Food Source Profitability Research Articles

Honey bee waggle dance communication: signal meaning and signal noise affect dance follower behaviour

Returning honey bee foragers perform waggle dances to inform nestmate foragers about the presence, location and odour of profitable food sources and new nest sites. The aim of this study is to investigate how the characteristics of waggle dances for natural food sources and environmental factors affect dance follower behaviour. Because food source profitability tends to decrease with increasing foraging distance, we hypothesised that the attractiveness of a dance, measured as the number of dance followers and their attendance, decreases with increasing distance to the advertised food location. Additionally, we determined whether time of year and dance signal noise, quantified as the variation in waggle run direction and duration, affect dance follower behaviour. Our results suggest that bees follow fewer waggle runs as the food source distance increases, but that they invest more time in following each dance. This is because waggle run duration increases with increasing foraging distance. Followers responded to increased angular noise in dances indicating more distant food sources by following more waggle runs per dance than when angular noise was low. The number of dance followers per dancing bee was also affected by the time of year and varied among colonies. Our results provide evidence that both noise in the message, that is variation in the direction component, and the message itself, that is the distance of the advertised food location, affect dance following. These results indicate that dance followers may pay attention to the costs and benefits associated with using dance information.

The recruiter's excitement – features of thoracic vibrations during the honey bee's waggle dance related to food source profitability

The honey bee's waggle dance constitutes a remarkable example of an efficient code allowing social exploitation of available feeding sites. In addition to indicating the position (distance, direction) of a food patch, both the occurrence and frequency of the dances depend on the profitability of the exploited resource (sugar concentration, solution flow rate). During the waggle dance, successful foragers generate pulsed thoracic vibrations that putatively serve as a source of different kinds of information for hive bees, who cannot visually decode dances in the darkness of the hive. In the present study, we asked whether these vibrations are a reliable estimator of the excitement of the dancer when food profitability changes in terms of both sugar concentration and solution flow rate. The probability of producing thoracic vibrations as well as several features related to their intensity during the waggle phase (pulse duration, velocity amplitude, duty cycle) increased with both these profitability variables. The number of vibratory pulses, however, was independent of sugar concentration and reward rate exploited. Thus, pulse number could indeed be used by dance followers as reliable information about food source distance, as suggested in previous studies. The variability of the dancer's thoracic vibrations in relation to changes in food profitability suggests their role as an indicator of the recruiter's motivational state. Hence, the vibrations could make an important contribution to forager reactivation and, consequently, to the organisation of collective foraging processes in honey bees.

Foraging energetics of a nectar-feeding ant: metabolic expenditure as a function of food-source profitability

We examined the quantitative relationship between the energetic costs and benefits of nectar collection by nectar-feeding ants, Camponotus rufipes. In the laboratory, individual workers were trained to visit an artificial feeder that provided a sucrose solution of 1%, 5%, 10%, 30% or 50% at controlled flows, in a similar span range to those observed in natural nectar sources. We measured foraging times, nectar loads collected, and CO(2) production during actual feeding, as an indication of the energy expenditure for a single forager. Results show an increase in individual metabolic rates with increasing flow rate of sugar solution, but no dependence on sucrose concentration. This increase in metabolic expenditure does not depend on the crop load attained while feeding, as intuitively expected, and is therefore a result of an increased activity brought about by the food-source profitability experienced by the forager. The energy gained during collection of sugar solution is always higher than the energy spent by the ant. Even with a food source of lower quality than a natural source, the ants gain ca. tenfold of what they spend. Based on a simplified model, we calculated that foragers of C. rufipes could travel from 0.5 to 9 km with the energy gained in a single foraging trip only. These results suggest that decreasing foraging time is more important than increasing individual energetic efficiency when workers of the nectar-feeding ant C. rufipes decide to stop drinking and return to the nest with partial crop loads.

Antennation of nectar-receivers encodes colony needs and food-source profitability in the ant Camponotus mus

In social insects, interactions among individuals are important in colony organisation because they can be used in decision making. During trophallaxis in ants, antennal and foreleg contacts between both partners are established. It has been suggested that a modulatory communication channel could be involved in such contacts, but it remains undemonstrated. The aim of this work was to find variables plausible to be encoded in such contacts and quantify the consequent changes in the tactile stimulation the food-donor ant receives. We recorded nectar transference between pairs of workers in experimental arenas once one of them had returned from collecting sucrose solution (15 or 40%w/w), with different situations of colony’s sugar deprivation. The frequency of antennal strokes that the food-donor ant received on her head depended on both the colony’s sugar-deprivation and the concentration, the latter showed differences within 3–5 deprivation days. Antennal and foreleg movements of the food-receiver increase with increasing level of colony’s carbohydrate deprivation, as well as with increasing concentration of the transferred food. Not only does this study reopen an interesting question, but it gives evidence that variables related to the appetitive context are indeed encoded in the tactile stimulation during the trophallaxis as well. Consequently, they have the effective potentiality to play a communicational role in the organization of colony activities.

