22
Southern elephant seals: A top predator of the southern ocean and a useful vehicle to study its environment Susan Gallon
Southern elephant seals: A top predator of the southern ocean and a useful vehicle to study its environment
Susan Gallon
Southern elephant seals(Mirounga leonina)
Largest pinniped species ( 1500-3000 Kg, 400-600 Kg)♂ ♀
Extremely sexually dimorphic: male up to 10 times larger than adult female
2 annual migrations from their breeding and molting sites
Major consumers of Southern Ocean biomass
Long (up to 2 hours), deep (up to 2500 m) and nearly continuous diving at sea (90 % diving)
Study site:Elephant Island (61°S 55°W)29 southern elephant seals (5 PM SA
, 20 PM and 4 PR )♂ ♀ ♀
Satellite tags (SMRU, St Andrews, UK)
To track individual seals at sea and monitor their diving behaviourState Space Models (SSM) were used to infer foraging areas during seals’ migration.In these foraging areas we calculated: dive duration, dive depth, diel migration, shelf foraging and benthic foraging
Whisker SI analyses 15N a proxy for the trophic position of predator13C a proxy for foraging habitat
1- INVESTIGATING FORAGING STRATEGIES
1- INVESTIGATING FORAGING STRATEGIES
Satellite tracked animals and kernel density of foraging area
1- INVESTIGATING FORAGING STRATEGIES
15N 13C 15N 13C
15N 13C
Samples taken in November 2008 and 2009 and January 2009 for F203-262Samples taken in January 2008 and 2009 for F255-263 and F229-265
1- INVESTIGATING FORAGING STRATEGIES
15N 13C 15N 13C
15N 13C
Samples taken in November 2008 and 2009 and January 2009 for F203-262Samples taken in January 2008 and 2009 for F255-263 and F229-265
Similar profiles in consecutive years fidelity to foraging area and prey
1- INVESTIGATING FORAGING STRATEGIES
15N 13C
WAP: Feed on the shelf, some benthic dives, lower 13C and higher 15N
OPEN WATER: No shelf, no benthic dives, higher 13C and lower 15N
MIXED: Shelf, benthic dives, open water, mixed 13C and 15N values
1- INVESTIGATING FORAGING STRATEGIES
15N 13C
WAP: Feed on the shelf, some benthic dives, lower 13C and higher 15N
OPEN WATER: No shelf, no benthic dives, higher 13C and lower 15N
MIXED: Shelf, benthic dives, open water, mixed 13C and 15N values
Different C and N profiles Different isotopic signature for seals feeding in different geographic areas
1- INVESTIGATING FORAGING STRATEGIES
15N 13C
15N 13C
1- INVESTIGATING FORAGING STRATEGIES
15N 13C
15N 13C Similar C profile but different N profile
Seals (from same gender and age class) that forage in same habitat feed on prey from
different trophic levelWhy? How?
1- INVESTIGATING FORAGING STRATEGIES
2- IDENTIFYING FORAGING EVENT
Translocation study:Kerguelen Island (49°S 69°E)3 adult female southern elephant seals (T3, T4 and T5)
Satellite tags (SMRU, St Andrews, UK):Provided an estimate of the location of the animal at sea and on land
Accelerometer tags (Loggend, CNRS, France):Placed on neck of the animal to detect feeding event2-D accelerations (heave and surge) at 8 Hz (T4 and T5) and 16 Hz (T3)Depth sensor at 1 Hz
Heave Surge
400 m
Static acceleration gravity or pitchDynamic acceleration movements of the seals resulting from either stroking and/or rapid head movements
2- IDENTIFYING FORAGING EVENT
Matlab (version 7.0.1) Low pass filter to extract static (gravitational) accelerationFeeding event acceleration spikes over the thresholdFeeding dive acceleration profiles with more than one spike present in both the surge and heave axes
Heave Surge Threshold
400 m
2- IDENTIFYING FORAGING EVENT
2- IDENTIFYING FORAGING EVENT
Oceanographic conditions
Distribution and availability of prey
Oceanographers Biologists
ClimateOcean resourcesDemography
- Temperature- Salinity- Fluorescence- Dissolve oxygen
- Prey species- Prey encounter- Foraging efficiency- Life history
3- FUTURE WORK
4- Merging expertise
It may be possible to use seal tracking data to locate deep-sea coral habitats and furthermore to use bio-logging equipment attached to seals as platforms for ocean sensors to relay physical ocean data (e.g. salinity, temperature) from the areas they frequent. These physical data may be in turn be used to better identify and protect cold water coral habitats.
Thank you
