Acquisition of a time-memory in forager honey bees

Forager honey bees can associate the time of day with the presence of food at locations outside the hive. It is thought that this time-memory enables the bee to make a spatio-temporal match between its behavior and floral nectar secretion rhythms. Despite a long tradition of research, the mechanisms by which the time-memory becomes established are unknown. We investigated the influences of two experiential factors on the acquisition of time-memory: (1) the number of collecting visits made by the forager within a feeding bout during a restricted time of day and (2) the number of days of exposure to the restricted feeding time. Our results indicate that these two factors control different processes. The number of days of experience influences the temporal accuracy of reconnaissance behavior to the food source. The cumulative number of collecting visits within the feeding bouts has no apparent effect on time-accuracy but, instead, determines the probability of exhibiting food-anticipatory behavior and, if that overt behavior is performed, the intensity of its expression. This paper is dedicated to the memory of Prof. James L. Larimer.     

Optimal patch residence time of a sit-and-wait forager

This paper addresses optimal giving-up time of a sit-and-waitforager by a rate maximization model. It was assumed that aforager takes at most only one prey item in a patch in one trial,that is, the forager leaves a patch with a prey item (if itattacks it) or without prey (if it gives up). Some kinds ofsit-and-wait foragers, like owls, hunt in this manner. The followingassumptions were made: (1) A forager recognizes the habitattype of patches (e.g., forest type or grassland type). (2) Spatialor temporal heterogeneity generates the uncertainty of the environmentin each habitat type. It was assumed that in a patch (in habitattype i), prey encounter rate (X) is fixed during the trial andencounter with prey depends on a Poisson process. However, preyencounter rate varies across trials within each habitat typeaccording to _i-(). Thus the forager does not know the prey encounterrate that is assigned to each patch in the type, but it knowsthe probability density function, _i-(). (3) The forager encounterseach habitat type randomly in the environment. The patch residencetime for each habitat type was considered as the only decisionparameter. Considering stochastic change of prey encounter ratein patches of a habitat type, information limitation for theforaging animal can be treated. Patch residence time was influencedby the pattern of the stochasticity. When the forager knowsperfectly the encounter rate of prey in each patch (i.e., nostochasticity), the optimal giving-up time is infinite or zero(reject the patch). With the limited information (stochasticenvironment), the condition for a finite, nonzero optimal giving-uptime in patches of a habitat depends on how far the worst caseis below the average among patches of the habitat and how badthe worst case is compared to the average of the whole environment.In a negatively skewed habitat, these conditions tend to holdeasily. The optimal forager should perform pessimistically ordoubt whether the patch contains prey, that is, set a finitegiving-up time. In a positively skewed habitat, the optimalforager should perform optimistically, that is, set an infinitegiving-up time. The expected gain is higher in the positivelyskewed habitat than in the negatively skewed habitat. When theforager must choose between the two habitats, it should choosethe positively skewed habitat. [Behav Ecol 1991;2:283–294]     

Amino acid content and nectar choice by forager honeybees (Apis mellifera L.)

Dual choice feeding tests were performed to determine a preference of forager honeybees for specific amino acids. Artificial nectar containing proline was preferred over those containing only sugars. Nectar containing alanine was preferred on the first day, but preference was no longer significant thereafter. On the contrary, a negative response was found for serine. When the bees were given the choice between two nectars enriched with different compounds, proline was preferred above both alanine and serine, and alanine above serine.     

Crop scents affect the occurrence of trophallaxis among forager honeybees

Previous evidence indicates that the recognition of the nectar delivered by forager honeybees within the colony may have been a primitive method of communication on food resources. Thus, the association between scent and reward that nectar foragers establish while they collect on a given flower species should be retrieved during trophallaxis, i.e., the transfer of liquid food by mouth, and, accordingly, foraging experience could affect the occurrence of these interactions inside the nest. We used experimental arenas to analyze how crop scents carried by donor bees affect trophallaxis among foragers, i.e., donors and receivers, which differ in their foraging experience. Results showed that whenever the foragers had collected unscented sugar solution from a feeder the presence of scents in the solution carried by donors did not affect the occurrence of trophallaxis nor its dynamics. In contrast, whenever the foragers had previous olfactory information, new scents present in the crop of the donors negatively affected the occurrence, but not the dynamics of trophallaxis. Thus, the association learned at the food source seems to be retrieved during trophallaxis, and it is possible that known scents present in the mouthparts of nest-mates may operate as a triggering stimulus to elicit trophallactic behavior within the hive.     

