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Spatial distribution of dive activity in chick-rearingSpatial distribution of dive activity in chick-rearingSnares penguins Snares penguins Eudyptes robustusEudyptes robustus
Thomas MatternThomas Mattern11, Katrin Ludynia, Katrin Ludynia22, Dave Houston, Dave Houston33 & Lloyd Davis & Lloyd Davis11
11 Department of Zoology, University of Otago, Dunedin, NZ Department of Zoology, University of Otago, Dunedin, NZ22 Research &Technology Research &Technology CentreCentre ( (BüsumBüsum), CAU Kiel, Germany), CAU Kiel, Germany
33 Department of Conservation Department of Conservation, Wellington, NZ, Wellington, NZ
The Snares Islands
The Snares Islands
THE SNARES THE SNARES (48°S, 166°E)
- ca. 120 km south of South Is.
- surface area: < 3.6 km²
- supports extensive populations of seabirds, including the Snares penguin
Snares Penguin (Eudyptes robustus)
STATUS:- endemic to the Snares (IUCN: vulnerable)
- 25.000-30.000 pairs- population stable (unlike other NZ eudyptids)
no historic changes in prey availability
DIET: DIET: (Mattern 2006)(Mattern 2006)
- KrillKrill (~60% of food load)(~60% of food load)
- - SquidSquid (~20%)(~20%)
- FishFish (~20%)(~20%)
Primarily Primarily juvenile juvenile stagesstages
Associated Associated to primary to primary productionproduction
Beneficial oceanographic features
Beneficial oceanographic features
Male penguin foraging (incubation)
Long trips: Long trips: - 12-16 d12-16 d- 150+ km from island150+ km from island
Destination:Destination:Subtropical Front Subtropical Front (STF) – convergence (STF) – convergence zonezone
Reason:Reason:Predictable, elevated Predictable, elevated productivity in early productivity in early springspring
chl a concentrationchl a concentration16-23. 10. 200316-23. 10. 2003
Mattern et al., IPC5 Ushuaia, 2004Mattern et al., IPC5 Ushuaia, 2004
But too far away But too far away when feeding chickswhen feeding chicks
GPS logger deployments
1. Field work periods:- October/November 2003 & 2004
2. earth&Ocean GPS-TDlogs- geographic position after each dive- dive depth (resolution: ~0.1m) - temperature (~0.01°K)
3. Number of penguins equipped:- 2003: 8 females (chick guard)- 2004: 16 females (chick guard)
4. Deployment period: - both years: 2-4 days (ca. 1-2 foraging trips)
1 s interval
Basic foraging parameters
n = 5 birds n = 14 birds
114.6 ± 23.3 km vs. 127.5 ± 39.9 km
71.9 ± 16.2 km vs. 76.6 ± 22.9
31.7 ± 4.9 h vs. 36.9 ± 11.4 h
Travel distance:
Max. Range:
Trip duration:
t=-0.81, p=0.434
t=-1.29, p=0.221
t=-0.47, p=0.649
2004/052003/04
2003/04 2004/05
Spatial Analysis
n = 5 birds n = 14 birds
1. Linear extrapolation of tracks
2. Assign position to each dive
3. Analysis grid (0.04° x 0.04°)
4. Calculate means of dive parameters for each cell
5. Visualize via contour plots
DIVE PARAMETERS:DIVE PARAMETERS:
1.1.Horizontal speed Horizontal speed (consecutive dive events: distance / time interval)(consecutive dive events: distance / time interval)
2.2.Duration of diveDuration of dive
3.3.Maximum depth Maximum depth (greatest depth reached during dive)(greatest depth reached during dive)
4.4.Repeated Maximum Depth dive? Repeated Maximum Depth dive? (max depth±10% of preceding dive)(max depth±10% of preceding dive)
5.5.Ambient temperature at depths 5-10m Ambient temperature at depths 5-10m (from sensor records)(from sensor records)
2003/04 2004/05
No of birds / grid cell
n = 5 birds n = 14 birds
2003/04 2004/05
No of birds / grid cell
n = 5 birds n = 14 birds
Horizontal speed
2004/052003/04
Dive duration
2004/052003/04
Max depth
2004/052003/04
Repeated Maximum Depth
2004/052003/04
Ambient temperature (5-10m)
2004/052003/04
SENSOR FAILUREno temperature data
Results in a nutshell
Within 50 km radius: • High horizontal speeds• Short, shallow dives• Cool water
TRAVELLING
Outside 50 km radius: • Low horizontal speeds• Long, deep, RMD dives• Warm water
SEARCHING/FEEDINGPenguins seek Penguins seek warmerwarmer waters to forage waters to forage
A rule of thumb in foraging ecology
Cold water stands for high productivity:
“UPWELLING”
Then... Why forage in warm waters?
(e.g. Humboldt Current, Benguela Current)(e.g. Humboldt Current, Benguela Current)
Why forage in warm waters?
Tasm
an C
urre
nt
South
land
Curre
nt
Why forage in warm waters?
SST (mean, Oct – Dec 2004)
MODIS/Aqua
** **
MODIS/Aqua
SST (mean, Oct – Dec 2003)
Why forage in warm waters?Why forage in warm waters?
MODIS/Aqua
** **
MODIS/Aqua
Chl a (mean, Oct – Dec 2003)Chl a (mean, Oct – Dec 2003) Chl a (mean, Oct – Dec 2004)Chl a (mean, Oct – Dec 2004)
High effort in colder conditions
SST (spring)SST (spring)Chl a (spring)Chl a (spring)
MODIS/Aqua
SST, productivity & body condition
MODIS/Aqua BCI: residuals from regression of body mass vs. bill length
MODIS/Aqua
Why forage in warm waters?Why forage in warm waters?
Tasman Current:Tasman Current:Nutrient rich and Nutrient rich and warmwarm Central Tasman WaterCentral Tasman Water
With the current: With the current: horizontal transport of horizontal transport of ... nutrients... nutrients... planktonic prey... planktonic prey
NotNot UPWELLING UPWELLINGbut ratherbut rather
““SIDEWELLING”SIDEWELLING”
Snares penguins areSnares penguins areWarm-water diversWarm-water divers
Thank you...
… the Snares penguins for their cooperation and endurance
… our friends and collegues Ursula Ellenberg and Alvin Setiawan for their invaluable help in the field
… Pete McLelland (Department of Conservation, Invercargill) for the permits to work on the Snares
… Gerrit Peters for designing the loggers and quick answers to stupid questions