What drives

dispersal?

Mark Andruskiw

Costs & benefits

Long Distance: Short (philopatry):

Cost: • predation risk

• missed opportunity

• inbreeding

• parent-offspring conflict

Benefit: • unexploited resources

• unrelated mates

• parental resources

• safety

Traditional hypotheses:

1) Competition for resources

2) Competition for mates

3) Inbreeding avoidance

Berteaux and Boutin 2000

Cone abundance:

Population density:

Philopatry vs. dispersal: mom kids

Berteaux and Boutin 2000

Model mom’s decision:

Model mom’s decision:

)...*()*()()...()( 3222112211 XXfXXfXfXfXfY nnnn

where:

Y = mother’s behavior (keep, share, bequeath) X1..Xn = explanatory variables

Model mom’s decision:

Variable: Sig. to philopatry:

mother’s age increase

# offspring at weaning increase

cone production increase

cone reserves decrease

# vacant middens 150 m increase

Model mom’s decision:

Variable: Sig. to philopatry:

mother’s age increase

# offspring at weaning increase

cone production increase

cone reserves decrease

# vacant middens 150 m increase

Individual level

Model mom’s decision:

Variable: Sig. to philopatry:

mother’s age increase

# offspring at weaning increase

cone production increase

cone reserves decrease

# vacant middens 150 m increase

Individual level

Weight by quality

Expand neighborhood

# potential dispersers

# predators

# alternate prey

Model mom’s decision:

Variable: Sig. to philopatry:

mother’s age increase

# offspring at weaning increase

cone production increase

cone reserves decrease

# vacant middens 150 m increase

Individual level

Weight by quality

Expand neighborhood

Survival cost:

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

on terr off terr

locationsmortality

Pro

babi

lity

Model kid’s decision:

)...*()*()()...()( 3222112211 XXfXXfXfXfXfY nnnn

where:

Y = dispersal distance X1..Xn = explanatory variables

Model kid’s decision:Category: Variable:

Individual sex

cumulative foray distance

maximum foray distance

parturition date

mother’s dispersal distance

Resource availability local cone production

local cone reserves

local vacancy of middens

Spatial conspecifics local density of opposite sex

local density of opposite-sex kin

Predation risk predator density

density of alternate prey

Manipulations:

F

r1

male

r2

fem

r3

maler8

fem

r10

male

r9

fem

r7

male

r6

fem

r4

fem

r5

fem

Core squirrel data:

1) Family information

2) Paternity

3) Midden ownership (vacancy, disp. dist)

4) Cone counts

5) Seen sheets (predators, alternate prey)

Links to other projects:

Logistic needs:

35+ radios

2 receivers

1 technician

1 telemetry flight (?)

2005 papers:

Nest switching in relation to flea load

2005 papers:

Kin recognition in red squirrels

Dad?