Killer whales (<i>Orcinus orca</i>) at Marion Island, Southern Ocean

Keith, Mark; Bester, Marthán N; Bartlett, Peter; Baker, D. James

doi:10.1080/15627020.2001.11657134

Cited by 40 publications

(62 citation statements)

References 13 publications

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“…Killer whales exhibited restricted search behaviour mainly close inshore to Marion Island and Prince Edward Island. This movement pattern suggests that killer whales spend a large proportion of their time hunting seals and penguins near these land-based prey's breeding and moulting sites, and agrees with the findings of previous shore-based observational studies at Marion Island (Condy et al, 1978;Keith et al, 2001;Pistorius et al, 2002Pistorius et al, , 2012Reisinger et al, 2011c). This contrasts with the at-sea distribution of seals and penguins; the high density of seals and penguins near their rookeries seems to present killer whales with more favourable hunting than the dispersed distribution of seals and penguins at sea.…”

Section: Discussionsupporting

confidence: 81%

“…Killer whales frequently occur very close inshore at the PEIs (Keith et al, 2001;Reisinger et al, 2011a) and even a small discrepancy between the SSSM position estimate and the true geographic location of the individual could have resulted in SSSM position estimates on land. Instead of removing positions estimates on land, which would bias subsequent analyses against positions very close inshore, on land position estimates were shifted to the nearest point 50 m offshore using Geospatial Modelling Environment (Beyer, 2012) (coastline data provided by the South African Navy Hydrographic Office).…”

Section: Animalmentioning

confidence: 99%

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Movement and diving of killer whales ( Orcinus orca ) at a Southern Ocean archipelago

Reisinger

Keith

Andrews

et al. 2015

Journal of Experimental Marine Biology and Ecology

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Eleven satellite tags were deployed on 9 killer whales at the Prince Edwards Islands in the Southern Ocean. State-space switching models were used to generate position estimates from Argos location data, while two behavioural modes were estimated from the data. Individuals were tracked for 5.6-53.2 days, during which time they moved 416-4,470 km (mean 82.7 km day -1 ) but 69% of position estimates were within the 1000 m depth contour around the islands (<35 km from the tagging site). Killer whales showed restricted behaviour close to the islands, particularly inshore where they can effectively hunt seals and penguins, and at seamounts to the north of the islands.Generalized linear mixed effect models were used to explore the relationship between environmental variables and behavioural mode. The best model included depth, sea surface temperature, latitude, sea surface height anomaly and bottom slope, but killer whales did not clearly target features such as fronts and apparent mesoscale eddies. Killer whales showed restricted behaviour in shallow water, at high latitudes and low sea surface temperature -the conditions characterising the archipelago.Dive data from two individuals largely revealed shallow dives (7.5-50 m deep), but deeper dive bouts to around 368 m were also recorded. Dives were significantly deeper during the day and maximum dive depths were 767.5 and 499.5 m, respectively. This suggests that killer whales might also prey on vertically migrating cephalopods and perhaps Patagonian toothfish.Three individuals made rapid and directed long-distance movements northwards of the islands, the reasons for which are speculative.

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Section: Discussionsupporting

confidence: 81%

Section: Animalmentioning

confidence: 99%

Movement and diving of killer whales ( Orcinus orca ) at a Southern Ocean archipelago

Reisinger

Keith

Andrews

et al. 2015

Journal of Experimental Marine Biology and Ecology

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“…Most killer whales sighted off Marion Island are predominantly in the near-shore area (Keith et al 2001; where newly weaned southern elephant seal pups remain during play and local postweaning dispersion (Lenglart & Bester 1982;Wilkinson & Bester 1990). This age class is therefore likely to form the preferential prey and a high predation rate by killer whales on juveniles have been reported at Îles Crozet (Guinet et al 1992).…”

Section: Discussionmentioning

confidence: 99%

Evidence for density dependent population regulation in southern elephant seals in the southern Indian Ocean

et al. 2008

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The means by which populations are regulated form a central theme in conservation biology, and much debate has revolved around density dependence as a mechanism driving population change. Marion Island (46°54'S, 37°45'E) is host to a relatively small breeding population of southern elephant seals, which like its counterparts in the southern Indian and southern Pacific Oceans, have declined precipitously over the past few decades. An intensive markrecapture study, which commenced in 1983, has yielded a long time-series of resight data on this population. We used the program MARK to estimate adult female survival in this population from resight data collected over the period 1986-1999. Including concurrent population counts as covariates significantly improved our mark-recapture models and suggests density dependent population regulation to be operational in the population. Although predation may have been involved, it is far more likely that density dependent regulation has been based on a limited food supply. A significant increase in adult female survival was evident which is likely to have given rise to recent changes in population growth.

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“…Given the scaling relationships between morphological measures and body size/mass, various photogrammetric techniques (the use of photographs to measure objects) have been used to determine diverse morphological measures of mammals; these techniques include shoulder height and back length of African elephants Loxodonta africana (Hall-Martin & Rüther 1979, Schrader et al 2006, dorsal fin analyses of killer whales Orcinus orca (Keith et al 2001) and baleen rack shape and size in bowhead whales Balaena mysticetus (Lambertsen et al 2005). In pinnipeds, Haley et al ABSTRACT: Several studies have developed photogrammetric techniques for indirect mass estimation of seals.…”

Section: Introductionmentioning

confidence: 99%

How to weigh an elephant seal with one finger: a simple three-dimensional photogrammetric application

Bruyn¹,

Bester²,

Carlini³

et al. 2009

Aquat. Biol.

104

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Killer whales (Orcinus orca) at Marion Island, Southern Ocean

Cited by 40 publications

References 13 publications

Movement and diving of killer whales ( Orcinus orca ) at a Southern Ocean archipelago

Movement and diving of killer whales ( Orcinus orca ) at a Southern Ocean archipelago

Evidence for density dependent population regulation in southern elephant seals in the southern Indian Ocean

How to weigh an elephant seal with one finger: a simple three-dimensional photogrammetric application

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