Floral CO2 reveals flower profitability to moths.

The hawkmoth Manduca sexta (Lepidoptera: Sphingidae), an experimentally favorable Lepidopteran that is highly sensitive to carbon dioxide (CO2), feeds on the nectar of a range of flowering plants, such as Datura wrightii (Solanaceae). Newly opened Datura flowers give off dramatically elevated levels of CO2 and offer ample nectar. Thus, floral CO2 emission could indicate food-source profitability. This study documents that foraging Manduca moths prefer surrogate flowers that emit high levels of CO2, characteristic of newly opened Datura flowers. We show for the first time that CO2 may play an important role in the foraging behavior of nectar-feeding insects.

Trophallaxis in honeybees, Apis mellifera (L.), as related to their past experience at the food source

Forager honeybees returning to the hive after a successful foraging trip unload the collected liquid to recipient hivemates through mouth-to-mouth food exchange contacts (trophallaxis). The speed at which the liquid is transferred (unloading rate) from donor to recipient is related to the profitability offered by the recently visited food source. However, because a forager's evaluation of the profitability of a food source, as measured by dancing behaviour, is influenced by previous foraging experience, we investigated whether trophallaxis might also be influenced by previous foraging experience. We measured unloading rate for a given profitability condition at the food source (in terms of solution flow rate) in three groups of foragers that differed in their previous experience at the source. One group experienced the same flow rate of solution in five successive visits (control group), another group experienced a lower flow rate in the first four visits and the third group experienced a higher flow rate in the first four visits. The results of the present study show that animals trained to a lower flow rate increased their unloading rate compared with the control group, indicating an influence of past foraging experience on their evaluation of food source profitability. This influence was not observed in the group trained to a higher flow rate, which responded as the control group. Additional experiments indicated that foragers appear to evaluate the profitability of the source by integrating an overall flow rate throughout the entire visit, instead of measuring only the current flow rate delivered by the feeder. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.

Descriptive study of antennation during trophallactic unloading contacts in honeybees Apis mellifera carnica

Trophallaxis, the mouth-to-mouth transfer of food, is a widespread behavior occurring between individuals of eusocial insect societies. Antennal movements during food transfer are, in honeybees, too rapid to be characterized using standard video recordings. Using a high-speed camera (200 frames/s), we recorded nectar unloading performed by forager honeybees (Apis mellifera carnica Spinola) within the hive once they returned from collecting sugar solution at a feeder that delivered nectar at a variable rate. Frequency patterns attained a mean value of 13 Hz. Antennation intensity showed a tendency to increase with the reward rate recently exploited by the food donor. This raises the question whether or not antennation intensity is a reliable parameter providing modulatory information related to food-source profitability.

The effect of octopamine on behavioral responses of free-foraging bumblebees to a change in food source profitability.

The invertebrate neuromodulator octopamine is known to be involved in bees' associative learning, enhancing the responsiveness of a bee to a conditioned stimulus. In this study, we tested the effect of octopamine on the choice behavior of free-flying bumblebees using a two-phase experiment in an array of artificial flowers. During the first phase of the experiment, the bee was allowed to collect octopamine-laden sugar water from two types of equally rewarding flowers (yellow versus blue). In the second phase, one type of flower was set to be unrewarding. The behavior of the bee (proportion of visits to the unrewarding flowers) over the two phases was fitted to a sigmoid regression model. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee.

Assessment of food source profitability in honeybees (Apis mellifera): how does disturbance of foraging activity affect trophallactic behaviour?

