Adaptive caste allocation modulated by resource distance in Pheidole oxyops

Caste deployment in social insects reflects trade-offs between resource profitability and spatial costs. We examined how Pheidole oxyops allocates minor and major workers when foraging on carbohydrate- (honey) and protein-rich (sardine) baits placed at two distances (1 m and 5 m) from the nest. Minor worker abundance at bait was significantly higher at protein-rich (sardine) than carbohydrate-rich (honey) baits and declined with increasing distance from the nest. Food type and distance exerted independent effects on minor worker abundance. In contrast, major workers were rarely observed and occurred almost exclusively at sardine baits located 1 m from the nest, indicating that deployment of this caste was strongly restricted to nearby protein-rich resources. These patterns are consistent with central place foraging theory indicating that worker allocation is independently influenced by food type and travel costs. The restricted occurrence of majors suggests that their deployment is context-dependent and likely limited to situations in which high-value resources are both accessible and profitable. Overall, our results show how spatial constraints and caste-specific roles interact to shape foraging dynamics in P. oxyops.