Patch departure rules in Bumblebees: Evidence of a decremental motivational mechanism

Behavioral Ecology and Sociobiology (Impact Factor: 2.35). 08/2007; 61(11):1707-1715. DOI: 10.1007/s00265-007-0402-6


The patch living rules of a pollinator, the bumblebee Bombus terrestris L., are studied here in the framework of motivational models widely used for parasitoids: The rewarding events found during the foraging process are supposed to increase or decrease suddenly the tendency of the insect to stay in the current patch and therefore to adjust the patch residence time to the patch profitability. The foraging behaviour of these pollinators was observed in two environment types to determine their patch-leaving decisions. The rich environment was composed of male-fertile flowers, offering pollen and nectar, and the poor one of male-sterile flowers, offering little nectar and no pollen. The experimental design consisted of a patch system in which inflorescences were evenly arranged in two rows (1 m distance). Residence times of foragers inside inflorescences and rows were analysed by a Cox proportional hazards model, taking into account recent and past experience acquired during the foraging bout. Most of the results showed a decremental motivational mechanism, that is, a reduction in the residence time on the inflorescence or in the row related to exploitation of flowers within inflorescences and inflorescences within rows These results indicate that bumblebees tend to leave the patch using departure rules similar to those found in parasitoids. The results also provide information on the memory, learning and evaluating capabilities of bumblebees especially when rich and poor environments were compared. The patch-leaving mechanism suggested by this study is consistent with the central place foraging theory.

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Available from: Jean-Sébastien Pierre
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    • "P. polycephalum uses the number of food items it has engulfed as a rule of thumb such that each encounter with a high-quality food item (the effect is less strong when food items are of lesser quality) decreases the likelihood that the plasmodium leaves the patch [40]. Such incremental departure rules had previously been found in parasitoid wasps [41], bumblebees [42] [43] and even humans [44] [45] [46]. "
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    ABSTRACT: Because of its peculiar biology and the ease with which it can be cultured, the acellular slime mould Physarum polycephalum has long been a model organism in a range of disciplines. Due to its macroscopic, syncytial nature, it is no surprise it has been a favourite amongst cell biologists. Its inclusion in the experimental tool kit of behavioural ecologists is much more recent. These recent studies have certainly paid off. They have shown that for an organism that lacks a brain or central nervous system P. polycephalum shows rather complex behaviour. For example it is capable of finding the shortest path through a maze, can construct networks as efficient as those designed by humans, solve computationally difficult puzzles, makes multi-objective foraging decisions, balances its nutrient intake and even behaves irrationally. Are the slime mould's achievements simply 'cute', worthy of mentioning in passing, but nothing to take too seriously? Or do they hint at the fundamental processes underlying all decision-making? We will address this question after reviewing the decision-making abilities of the slime mould. Copyright © 2015. Published by Elsevier Ltd.
    Full-text · Article · Jul 2015 · Journal of Molecular Biology
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    • "Briefly, the Cox proportional hazards model is a flexible statistical tool that can be used to test the effect of explanatory variables on the baseline patch-leaving tendency of an organism (Wajnberg, 2006). It has been used to identify patch-leaving rules in a variety of animals (for example, Driessen and Bernstein, 1999; Wajnberg et al., 2000, 2003; Boivin et al., 2004; Wajnberg, 2006; Lefebvre et al., 2007; Louâpre et al., 2011). Proportional hazard models yield a hazard function that describes the probability per unit time that a plasmodium will leave the patch (given that it is still on it), and a risk ratio that describes how the tendency to leave a patch is changed by each explanatory variable. "
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    ABSTRACT: Animals foraging in patchy, non- or slowly-renewing environments must make decisions about how long to remain within a patch. Organisms can use heuristics ('rules of thumb') based on available information to decide when to leave the patch. Here we investigate proximate patch departure heuristics in two species of giant, brainless amoeba: the slime moulds Didymium bahiense and Physarum polycephalum. We explicitly tested the importance of information obtained through experience by eliminating chemosensory cues of patch quality. In Physarum polycephalum, patch departure was influenced by the consumption of high, and to a much lesser extent low, quality food items such that engulfing a food item increased patch residency time. Physarum polycephalum also tended to forage for longer in darkened, 'safe' patches. In Didymium bahiense, engulfment of either a high or low quality food item increased patch residency irrespective of that food item's quality. Exposure to light had no effect on the patch residency time of D. bahiense. Given that our organisms lack a brain, our results illustrate how the use of simple heuristics can give the impression that individuals make sophisticated foraging decisions. © 2015. Published by The Company of Biologists Ltd.
    Preview · Article · Feb 2015 · Journal of Experimental Biology
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    • "An important number of both experimental and theoretical studies have proposed several different patch-leaving decision rules foraging animals should adopt to optimise their patch residence time. Such proximate decision-making processes are based on animals' motivation that has been called " foraging motivation " (e.g., Lefebvre et al. 2007), " responsiveness " (e.g., to the patch edge) (e.g., Waage 1978, 1979; van Alphen et al. 2003; Wajnberg 2006), " tendency " (to stay or to leave) (e.g., Pierre et al. 2012; Wajnberg 2012) or even " estimated number of remaining resource items " (e.g., Iwasa et al. 1981). The concept of motivation can perhaps best be replaced, or complemented by demonstrated mechanistic behaviours involved in finding and exploiting resources, thus reducing the need for intervening motivational state variables (Bell 1991). "
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    ABSTRACT: Several optimisation models, like the marginal value theorem (MVT), have been proposed to predict the optimal time foraging animals should remain on patches of resources. These models do not clearly indicate, however, how animals can follow the corresponding predictions. Hence, several proximate patch-leaving decision rules have been proposed. Most if not all of these are based on the animals’ motivation to remain on the patches, but the real behaviours involved in such motivation actually still remain to be identified. Since animals are usually exploiting patches of resources by walking, we developed a model simulating the intra-patch movement decisions of time-limited animals exploiting resources distributed in delimited patches in environments with different resource abundances and distributions. The values of the model parameters were optimised in the different environments by means of a genetic algorithm. Results indicate that simple modifications of the walking pattern of the foraging animals when resources are discovered can lead to patch residence times that appear consistent with the predictions of the MVT. These results provide a more concrete understanding of the optimal patch-leaving decision rules animals should adopt in different environments.
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