East. Three distinct breeding areas are known to develop during the sea ice maximum season each spring: in the eastern Bering Sea of the outer Bristol Bay region; south of Saint Lawrence Island in the central northern Bering Sea; and within the Gulf of Anadyr in the northwestern Bering Sea. USGS investigated whether these distinct breeding regions may result in distinct stocks that may merit separate management efforts. Investigations based on signatures from heavy metal isotopes characteristic of the two western breeding regions suggested that walruses in these regions had distinct isotopic signatures, suggesting that each region hosted walruses that habitually returned to that region. However, genetic characterization of walruses from the three breeding regions determined that walruses freely moved amongst breeding regions, indicating that the Pacific walrus sub-species may be considered as a single stock.
Below are other science projects associated with this project.
Below are data or web applications associated with this project.
Below are multimedia items associated with this project.
Below are publications associated with this project.
Estimating age ratios and size of Pacific walrus herds on coastal haulouts using video imaging
Potential population-level effects of increased haulout-related mortality of Pacific walrus calves
Spatial genetic structure and asymmetrical gene flow within the Pacific walrus
Walrus distributional and foraging response to changing ice and benthic conditions in the Chukchi Sea
Bioenergetics model for estimating food requirements of female Pacific walruses (Odobenus rosmarus divergens)
Polar bear and walrus response to the rapid decline in Arctic sea ice
Walrus areas of use in the Chukchi Sea during sparse sea ice cover
Results and evaluation of a survey to estimate Pacific walrus population size, 2006
Projected status of the Pacific walrus (Odobenus rosmarus divergens) in the twenty-first century
Divergent movements of walrus and sea ice in the northern Bering Sea
Enumeration of Pacific walrus carcasses on beaches of the Chukchi Sea in Alaska following a mortality event, September 2009
An improved procedure for detection and enumeration of walrus signatures in airborne thermal imagery
Below are news stories associated with this project.
- Overview
The USGS Alaska Science Center conducts long-term research on the Pacific walrus to provide scientific information to Department of Interior management agencies and Alaska Native co-management partners. In addition, the USGS Pacific walrus research program collaborates with the U.S. Fish and Wildlife Service (USFWS) and the State of Alaska’s Department of Fish and Game and Alaska Native co-management partners to deliver scientific products that advance knowledge of walrus ecology and the importance of walrus in northern ecosystems. Because addressing population-level questions requires collaboration between U.S. and Russian scientists, many USGS studies have relied on Russian partnership.
Return to Ecosystems >> Marine Ecosystems
Population dynamics
Department of Interior partner agencies require information on Pacific walrus survival, reproduction, population abundance, and population trend to inform management decisions and address statutory responsibilities. US and Russian partners conducted aerial surveys in 1975, 1976, 1980, 1985, and 1990 to estimate population abundance. In 2006, USGS collaborated with US Fish and Wildlife Service (USFWS) and Russian partners to estimate population abundance from an offshore aerial survey that accounted for the proportion of walruses that were in-water and therefore unavailable to be counted, and was the first to rigorously account for uncertainty in the population abundance estimate. Because these offshore survey efforts resulted in large uncertainty in the estimated population size, development began on alternative abundance estimation methods. The USFWS has led an effort, with USGS support, to estimate Pacific walrus population abundance using genetic mark-recapture methods. USGS efforts developing methods to determine sex and age of walruses from remotely collected biopsies support this effort. USGS developed methods to estimate regional population size at a large coastal haulout and has refined these methods through use of unoccupied aerial systems (UAS or survey drones) through support of the USGS National Uncrewed Systems Office to estimate the regional walrus abundance in the U.S. Chukchi Sea autumn waters during 2018 and 2019.
Age structure surveys provide information on population demographics required by USFWS statutory responsibilities under the Marine Mammal Protection Act (MMPA). In the 1950’s, F.H. Fay pioneered methods for collecting walrus sex and age structure data by observing facial and tusk characteristics. These methods were applied to collect age structure data on offshore surveys from 1981-1999 with Department of the Interior support. The State of Alaska’s Department of Fish and Game evaluated these methods and found them to provide invaluable information on population demographics.USGS developed integrated population models that estimated Pacific walrus survival, reproduction, and population trend. These models used all available age structure and population survey data to estimate population parameters required by the MMPA. These models found the age structure data to strongly influence estimated population trends, prompting USGS and FWS with support from the Alaska Department of Fish and Game to collect additional age structure data during 2013 - 2017. USGS is pursuing further age structure data collection beginning in 2023. Development of integrated population models has allowed USGS and collaborators to evaluate threats posed to the Pacific walrus population from climate related changes in the Arctic. For example, an increase in deaths of young walruses resulting from disturbances at large coastal haulouts can affect population trend.