When forager honeybees (Apis mellifera) return to the hive after a successful foraging trip, they unload the collected liquid to recipient hive mates through mouth-to-mouth contacts (trophallaxis). The speed at which the liquid is transferred (unloading rate) from donor to recipient is related to the profitability of the recently visited food source. Two main characteristics that define this profitability are the flow of solution delivered by the feeder and the time invested by the forager at the source (visit time). To investigate the effect of visit time on trophallactic behaviour, donor foragers were trained to a rate feeder that could deliver different flows of solution. We dissociated visit time and flow of solution by introducing pauses in the solution's deliverance at different moments of the foraging visit. We analysed whether timing of the non-deliverance period within the visit is important for the forager's assessment of resource profitability. During the subsequent trophallactic encounter with a hive mate, unloading rate was related to the total time invested by the forager at the food source only if the ingestion process had already been started. These results together with previous ones suggest that foragers integrate an overall flow rate of solution of the feeder throughout the entire foraging visit.

Individual recruitment in honeybees, Apis mellifera L. The effect of food source profitability on the rate of bees arriving at the feeding place

The recruitment of honeybee foragers individually exploiting a low-flow rate-feeder that presented different temporal reward programs was experimentally analyzed. By capturing hive bees that landed at the feeder in a 2-h period, the arrival rate of incoming bees could be obtained. With this procedure we quantitatively analyzed the maximum number of hive bees that can be brought to the feeding station by single foragers. Test bees collected sucrose solution during 12 visits to a rate-feeder located 160 m from the hive. The constant programs offered 0.6, 1.2, or 2.4 M sugar for all 12 visits, while the variable programs delivered either 0.6, 1.2, or 0.6 M or 0.6, 2.4, or 0.6 M, with four visits for each molarity. Results showed that the sucrose concentration exploited by single foragers increased the arrival rate. Moreover, there was a linear relationship within this range of sucrose concentrations that presented a slope of 1.58. Since the sugar solutions were provided at the same flow rate (5 µl/min) in all the programs, the arrival rate expressed in terms of sucrose flow rate (milligrams of sucrose/minute) shows that one additional incoming bee per hour arrived when the single forager assessed an increase in the sucrose flow rate of 0.75 mg sucrose/min at the rate-feeder. The absence of differences in the frequency of visits of the single foragers during the constant programs suggests that the differences observed in the arrival rate can mainly be explained by a more intensive display of the recruitment mechanisms performed per foraging trip instead of by their iterativeness throughout different foraging cycles. Variable reward programs showed that arrival rate is rapidly adjusted according to the reward change and is independent of its magnitude.

Sounds in Melipona costaricensis (Apidae: Meliponini): effect of sugar concentration and nectar source distance

Universidad de Costa Rica. Centro de Investigaciones Apicolas Tropicales, Universidad Nacional.

Honeybees assess changes in nectar flow within a single foraging bout

Forager honeybees returning to the hive after a successful foraging trip unload the collected liquid to recipient hivemates through mouth-to-mouth food exchange contacts (trophallaxis). The speed at which the liquid is transferred (unloading rate) from donor to recipient is related to the profitability offered by the recently visited food source. Two of the main characteristics that define food source profitability are the flow of solution delivered by the feeder and the time invested by the forager feeding at the source (feeding time). To investigate which of these two variables is related to unloading rate, we individually trained donor foragers to a regulated-flow feeder that presented changes in the delivered flow of solution within a single foraging bout, while feeding time remained constant. With the range of flows used, bees attained maximum crop loads in all experiments. During the subsequent trophallactic encounter with an unfed recipient hivemate, unloading rate was differentially affected by the changes in flow of solution presented during the previous foraging trip at the source, depending on whether there had been an increase or a decrease of flow rate within that visit. Foragers unloaded at lower rates when they experienced a decrease in flow rate, but did not increase the unloading rate when presented with an increase at the food source. Thus, forager honeybees seem to be able to detect variations in the delivered flow of solution, since they modulate unloading rate in relation to these changes, although decreases in food value seem to be perceptually weighted in relation to increases, independently of the time invested in the food-gathering process.

Changes in food source profitability affect the trophallactic and dance behavior of forager honeybees ( Apis mellifera L.)

