primary thesis objectives
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Linking spatial and temporal patterns in resource availability,
individual performance, & population dynamics.
Primary thesis objectives
• Determine how much individual detail is needed in models of population dynamics.
• Relate explicitly spatial and temporal variation in resource abundance to individual “success”.
For today….
• Population level dynamics of red squirrels in Kluane valley
• Temporal/spatial variation in resource abundance and territory sizes
Red Squirrel (Tamiasciuris hudsonicus)
Population dynamics
1. Population dynamics:
– Holistic approach assumes:• Habitat is homogeneous
• All individuals are identical
– Reductionist approach assumes:• individual level of detail is important
Go with Holistic View - for now
Midden locations
60 m
60 m
SU
KL
Female densities
Population models
• 4 competing models• Density independent: Nt+1 = Nt•ea
• Density dependent: Nt+1 = Nt•ea+bNt
• Delayed density dependent: Nt+1 = Nt•ea+bNt+cNt-1
• Response Surface model: Nt+1 = Nt•ea+bNt+cNt-1+dNt2+eNt-12+fNtNt-1
• AICc used to compare model fit to data
Population models: AICc results
KL SUModel AICc dAICc AICc dAICc
DI 13.51 0.00 18.52 3.57DD 13.55 0.04 14.95 0.00
DDD 16.66 3.14 17.42 2.47RSM 26.80 13.29 30.35 15.40
Population models: Density dependence??
SU
What about food??
KL
Population summary
• Food and density effects appear to differ between these ‘populations’
• KL - Density independent/Density dependent • SU - Density dependent
• Habitat quality too???
Why are they different?• Different birth rates, survival patterns?
– λ-contribution analysis (λ=er)
• which life-history characteristic best-tracks changes in population growth-rate?
» begin to tease apart what life-history is related to changes in the population growth rate (ie. fecundity, survival)
» also, investigate spatial variation in this “key-factor” within each population, and relate to territory ‘quality’
CONESAND TERRITORY SIZE
Annual cone production
• White spruce - a masting species
• Cone index - count top 3m of tree
• Cone calibration - count all cones!!
3m
White spruce cone production index vs. actual
0
1
2
3
4
5
6
7
8
0 1 2 3 4 5 6 7 8
ln(count)
ln(a
ctu
al)
Actual cone range: 1 - 2774
y=1.185*xr2=0.996
* ** * *
Sp
ruce
Co
nes
1988 1990 1992 1994 1996 1998 20000
50
100
150
200
250
300
350
* ** * *
Methods:
- individual squirrels visually observed- territorial behaviours & locations noted- 100 % MCP
60 m
1994 and 2001
Territory size
Temporal patterns
* ** * *
Temporal patterns
* ** * *
Linking food availability to reproductive output
Year1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Num
ber o
f birt
hs
0
1
2
3
4
5
Number of offspring per female per year.
ANOVA P > 0.05 NS
* ** * *
SE_WEAN
Year1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Num
ber w
eane
d
0
1
2
3
Number of squirrels weaned per female per year.
ANOVA P < 0.001
* ** * *
Year1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Num
ber s
urviv
ing
one
year
0
1
2
Number of squirrels born surviving to one year.
ANOVA P < 0.001
* ** * *
• Territory size decreases after a mast year, otherwisesize appears mostly constant
• No significant effect of resource fluctuations on litter size, BUT significant effect on juvenile survival to weaning, 1-yr
Territory Size - temporal summary
Recall: assumption of spatial homogeneity
IS IT?
