Fig. 4

Contest escalation when colony pairs competed for food resources. a The number of workers at the display ground contesting food of high (the paired colonies was pre-fed with honey solution) or low (the paired colonies was pre-fed with tuna) value at different stages (early and late) of summer (N = 55). b The proportion of contests that escalated to grapples when competing over high (the paired colonies was pre-fed with honey solution) or low value food (the paired colonies was pre-fed with tuna) (N = 55). c The correlation between the probability of escalation and the number of workers at the contesting site (N = 55). d The proportion of grappling ants is not influenced by the number of workers at the contesting site (N = 18). A re-analysis of these data, excluding the point for 596 workers, revealed a weak negative effect of worker number on the rate of (log-transferred) grappling ants (F = 5.4, p = 0.04)