Since nectar constitutes a highly variable resource, forager honeybees (Apis mellifera) always adjust their social foraging activities according to the current profitability of the nectar sources they exploit. If trophallaxis, food exchange among individuals of the same colony, serves to improve the coordination among nectar foragers, as occurs with the dance behavior, a high correlation might be expected between the foragers' trophallactic behavior and the profitability of the food sources they exploited. The aim of this work was to analyze whether a forager bee changes her trophallactic behavior with the varying profitability of a food source. In addition, since food source profitability affects dance behavior, we also analyzed the degree of coupling between the trophallactic and dance behavior of returning honeybees. Results show that trophallaxis by forager bees inside the hive changed rapidly with fluctuations in food source profitability. After an increase in profitability, returning foragers (1) increased the number of trophallactic offering contacts, (2) decreased the average duration of offering contacts, (3) shifted the temporal distribution of offering contacts from being mainly near the beginning of the time in the hive to being more evenly distributed throughout the entire visit, (4) begged for food less frequently, and (5) shifted their begging toward the very end of the visit. Regarding their dance behavior, foragers danced earlier in their visits to the hive and performed more waggle runs when the profitability of the food source was increased. Furthermore, the trophallactic and dance behaviors were affected not only by the absolute profitability of the food source but also by changes in profitability. Taken together, these results indicate that, in addition to dance behavior, short trophallactic interactions of returning foragers (which include both offering and begging contacts) may help foragers to communicate information about rapidly fluctuating resource opportunities.

Dancing bees tune both duration and rate of waggle-run production in relation to nectar-source profitability.

For more than 50 years, investigators of the honey bee's waggle dance have reported that richer food sources seem to elicit longer-lasting and livelier dances than do poorer sources. However, no one had measured both dance duration and liveliness as a function of food-source profitability. Using video analysis, we found that nectar foragers adjust both the duration (D) and the rate (R) of waggle-run production, thereby tuning the number of waggle runs produced per foraging trip (W, where W= DR) as a function of food-source profitability. Both duration and rate of waggle-run production increase with rising food-source profitability. Moreover, we found that a dancing bee adjusts the rate of waggle-run production (R) in relation to food-source profitability by adjusting the mean duration of the return-phase portion of her dance circuits. This finding raises the possibility that bees can use return-phase duration as an index of food-source profitability. Finally, dances having different levels of liveliness have different mean durations of the return phase, indicating that dance liveliness can be quantified in terms of the time interval between consecutive waggle runs.

Trophallaxis in filled-crop honeybees (Apis mellifera L.): food-loading time affects unloading behaviour.

Honeybees ingested 50% w/w (1.8 M) sucrose solution at a rate feeder offering either 16.5, 32.5 or 65 microliters/min. While the time spent ingesting solution at the feeder decreased significantly with increasing flow of solution, bees attained maximum crop loads with this range of flows. Different parameters related to mouth-to-mouth food exchange (trophallaxis) showed important modulations as the offered flow of solution was incremented. Trophallactic transfer rate, i.e. the speed at which liquid food is transferred from donor to recipient bee, was found to increase along with increasing profitability at the rate feeder. In the present case, food source profitability could have been evaluated by foragers either by measuring the time invested in ingesting the solution, or by direct assessment of the flow rate of the feeder. Thus it seems that perception of profitability conditions at the food source suffices for later representation in the hive through trophallactic contacts, independently of crop-filling state.

Trophallaxis in the honeybee Apis mellifera (L.): the interaction between flow of solution and sucrose concentration of the exploited food sources

Forager bees arriving at the hive after visiting a nectar source, unload the collected liquid food to recipient hivemates through mouth-to-mouth contact (trophallaxis). We analysed whether the main characteristics that define nectar in energetic terms, that is, rate of production (flow of solution), sucrose concentration and rate of sucrose production (sucrose flow) influence trophallactic behaviour. Individual bees trained to feed at a regulated-flow feeder offering sucrose solution were captured once the foraging visit was complete and placed in an acrylic arena with a recipient bee that had not been fed. The rate at which liquid was transferred during the subsequent trophallactic contact (transfer rate) was analysed as a function of the different solution flows and sucrose concentrations offered at the feeder. A relationship was found between transfer rate during trophallaxis and the flow of solution previously presented at the feeder. This relationship was independent of sucrose concentration when above a certain threshold value (ca.22% weight on weight). We also analysed whether the rate of sucrose deliverance of the food source (sucrose flow) influenced the rate at which the solution was transferred. No clear relationship was found between the rate of sucrose deliverance during trophallactic events (sucrose transfer rate) and the sucrose flow presented at the feeder. The possibility that trophallaxis could be a communication channel through which quantitative information on food source profitability is transmitted among hivemates is discussed.