Seasonal distribution and habitat use
Pacific walruses primarily consume invertebrates that live in bottom sediments of the shallow continental shelf waters that extend across the Bering and Chukchi seas. In response to the understanding that sea ice loss causes walruses to change their movement and foraging behavior in ways that may affect survival and reproduction, USGS has developed minimally invasive methods to track walruses with small satellite-linked tags and has collected behavior and movement data from walruses across the Bering and Chukchi seas in support of numerous studies. These studies include correcting aerial survey estimates for walruses in-water and therefore unavailable to be counted; understanding how walruses move within their habitat relative to sea ice movement in the northern Bering Sea; identifying how they move relative to sea ice and benthic biomass distributions in the Bering, and Chukchi Seas; and understanding how their resting and foraging efforts change when summer sea ice disappears. The tracking data have also revealed walrus foraging areas within the Chukchi Sea and contributed to a broader understanding of marine mammal seasonal distributions in the Pacific Arctic. The tracking data are currently being analyzed to better understand how Pacific walruses utilize the largest coastal haulout in northwestern Alaska.
Recorded Talk: Pacific Walruses: Responding to Change? Strait Science, April 2023
Monitoring large coastal haulouts
Walruses haul out of the water and rest between foraging bouts. They rest on sea ice when it is available but use land when waters are ice free. The Chukchi Sea continental shelf has been ice-free during most summers since 2007, and the seasonal duration of ice-free conditions will increase in the decades ahead. When walruses gather in large numbers to rest on shore at locations that are termed “haulouts”, they are at risk from large mortality events resulting from disturbances that cause stampedes. They are also at increased risk from any vessel spill events because walrus distributions are so densely concentrated at and around coastal haulouts. To reduce these risks, managers require an understanding of the distribution and occurrence of large coastal haulouts. USGS has partnered with the USFWS and a Russian collaborator to document the occurrence and distribution of Pacific walrus haulouts. USGS is supporting a revision of the Pacific Walrus Haulout Database in collaboration with USFWS.
USGS has developed methods to monitor walruses resting on shore through use of Earth observing satellite imagery. USGS is supporting local management of haulouts by providing satellite imagery analysis to local managers during the haulout season. USGS has worked with Russian partners to extend these methods at haulout sites with complex substrates and terrain and plans to continue this work at Alaskan study sites with State of Alaska, FWS and academic partners. To support that effort, the USGS Advanced Research Computing center is using trail camera ground-truth imagery collected by partner agencies to teach deep neural networks to recognize walruses so they can more rapidly detect walruses remotely. USGS is also collaborating to automate interpretation of the walrus haulouts apparent in optical Earth observing imagery so that information can be transferred to management partners in real-time, and USGS has supported harmonization of aerial survey imagery collection efforts conducted in the U.S. and Russia so that haulout monitoring studies and results may be unified range-wide.
Consequences of shifting prey base and increased energetic demands
The loss of sea ice has caused shifts in walrus space use, is forecasted to increase the energetic demands for lactating walruses and may cause changes to walrus prey. By coupling walrus behavior models with an understanding of the energy demands throughout the reproductive life of female walruses, USGS evaluated the energetic consequences of forecasted sea ice loss over the next century. This study found that continued sea ice loss will increase walrus energetic demands, but there was uncertainty about the impact increased energetic demands might have on body condition and how that may affect reproduction rates. To understand how the walrus population may respond to the increased energetic demands, USGS is evaluating methods to monitor possible changes in walrus reproductive success over time as environmental conditions change. Using information collected by Native Alaskan communities in the Bering Strait region, from captive walruses in zoos and aquaria, and from aerial imagery from drones at coastal haulouts, USGS is investigating different methods to monitor walrus body condition and how variation in body condition may affect female reproductive success.
In support of this study USGS has (1) collaborated to determine how to reliably measure fat stores from harvested walruses; (2) evaluated the condition and composition of walrus fat stores; (3) collaborated to evaluate energetic costs for resting walruses across the range of reproductive conditions and across juvenile age-classes; (4) collaborated to evaluate energetic cost of swimming, diving, and resting in water; and (5) explored the development of diving capabilities in young walruses. Finally, the loss of sea ice may cause changes to walrus prey and understanding the consequences of a shift in the prey base requires methods to understand walrus diet. So, USGS developed non-invasive methods to monitor walrus diet.
