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

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breeders non-breeders breeders non-breeders

food-add control

Number of breeding females

Number of females surviving

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control

food-add control20-Mar

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12-Jun

food-add control

Parturition dates

Litter sizes

food-add

control

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food-add (n=9) control (n=5)

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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

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Individual growth rates

food-add control

Average growth rates

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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

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did not settle

settled

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Ag

e (

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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)

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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)

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distance (m)

food-add

control

Team Lloyd

Territory mapping– juveniles radio-collared– radio-tracked territory boundary– ≥ 30 data points

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-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

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Proportion of total juveniles settled

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success

Too cute not to include