Movement Patterns of Honeybee Foragers: Motivation and Decision Rules Dependent On the Rate of Reward

[The movement pattern of honeybees Apis mellifera working on a patch of artificial flowers and its dependence on food-source profitability were analysed by varying the flow rate of sucrose solution provided by a set of artificial flowers. Three sucrose flow rates were used (0.085, 0.17 and 0.34 μl/min per flower) and twenty bees per flow rate were measured over one entire visit to the patch. It is shown that 1) bees had the same landing rate at the lower and the intermediate flow rates but foraged significantly faster at the higher flow rate. 2) For the three flow rates tested, the landing rate remained constant throughout the entire foraging visit, thus being unaffected by the progressive increase in the weight transported in the crop. 3) Only the probability of an immediate return to a previously visited flower significantly increased with the flow rate. Such immediate returns occurred whenever the reward experienced at a flower greatly surpassed the mean reward expectation per flower. 4) However, bees returning immediately to the last visited flower did not find reward in it. It is suggested that bees go faster when the offer becomes better as a result of an increase in the foraging motivation that would lead to an incitement of foraging movements and that the progressive increase in the weight transported does not change the motivational levels, primarily defined by the food-source profitability. Finally, the immediate return to the flower just depleted is interpreted as a win-stay strategy, in which bees return to places where they previously found food though there is no differential reinforcement for such repetition. Such a response depends on the quantity of the reinforcer., The movement pattern of honeybees Apis mellifera working on a patch of artificial flowers and its dependence on food-source profitability were analysed by varying the flow rate of sucrose solution provided by a set of artificial flowers. Three sucrose flow rates were used (0.085, 0.17 and 0.34 μl/min per flower) and twenty bees per flow rate were measured over one entire visit to the patch. It is shown that 1) bees had the same landing rate at the lower and the intermediate flow rates but foraged significantly faster at the higher flow rate. 2) For the three flow rates tested, the landing rate remained constant throughout the entire foraging visit, thus being unaffected by the progressive increase in the weight transported in the crop. 3) Only the probability of an immediate return to a previously visited flower significantly increased with the flow rate. Such immediate returns occurred whenever the reward experienced at a flower greatly surpassed the mean reward expectation per flower. 4) However, bees returning immediately to the last visited flower did not find reward in it. It is suggested that bees go faster when the offer becomes better as a result of an increase in the foraging motivation that would lead to an incitement of foraging movements and that the progressive increase in the weight transported does not change the motivational levels, primarily defined by the food-source profitability. Finally, the immediate return to the flower just depleted is interpreted as a win-stay strategy, in which bees return to places where they previously found food though there is no differential reinforcement for such repetition. Such a response depends on the quantity of the reinforcer.]

Acoustical signals in the dance language of the giant honeybee, Apis dorsata

Acoustical signals emitted by dancing bees have recently been shown to transmit information about the location of food sources in the western honeybee, Apis mellifera. Towne (1985) reported that in the Asian honeybee species Apis dorsata, which builds a single comb in the open under overhanging rocks or tree branches, sound signals were not emitted by the dancers. This led to the conclusion that acoustical communication is restricted to bees that nest in the dark, like A. mellifera. Here we show that in fact A. dorsata produces dance sounds similar to those emitted by A. mellifera, and that these acoustical signals contain information about distance, direction and profitability of food sources. The acoustical transfer of information has thus evolved independently of nesting in dark cavities. The significance of nocturnal activity in Apis dorsata for the evolution of sound communication is discussed.

Acoustical and Behavioral Correlates of Profitability of Food Sources in Honey Bee Round Dances

AbstractThe effects of the profitability of food sources on round dance behavior of honey bees (Apis mellifera) were studied by varying the concentration of sucrose solution imbibed at an artificial flower. The probability of dancing and the rate of reversals in the dance increased with concentration, as did several aspects of the dance sounds: mean carrier frequency, duration of the sound bursts, pulse repetition rate, number of sound bursts per dance, and amplitude. Significant variation among bees was detected in rate of reversals, but not for the other variables. The question of how bees communicate profitability in the round dance is discussed and further work is suggested.

Trophallaxis in the honeybee, Apis mellifera (L.) as related to the profitability of food sources

Trophallaxis by honeybees was studied in two series of experiments. Honeybees were fed to satiation with sucrose solutions from 10 to 50% w/w (sugar concentration experiment), or with different amounts of a 50% w/w sucrose solution (crop load experiment). By increasing the concentration of solutions, the transfer rate was increased up to a maximum value for the 30–40% sucrose solution. With increasing crop load, maximum transfer rate was attained for satiated bees. The amount of sucrose transferred during trophallactic contact was related to the amount of sucrose carried in the honey sac for both experimental series. Results are discussed in relation to the foraging and recruiting patterns displayed by foragers.