Sea lions in drag, fur seals incognito: Insights from the otariid deviants

Arnould, John P. Y.; Costa, Daniel P.

doi:10.4027/slw.2006.22

Cited by 36 publications

(52 citation statements)

References 43 publications

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“…However, once wild seals commence processing, the prey is likely already dead or stunned, and so would likely present itself in a similar way to how it was encountered during out trials. Both fur seal species used a very similar range of behaviors, despite Australian fur seals being primarily benthic foragers, while subantarctic fur seals are epipelagic foragers (Arnould and Costa ). This similarity in the range of behaviors displayed is likely due to their similar otariid body plan, with a long flexible neck, highly specialized forelimbs and simple, sharp teeth.…”

Section: Discussionmentioning

confidence: 99%

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Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Hocking

Fitzgerald

Salverson

et al. 2015

Marine Mammal Science

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When hunting at sea, pinnipeds should adapt their foraging behaviors to suit the prey they are targeting. We performed captive feeding trials with two species of otariid seal, Australian fur seals (Arctocephalus pusillus doriferus) and subantarctic fur seals (Arctocephalus tropicalis). This allowed us to record detailed observations of how their foraging behaviors vary when presented with prey items that cover the full range of body shapes and sizes encountered in the wild. Small prey were captured using suction alone, while larger prey items were caught in the teeth using raptorial biting. Small fish and long skinny prey items could then be swallowed whole or processed by shaking, while all prey items with body depths greater than 7.5 cm were processed by shaking at the water's surface. This matched opportunistic observations of feeding in wild Australian fur seals. Use of “shake feeding” as the main prey processing tactic also matches predictions that this method would be one of the only tactics available to aquatic tetrapods that are unable to secure prey using their forelimbs.

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Section: Discussionmentioning

confidence: 99%

“…Australian fur seals are primarily benthic foragers that target a wide range of large and small prey types near the sea floor (Gales and Pemberton , Arnould and Hindell , Hume et al . , Arnould and Costa , Littnan et al . , Kirkwood et al .…”

mentioning

confidence: 99%

Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Hocking

Fitzgerald

Salverson

et al. 2015

Marine Mammal Science

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“…However, while redbait were recorded as forming a larger proportion of the Australian fur seal diet from 2002 to 2005, it is not known whether this species was in relatively greater abundance than usual in comparison to other prey and/or whether total prey availability was different. In addition, due to their manoeuvrability, small schooling fish such as redbait may be harder for Australian fur seals to capture than larger prey such as Gould's squid and barracouta (Fish et al 2003); thus, even at higher abundance, they may be less profitable (Arnould & Costa 2006).…”

Section: Inter-annual and Inter-individual Variationmentioning

confidence: 99%

Stable isotopes reveal inter-annual and inter-individual variation in the diet of female Australian fur seals

Arnould¹,

Cherel²,

Gibbens³

et al. 2011

Mar. Ecol. Prog. Ser.

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“…1). Galapagos fur seals outnumber Galapagos sea lions in sympatric breeding colonies approximately fivefold (J. W. E. Jeglinski, unpublished data), and fur seal population numbers seem to be increasing, whereas sea lion numbers seem to be declining (F. Trillmich, unpublished data), a showcase of the global situation of sympatric fur seal sea lion populations (Arnould & Costa 2006). The little information available indicates dietary niche segregation and differences in foraging strategy between sympatric adult Galapagos sea lions and adult fur seals (Kooyman & Trillmich 1986a,b;Horning & Trillmich 1997;Dellinger & Trillmich 1999;Pae´z-Rosas et al 2012), similar to a distinct niche segregation between adults of other sympatric sea lion and fur seal species (Antonelis, Stewart & Perryman 1990;Goldsworthy & Page 2007;Franco-Trecu et al 2012;Waite et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Same size – same niche? Foraging niche separation between sympatric juvenile Galapagos sea lions and adult Galapagos fur seals

Jeglinski

Goetz

Werner

et al. 2013

Journal of Animal Ecology

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Summary 1.In vertebrates, patterns of resource utilization change throughout development according to age-and or size-specific abilities and requirements. Thus, interspecific competition affects different age classes differently. 2. Adults of sympatric species often show distinct foraging niche segregation, but juvenile resource use might overlap with adult competitors of similar body size. Resultant negative effects on juveniles can have important consequences for population dynamics, yet such interactions have received little attention in studies of mammalian communities. 3. Using GPS tracking devices, time-depth recorders and stable isotope data, we compared diving depth, activity time, trophic position and foraging habitat characteristics to investigate foraging niche overlap between similar-sized sympatric juvenile Galapagos sea lions (Zalophus wollebaeki) and adult Galapagos fur seals (Arctocephalus galapagoensis) and compared each group with much larger-bodied adult Galapagos sea lions. 4. We found little indication for direct competition but a complex pattern of foraging niche segregation: juvenile sea lions and adult fur seals dived to shallow depths at night, but foraged in different habitats with limited spatial overlap. Conversely, juvenile and adult sea lions employed different foraging patterns, but their foraging areas overlapped almost completely. 5. Consistency of foraging habitat characteristics between juvenile and adult sea lions suggests that avoidance of competition may be important in shaping foraging habitat utilization. Resultant specialization on a limited habitat could contribute to low sea lion numbers that contrast with high fur seal abundance. Our data suggest that exploitation by multiple predators within spatially restricted foraging ranges of juveniles might negatively impact juvenile foraging success and ultimately influence population dynamics.

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Sea lions in drag, fur seals incognito: Insights from the otariid deviants

Cited by 36 publications

References 43 publications

Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Prey capture and processing behaviors vary with prey size and shape in Australian and subantarctic fur seals

Stable isotopes reveal inter-annual and inter-individual variation in the diet of female Australian fur seals

Same size – same niche? Foraging niche separation between sympatric juvenile Galapagos sea lions and adult Galapagos fur seals

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