Preliminary analyses on sea otter population dynamics and foraging ecology in Washington State. Talk given at NWSSMM (Corvallis, Oregon, May 2015)

1. Population Dynamics and Foraging
Ecology of Northern Sea Otters
(Enhydra lutris kenyoni) in Washington
State
Jessica Hale1, Kristin Laidre2, Ron Jameson3, Steve Jeffries4
1University of Washington, SAFS
2University of Washington, SAFS & Polar Science Center
2USGS
3WDFW

2. Clara L. Minard

3. WDFW, 2004

4. Objectives
1. Understand population growth and range expansion of
northern sea otters in Washington State since reintroduction;
2. Quantify changes in the diet of sea otters over the 46-year
period of population growth since reintroduction.

5. Methods
• Develop a spatially explicit demographic population model
for northern sea otters in Washington State
• Compare diet across a gradient of occupation time using
space-for-time approach
• Evaluate diet changes overtime by comparing foraging data
collected in 1993-1999 to current diet at same sites

6. Most recent index of
population size: 1573
total
0
200
400
600
800
1000
1200
1400
1600
1975 1980 1985 1990 1995 2000 2005 2010 2015
IndexofPopulationSize
Year
Independents
Pups

13. 0
200
400
600
800
1000
1200
1400
1600
0 5 10 15 20 25 30 35 40
IndependentCount
Year
Observed
Predicted
1975 1980 1985 1990 1995 2000 2005 2010 2015
( )
( 1) ( ) 0.19 ( ) 1
1149.59
N t
N t N t N t
 
    
 

14. WDFW, 2004
NORTH
SOUTH

15. 0
10
20
30
40
50
60
70
80
90
100
1975 1980 1985 1990 1995 2000 2005 2010 2015
PercentofTotalPopulationIndex
Year
% North
% South
Population Distribution between
North and South
NORTH
SOUTH

16. 0
50
100
150
200
250
300
350
400
450
500
1975 1980 1985 1990 1995 2000 2005 2010 2015
IndependentCount
Year
North Segment
Observed
Predicted
( )
( 1) ( ) 0.30 ( ) 1
336.69
N t
N t N t N t
 
    
 
NORTH

17. 0
200
400
600
800
1000
1200
1975 1980 1985 1990 1995 2000 2005 2010 2015
IndependentCount
Year
South Segment
Observed
Predicted
( )
( 1) ( ) 0.23 ( ) 1
1150.64
N t
N t N t N t
 
    
 
SOUTH

18. Prey frequency was different among years (χ2=10012, d.f. = 60, p <0.001).
1993-1999 Foraging Analyses by Year
© Caroline Hempstead

19. Prey frequency was different among seasons (χ2=7139, d.f. = 30, p <0.001).
1993-1999 Foraging Analyses by Season

20. Prey frequency was different between male and female sea otters (χ2=148, d.f. = 10, p <0.001).
1993-1999 Foraging Analyses by Sex

21. Fisheries Species

22. 1993-1999 Foraging Analyses – Fisheries Species
0
10
20
30
40
50
60
70
80
90
100
1993 1994 1995 1996 1997 1998 1999
PercentofDiet
Year
Fisheries Species
Non-fisheries Species

23. Preliminary Foraging Observations

24. Planned Analyses
• Bayesian State-Space Model
• Re-calculate carrying capacity using recent survey indices
• Create a Spatially Explicit population model
• Space-for-time diet comparison
• Historical diet comparison at same sites

25. Tinker et al. 2008

26. Acknowledgments
• Pilot Jeff Well from Rite Bros. Aviation
• Mick Cope, Anita McMillan, and Shelley Ament from WDFW
• Deanna Lynch and Sue Thomas from USFWS
• Shawn Larson, Pat McMahon, and Caroline Hempstead from the
Seattle Aquarium
• Lisa Triggs, Mandy Betz, and Terre Zorman from Point Defiance Zoo
and Aquarium
• Richard McGovern, Donna Hauser, and Erica Escajeda
• Funding from NOAA Dr. Nancy Foster Scholarship Program

27. Thanks!
Twitter: @HaleJessie
Email: jrh33@uw.edu
Blog: halejessie.wordpress.com