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Predators feeding in a highly dynamic environment have evolved strategies to respond to patchy resource distribution. However, studying these ecological interactions is challenging in the marine environment, as both predators and elements in their environment are often highly mobile and difficult to monitor. We used sensors deployed on female southern elephant seals Mirounga leonina to collect data as they foraged hundreds of metres below a large recurrent phytoplankton plume east of the Kerguelen Islands (49°15’S, 69°10’E). Data collected by animal-borne light sensors were used to reconstruct phytoplankton patterns encountered by the seals. Prey encounter events (PEEs) recorded by seal-borne accelerometers below the euphotic zone were compared with phytoplankton estimates at 2 scales: mesoscale (10s to 100s km) and small scale (inter-dive). These analyses were performed on data recorded during daylight hours only, and did not include data at night due to the sensitivity threshold of the light sensors. Our results showed that elephant seals moved through alternating patches of high- and low-density phytoplankton, but the timing and locations of these bloom patches were different between the upper and lower euphotic layers. Seals recorded more PEEs and shallower dives below high-density patches of phytoplankton. We propose that phytoplankton density at the mesoscale facilitates prey aggregation (direct effect). However, phytoplankton density between dives (small scale) likely facilitates vertical access to prey via the shading effect of phytoplankton (indirect effect). Our study shows how a deep-diving marine predator may use its environment to maximise net energy intake, and we demonstrate its resilience in a highly dynamic ecosystem.

Item Type:	Refereed Article
Keywords:	dive behaviour, Kerguelen, phytoplankton plume, prey access, Mirounga leonina, foraging strategy, prey encounter events
Research Division:	Environmental Sciences
Research Group:	Environmental management
Research Field:	Wildlife and habitat management
Objective Division:	Environmental Management
Objective Group:	Coastal and estuarine systems and management
Objective Field:	Assessment and management of coastal and estuarine ecosystems
UTAS Author:	O'Toole, M (Dr Malcolm O'Toole)
UTAS Author:	Lea, MA (Professor Mary-Anne Lea)
UTAS Author:	Hindell, MA (Professor Mark Hindell)
ID Code:	121853
Year Published:	2017
Web of Science® Times Cited:	9
Deposited By:	Ecology and Biodiversity
Deposited On:	2017-10-17
Last Modified:	2018-05-30
Downloads:	4 View Download Statistics