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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"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 . Such incremental departure rules had previously been found in parasitoid wasps , bumblebees   and even humans   . "
"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 Wajnberg et al., , 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. "
[Show abstract][Hide abstract]ABSTRACT: Animals exploit complex environments in an optimal way, often with limited brain capacities. Interestingly, it is largely unknown, how they do so. This thesis comprises five studies investigating proximate mechanisms modulating the searching behaviour of parasitoid wasps. These organisms serve as excellent organisms for such questions due to their tight link of searching success and fitness. While the first study assumed a simple motor response to serve as a heuristic, yet effective, mechanism, the remaining studies focussed on the role of octopamine [OA] and dopamine [DA]. Both substances being essential in the assessment of reward and aversive stimuli, respectively. Neither the assumed motor response could be met nor did OA or DA reveal any consistent effects with respect to the assessment of rewards and costs. DA slightly impacted the movement pattern. Treatment with OA revealed numerous effects, in total indicating an influence on stress level. Both is in line with studies on other species. Yet, although OA significantly influences searching behaviour, the underlying mechanism is considerably more complex than initially assumed. Last, it was shown that a generalisation on the basis of a few studies and stimuli with respect to the role of OA in the integration of rewards is a simplification.