Optimal foraging experiments on captive Steller sea lions: a feasibility study

This study - run by WFSC Ph.D. candidate Leslie Cornick - is testing the feasibility of simulating different prey density and distribution scenarios during feeding dives of captive juvenile Steller sea lions held at the Alaska SeaLife Center at Seward, AK. The goal of our study is to find out whether we can learn from captive animals how changes in relative prey accessibility are reflected in behavioral parameters that we can later observe via telemetry on free-ranging Stellers.

In the large Steller sea lion habitat tank at the SeaLife Center, several PVC pipes with remotely operated trapdoors for fish release are used as feeder tubes. The sea lions have to swim between these feeder tubes during their simulated dives.

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From a console in front of a large viewing window into the Steller sea lion habitat, light targets used for training and fish release from the feeder tubes are controlled. The sea lions have to swim between the feeders to obtain food. Sea Life Center visitors are fascinated by these experiments. View video clips!

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Fish is released at various times. Leslie is testing how long the sea lions will remain submerged for different fish encounter rates, how fast they swim, and what distances they cover.

To view videoclips of the Steller sea lion foraging experiments, visit the video clip page.

PRELIMINARY RESULTS:

The preliminary results presented below are based on the partial analysis of nearly 500 simulated dives performed by three juvenile Steller sea lions during 70 foraging sessions. Prey release rate was varied from 0-16 fish per dive. Various dive depths were simulated by delaying initial prey release after the onset of a dive up to one minute, corresponding to estimated dive depths in excess of 60 meters.

• Dive Efficiency vs Simulated Depth
• CPUE vs Simulated Depth
• Foraging Cost Manipulation

All graphs and data are © L.A.Cornick, 2000.

PUBLICATIONS:

• A test of hypotheses based on optimal foraging considerations for a diving mammal using a novel experimental approach. Cornick LA, and Horning M. Canadian Journal of Zoology 81(11): 1799-1807 (2003). Full text (pdf).
  
  
• Cornick LA, Inglis SD, Willis K, Horning M (in press)
  Effects of increased swimming costs on foraging behavior and efficiency of captive Steller sea lions:
  evidence for behavioral plasticity in the recovery phase of dives.
  Journal of Experimental Marine Biology and Ecology.

Find out more about Steller sea lions:

More about Stellers
The NMML/NMFS Steller page
ADF&G's Steller sea lion page

This project is sponsored by:

• National Fish & Wildlife Foundation
• National Oceanic and Atmospheric Administration (NOAA)

Principal Investigator:

• Markus Horning.

Co-investigators:

• Leslie Cornick
  Leslie Cornick was supported in part by a graduate research fellowship from the Texas Institute of Oceanpgraphy for this work.
  
• Graham Worthy

Collaborator:

• Tom Loughlin.

This project / work is being / was carried out under one or more of these permits:
TAMU ULACC AUP# 9-170, 9-171, 2001-112
ASLC IACUC AUP# 00-004, 00-006, 01-001
MMPA permit # 881-1443 to the ASLC

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