Testing for size-dependent trade- offs of clustering in Nephila
clavipes Laura Sauvage (CMC 14) & Haley Godtfredsen (Scripps
16)
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Introduction Web ecology Prey capture Males Kleptoparasites
Predation
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Nephila clavipes LargeMediumSmall
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Another component of web environment: Solitary (built
alone)Clustered (attached to other webs)
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Theoretical costs and benefits of cluster formation: Cost =
competition for food Benefit = less predation risk per spider
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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.
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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
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Methods Firestone Center for Restoration Ecology Baru, Costa
Rica
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Spider IDSolitary/ Clustered Date Found ColorNeighbor Females
Spider Size (mm) Web Size (m) 1S7/5/2013N/A 1.780.18 2S7/5/2013N/A
4.740.43 3C7/5/2013Blue42.570.30 4C7/6/2013Green32.910.31
5S7/6/2013N/A 3.400.36 Initial Measurements (example data)
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Spider ID DateWeb Condition # Prey# Legs# Neighbor Females
17/15/2013Good08N/A 27/15/2013Good28N/A 37/15/2013Poor071
47/15/2013Good081 57/15/2013Okay17N/A Monitoring Data (example
data)
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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
ClusteringPrey Capture Leg Autotomy Spider/Web Fate Spider Size
NS + Influence of spider size on NS = not significant + = positive
correlation
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ClusteringPrey Capture Leg Autotomy Spider/Web Fate Spider Size
NS + Influence of spider size on Influence of clustering on Prey
Capture Leg Autotomy Spider/Web Fate Clustered compared to Solitary
NS
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Significance Studying the costs/benefits of living in a group
(cluster) Do these trade-offs differ with spider size?
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Prey capture Preliminary Data Predation Spider Size Clustering
X X X
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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
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Acknowledgements Keck Science Department Professor E. Ferree
Professor D. McFarlane Greddy Arias-- Firestone Caretaker Pitzer
College
Slide 21
Preliminary Results Mean web diameter (mm) Bigger spiders have
bigger webs. n=17 n=183 n=138
