Colony Foraging Research Articles

Organization of honeydew collection by foragers of different species of ants (Hymenoptera: Formicidae): Effect of colony size and species specificity

Aphid honeydew is one of the main energy sources for various ants in the temperate zone, nevertheless relatively little is known about the organization of the work of honeydew foragers (aphid milkers). This study focuses the honeydew collecting strate- gies used by different ants in steppe and forest multi-species communities in Western Siberia. The behaviour of marked foragers of 12 species (Formica - 7, Lasius - 2, Camponotus - 1, Myrmica - 2) was recorded. Depending the degree of the aphid milker specializa- tion and degree of protection of the aphids five honeydew collecting strategies of various complexity were distinguished: unspecialized foragers in (I) unprotected aphid colonies (attended by ants 95% of time); (III) low professional specialization (ants on duty constantly attending aphid colonies); (IV) medium and (V) high professional specialization (clear division of tasks: honeydew collecting by shepherds and protection of trophobionts by guards; and honeydew transportation by transporters in V). Task specialization of the honeydew foragers is facultative: different ant taxa demonstrate a certain range of the honeydew collecting strategies of different complexities (Formica - I-V, Lasius - I-II, Camponotus - III, Myrmica - I-II) depending the needs of their colony. The strategy used by ants did not depend the species of aphid attended, but is strongly dependent the species of ant, their colony size, available food resources and seasonality. In summer, the aphid milker specialization becomes more complex as ant colony size increases at both intra- and inter-specific levels and when food is scarce. In autumn Formica s. str. ants, which have the most advanced foraging strategy, adopt a simpler honeydew collecting strategy. Overall, the variety of hon- eydew foraging strategies seems to reflect the unequal contribution of dif ferent ants in forming trophobiotic interactions with aphids.

Sexual castes of Trachymyrmex fuscus (Formicidae: Attini) performing worker tasks

ABSTRACT: The main of this research was to report an atypical foraging behavior in a colony of Trachymyrmex fuscus, situated in "Cerrado" (savanna ecoregion of Goiás, Brazil). The colony foraging activity was performed only by sexual caste. Comparison of the foraging rhythm of this colony with another of the same specie where foraging was performed only by worker caste, showed that working time hours were very similar. After observations on the foraging behavior, both colonies were excavated in order to characterize them (nest size, population composition and estimating of the symbiotic fungus volume). Besides the foraging activity performed only by sexual females, other important observations were highlighted in that colony: low number of workers, presence of worker larvae and pupae (45 and 43 respectively) and apparently normal growth of the symbiotic fungus. Our hypothesis is that sexual females were in charge of the entire colony maintenance. This could be a strategy of colony survival when the worker caste is reduced.

Effects of sublethal doses of glyphosate on honeybee navigation

Glyphosate (GLY) is a herbicide that is widely used in agriculture for weed control. Although reports about the impact of GLY in snails, crustaceans and amphibians exist, few studies have investigated its sublethal effects in non-target organisms such as the honeybee Apis mellifera, the main pollen vector in commercial crops. Here, we tested whether exposure to three sublethal concentrations of GLY (2.5, 5 and 10 mg l(-1): corresponding to 0.125, 0.250 and 0.500 μg per animal) affects the homeward flight path of honeybees in an open field. We performed an experiment in which forager honeybees were trained to an artificial feeder, and then captured, fed with sugar solution containing traces of GLY and released from a novel site either once or twice. Their homeward trajectories were tracked using harmonic radar technology. We found that honeybees that had been fed with solution containing 10 mg l(-1) GLY spent more time performing homeward flights than control bees or bees treated with lower concentrations. They also performed more indirect homing flights. Moreover, the proportion of direct homeward flights performed after a second release from the same site increased in control bees but not in treated bees. These results suggest that, in honeybees, exposure to levels of GLY commonly found in agricultural settings impairs the cognitive capacities needed to retrieve and integrate spatial information for a successful return to the hive. Therefore, honeybee navigation is affected by ingesting traces of the most widely used herbicide worldwide, with potential long-term negative consequences for colony foraging success.