Potential effects of increased vessel traffic
Arctic marine mammals have historically had low exposure to vessel traffic and noise, but sea ice loss has increased accessibility of Arctic waters to vessels. Thus, Arctic vessel traffic is expected to increase, yet its effect on walruses is unknown. Vessel exposure has the potential to change walrus population dynamics by altering how much time walruses use to rest, travel, and forage. Such changes may require walruses to consume more calories or reduce their energy stores which are needed to support growth, reproduction, and maintenance. The USGS conducted an initial study of effects of vessel exposure on Pacific walrus behavior in the Chukchi Sea using data from satellite-tagged walruses (collected by USGS, Russian collaborators, and the State of Alaska’s Department of Fish and Game) and vessel locations. Foraging walruses were no more likely to stop foraging and start traveling when they were within 17 km of vessels than when they were greater than 17 km from vessels. Due to the small number of walruses exposed to vessels at close distances, this study did not determine at what distance vessel exposure affects walrus behaviors; however, it provided an upper bound on the distance at which the vessels encountered may disturb foraging walruses. Furthermore, USGS developed extensive analytical methods that will help detect the effect of vessel exposure on walrus behavior when sufficient walrus tracking data are available with improved resolution. USGS also supported a study to evaluate walrus in-air hearing range.
Stock Definition
The Marine Mammal Protection Act requires an understanding of whether there are distinct stocks within the Pacific walrus sub-species. Pacific walruses range across the shallow waters of the continental shelf that extends between Alaska and the Russian Far East. Three distinct breeding areas are known to develop during the sea ice maximum season each spring: in the eastern Bering Sea of the outer Bristol Bay region; south of Saint Lawrence Island in the central northern Bering Sea; and within the Gulf of Anadyr in the northwestern Bering Sea. USGS investigated whether these distinct breeding regions may result in distinct stocks that may merit separate management efforts. Investigations based on signatures from heavy metal isotopes characteristic of the two western breeding regions suggested that walruses in these regions had distinct isotopic signatures, suggesting that each region hosted walruses that habitually returned to that region. However, genetic characterization of walruses from the three breeding regions determined that walruses freely moved amongst breeding regions, indicating that the Pacific walrus sub-species may be considered as a single stock.
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Below are other science projects associated with this project.
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Filter Total Items: 21No Result Found - Multimedia
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Filter Total Items: 42No results found. - Publications
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Filter Total Items: 56Estimating age ratios and size of Pacific walrus herds on coastal haulouts using video imaging
During Arctic summers, sea ice provides resting habitat for Pacific walruses as it drifts over foraging areas in the eastern Chukchi Sea. Climate-driven reductions in sea ice have recently created ice-free conditions in the Chukchi Sea by late summer causing walruses to rest at coastal haulouts along the Chukotka and Alaska coasts, which provides an opportunity to study walruses at relatively acceAuthorsDaniel H. Monson, Mark S. Udevitz, Chadwick V. JayPotential population-level effects of increased haulout-related mortality of Pacific walrus calves
Availability of summer sea ice has been decreasing in the Chukchi Sea during recent decades, and increasing numbers of Pacific walruses have begun using coastal haulouts in late summer during years when sea ice retreats beyond the continental shelf. Calves and yearlings are particularly susceptible to being crushed during disturbance events that cause the herd to panic and stampede at these largeAuthorsMark S. Udevitz, Rebecca L. Taylor, Joel L. Garlich-Miller, Lori T. Quakenbush, Jonathan A. SnyderSpatial genetic structure and asymmetrical gene flow within the Pacific walrus
Pacific walruses (Odobenus rosmarus divergens) occupying shelf waters of Pacific Arctic seas migrate during spring and summer from 3 breeding areas in the Bering Sea to form sexually segregated nonbreeding aggregations. We assessed genetic relationships among 2 putative breeding populations and 6 nonbreeding aggregations. Analyses of mitochondrial DNA (mtDNA) control region sequence data suggest tAuthorsSarah A. Sonsthagen, Chadwick V. Jay, Anthony S. Fischbach, George K. Sage, Sandra L. TalbotWalrus distributional and foraging response to changing ice and benthic conditions in the Chukchi Sea
