Behavioral and structural determinants of colony development in Apis cerana: insights into foraging efficiency under tropical field conditions

Abstract

Sustainable development of Apis cerana colonies is highly influenced by nutritional adequacy and efficiency of pollen foraging. Due to limited scientific research on Apis cerana in Sri Lanka, a systematic understanding of its nutritional dynamics is essential for ensuring sustainable beekeeping practices. This study was conducted over two months, from March to May 2025, in the Kalutara District (Low Country Wet Zone), Sri Lanka, to assess the impact of protein availability and pollen collection on colony development stages across eight Apis cerana hives under tropical field conditions. Pollen collection was quantified at one-day intervals using repeated one-minute forager counts conducted in the mid-morning. A forager was defined as a worker bee returning with visible pollen loads, averaged over four replicates per hive. Concurrent photographic inspections were conducted every two weeks to evaluate the Colony Status Index (CSI), based on total brood area, honey reserves and pollen stores, providing a comprehensive measure of colony health and growth. Results demonstrated a strong positive correlation between total brood area and pollen foraging activity, described by the regression model y = 0.1285x with a determination coefficient (R²) of 0.814, indicating that pollen collection rate is closely linked to brood development. Colonies with brood areas greater than 774 cm² showed significantly higher pollen collection rates (>20 loads/min), while those below 322 cm² displayed lower rates (<12 loads/min). Higher CSI scores were associated with increased brood density and honey storage, validating pollen intake as a key driver of internal colony productivity. Simple linear regression and one-way ANOVA were used to analyse these relationships, with regression emphasized for model fitting and prediction. This research highlights the predictive power of integrating behavioural data (pollen foraging) with the Colony Status Index to evaluate and forecast colony sustainability. The findings emphasize that maintaining continuous pollen availability could enhance colony performance and long-term sustainability in artificial Apis cerana hives.