Interindividual Behavioral Variation Post-Predation: Week 2

Introduction

In social invertebrate colonies, individual behavioral differences may either remain fixed across fluctuating ecological contexts (representing static personality syndromes) or adjust dynamically following energetic inputs, predatory stress, or foraging success.

In this follow-up investigation, surviving individuals from the Week 1 Stegodyphus cohort were maintained communally for seven days, during which they constructed a dense communal silk retreat web. We introduced live prey (Tribolium castaneum and Tenebrio molitor larvae) to stimulate vibration-guided communal predatory responses, followed by post-foraging re-assessment of individual boldness and aggression scores.

Hypothesis: Relative rank-order personality scores remain stable across repeated trials, with no fundamental realignment of behavioral syndromes post-predation.

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Materials and Methods

Materials

• 4 surviving velvet spiders from Week 1 cohort (2 individuals died prior to Week 2 testing)
• Live insect prey: Tribolium castaneum larva (small), Tenebrio molitor larva (large)
• Stereomicroscope, fine forceps, blunt tactile probes
• Digital stopwatch

Methods

Spiders were monitored in their communal webbed arena. A T. castaneum larva was positioned at the dense central retreat hub, and behavioral interactions were recorded for 25 minutes. A larger T. molitor larva was subsequently introduced, with observations recorded for an additional 25 minutes.

Following prey capture interactions, spiders were separated into individual chambers and re-tested using the identical pneumatic boldness assay and tactile aggression scale established in Week 1.

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Data

Boldness Scores Across Timepoints

ID	Name	Colour Mark	Boldness 1 (Pre)	Boldness 2 (Post)	Status
1	Olaf	White	540	529	Alive
2	Peter Parker	Blue/Red	543	—	Deceased
3	Nemo	Orange	577	576	Alive
4	Shrek II	Green	580	574	Alive
5	Barbie	Pink	531	—	Deceased
6	Bob	Yellow	536	503	Alive

Aggression Scores Across Timepoints

ID	Name	Mark	Aggression 1	Behaviour 1	Aggression 2	Behaviour 2	Status
1	Olaf	White	1	Huddle	1	Huddle	Alive
2	Peter Parker	Blue/Red	1	Huddle	—	—	Deceased
3	Nemo	Orange	1	Huddle	2	Run	Alive
4	Shrek II	Green	3	Walk	2	Run	Alive
5	Barbie	Pink	3	Walk	—	—	Deceased
6	Bob	Yellow	6	Leg raise	6	Leg raise	Alive

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Results

Summary Statistics ($n=4$)

Sample mean ($\overline{x}$), standard deviation ($s$), and standard error of the mean ($\text{SEM}$):

$$\overline{x}=\frac{1}{n}\sum _{i=1}^n{x}_i,s=\sqrt{\frac{1}{n-1}\sum _{i=1}^n(x_i-\overline{x}{)}^2},\text{SEM}=\frac{s}{\sqrt{n}}$$

Trait	Timepoint	$n$	Mean ($\overline{x}$)	Std Dev ($s$)	SEM
Boldness Score	Timepoint 1 (Pre)	4	558.25	23.47	11.74
	Timepoint 2 (Post)	4	545.50	35.69	17.84
Aggression Score	Timepoint 1 (Pre)	4	2.75	2.36	1.18
	Timepoint 2 (Post)	4	2.75	2.22	1.11

Cohort Mean Trait Shifts

Mean boldness score across timepoints ($\pm 1$ SEM)	Mean aggression score across timepoints ($\pm 1$ SEM)

Mean boldness declined modestly ($558.25\text{ s}\to 545.50\text{ s}$; $\mathrm{\Delta }=-12.75\text{ s}$), while mean aggression remained exactly identical ($2.75\to 2.75$).

Individual Behavioral Trajectories

Individual longitudinal boldness score trajectories	Individual longitudinal aggression score trajectories

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Discussion

Behavioral Specialization During Prey Encounters

During live prey exposure, individuals displayed consistent division of labor:

• Bob (Spider 6, Yellow): Showed the highest aggression score (6/6, leg raise) and served as the sole primary attacker, actively stalking, immobilizing, and envenomating the prey.
• Shrek II (Spider 4, Green): Exhibited persistent locomotor activity, engaging in web stabilization and wrapping the prey items in silk sheets.
• Olaf (Spider 1) and Nemo (Spider 3): Remained quiescent in retreat chambers, exhibiting lowest aggression scores.

Temporal Personality Stability

Every surviving individual exhibited a minor, uniform reduction in boldness score post-trial ($\mathrm{\Delta }\approx -1\text{ to }-33\text{ s}$), reflecting metabolic fatigue from web reconstruction and prey handling. Despite subtle shifts in absolute magnitude, the relative rank-order hierarchy was strictly preserved across both timepoints, validating the hypothesis that personality syndromes in social spiders represent durable individual traits.

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References

1. Wright, C.M. et al. (2014). Selection on social spider colonies for boldness and aggressiveness. Behavioral Ecology, 25(6), pp. 1485–1492.
2. Grinsted, L. et al. (2013). Subsocial and social spiders: behavioral traits and ecological specialization. PLOS ONE, 8(6), e65830.