Arctic species such as the Pacific walrus (Odobenus rosmarus divergens) are facing a rapidly changing environment. Walruses are benthic foragers and may shift their spatial patterns of foraging in response to changes in prey distribution. We used data from satellite radio-tags attached to walruses in 2009-2010 to map walrus foraging locations with concurrent sampling of benthic infauna to examiAuthorsChadwick V. Jay, Jacqueline M. Grebmeier, Anthony S. FischbachBioenergetics model for estimating food requirements of female Pacific walruses (Odobenus rosmarus divergens)
Pacific walruses Odobenus rosmarus divergens use sea ice as a platform for resting, nursing, and accessing extensive benthic foraging grounds. The extent of summer sea ice in the Chukchi Sea has decreased substantially in recent decades, causing walruses to alter habitat use and activity patterns which could affect their energy requirements. We developed a bioenergetics model to estimate caloric dAuthorsS.R. Noren, Mark S. Udevitz, C.V. JayPolar bear and walrus response to the rapid decline in Arctic sea ice
The Arctic is warming faster than other regions of the world due to positive climate feedbacks associated with loss of snow and ice. One highly visible consequence has been a rapid decline in Arctic sea ice over the past 3 decades - a decline projected to continue and result in ice-free summers likely as soon as 2030. The polar bear (Ursus maritimus) and the Pacific walrus (Odobenus rosmarus diverAuthorsKaren L. Oakley, Mary E. Whalen, David C. Douglas, Mark S. Udevitz, Todd C. Atwood, C. JayWalrus areas of use in the Chukchi Sea during sparse sea ice cover
The Pacific walrus Odobenus rosmarus divergens feeds on benthic invertebrates on the continental shelf of the Chukchi and Bering Seas and rests on sea ice between foraging trips. With climate warming, ice-free periods in the Chukchi Sea have increased and are projected to increase further in frequency and duration. We radio-tracked walruses to estimate areas of walrus foraging and occupancy in theAuthorsChadwick V. Jay, Anthony S. Fischbach, Anatoly A. KochnevResults and evaluation of a survey to estimate Pacific walrus population size, 2006
In spring 2006, we conducted a collaborative U.S.-Russia survey to estimate abundance of the Pacific walrus (Odobenus rosmarus divergens). The Bering Sea was partitioned into survey blocks, and a systematic random sample of transects within a subset of the blocks was surveyed with airborne thermal scanners using standard strip-transect methodology. Counts of walruses in photographed groups wereAuthorsSuzann G. Speckman, Vladimir I. Chernook, Douglas M. Burn, Mark S. Udevitz, Anatoly A. Kochnev, Alexander Vasilev, Chadwick V. Jay, Alexander Lisovsky, Anthony S. Fischbach, R. Bradley BenterProjected status of the Pacific walrus (Odobenus rosmarus divergens) in the twenty-first century
Extensive and rapid losses of sea ice in the Arctic have raised conservation concerns for the Pacific walrus (Odobenus rosmarus divergens), a large pinniped inhabiting arctic and subarctic continental shelf waters of the Chukchi and Bering seas. We developed a Bayesian network model to integrate potential effects of changing environmental conditions and anthropogenic stressors on the future statusAuthorsChadwick V. Jay, Bruce G. Marcot, David C. DouglasDivergent movements of walrus and sea ice in the northern Bering Sea
The Pacific walrus Odobenus rosmarus divergens is a large Arctic pinniped of the Chukchi and Bering Seas. Reductions of sea ice projected to occur in the Arctic by mid-century raise concerns for conservation of the Pacific walrus. To understand the significance of sea ice loss to the viability of walruses, it would be useful to better understand the spatial associations between the movements of seAuthorsChadwick V. Jay, Mark S. Udevitz, Ron Kwok, Anthony S. Fischbach, David C. DouglasEnumeration of Pacific walrus carcasses on beaches of the Chukchi Sea in Alaska following a mortality event, September 2009
On September 14, 2009, we encountered substantial numbers of fresh walrus carcasses on the Alaskan shores of the Chukchi Sea near Icy Cape. We enumerated 131 carcasses using geo-referenced strip transect photography and visual counts of solitary carcasses. All appeared to be young animals based on review of aerial photographs and reference to 12 carcasses that we examined on the ground. The eventsAuthorsAnthony S. Fischbach, Daniel H. Monson, C.V. JayAn improved procedure for detection and enumeration of walrus signatures in airborne thermal imagery
In recent years, application of remote sensing to marine mammal surveys has been a promising area of investigation for wildlife managers and researchers. In April 2006, the United States and Russia conducted an aerial survey of Pacific walrus (Odobenus rosmarus divergens) using thermal infrared sensors to detect groups of animals resting on pack ice in the Bering Sea. The goal of this survey was tAuthorsDouglas M. Burn, Mark S. Udevitz, Suzann G. Speckman, R. Bradley Benter - Web Tools
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