Post on 21-Dec-2015
Effects of resource availability on juvenile dispersal and settlement
Dispersal & Resources
• central determinant of a species’ ecology
• energetically expensive
• dispersal behaviour related to physical condition or access to energy reserves
Energetic mediation of dispersal
Belding’s ground squirrel(Spermophilus beldingi)Nunes et al. 1999
Greater flamingo(Phoenicopterus ruber roseus)Barbraud et al. 2003
Common lizard(Lacerta vivipara)Massot and Clobert 1995
Spanish imperial eagle(Aquila adalberti)Ferrer et al. 1992
photo by Don Baccus
photo by Howard Inns
photo from Smithsonian Institute
photo from Just Birds
Resource paradox
• Do increased local resources encourage or provide an advantage for dispersal or philopatry?
Photo by Sébastien Descamps
Dispersal trade-off
Costs• energetically expensive• predation risk• territory quality
Benefits• avoid kin competition• avoid inbreeding• territory quality
Objectives and Expectations
Determine energetic influences on:
• growth rate
• exploratory forays
• degree of dispersal or philopatry
• territory takeover attempts
• size and quality of territory settled
• successful settlement and survival
• maternal food supplementationautumn 2003 to Spring 2004
• autumn 2003 n=31 females
• winter 2004food add n=15
control n=13
Team Lloyd
0
2
4
6
8
10
12
14
16
breeders non-breeders breeders non-breeders
food-add control
Number of breeding females
Number of females surviving
0
2
4
6
8
10
12
14
16
breeders non-breeders
food-add control
disappear/predation
survive
control
food-add control20-Mar
03-Apr
17-Apr
01-May
15-May
29-May
12-Jun
food-add control
Parturition dates
Litter sizes
food-add
control
0
1
2
3
4
5
6
1 2 3 4 5
litter size
freq
uen
cy
0
1
2
3
4
5
6
1 2 3 4 5
litter size
freq
uen
cy
0
5
10
15
20
25
emerged failed emerged failed
food-add (n=9) control (n=5)
0
0.2
0.4
0.6
0.8
1
0 1 2 3
Juvenile emergence
Number of emerged vs failed juveniles
Average proportion of litter emerged
food-add control
Team Lloyd
Circuit trapping– all middens within 90 m radius of natal area– until 100 days old– 150-175 hours of trapping per litter– weight taken at each capture
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 50 100 150 200
age (days)
mas
s (g
)
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 50 100 150 200
age (days)m
as
s (
g)
Individual growth rates
food-add control
Average growth rates
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0 50 100 150 200
age (days)
mas
s (g
)
food-add
control
Settlement criteria
1. rattled on midden on more than one day
2. trapped at least 3 times at same midden
3. assumption for one rattle during August census – late litters
4. day 100?
Settlement criteria
1. rattled on midden on more than one day
2. trapped at least 3 times at same midden
3. assumption for one rattle during August census – late litters
4. day 100?
Settlement criteria
1. rattled on midden on more than one day
2. trapped at least 3 times at same midden
3. assumption for one rattle during August census – late litters
4. day 100?
Settlement criteria
1. rattled on midden on more than one day
2. trapped at least 3 times at same midden
3. assumption for one rattle during August census – late litters
4. day 100?
Settlement criteria
1. rattled on midden on more than one day
2. trapped at least 3 times at same midden
3. assumption for one rattle during August census – late litters
4. day 100?
Settlement of emerged juveniles
90% settlement in both food-add and control at individual level
food-add litters n= 12 control litters n=5
0
5
10
15
20
25
30
food-add control
did not settle
settled
0
20
40
60
80
100
120
140
0 1 2 3
Ag
e (
da
ys
)Age at settlement
food-add control
Maximum foray distance
food-add n = 28 from 12 litters (154.84 ± 179.60)
control n= 10 from 5 litters (95.41 ± 37.96)
0
1
2
3
0 100 200 300 400 500 600 700 800
distance (m)
food-add
control
Maximum settlement distance
food-add n = 24 from 12 litters (116.19 ± 172.84)
control n= 9 from 5 litters (76.47 ± 56.56)
0
1
2
3
0 100 200 300 400 500 600 700 800
distance (m)
food-add
control
Team Lloyd
Territory mapping– juveniles radio-collared– radio-tracked territory boundary– ≥ 30 data points
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
-10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0
square = food add circle = controlgrid line = 150 m
Juvenile territory mapping
Team Lloyd
Territory quality indexMidden condition
• ranked midden quality and activity
Cone production• assessed with cone
counts
Tree density
Spruce bark beetle kill
Survival of settled juveniles
0
5
10
15
20
25
30
food-add control
disappear
survive
Proportion of total juveniles settled
0.0
20.0
40.0
60.0
80.0
100.0
food-add control
%
failure
success
Too cute not to include