Foraging-related tasks inside the hive: Reward rate at the nectar source affects behavior of receiver honeybees (Apis mellifera L.)

PÍREZ, N.; FARINA, W.M.

Berlin, Alemania

Conferencia; Proceedings of the 2001 Berlin Meeting of the European Sections of the International Union for the Study of Social Insects; 2001

International Union for the Study of Social Insects

Honeybee foragers adjust their foraging activities in accordance to the profitability offered by the food sources exploited. Once returning from a feeding place nectar foragers transfer food via trophallaxis to hive-mates that mainly process and store the nectar collected. Previous studies have shown that the forager´s trophallactic offering contacts are modulated in accordance to the food source profitability. The aim of this study was to analyze whether hive-bees modify their nectar-processing tasks after receiving food from foragers that exploited different profitable food sources. To address this issue, the behavior of hive bees was analyzed after receiving food from a trained forager that individually exploited a feeding place with different reward rate. Two rate-feeders were simultaneously used offering an unscented sugar solution of 1.8 M. The first one was located at the end of a corridor that measured 100 x 15 x 1.5 cm, while the other one was inside a flight chamber of 6 x 3 x 2 m. The corridor rate-feeder delivered 1.6 ul/min or 11.7 ul/min of sugar solution, while the flight enclosure rate-feeder delivered a constant reward rate (100 ul/min) during the whole experiment. In order to keep constant the colony´s intake rate during the experiment this was the only food source exploited by the hive. The longest trophallaxis performed by the trained donor-foragers and all the behaviors performed later by the receiver bee placed just in front of the donor were video recorder. Receivers could return to the nectar delivery area either after transfering food trough trophallaxis or after visiting honeycombs or after performing both tasks. When they only performed a single task, either the occurrence of visiting honeycombs increased or the proportion of performing unloading contacts decreased for the highest reward rate exploited by the foragers. However, receivers could transfer food besides visiting honeycombs during the same processing cycle. During these cycles, the unloading contact times increased with the feeder´s reward rate, suggesting that the food transferred from the first receiver to the other bees is greater (in absolute and relative terms) the higher the reward rate exploited by the donor foragers. Moreover, once a bee received food from a low-profitable donor forager often unloaded food exclusively via trophallaxis. This seems to be caused by the smaller amount retained into their crops after trophallaxis, preventing bees from going to the honeycombs. This is sustained by a temporal analysis that indicates that, when receivers performed trophallaxis and visited honeycombs during the same cycle, trophallactic contacts concluded before visiting honeycombs. Thus, bees receiving food from high-profitable nectar foragers reduce task partitioning during nectar processing in order to directly unload food into the honeycombs. As an alternative, and without interrupting their visits to the honeycombs, they can partition more of the nectar received among hive bees. Thus, the profitability of the food source exploited by food-donors, expressed in terms of reward rate, can affect individual foraging-related tasks inside the hive, such as food storing and nectar handling.