Spatial vegetation patterns
• Vegetation transects every 60m - 3 transects 1200, 2400, 3600
- each transect 4m x 25m
• Kriged surfaces based on transects (10m2 cell size)- ws density- ws density >5cm dbh, alive- bark beetle killed trees- aspen- willow
60 m
Legend
<VALUE>
0.16 - 1.1
1.2 - 1.9
2 - 2.7
2.8 - 3.6
3.7 - 6.3
# kl_su_midden_gps
Value
0 - 0.0005
0.00051 - 0.025
0.026 - 0.083
0.084 - 0.15
0.16 - 0.23
0.24 - 0.38
<VALUE>
0 - 0.002
0.002 - 0.022
0.023 - 0.063
0.064 - 0.11
0.12 - 0.16
0.17 - 0.25
Total white spruce density
60 m
Legend
<VALUE>
0.16 - 1.1
1.2 - 1.9
2 - 2.7
2.8 - 3.6
3.7 - 6.3
# kl_su_midden_gps
Value
0 - 0.0005
0.00051 - 0.025
0.026 - 0.083
0.084 - 0.15
0.16 - 0.23
0.24 - 0.38
<VALUE>
0 - 0.002
0.002 - 0.022
0.023 - 0.063
0.064 - 0.11
0.12 - 0.16
0.17 - 0.25
Midden placement (total ws den)
60 mWhite spruce (>5cm dbh, alive) density
Legend
<VALUE>
0.098 - 0.49
0.5 - 0.84
0.85 - 1.2
1.3 - 2
2.1 - 3.7
60 mBark beetle killed spruce density
Legend
Value
0 - 0.0005
0.00051 - 0.025
0.026 - 0.083
0.084 - 0.15
0.16 - 0.23
0.24 - 0.38
60 mAspen density
Legend
<VALUE>
0 - 0.045
0.046 - 0.26
0.27 - 0.63
0.64 - 1.1
1.2 - 1.8
60 mWillow density
Legend
Value
0.23 - 0.59
0.6 - 0.79
0.8 - 0.96
0.97 - 1.2
1.3 - 1.6
Spatial patterns in territory size
60 mWhite spruce (>5cm dbh, alive) density and August 2002 territories
Legend
<VALUE>
0.098 - 0.49
0.5 - 0.84
0.85 - 1.2
1.3 - 2
2.1 - 3.7
60 m
Legend
<VALUE>
0.098 - 0.49
0.5 - 0.84
0.85 - 1.2
1.3 - 2
2.1 - 3.7
White spruce (>5cm dbh, alive) density, June and August territories
60 m
Legend
<VALUE>
0.098 - 0.49
0.5 - 0.84
0.85 - 1.2
1.3 - 2
2.1 - 3.7
123
110
170
84
166
579
293
399
139120
28695
5828 41
101
333
57
579
258
429
700
310
652
735
175
400
248
1034
143
122
70
119
40
90
Number of white spruce (>5cm dbh) and August territories
Spatial patterns in cone production
IS IT SPATIALLY HOMOGENEOUS???
• Additional cone count trees established in 2002
• Modelling cone production- independent variables: dbh, density of surrounding trees, dbh of surrounding trees, location (r2 = 0.38)plus.. slope, aspect, height, basal light class (r2 = 0.60)
Cone Production 2002
6760900
6761100
6761300
6761500
6761700
6761900
659800 660000 660200 660400 660600 660800 661000 661200
UTM X
UT
M Y
= 500
6760900
6761100
6761300
6761500
6761700
6761900
659800 660000 660200 660400 660600 660800 661000 661200
UTM X
UT
M Y
= 500
Cone Production 2003
p<0.05
Change in June territory size 2002-03
Goal - to map variation in habitat quality
6760900
6761100
6761300
6761500
6761700
6761900
659800 660000 660200 660400 660600 660800 661000 661200
UTM X
UT
M Y
= 500
=
c
cc
c
c
c
+
Continuing Objectives
• Continue to develop cone production models
• Link spatial and temporal cone availabity and territory size to territory quality & “success”
• Investigate individual contributions to overall population dynamics
Long-Term Food Add Thoughts
• What happens to territory size when under constant high food conditions?
• Will females maintain high reproductive output under high food?
• What’s the key factor for recruitment?
• (What is the effect of lack of cues for increased cone production?)
Summer 2002 – field methods1. Territory mapping
June AugustAdult Female 27 19 Male 9 8
Juvenile Female - 5 Male - 3Total 36 35
Population growth rate
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
KL SU
terr
ito
ry s
ize
(h
a)
June
August
NSpaired t-test
June and August 2002 territory sizes.(paired data only)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
1994 1995 1996 1997 1998 1999 2000 2001
Year
Terr
itory
siz
e (h
a)
* *
Changes in an individual’s territory size
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