The tail plays a major role in the differing manoeuvrability of two sibling species of mouse-eared bats (Myotis myotis and Myotis blythii)

Two sympatrically occurring bat species, the greater mouse-eared bat (Myotis myotis (Borkhausen, 1797)) and the lesser mouse-eared bat (Myotis blythii (Tomes, 1857)) (Chiroptera, Vespertillionidae), share numerous similarities in morphology, roosting behaviour, and echolocation and are often difficult to distinguish. However, despite these similarities, their foraging behaviour is noticeably different. Our aim was to examine the extent to which these different foraging strategies reflect morphological adaptation. We assessed whether the morphology of the wing, body, and tail differed between M. myotis and M. blythii. In addition, in a laboratory experiment involving an obstacle course, we compared differences in manoeuvrability by relating them to our morphological measurements. The two species differed in their overall size, wing-tip shape, and tail-to-body length ratio. The generally smaller sized M. blythii performed better in the obstacle course and was therefore considered to be more manoeuvrable. Although differences in wing-tip shape were observed, we found the most important characteristic affecting manoeuvrability in both species to be the tail-to-body length ratio. Additionally, when we compared two bats with injured wing membranes with unharmed bats of the same species, we found no difference in manoeuvrability, even when the wing shape was asymmetric. We therefore postulate that morphometric differences between the two species in their overall size and, more importantly, in their tail-to-body length ratio are the main physical characteristics providing proof of adaptation to different foraging and feeding strategies.

Within-plant distribution of 1,4-benzoxazin-3-ones contributes to herbivore niche differentiation in maize

Plant defences vary in space and time, which may translate into specific herbivore-foraging patterns and feeding niche differentiation. To date, little is known about the effect of secondary metabolite patterning on within-plant herbivore foraging. We investigated how variation in the major maize secondary metabolites, 1,4-benzoxazin-3-one derivatives (BXDs), affects the foraging behaviour of two leaf-chewing herbivores. BXD levels varied substantially within plants. Older leaves had higher levels of constitutive BXDs while younger leaves were consistently more inducible. These differences were observed independently of plant age, even though the concentrations of most BXDs declined markedly in older plants. Larvae of the well-adapted maize pest Spodoptera frugiperda preferred and grew better on young inducible leaves irrespective of plant age, while larvae of the generalist Spodoptera littoralis preferred and tended to grow better on old leaves. In BXD-free mutants, the differences in herbivore weight gain between old and young leaves were absent for both species, and leaf preferences of S. frugiperda were attenuated. In contrast, S. littoralis foraging patterns were not affected. In summary, our study shows that plant secondary metabolites differentially affect performance and foraging of adapted and non-adapted herbivores and thereby likely contribute to feeding niche differentiation

Sugar concentration influences decision making in <i>Apis mellifera</i> L. workers during early-stage honey storage behaviour

Decision making in honeybees is based on in- formation which is acquired and processed in order to make choices between two or more al- ternatives. These choices lead to the expression of optimal behaviour strategies such as floral constancy. Optimal foraging strategies such as floral constancy improve a colony’s chances of survival, however to our knowledge, there has been no research on decision making based on optimal storage strategies. Here we show, using diagnostic radioentomology, that decision mak- ing in storer bees is influenced by nectar sugar concentrations and that, within 48 hours of col- lection, honeybees workers store carbohydrates in groups of cells with similar sugar concentra- tions in a nonrandom way. This behaviour, as evidenced by patchy spatial cell distributions, would help to hasten the ripening process by reducing the distance between cells of similar sugar concentrations. Thus, colonies which ex- hibit optimal storage strategies such as these would have an evolutionary advantage and im- prove colony survival expectations over less efficient colonies and it should be plausible to select colonies that exhibit these preferred traits.

Floral scents affect the distribution of hive bees around dancers

Floral scents are important information cues used to organize foraging-related tasks in honeybees. The waggle dance, apart from encoding spatial information about food sources, might facilitate the transfer of olfactory information by increasing the dissipation of volatiles brought back by successful foragers. By assuming that food scents are more intensive on specific body parts of returning foragers, i.e., the posterior legs of pollen foragers and mouthparts of nectar foragers, we quantified the interactions between hive mates and foragers during dances advertising different types of food sources. For natural sources, a higher proportion of hive mates contacted the hind legs of pollen dancers (where the pollen loads were located) with their heads compared to non-pollen dancers. On the other hand, the proportion of head-to-head contacts was higher for non-pollen foragers during the waggle runs. When the food scent was manipulated, dancers collecting scented sugar solution had a higher proportion of head-to-head contacts and a lower proportion around their hind legs compared to dancers collecting unscented solution. The presence of food odors did not affect in-hive behaviors of dancers, but it increased the number of trophallaxes in-between waggle runs (i.e., during circle phases). These results suggest that the honeybee dance facilitates the olfactory information transfer between incoming foragers and hive mates, and we propose that excitatory displays in other social insect species serve the same purpose. While recent empirical and theoretical findings suggested that the colony level foraging benefits of the spatial information encoded in the waggle dance vary seasonally and with habitats, the role of the dance as a compound signal not only indicating the presence of a profitable resource but also amplifying the information transfer regarding floral odors may be important under any ecological circumstances.