Tunnel specificity and forager movement in subterranean termites (Isoptera: Rhinotermitidae and Termitidae)

The movement of foragers of two species of Australian, subterranean, mound-building termites, Coptotermes lacteus (Froggatt) (Rhinotermitidae) and Nasutitermes exitiosus (Hill) (Termitidae), was investigated in their natural habitat using artificial feeding sites along trenches dug to mimic natural forager tunnels that radiate out from the central mound-nests. Termites were dyed by self-feeding on cardboard soaked with histological fat-stains on one or two trenches and then termites were collected from other feeding sites at two and four weeks after the fat-stains were placed. At two and four weeks after marking commenced, 60-75% of marked termites were found in trenches containing the marked paper, and 2-16% were found in trenches on the opposite side of the nest. The proportion of marked termites in a sample was three to eight times greater in the trenches containing the marked paper relative to other trenches. Although difficulties with fat-stains used as markers might explain some of the observed patterns, it is evident that C. lacteus and N. exitiosus foragers do not move randomly between feeding sites in their natural habitat.     

Low individual-level dietary plasticity in an island-invasive generalist forager

The ability of invasive mammals to adjust their diet in response to new or variable resources is often proposed to explain their invasion success on islands with differing environmental conditions, especially islands with strong spatiotemporal changes in the nature and abundance of their resources. In this study, we investigated how habitat heterogeneity and seasonal fluctuation in resource quality affect dietary breadth and plasticity in an island-invasive rodent, the black rat Rattus rattus, on a small Mediterranean island. We tested for dietary plasticity of rats at both the individual and population levels by using traditional dietary and stable isotope analyses at successively increasing time scales, coupled with a long-term study of individual rats in three habitats of close proximity. Dietary and movement analyses both indicated that R. rattus is able to exploit a wide range of resources and habitats. However, dietary plasticity and habitat breadth were far narrower at the individual level. Results revealed that rats exclusively used resources found in their local habitat, and very few individuals moved among adjacent habitats in pursuit of higher-quality resources, despite those resources being abundant in their immediate environment. This counterintuitive finding suggests that intraspecific interactions must restrict rat mobility. Our results suggest that even on small islands, accessibility of patchy and high-quality resources to individuals from the entire population is not systematic. This result has important implications when quantifying invasive rodent impacts on patchily distributed species, especially when studies use indirect methods such as dietary analyses as a substitute for direct observations of predatory behavior.     

Net costs of group living in a solitary forager, the Eurasian badger (Meles meles)

Group living is expected to evolve under two extreme conditions:when there are net benefits to the individual of living in agroup and when there are net costs to living in a group togetherwith strong ecological constraints on dispersal and independentbreeding. A third condition may facilitate group formation:when the territorial defense of resources that are dispersedwidely or renewed at high rates allows groups to form at nocost to group members. Eurasian badgers are solitary over alarge part of their geographic distribution and forage aloneeven where diey live in territorial groups. To determine whichof the three conditions best explains group living in badgers,we analyzed dispersal and breeding patterns. Using these datawe describe the mechanism of group formation and the net costsor benefits of group living in 16 badger groups in one population.Groups form primarily by the retention of young on their natalterritory. Typically, groups contain one or more sexually maturebut nonbreeding females in addition to one or more breedingfemales. Females do not benefit from group living as indicatedby the lack of relationships, or perhaps negative relationships,between the proportion of adult females that bred in a groupand mean reproductive success, on the one hand, and group sizeand components of group size, on the other. A high reproductivefailure rate among females in this and other populations ofsocial badgers, as compared with a population of solitary badgers,suggests that there is a cost of group living to females. Wepropose that if badgers defend resources whose spatial distributionor high renewal rates allow groups to form on a territory atlitde or no cost to group members, weak ecological constraintson dispersal and independent breeding are sufficient to explainthe formation of groups. Badgers appear to have not evolvedcooperative breeding in response to these ecological conditions,perhaps because badger groups represent an early stage in theevolution of carnivore sociality.     

Games fish play: Making decisions as a social forager

Suppose a customer wishes to buy a bag of fruit in a market hall during his lunch break and has the choice between two crowded fruiterers' shops. The complexity of problems inherent in such a situation has been increasingly appreciated by behavioural ecologists interested in social foraging of animals. The recognition of consistent individual differences in competitive ability and their incorporation into classical game theoretical models has recently facilitated a step forward in our understanding of social foraging. Here I review theoretical developments in connection with experiments on resource sharing in foraging fish.     

On the dynamics of predation risk perception for a vigilant forager

There has been much recent interest in modelling epidemics on networks, particularly in the presence of substantial clustering. Here, we develop pairwise methods to answer questions that are often addressed using epidemic models, in particular: on the basis of potential observations early in an outbreak, what can be predicted about the epidemic outcomes and the levels of intervention necessary to control the epidemic? We find that while some results are independent of the level of clustering (early growth predicts the level of ‘leaky’ vaccine needed for control and peak time, while the basic reproductive ratio predicts the random vaccination threshold) the relationship between other quantities is very sensitive to clustering.     

Plankton‐picking by the goatfish Pseudupeneus maculatus(Mullidae), a specialized bottom forager

Although goatfishes (Mullidae) include c . 50 specialized bottom foraging species, juvenile and adult spotted goatfish Pseudupeneus maculatus were recorded feeding on plankton on rocky reefs off southern and north‐eastern Brazil, respectively.     