Ergonomic skew and reproductive queuing based on social and seasonal variation in foraging activity of eastern carpenter bees (Xylocopa virginica)

Reproductive division of labour in social carpenter bees differs from that in classically eusocial insects because reproductive output and ergonomic inputs are positively correlated—dominant females monopolize both foraging and reproduction. We quantified ergonomic skew in the facultatively social bee Xylocopa virginica (L., 1771) (eastern carpenter bee) based on detailed observations of foraging activity by individually marked females in 2009. Unusually for a univoltine bee, this species exhibits a spring foraging phase during which females feed pollen to other adults, probably as part of behavioural interactions to establish dominance hierarchies. During brood-provisioning, foraging in social nests was dominated by one female at a time, with replacement by a succession of foragers as dominants disappeared and were succeeded by a subordinate. The principal foragers (individuals that did the largest share of foraging in each colony) did 85%–100% of all pollen trips, so contributions to pollen-provisioning by female nest mates were highly uneven. Individual foraging rate was unaffected by group size and total colony foraging effort was a function of the number of foragers per group. Transient females that moved to new nests were as successful in achieving dominant forager status as females resident in their natal nests. This evidence indicates that colony social organisation is based on reproductive queues, whereby the first-ranked bee is the dominant forager and subordinates queue for opportunities to replace her.

Parameter identification of PEMFC model based on hybrid adaptive differential evolution algorithm

In this paper, a HADE (hybrid adaptive differential evolution) algorithm is proposed for the identification problem of PEMFC (proton exchange membrane fuel cell). Inspired by biological genetic strategy, a novel adaptive scaling factor and a dynamic crossover probability are presented to improve the adaptive and dynamic performance of differential evolution algorithm. Moreover, two kinds of neighborhood search operations based on the bee colony foraging mechanism are introduced for enhancing local search efficiency. Through testing the benchmark functions, the proposed algorithm exhibits better performance in convergent accuracy and speed. Finally, the HADE algorithm is applied to identify the nonlinear parameters of PEMFC stack model. Through experimental comparison with other identified methods, the PEMFC model based on the HADE algorithm shows better performance.

Assessing Honey Bee (Hymenoptera: Apidae) Foraging Populations and the Potential Impact of Pesticides on Eight U.S. Crops.

Beekeepers who use honey bees (Apis mellifera L.) for crop pollination services, or have colonies making honey on or in close proximity to agricultural crops, are concerned about the reductions of colony foragers and ultimate weakening of their colonies. Pesticide exposure is a potential factor in the loss of foragers. During 2009–2010, we assessed changes in the field force populations of 9–10 colonies at one location per crop on each of the eight crops by counting departing foragers leaving colonies at regular intervals during the respective crop blooming periods. The number of frames of adult bees was counted before and after bloom period. For pesticide analysis, we collected dead and dying bees near the hives, returning foragers, crop flowers, trapped pollen, and corn-flowers associated with the cotton crop. The number of departing foragers changed over time in all crops except almonds; general patterns in foraging activity included declines (cotton), noticeable peaks and declines (alfalfa, blueberries, cotton, corn, and pumpkins), and increases (apples and cantaloupes). The number of adult bee frames increased or remained stable in all crops except alfalfa and cotton. A total of 53 different pesticide residues were identified in samples collected across eight crops. Hazard quotients (HQ) were calculated for the combined residues for all crop-associated samples and separately for samples of dead and dying bees. A decrease in the number of departing foragers in cotton was one of the most substantial crop-associated impacts and presented the highest pesticide risk estimated by a summed pesticide residue HQ.

Effects of sub-lethal doses of glyphosate on honeybee navigation.