Nectar distribution and its relation to food quality in honeybee (Apis mellifera) colonies

In honeybees (Apis niellifera), the process of nectar collection is considered a straightforward example of task partitioning with two subtasks or two intersecting cycles of activity: (1) foraging and (2) storing of nectar, linked via its transfer between foragers and food processors. Many observations suggest, however, that nectar colleclion and processing in honeybees is a complex process, involving workers of other sub-castes and depending on variables such as resource profitability or the amount of stored honey. It has been observed that food processor bees often distribute food to other hive bees after receiving it from incoming foragers, instead of storing it immediately in honey cells. While there is little information about the sub-caste affiliation and the behaviour of these second-order receivers, this stage may be important for the rapid distribution of nutrients and related information. To investigate the identity of these second-order receivers, we quantified behaviours following nectar transfer and compared these behaviours with the behaviour of average worker hive-bees. Furthermore, we tested whether food quality (sugar concentration) affects the behaviour of the second-order receivers. Of all identified second-order receivers, 59.3% performed nurse duties, 18.5% performed food-processor duties and 22.2% performed forager duties. After food intake, these bees were more active, had more trophallaxes (especially offering contacts) compared to average workers and they were found mainly in the brood area, independent of food quality. Our results show that the liquid food can be distributed rapidly among many bees of the three main worker sub-castes, without being stored in honey cells first. Furthermore, the results suggest that the rapid distribution of food partly depends on the high activity of second-order receivers.

A Foraging Cost of Migration for a Partially Migratory Cyprinid Fish

Migration has evolved as a strategy to maximise individual fitness in response to seasonally changing ecological and environmental conditions. However, migration can also incur costs, and quantifying these costs can provide important clues to the ultimate ecological forces that underpin migratory behaviour. A key emerging model to explain migration in many systems posits that migration is driven by seasonal changes to a predation/growth potential (p/g) trade-off that a wide range of animals face. In this study we assess a key assumption of this model for a common cyprinid partial migrant, the roach Rutilus rutilus, which migrates from shallow lakes to streams during winter. By sampling fish from stream and lake habitats in the autumn and spring and measuring their stomach fullness and diet composition, we tested if migrating roach pay a cost of reduced foraging when migrating. Resident fish had fuller stomachs containing more high quality prey items than migrant fish. Hence, we document a feeding cost to migration in roach, which adds additional support for the validity of the p/g model of migration in freshwater systems.

The Role of Plant Primary and Secondary Metabolites in Root-Herbivore Behaviour, Nutrition and Physiology

Many insect herbivores feed on belowground plant tissues. In this chapter, we discuss how they have adapted to deal with root primary and secondary metabolites. It is becoming evident that root herbivores can use root volatiles and exudates for host location and foraging. Their complex sensory apparatus suggests a sophisticated recognition and signal transduction system. Furthermore, endogenous metabolites trigger attractive or repellent responses in root feeders, indicating that they may specifically fine-tune food uptake to meet their dietary needs. Little evidence for direct toxic effects of root secondary metabolites has accumulated so far, indicating high prevalence of tolerance mechanisms. Root herbivores furthermore facilitate the entry of soil microbes into the roots, which may influence root nutritional quality. Investigating the role of plant metabolites in an ecologically and physiologically relevant context will be crucial to refine our current models on root-herbivore physiology and behaviour in the future.

Effects, but no interactions, of ubiquitous pesticide and parasite stressors on honey bee (Apis mellifera) lifespan and behaviour in a colony environment

Interactions between pesticides and parasites are believed to be responsible for increased mortality of honey bee (Apis mellifera) colonies in the northern hemisphere. Previous efforts have employed experimental approaches using small groups under laboratory conditions to investigate influence of these stressors on honey bee physiology and behaviour, although both the colony level and field conditions play a key role for eusocial honey bees. Here, we challenged honey bee workers under in vivo colony conditions with sublethal doses of the neonicotinoid thiacloprid, the miticide tau-fluvalinate and the endoparasite Nosema ceranae, to investigate potential effects on longevity and behaviour using observation hives. In contrast to previous laboratory studies, our results do not suggest interactions among stressors, but rather lone effects of pesticides and the parasite on mortality and behaviour, respectively. These effects appear to be weak due to different outcomes at the two study sites, thereby suggesting that the role of thiacloprid, tau-fluvalinate and N. ceranae and interactions among them may have been overemphasized. In the future, investigations into the effects of honey bee stressors should prioritize the use of colonies maintained under a variety of environmental conditions in order to obtain more biologically relevant data.