Attacks on Sea Otters by Killer Whales

Hatfield, Brian B.; Marks, Dennis K.; Tinker, M. Tim; Nolan, Kellie; Peirce, Joshua.

doi:10.1111/j.1748-7692.1998.tb00775.x

Cited by 38 publications

(32 citation statements)

References 6 publications

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“…1992) and harbor seals (Frost et al 1994) in Alaska to less than one-half of their original numbers may have forced killer whales to search for alternate food sources in recent years. This possible switch in prey base correlates with the apparent rise in killer whale encounters in upper Cook Inlet (reported here) and in Bristol Bay (Frost et al 1992), as well as the increased take of sea otters, Enhydra lzltris (Estes et al 1998, Hatfield et al 1998. Of the 54 transient whales identified in the Gulf of Alaska, i t is likely that very few visit the upper Inlet and pursue belugas.…”

Section: Timingsupporting

confidence: 61%

Killer Whale Predation on Belugas in Cook Inlet, Alaska: Implications for a Depleted Population

Shelden

Rugh

Mahoney

et al. 2003

Marine Mammal Science

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Killer whale predation on belugas in Cook Inlet, Alaska, has become a concern since the decline of these belugas was documented during the 1990s. Accordingly, killer whale sightings were compiled from systematic surveys, observer databases, and anecdotal accounts. Killer whales have been relatively common in lower Cook Inlet (at least 100 sightings from 1975 to 2002), but in the upper Inlet, north of Kalgin Island, sightings were infrequent (18 in 27 yr), especially prior to the 1990s. Beach cast beluga carcasses with teeth marks and missing flesh also provided evidence of killer whale predation. Most observed killer whale/beluga interactions were in the upper Inlet. During 11 of 15 observed interactions, belugas were obviously injured or killed, either through direct attacks or indirectly as a result of stranding. Assuming at least one beluga mortality occurred during the other four encounters, we can account for 21 belugas killed between 1985 and 2002. This would suggest a minimum estimate of roughly 1/yr and does not include at least three instances where beluga calves accompanied an adult that was attacked.

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Section: Timingsupporting

confidence: 61%

Killer Whale Predation on Belugas in Cook Inlet, Alaska: Implications for a Depleted Population

Shelden

Rugh

Mahoney

et al. 2003

Marine Mammal Science

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“…Higher sea otter mortality rates were observed in oil-affected areas of PWS through 1998, perhaps as a result of exposure to oil (Ballachey et al 2000, Monson et al 2000a). Furthermore, predation by killer whales (Estes et al 1998, Hatfield et al 1998, Garshelis & Johnson 1999) and other hunters (Bodkin et al 2001) may have contributed to the lack of recovery. Populations occupying habitats with low-potential food supplies are more prone to being regulated at low densities by predation (Messier 1994) or possibly by oil-induced mortality.…”

Section: Discussionmentioning

confidence: 99%

Food limitation and the recovery of sea otters following the 'Exxon Valdez' oil spill

Dean¹,

Bodkin²,

Fukuyama³

et al. 2002

Mar. Ecol. Prog. Ser.

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We examined the potential role of food limitation in constraining the recovery of sea otters Enhydra lutris in Prince William Sound, Alaska, following the 'Exxon Valdez' oil spill. The spill resulted in the removal of a large number of sea otters in 1989, and as of 1998, the portion of the population in the heavily oiled northern Knight Island region had not fully recovered. Between 1996 and 1998, prey consumption rate was higher and the condition of sea otters was better at northern Knight Island than in an unoiled area of the sound (Montague Island). Estimates of prey energy available per unit mass of sea otter were about 4 times higher at Knight than Montague Island, albeit not significantly different between the 2 areas. Over this same period, the number of sea otters remained constant at northern Knight Island but increased at Montague Island. These data suggest that food was at least as abundant at Knight than at Montague Island, and that recovery of sea otters via intrinsic population growth was limited by factors other than food. However, the availability of food, the prey consumption rate, and the condition of sea otters were all much lower at both Knight and Montague Islands than in areas newly occupied by sea otters where the population growth rate was near the theoretical maximum. It is possible that the relatively short supply of food (compared to areas where sea otter population growth rate was high) may have inhibited immigration or interacted with other factors (e.g. oil-induced mortality or predation) to restrict sea otter population growth. Nonetheless, these data suggest that impacts of anthropogenic disturbances on large, often food-limited vertebrate predators can persist in spite of the availability of food resources that are sufficient for intrinsic population growth.

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“…The killer whale (Orcinus orca), as a species, is an eclectic feeder, taking a wide range of prey (Grachyov & Mymrin, 1986;Sarti et al, 1994;Similä et al, 1996;Ford et al, 1998;Hatfield et al, 1998;Visser & Bonaccorso, 2003;Jones, 2006;Matkin et al, 2007;Visser et al, 2008). However, in some areas, sympatric populations show different foraging strategies as well as prey preference (foraging ecotypes).…”

Section: Introductionmentioning

confidence: 99%

First Record of Predation on False Killer Whales (<I>Pseudorca crassidens</I>) by Killer Whales (<I>Orcinus orca</I>)

Visser¹,

Zaeschmar²,

Halliday³

et al. 2010

aquatic mammals

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The first record of killer whale (Orcinus orca) predation on false killer whales (Pseudorca crassidens) is reported here. On 25 March 2010, a group of 50 to 60 false killer whales, including approximately 15 calves and accompanied by three to five bottlenose dolphins (Tursiops sp.), were sighted in the Bay of Islands, New Zealand. Within 30 min, they were approached by a group of approximately eight killer whales. Five false killer whales were attacked, with at least three rammed from below, forcing them out of the water. After 29 min, the killer whales were milling at the surface and feeding on the carcass of a false killer whale calf, possibly the only individual killed. The killer whales had prolific fresh and healed oval wounds, which were attributed to cookie cutter shark (Isistius sp.) bites.

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Attacks on Sea Otters by Killer Whales

Cited by 38 publications

References 6 publications

Killer Whale Predation on Belugas in Cook Inlet, Alaska: Implications for a Depleted Population

Killer Whale Predation on Belugas in Cook Inlet, Alaska: Implications for a Depleted Population

Food limitation and the recovery of sea otters following the 'Exxon Valdez' oil spill

First Record of Predation on False Killer Whales (<I>Pseudorca crassidens</I>) by Killer Whales (<I>Orcinus orca</I>)

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