Glyphosate (GLY) is a herbicide that is widely used in agriculture for weed control. Although reports about the impact of GLY in snails, crustaceans and amphibians exist, few studies have investigated its sub-lethal effects in non-target organisms such as the honeybee Apis mellifera, the main pollen vector in commercial crops. Here, we tested whether exposure to three sub-lethal concentrations of GLY (2.5, 5 and 10 mg/L corresponding to 0.125, 0.250 and 0.500 µg/animal) affects the homeward flight path of honeybees in an open field. We performed an experiment in which forager honeybees were trained to an artificial feeder, and then captured, fed with sugar solution containing GLY traces and released from a novel site (the release site, RS) either once or twice. Their homeward trajectories were tracked using harmonic radar technology. We found that honeybees that had been fed with solution containing 10 mg/L GLY spent more time performing homeward flights than control bees or bees treated with lower GLY concentrations. They also performed more indirect homing flights. Moreover, the proportion of direct homeward flights performed after a second release at the RS increased in control bees but not in treated bees. These results suggest that, in honeybees, exposure to GLY doses commonly found in agricultural settings impairs the cognitive capacities needed to retrieve and integrate spatial information for a successful return to the hive. Therefore, honeybee navigation is affected by ingesting traces of the most widely used herbicide worldwide, with potential long-term negative consequences for colony foraging success.

RETRACTED: Personality and morphology shape task participation, collective foraging and escape behaviour in the social spider Stegodyphus dumicola

Determining the drivers of complex systems is a major challenge felt by virtually all of biology. For complex societies, there is considerable interest in how individuals' traits determine their social roles and how the milieu of trait variants within groups shapes emergent group-level phenotypes. In this study, we tested in spiders whether individual differences in behaviour, morphology, or both shape individuals' participation in foraging. We then tested which aspects of group composition (e.g. morphological composition, personality composition, group size) predict colony-level foraging and escape behaviour. We performed these studies both under (1) standardized laboratory conditions, where colonies' ability to build webs was constrained, and (2) under more free-living conditions in the field. Regardless of the laboratory/field distinction, we found that individual task participation was regulated by individuals' body size and group size: larger individuals and individuals in smaller groups tended to participate more in foraging tasks. At the colony level, colonies composed of bolder spiders attacked prey with a larger number of attackers regardless of the laboratory/field distinction. However, our field assessments of colony foraging revealed that the speed with which colonies responded to prey was determined by their group size, morphological composition and personality composition; none of these effects were detected under laboratory conditions. Finally, we found that colonies took longer to retreat from aversive stimuli when more spiders were outside the nest. Taken together, our results suggest that colonies' social organization and collective behaviour are determined by spiders' morphology, behavioural tendencies and colony demographics. • We tested effects of personality, morphology and group size on social organization in spiders. • Larger individuals and those in smaller groups tended to participate more in cooperative foraging. • Collective foraging behaviour was associated with personality (boldness) and morphology (body size). • Escape behaviour during an attack was determined by the number of individuals outside the nest. • Collective behaviour, but not task participation, differed under laboratory and field conditions.

Collective decision making in a heterogeneous environment: Lasius niger colonies preferentially forage at easy to learn locations

Many ants forage in complex environments and use a combination of trail pheromone information and route memory to navigate between food sources and the nest. Previous research has shown that foraging routes differ in how easily they are learned. In particular, it is easier to learn feeding locations that are reached by repeating (e.g. left–left or right–right) than alternating choices (left–right or right–left) along a route with two T-bifurcations. This raises the hypothesis that the learnability of the feeding sites may influence overall colony foraging patterns. We studied this in the mass-recruiting ant Lasius niger. We used mazes with two T-bifurcations, and allowed colonies to exploit two equidistant food sources that differed in how easily their locations were learned. In experiment 1, learnability was manipulated by using repeating versus alternating routes from nest to feeder. In experiment 2, we added visual landmarks along the route to one food source. Our results suggest that colonies preferentially exploited the feeding site that was easier to learn. This was the case even if the more difficult to learn feeding site was discovered first. Furthermore, we show that these preferences were at least partly caused by lower error rates (experiment 1) and greater foraging speeds (experiment 2) of foragers visiting the more easily learned feeder locations. Our results indicate that the learnability of feeding sites is an important factor influencing collective foraging patterns of ant colonies under more natural conditions, given that in natural environments foragers often face multiple bifurcations on their way to food sources.

