evolution of group living: insights from a social foraging bat

Evolution of group living:insights from a social foraging bat

Dina Dechmann

Teague O’Mara

Rachel Page’s lab

Olivier Gimenez

Stephen Rossiter’s lab

Yann GAGER

“True sociality:

Persistence in associations

between individuals

in space and time

[Lee 1994]

[Van Schaik & VanHoof 1983]

[Schult et al. 2001]

Multiple

Convergent

evolution

of sociality

e.g. Primates

Ecological drivers

of sociality

Predators

Temperature Roost

Food

Spatial and temporal food constraints

Spatial Temporal

Sunrise Sunset

Time

Social foraging & information transfer

[Safi & Kerth 2007]

Social foraging

in bats

=

+

Feeding buzzes (cues)

Solitary=

Echoes up to 5m

Group=

Eavesdropping up to 50 m

Numerous benefits and costs of group living

Fitness ~ Group size

[Van Schaik & VanHoof 1983]

How does group size affect fitness components?

Group size

Fitn

ess

Foraging efficiency ~ Group size?

Group size

Fora

gin

g

effi

cien

cy

[Beauchamp 1998]

Group size

Su

rviv

al

[Beauchamp 1998]

Survival ~ group size ?

How does group size affect fitness components?

Survival?

Foraging efficiency?

Group size

The social bat M. molossus

Total size of social groups

Adult size of social groups

Sunset

Sunrise

Morning foraging

period

Evening foraging

period

A narrow ecological niche

[Dechmann et al. 2010]

Two energetic strategies

Group foraging

Lowered metabolism

[Dechmann et al. 2011]

Weight at return

Weight at emergence

The mass data

Foraging efficiency ~ group size

5 social groups with automated recorders

Artificial group size manipulation

Linear Mixed-Effect Model+ Bayesian simulations

Molecular ecology

78 marked individuals

20 to 50% of individuals

kept in captivity

Fixed + Random effects

5000 simulations

Up to 18 microsatellites

for most individuals

Mass variation over foraging period

- Linear model with Mixed-effects

- Ecological + genetic data

- Polynomial function for group size

- Interactions with time

Model: Quadratic function of group size (+ 95% CrI )

Survival ~ group size

201 recaptures of 126 adult females of 14 social groups

Survival ~ group size

No influence of group size on survival

Continuous monitoring of 63 marked adult females from 4 social groups

Survival ~ group size

Transitions between group size

Continuous monitoring of 63 marked adult females from 4 social groups

Main results

Foraging efficiency ~ GS

Survival ~ GS

Fitness components ~ group size:

Various patterns!

PhD Milestones

Next months: - Write foraging efficiency chapter- Analyses on reproductive success - Analyses on emergence order

December 2015: PhD defense (Konstanz)

Next weeks: - Submit survival chapter- Finish microsatellite note

@Bat_Yann

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