Testing for size-dependent trade-offs of clustering in Nephila clavipes

Laura Sauvage (CMC ‘14)& Haley Godtfredsen (Scripps ‘16)

IntroductionWeb ecology

• Prey capture • Males • Kleptoparasites • Predation

Nephila clavipes

Large Medium Small

Another component of web environment:

Solitary (built alone) Clustered (attached to other webs)

Theoretical costs and benefits of cluster formation:

Cost = competition for food

Benefit = less predation risk per spider

Daniella Barraza, 2012

• Cost: Medium spiders caught more prey if solitary than clustered. - No difference for small spiders.

• Benefit: Longer web tenure if clustered. - More so for medium than small spiders.

Sauvage & Godtfredsen, 2013

Hypothesis: Costs & benefits of clustering will be size-dependent.

Preliminary data-• Frequency of

clustering• Variation in web

experience based on spider size and clustering

Methods

• Firestone Center for Restoration Ecology• Baru, Costa Rica

Spider ID Solitary/ Clustered

Date Found

Color Neighbor Females

Spider Size (mm)

Web Size (m)

1 S 7/5/2013 N/A N/A 1.78 0.18

2 S 7/5/2013 N/A N/A 4.74 0.43

3 C 7/5/2013 Blue 4 2.57 0.30

4 C 7/6/2013 Green 3 2.91 0.31

5 S 7/6/2013 N/A N/A 3.40 0.36

Initial Measurements

(example data)

Spider ID

Date Web Condition

# Prey # Legs # Neighbor Females

1 7/15/2013 Good 0 8 N/A

2 7/15/2013 Good 2 8 N/A

3 7/15/2013 Poor 0 7 1

4 7/15/2013 Good 0 8 1

5 7/15/2013 Okay 1 7 N/A

Monitoring Data

(example data)

Measuring costs and benefits of cluster formation:

Competition for food: prey capture rate

Lower predation risk● Web duration● Leg autotomy● Web condition● Reason for disappearance

Clustering Clustered: 191 webs (48%)

Solitary: 209 webs (52%)

Frequencies of….

Clustering Leg AutotomyClustered: 191 webs (48%) No: 367 webs (94%)

Solitary: 209 webs (52%) Yes: 25 webs (6%)

Frequencies of….

Clustering Leg Autotomy Web FateClustered: 191 webs (48%) No: 367 webs (94%) Moved: 160 webs (65%)

Solitary: 209 webs (52%) Yes: 25 webs (6%) Depredated: 86 webs (35%)

Frequencies of….

Clustering Prey Capture

Leg Autotomy

Spider/Web Fate

Spider Size NS + NS NS

Influence of spider size on …

NS = not significant+ = positive correlation

Clustering Prey Capture

Leg Autotomy

Spider/Web Fate

Spider Size NS + NS NS

Influence of spider size on …

Influence of clustering on …Prey

CaptureLeg

AutotomySpider/Web

Fate

Clustered compared to Solitary

NS NS NS

Significance ● Studying the

costs/benefits of living in a group (cluster)

● Do these trade-offs differ with spider size?

Prey capture

Preliminary Data

Predation

Spider Size

Clustering X X

X

To Be Determined

• Do size-dependent trade-offs

exist in clusters?● Frequency with which spiders

of different sizes are clustered or

solitary.

• Cluster formation

• Order of arrival

• Effect of size

Acknowledgements

Keck Science Department Professor E. Ferree

Professor D. McFarlaneGreddy Arias-- Firestone Caretaker

Pitzer College

Preliminary ResultsM

ean

web

dia

met

er (m

m)

Bigger spiders have bigger webs.

n=17

n=183n=138