Meal plan search engine inspired by ant colony’s foraging

Currently, the communication link between consumer electrical appliances and information devices is developing; for example, a refrigerator, which keeps food fresh, now also manages information about the food ingredients it contains. This environment, known as "Ubiquitous computing" or "Smart home appliance," has the potential for further research and development. In this environment, we consider a system that recommends food recipes or meal plans that can be cooked with the available ingredients in the refrigerator. However, a conventional keyword search is not effective for such a system, and therefore, in this paper, we propose an algorithm for the search engine that is inspired by an ant colony's foraging. In addition, we validate the effectiveness of the proposed search engine through simulations.

Colony foraging allocation is finely tuned to food distance and sweetness even close to a bee colony

AbstractSocial bee colonies can allocate their foraging resources over a large spatial scale, but how they allocate foraging on a small scale near the colony is unclear and can have implications for understanding colony decision‐making and the pollination services provided. Using a mass‐foraging stingless bee, Scaptotrigona pectoralis (Dalla Torre) (Hymenoptera: Apidae: Meliponini), we show that colonies will forage near their nests and allocate their foraging labor on a very fine spatial scale at an array of food sources placed close to the colony. We counted the foragers that a colony allocated to each of nine feeders containing 1.0, 1.5, or 2.0 M sucrose solution [31, 43, and 55% sucrose (wt/wt), respectively] at distances of 10, 15, and 20 m from the nest. A significantly greater number of foragers (2.6–5.3 fold greater) visited feeders placed 10 vs. 20 m away from the colony. Foraging allocation also corresponded to food quality. At the 10‐m feeders, 4.9‐fold more foragers visited 2.0 M as compared to 1.0 M sucrose feeders. Colony forager allocation thus responded to both differences in food distance and quality even when the travel cost was negligible compared to normal colony foraging distances (10 m vs. an estimated 800–1 710 m). For a nearby floral patch, this could result in unequal floral visitation and pollination.

Honey bee dance decoding and pollen-load analysis show limited foraging on spring-flowering oilseed rape, a potential source of neonicotinoid contamination

Neonicotinoid insecticides used to treat the seeds of bee-attractive crops occur in trace amounts in nectar and pollen. Possible harm to bees has resulted in the European Commission imposing a precautionary two-year moratorium on the use of neonicotinoids on bee-attractive crops from 2013. Recent laboratory and semi-field studies on colony-level effects of neonicotinoids assumed exclusive or near-exclusive levels of colony foraging on a treated crop. But is this a realistic assumption? Six honey bee (Apis mellifera) colonies were monitored over two springs (April–May 2011/12) in two neighbouring locations (urban and rural) in and near Brighton, UK, to quantify foraging on oilseed rape, the most widespread bee-attractive crop in the UK, by decoding waggle dances and trapping pollen. The study area was representative of the UK agricultural landscape in that the percentage area cover of the blooming oilseed rape fields around the rural location was similar to the national average (3.3–3.9% vs 3.1%). The amount of foraging on oilseed rape fields, as indicated by dance decoding, was variable, but low, 0–0.02% for the urban and 2–26% for the rural location. Almost all foraging, 91–99%, was within 2km, even though honey bees can forage at distances of over 10km. Pollen trapping in 2012 supported the dance decoding results, with oilseed rape pollen comprising 14% of pollen pellets collected by foragers from rural and 4% from urban hives. The results of this study have implications for policy as they cast doubt on the generality of some previous studies on colony-level effects on social bees conducted in laboratory and semi-field settings.

Spatially Heterogeneous Nest-Clearing Behavior Coincides with Rain Event in the Leaf-Cutting Ant Atta cephalotes (L.) (Hymenoptera: Formicidae).