Thermal ecology and behaviour of the nomadic social forager Malacosoma disstria

The present study examines whether the nomadic social caterpillar Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae) can thermoregulate despite the lack of a tent, and evaluates the role of thermoregulation in directing the colony's behaviour. The presence of a radiant heat and light source (i.e. a lamp in the laboratory experiments and the sun in the field observations) enables caterpillar colonies to increase body temperature by basking (remaining still under a heat source) and this is only effective when caterpillars cluster in groups. Body temperatures achieved when basking in a group coincide with the temperatures at which the development rate is maximal for this species. Indeed, in the laboratory experiments, the presence of a lamp results in higher growth rates, confirming that thermoregulation is an advantage to group living. When a radiant heat/light source is provided at a distance from the food in the laboratory, caterpillars behave to maximize thermal gains: colonies move away from the food to bivouac (i.e. group together and remain still on a silk mat) under the lamp, spend more time on the bivouac and cluster in a more cohesive group. Thermal needs thus influence habitat selection and colony aggregation. Malacosoma disstria relies on developing rapidly, despite low seasonal temperatures, aiming to benefit from springtime high food quality and low predation rates; however, unlike others in its genus, it does not build a tent but instead exhibits collective nomadic foraging (i.e. the whole colony moves together between temporary resting and feeding sites). In this species, collective thermoregulatory behaviour is not only possible and advantageous, but also drives much of the colony's behaviour, in large part dictating the temporal and spatial patterns of movement. These findings suggest that thermoregulation may be an important selection pressure keeping colonies together.     

Low forager fertility: demographic characteristic or methodological artifact?

Anthropological literature has long held that traditional foraging populations have low fertility levels. This research examines the number of live births per woman for 9 non-western forager groups who have been investigated in the last 20 years. Data are derived from 1) birth registration systems, 2) surveys conducted during short stays with the group, and 3) surveys conducted as part of longer ethnographic studies. Fertility rates for the groups are 1) 3.5 for the Kiunga area of Papula, New Guinea, 2) 4.2 for Northern Territory Australian aborigines, 3) 5.0 for Cayapo groups in Brazil, 4) 5.3 for Hiowe people of New Guinea, 5) 5.7 for 3 Xavante groups in Brazil, 6) 6.0 for West Alaskan Eskimos, 7) 6.9 for Nunamiut Eskimos of Alaska, 8) 7.6 for the Bisman-Asmat group of Indonesian New Guinea, and 9) 8.4 for the Winikina Warao of Venezuela. Since fertility rates are highest when ethnographic studies, which allow for question clarification, memory recall, and cross-checking, are used, the author believes that high fertility rates most accurately represent forager societies. Research on the Dobe ]Kung (fertility rate - 4.7), may contradict these findings, but the author believes that the ]Kung fertility rates are higher than reported because of infanticide practices, sexual abstinence during lactation, and disease related fertility problems. In summary, the study finds high fertility (7-9 births) in traditional foraging societies. Although the study examines small populations, correlation strength and overall consistency help verify the results.     

The microRNA ame-miR-279a regulates sucrose responsiveness of forager honey bees (Apis mellifera)

Increasing evidence demonstrates that microRNAs (miRNA) play an important role in the regulation of animal behaviours. Honey bees (Apis mellifera) are eusocial insects, with honey bee workers displaying age-dependent behavioural maturation. Many different miRNAs have been implicated in the change of behaviours in honey bees and ame-miR-279a was previously shown to be more highly expressed in nurse bee heads than in those of foragers. However, it was not clear whether this difference in expression was associated with age or task performance. Here we show that ame-miR-279a shows significantly higher expression in the brains of nurse bees relative to forager bees regardless of their ages, and that ame-miR-279a is primarily localized in the Kenyon cells of the mushroom body in both foragers and nurses. Overexpression of ame-miR-279a attenuates the sucrose responsiveness of foragers, while its absence enhances their sucrose responsiveness. Lastly, we determined that ame-miR-279a directly target the mRNA of Mblk-1. These findings suggest that ame-miR-279a plays important roles in regulating honey bee division of labour.     

Dynamics of forager arrivals and nectar renewal in flowers of Anchusa strigosa

Summary Long-tongued Anthophora spp. bees collecting nectar from flowers of Anchusa strigosa (Boraginaceae) exhibit systematic foraging. Successive forager arrivals at individual flowers are not independent, and the time elapsed between successive arrivals at a particular flower is distributed more uniformly than be expected on the basis of a random arrival process. Distributions of inter-arrival time for individual flowers show standard deviation/mean ratios of 0.44–0.79, a range which is consistent with results obtained for two other plant-pollinator systems. The rate at which nectar is renewed between successive forager arrivals is independent of the amount of nectar in the flower, and the renewal process is strongly linear. Practical and theoretical implications of these results are discussed.