Biology subjects

Somanathan, H.

Publications and source records attributed to Somanathan, H..

3 recordsLinked to original sources

bioRxiv2026

Human landscape modification shapes foraging preferences and sucrose responsiveness of honey bees in Asia

Landscape composition is central in shaping how pollinators utilise floral resources, yet its influence on foraging behaviour of co-occurring Asian honey bees remains underexplored. Resolving this gap is crucial to understand how closely-related, native and introduced species maintain foraging efficiency in rapidly changing environments. We investigated nectar preferences, sucrose responsiveness, and foraging task partitioning in three co-occurring honey bee species in India: Apis florea (native open-nesting), Apis cerana (native cavity-nesting), and Apis mellifera (introduced cavity-nesting), across forest, agricultural, and urban landscapes. Landscape type strongly influenced crop sugar concentrations of honey bees. While all species collected high-concentration nectar in forests, A. mellifera and A. cerana collected lower concentrations than A. florea in urban habitats. A. florea showed consistent preference for high-concentration nectar across landscapes. Complementing this, sucrose responsiveness assays revealed a lower responsiveness of A. florea compared to cavity-nesting species. Foraging task partitioning differed among species, but interestingly, also among landscapes. While A. cerana predominantly collected nectar, A. mellifera foraged equally for pollen, nectar and water, and A. florea shifted task allocation across landscapes. In conclusion, we provide the first comparative evidence that landscape composition and species characteristics jointly shape foraging preferences and organisation of foraging labour in Asian honey bees.

ecology↗

bioRxiv2026

Colour preference and constancy in the giant Asian honey bee Apis dorsata

Tropical pollinators forage in environments where floral resources vary in space and time, requiring flexible strategies to optimise foraging efficiency. One such strategy, floral constancy - the temporary restriction to a single flower type - strongly influences foraging success and plant-pollinator interactions. We aimed to: (1) quantify spontaneous colour preferences and constancy in the Asian giant honeybee Apis dorsata, (2) test whether reward concentration modulates these preferences, (3) evaluate how quickly learned associations override spontaneous biases, (4) determine whether bees can use multiple colour associations simultaneously, and (5) assess whether local floral spectral patterns correlate with bee preferences. Bees trained to a neutral UV-grey stimulus showed a strong spontaneous preference and high constancy to blue, revealing a robust short-wavelength bias. Crucially, the strength of this spontaneous bias depended on reward concentration; Low-reward conditions elicited strong blue constancy, whereas high-reward conditions weakened it, demonstrating that reward expectation shapes spontaneous colour choices. This bias was flexible. When bees learned that yellow was rewarding they switched their preferences. Bees sequentially trained to both colours visited blue and yellow, showing no overall bias, or effect of the last-trained colour, indicating that recent experiences disrupt colour-specific constancy and generate largely random foraging choices. Bees were capable of learning and retaining two colours simultaneously, effectively suppressing the influence of spontaneous preferences. Finally, analysis of the communitys floral spectral distribution revealed a strong dominance of short-wavelength flowers, suggesting that long-term selection by the local floral environment may underlie the spontaneous blue preference observed in A. dorsata.

animal behavior and cognition↗

bioRxiv2022

Defensive shimmering responses in the giant honeybee Apis dorsata are triggered by dark stimuli moving against a bright background

Giant honeybees, including the open-nesting Asian giant honeybee Apis dorsata, display a spectacular collective defence behaviour - known as "shimmering" - against predators, which is characterised by travelling waves generated by individual bees flipping their abdomens in a coordinated and sequential manner across the bee curtain. We examined if shimmering is visually-mediated by presenting moving stimuli of varying sizes and contrasts to the background (dark or light) in bright and dim ambient light conditions. Shimmering was strongest under bright ambient light, and its strength declined under dim-light in this facultatively nocturnal bee. A. dorsata shimmered only when presented with the darkest stimulus against a light background, but not when this condition was reversed (light stimulus against dark background). This response did not attenuate with repeated exposure to the stimuli, suggesting that shimmering behaviour does not undergo habituation. We suggest that this is an effective anti-predatory strategy in open-nesting A. dorsata colonies which are exposed to high ambient light, as flying predators are more easily detected when they appear as dark moving objects against a bright sky. Moreover, the stimulus detection threshold (smallest visual angular size) is much smaller in this anti-predatory context (1.6{degrees} - 3.4{degrees}) than in the context of foraging (5.7{degrees}), indicating that ecological context affects visual detection threshold.

animal behavior and cognition↗