Leaf-cutting ants of the genus Atta construct the probably largest nests among ants and are ecosystem engineers because they alter light and nutrient availability at nest sites. Besides creating canopy gaps in the forest, workers remove all vegetation from atop their nest mounds. Here, we examined the extent and spatial distribution of this nest-clearing behavior by transplanting Licania tomentosa seedlings on Atta cephalotes (Linnaeus) nest mounds in the Atlantic forest in northeast Brazil and documented defoliation patterns by the workers. Within 9 days, workers removed around 53% of the total leaf area planted per colony. All colonies showed a synchronized start of defoliation after a rain event in the fifth night after the seedlings had been transplanted. Defoliation increased with time elapsed since transplanting and with the number of entrances surrounding each seedling. In addition, workers started defoliation on the top of the mound. In contrast, the distance to the next entrance and the size of the seedling did not affect the defoliation pattern. Defoliation was not part of the colony foraging activities but was identified as an element of nest maintenance. Possible cues triggering nest-clearing behavior and the potential link between nest-clearing activities and the control of microclimate of ant nests are discussed.

Bacterial colony foraging for multi-mode product colour planning

In this work, in order to assist designer in colour planning during product development, an efficient synthesised evaluation model is presented to evaluate colour-combination schemes of multi-working modes products (MMP). A novel bacterial colony foraging (BCF) algorithm is proposed to search for the optimal colour-combination schemes of MMP based on the evaluation model. The proposed BCF extend original bacterial foraging algorithm to adaptive and cooperative mode by combining bacterial chemotaxis, cell-to-cell communication, and a self-adaptive foraging strategy. The experiment presents an exhaustive comparison of the proposed BCF and two successful bio-inspired search techniques, namely the genetic algorithm (GA) and particle swarm optimisation (PSO), on three MMP tested cases of different nature, namely a hair-drier with two-coloured areas and two working modes, and two arm-type aerial work platforms both two-coloured products while with two and three working modes, respectively. Simulation results demonstrate that the proposed method is feasible and efficient.

Trail pheromones: an integrative view of their role in social insect colony organization.

Trail pheromones do more than simply guide social insect workers from point A to point B. Recent research has revealed additional ways in which they help to regulate colony foraging, often via positive and negative feedback processes that influence the exploitation of the different resources that a colony has knowledge of. Trail pheromones are often complementary or synergistic with other information sources, such as individual memory. Pheromone trails can be composed of two or more pheromones with different functions, and information may be embedded in the trail network geometry. These findings indicate remarkable sophistication in how trail pheromones are used to regulate colony-level behavior, and how trail pheromones are used and deployed at the individual level.

Dancing bees improve colony foraging success as long-term benefits outweigh short-term costs.

Waggle dancing bees provide nestmates with spatial information about high quality resources. Surprisingly, attempts to quantify the benefits of this encoded spatial information have failed to find positive effects on colony foraging success under many ecological circumstances. Experimental designs have often involved measuring the foraging success of colonies that were repeatedly switched between oriented dances versus disoriented dances (i.e. communicating vectors versus not communicating vectors). However, if recruited bees continue to visit profitable food sources for more than one day, this procedure would lead to confounded results because of the long-term effects of successful recruitment events. Using agent-based simulations, we found that spatial information was beneficial in almost all ecological situations. Contrary to common belief, the benefits of recruitment increased with environmental stability because benefits can accumulate over time to outweigh the short-term costs of recruitment. Furthermore, we found that in simulations mimicking previous experiments, the benefits of communication were considerably underestimated (at low food density) or not detected at all (at medium and high densities). Our results suggest that the benefits of waggle dance communication are currently underestimated and that different experimental designs, which account for potential long-term benefits, are needed to measure empirically how spatial information affects colony foraging success.

How to not get stuck—Negative feedback due to crowding maintains flexibility in ant foraging

