Effects of a reward downshift on the consummatory behavior and flower choices of bumblebee foragers (original) (raw)
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Animal Behaviour, 1981
Worker bumblebees, Bombus edwardsii, preferably feed from artificial flowers yielding the same (continuous) reward on each visit rather than from flowers yielding variable (intermittent) rewards, even though the long-term expectation of reward is the same at each type of flower. However, variation in degree of preference among individual bees is high. Preferences after long foraging experience correspond closely to early preferences. Rate of flower visitation increases as mean reward increases, and may accelerate preference formation. Preferences are discussed in light of processes thought to control learning in honeybees. From these findings we propose that reward variance and expected time between reinforcements be considered as constraints in models of optimal foraging behaviour.
Variation in reward quality and pollinator attraction: The consumer does not always get it right
AoB plants, 2015
Nearly all bees rely on pollen as the sole protein source for the development of their larvae. The central importance of pollen for the bee life cycle should exert strong selection on their ability to locate the most rewarding sources of pollen. Despite this importance, very few studies have examined the influence of intraspecific variation in pollen rewards on the foraging decisions of bees. Previous studies have demonstrated that inbreeding reduces viability and hence protein content in Mimulus guttatus (seep monkeyflower) pollen and that bees strongly discriminate against inbred in favor of outbred plants. We examined whether variation in pollen viability could explain this preference using a series of choice tests with living plants, artificial plants, and olfactometer tests using the bumble bee Bombus impatiens. We found that B. impatiens preferred to visit artificial plants provisioned with fertile anthers over those provisioned with sterile anthers. They also preferred fertil...
The influence of past experience with flower reward quality on social learning in bumblebees
Bombus terrestris decision making flower choice foraging innate colour bias social learning Foraging decisions can be influenced by innate biases, previous individual experience and social information acquired from conspecifics. We examined how these factors interact to affect flower colour preference in the large earth bumblebee, Bombus terrestris dalmatinus. Individual bees with no experience foraging on coloured flowers were first tested for innate colour biases on an unrewarded array of blue and yellow artificial flowers. Depending on treatment, bees then acquired individual experience foraging on a colour (either blue or yellow) associated with high-quality sucrose rewards, or a colour with low-quality sucrose rewards, or they did not acquire any individual experience. Bees were then exposed to the alternative colour associated with conspecific demonstrator bees (social information) or the alternative colour with no social information. Bees that had no individual experience visited flower colours that were associated with conspecific demonstrators (social information) but only significantly if the socially demonstrated colour was one for which bees had an innate bias. When bees had individual experience foraging on a colour with high-quality rewards they continued foraging on that colour, and generally did not visit the socially demonstrated alternative colour, regardless of innate colour bias. Alternatively, when bees had individual experience foraging on colours with low-quality rewards, they made more visits to the socially demonstrated alternative flower colour, but only when the alternative colour was the colour for which they had an innate bias. Bees that had no access to social information continued to forage on low-reward coloured flowers. Thus we show that reward quality of resources with which bees have individual experience affects the use of social information but with an important role of innate biases.
The psychophysics of sugar concentration discrimination and contrast evaluation in bumblebees
Animal Cognition, 2012
The capacity to discriminate between choice options is crucial for a decision-maker to avoid unprofitable options. The physical properties of rewards are presumed to be represented on context-dependent, nonlinear cognitive scales that may systematically influence reward expectation and thus choice behavior. In this study, we investigated the discrimination performance of free-flying bumblebee workers (Bombus impatiens) in a choice between sucrose solutions with different concentrations. We conducted two-alternative free choice experiments on two B. impatiens colonies containing some electronically tagged bumblebees foraging at an array of computerautomated artificial flowers that recorded individual choices. We mimicked natural foraging conditions by allowing uncertainty in the probability of reward delivery while maintaining certainty in reward concentration. We used a Bayesian approach to fit psychometric functions, relating the strength of preference for the higher concentration option to the relative intensity of the presented stimuli. Psychometric analysis was performed on visitation data from individually marked bumblebees and pooled data from unmarked individuals. Bumblebees preferred the more concentrated sugar solutions at high stimulus intensities and showed no preference at low stimulus intensities. The obtained psychometric function is consistent with reward evaluation based on perceived concentration contrast between choices. We found no evidence that bumblebees reduce reward expectations upon experiencing non-rewarded visits. We compare psychometric function parameters between the bumblebee B. impatiens and the flower bat Glossophaga commissarisi and discuss the relevance of psychophysics for pollinator-exerted selection pressures on plants.
Animal Behaviour, 1999
We tested risk sensitivity towards variability in volume of reward with harnessed honeybees, Apis mellifera, in a proboscis-extension conditioning paradigm. We conditioned each subject to turn its head and extend its proboscis towards one of two presented odours; one odour was associated with a constant reward volume and the other with a variable reward volume that was either low or high, with probabilities P=0.75 and (1 P)=0.25, respectively. The volumes of rewards were varied among three experimental conditions. In conditions I and II, the variable reward option included a low reward of zero (i.e. reinforcement was withheld in the low reward value); in condition I, the mean of the variable and of the constant reward options were the same, and in condition II, the variable reward option had a higher mean reward than the constant reward option. The behaviour of subjects did not differ between treatments and the majority of individuals were risk averse. In condition III, the variable reward option did not include a zero reward and the mean reward did not differ between options. Very few of the individuals assigned to condition III developed a preference for either reward option. Thus, honeybees are risk sensitive to variability in volume of reward in some conditions and the degree of risk sensitivity depends on characteristics of the reward distributions. The most salient characteristic may be a relative measure of variability, such as the value of the coefficient of variation of reward. The experimental paradigm that we developed is a powerful tool for studying the mechanism of risk sensitivity in bees, as well as other aspects of learning, decision making, perception and memory.
As the distribution of food resources shifts over time, central place foragers are likely to be repeatedly faced with the question of when to abandon a forage site that is declining in value and to subsequently search elsewhere. Although there has been a great deal of investigation into how individual foragers allocate time between exploration and exploitation, few studies have sought to explore this issue within a larger functional context. We take a comparative approach to this problem by examining decision making in individual honeybees and bumblebees as they responded to a downshift in food reward. Our results show not only that honeybees and bumblebees have significantly divergent strategies with regards to abandoning a food source that is declining in value but also in terms of the subsequent tendency to seek an alternative food source. We interpret these results in terms of both biological and social distinctions between these species and highlight how group-level characteristics are likely to shape the evolutionarily derived foraging strategies of individual animals.
Does an Insect's Unconditioned Response to Sucrose Reveal Expectations of Reward
PLOS One, 2008
We asked whether and how a sequence of a honeybee's experience with different reward magnitudes changes its subsequent unconditioned proboscis extension response (PER) to sucrose stimulation of the antennae, 24 hours after training, in the absence of reward, and under otherwise similar circumstances. We found that the bees that had experienced an increasing reward schedule extended their probosces earlier and during longer periods in comparison to bees that had experienced either decreasing or constant reward schedules, and that these effects at a later time depend upon the activation of memories formed on the basis of a specific property of the experienced reward, namely, that its magnitude increased over time. An anticipatory response to reward is typically thought of as being rooted in a subject's expectations of reward. Therefore our results make us wonder to what extent a long-term 'anticipatory' adjustment of a honeybee's PER is based upon an expectation of reward. Further experiments will aim to elucidate the neural substrates underlying reward anticipation in harnessed honeybees. Citation: Gil M, Menzel R, De Marco RJ (2008) Does an Insect's Unconditioned Response to Sucrose Reveal Expectations of Reward?. PLoS ONE 3(7): e2810.