Foraging in an unsteady world: bumblebee flight performance in field-realistic turbulence.

Natural environments are characterized by variable wind that can pose significant challenges for flying animals and robots. However, our understanding of the flow conditions that animals experience outdoors and how these impact flight performance remains limited. Here, we combine laboratory and field experiments to characterize wind conditions encountered by foraging bumblebees in outdoor environments and test the effects of these conditions on flight. We used radio-frequency tags to track foraging activity of uniquely identified bumblebee (Bombus impatiens) workers, while simultaneously recording local wind flows. Despite being subjected to a wide range of speeds and turbulence intensities, we find that bees do not avoid foraging in windy conditions. We then examined the impacts of turbulence on bumblebee flight in a wind tunnel. Rolling instabilities increased in turbulence, but only at higher wind speeds. Bees displayed higher mean wingbeat frequency and stroke amplitude in these conditions, as well as increased asymmetry in stroke amplitude-suggesting that bees employ an array of active responses to enable flight in turbulence, which may increase the energetic cost of flight. Our results provide the first direct evidence that moderate, environmentally relevant turbulence affects insect flight performance, and suggest that flying insects use diverse mechanisms to cope with these instabilities.

Hypophysectomy disturbs the noradrenergic feeding system of the paraventricular nucleus.

Injection of norepinephrine (NE) into the hypothalamic paraventricular nucleus (PVN) of satiated rats is known to stimulate eating behavior. In addition, drinking behavior is potentiated just prior to the onset of eating, followed by a strong inhibition of water intake. To understand the relationship between these PVN noradrenergic phenomena and endocrine processes associated with the PVN, chronically hypophysectomized animals were tested for their behavioral responsiveness to PVN NE injection. Pituitary ablation was found to abolish the NE-elicited eating response and the NE drinking suppressive effect. However, hypophysectomy had no impact on the NE-elicited preprandial drinking response, nor did it affect drinking produced by carbachol, angiotensin, and histamine, or the feeding and drinking responses induced by insulin. These results demonstrate that hypophysectomy disturbs PVN noradrenergic mechanisms in a behaviorally and pharmacologically specific specific manner.