Ant foraging is an important model system in the study of adaptive complex systems. Many ants use trail pheromones to recruit nestmates to resources. Differential recruitment depending on resource quality coupled with positive feedback allows ant colonies to make rapid and accurate collective decisions about how best to allocate their work-force. However, ant colonies can become trapped in sub-optimal foraging decisions if recruitment to a poor resource becomes too strong before a better resource is discovered. Genetic algorithms and Ant Colony Optimisation heuristics can also suffer from being trapped in such local optima. Recently, two negative feedback effects were described, in which an increase in crowding (crowding negative feedback—CNF) or trail pheromones (pheromone negative feedback—PNF) caused a decrease in subsequent pheromone deposition. Using agent based simulations with realistic parameters I test whether these negative feedback effects can prevent simulated ant colonies from becoming trapped in sub-optimal foraging decisions. Colonies are presented with two food sources of different qualities, and these qualities switch part way through the experiment. When either no negative feedback effects are implemented or only PNF is implemented colonies are completely unable to refocus their foraging effort to the high quality feeder. However, when CNF alone is implemented at a realistic level 97% of colonies successfully refocus their foraging effort. This ability to refocus colony foraging efforts is due to the strong reduction of pheromone deposition caused by CNF. This suggests that CNF is an important behaviour enabling ant colonies to maintain foraging flexibility. However, CNF comes at a slight cost to colonies when making their initial foraging decision.

Stealing food from conspecifics: spatial behavior of kleptoparasitic Common Terns Sterna hirundo within the colony site

Amongst seabirds, kleptoparasitism is one of the most common types of exploitation in which individuals compete for food already procured by another forager. Here, we analyzed the within-colony spatial movements and foraging of transponder-marked Common Terns (Sterna hirundo) during the chick-rearing period in relation to the terns’ trophic strategy (kleptoparasitic vs. honest). Attendance patterns (time spent at the colony site per day, number and locations of resting platforms used) were compared between kleptoparasitic (N = 11) and honest individuals (N = 26). A total of 725 kleptoparasitic attacks were recorded during the chick-rearing period at the colony site. We found sex differences in the tactic used for stealing food and the area chosen for attacks: females attacked in the vicinity of their nest, while males attacked further away. Significant differences were found between both groups in the spatial pattern: kleptoparasites (particularly males) used more resting platforms and moved more widely across the colony site than honest individuals, and parasitic females were present in the colony longer during the day than honest ones. Our results show a differential use of the colony site dependent on the foraging strategy. Parasitic birds used the colony site as a foraging patch, monitoring the colony and looking for kleptoparasitic feeding opportunities without compromising their parental roles. In contrast, honest individuals spent much time outside the colony foraging for their chicks.

Bacterial colony foraging algorithm: Combining chemotaxis, cell-to-cell communication, and self-adaptive strategy

Inspired by the colony foraging behavior of Escherichia coli bacteria, this paper proposes a novel bacterial colony foraging optimization (BCFO) algorithm for complex optimization problems. The main idea of BCFO is to develop an adaptive and cooperative life-cycle model by combining bacterial chemotaxis, cell-to-cell communication, and self-adaptive searching strategies. The proposed BCFO is a more bacterially-realistic model that the bacteria split and die dynamically throughout the foraging process and the population size varies as the algorithm runs. The cell-to-cell communication enables the bacteria tumble towards better directions in the chemotactic steps to speed up convergence. With the self-adaptive searching strategy, each bacterium can maintain an appropriate balance between exploration and exploitation. Seven versions of BCFO combined by different strategies under the model were proposed and tested on both static and dynamic benchmarks. Then the proposed algorithm is applied to a real-world application of dynamic RFID network optimization. Statistical analysis of all these tests highlights the significant performance improvement due to the beneficial combination and shows that the proposed algorithm outperforms the reference algorithms.

Bacterial colony foraging optimization

This paper proposes a novel bacterial colony foraging (BCF) algorithm for complex optimization problems. The proposed BCF extend original bacterial foraging algorithm to adaptive and cooperative mode by combining bacterial chemotaxis, cell-to-cell communication, and a self-adaptive foraging strategy. The cell-to-cell communication enables the historical search experience sharing among the bacterial colony that can significantly improve convergence. With the self-adaptive strategy, each bacterium can be characterized by focused and deeper exploitation of the promising regions and wider exploration of other regions of the search space. A rigorous performance analysis is given where the proposed algorithm is benchmarked against four state-of-the-art reference algorithms using both a classical and a composition test function suites. The individual and collective bacterial foraging behaviors of the proposed algorithmic model are also studied. Statistical analysis of all these tests highlights the significant performance improvement due to the beneficial combination and shows that the proposed algorithm outperforms the reference algorithms.