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 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)
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)
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
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
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. McFarlane Greddy Arias-- Firestone Caretaker Pitzer College
Preliminary Results Mean web diameter (mm) Bigger spiders have bigger webs. n=17 n=183 n=138