Biology subjects

Chittka, L.

Publications and source records attributed to Chittka, L..

At least 19 recordsLinked to original sources

bioRxiv2025

Male bumblebees adapt foraging to environmental conditions to sustain mate-seeking efforts

Male bees navigate complex trade-offs between energy acquisition and reproductive signalling, yet their movement strategies remain understudied. Unlike workers that optimise foraging to support the colony, males forage independently to collect nectar and deposit sex pheromones on selected plants. Using high-resolution 3D tracking in an indoor flight cage, we investigated how the spatial arrangement of nectar and scent-marking sites, along with nectar availability, influence male movement patterns. We manipulated the distribution of feeders (artificial flowers) and scent-marking locations (branches), and varied nectar delivery rates, to assess effects on foraging, scent-marking, and patrolling. Males responded strongly to spatial structure: in clumped arrays with evenly spaced resources, movements between consecutive visits were shorter and more localised, while in dispersed arrays with irregular spacing, transitions were longer and more variable. The combination of dispersed spacing and low nectar availability imposed the highest foraging demands, resulting in fewer feeding events and reduced total feeding time. Despite these increased costs, males maintained consistent investment in reproductive behaviours, suggesting a prioritisation of mate-seeking over energy gain. Rather than reducing signalling, males adjusted their foraging strategy--favouring fewer but prolonged feeding bouts when nectar availability allowed. These findings reveal a unidirectional behavioural adjustment, in which foraging is modulated to sustain reproductive effort, and show how spatial resource structure and nectar availability together shape movement decisions in male pollinators. LAY SUMMARYMale bumblebees keep searching for mates even when food is scarce, adjusting how they forage to conserve energy. Using 3D tracking in a controlled environment, we found that males reduce foraging effort but maintain reproductive behaviours. This shows how animals balance survival and reproduction in changing environments, offering new insights into pollinator behaviour and resilience.

animal behavior and cognition↗

bioRxiv2025

Synaptic high-frequency jumping synchronises vision to high-speed behaviour

During high-speed behaviour, animals must synchronise perception and action despite rapid environmental and self-generated motion. How neural systems achieve such precision remains unclear. Here we show how the housefly (Musca domestica) maintains visual accuracy during fast motion. Using intracellular and photomechanical recordings during saccade-like stimulation, we traced information flow from photoreceptors to large monopolar cells (LMCs). Visual neurons achieved record-high information sampling ([~]2,500 bits{middle dot}s-1) and synaptic transmission ([~]4,100 bits{middle dot}s-1), far exceeding previous estimates. We identify a previously unknown mechanism - synaptic high-frequency jumping - in which photoreceptor-LMC synapses dynamically shift transmission toward higher frequencies during saccades, extending visual bandwidth to [~]1,000 Hz, effectively eliminating synaptic delays, and quadrupling classical flicker-fusion limits ([~]230 Hz). Behavioural experiments show flies respond synchronously within [~]13-20 ms, even before photoreceptor responses peak. A biophysically realistic model reveals how photomechanical-stochastic-refractory quantal sampling co-adapts with saccadic behaviour: through self-motion, flies efficiently translate image motion into temporally-precise, predictive high-speed vision.

neuroscience↗

bioRxiv2025

Bumblebee string-pulling skill spreads between colonies under open diffusion conditions

Socially-transmitted behavioural traits can, if they persist in a group of animals over time, give rise to locally-adapted phenotypes that can enhance survival. This capacity is widespread through the animal kingdom, and forms the foundation of cultural inheritance. While social learning is well-documented among insects, and particularly in social insects such as bumblebees, the extent to which such behaviours can spread beyond initial kin groups and persist over time remains largely unknown. String-pulling is a non-natural foraging behaviour where bees must manipulate a string to extract an out-of-reach artificial flower and collect a reward, and has previously shown to spread via social learning. However, this was demonstrated only in highly controlled paired-dyad settings, where interactions between bees were strictly limited. Here, we show that string-pulling can spread both within and between bumblebee colonies and persist over time, under previously-untested open diffusion conditions. These are of greater ecological validity compared with classical paired dyad paradigms, and involve the seeding of a manually-trained demonstrator into a group of naive conspecifics. From this single point of origin, string-pulling behaviour spread rapidly within original, primary colonies. Once the behaviour was established in the primary colonies, secondary colonies were introduced, and string-pulling was also acquired by these new foragers. Furthermore, string-pulling was acquired through individual trial-and-error learning by a small number of bees in control colonies, which lacked trained demonstrators. These results confirm and build upon previous findings in bumblebees, and contribute to a growing body of evidence suggesting that social learning enables animals to establish local behavioural adaptations in the absence of the computational power provided by large brains.

animal behavior and cognition↗

bioRxiv2025

Duration discrimination in the bumblebee Bombus terrestris

The ability to process temporal information is crucial for animal activities like foraging, mating, and predator avoidance. While circadian rhythms have been extensively studied, there is limited knowledge regarding how insects process durations in the range of seconds and sub-seconds. This study aimed to assess bumblebees (Bombus terrestris) ability to differentiate the durations of flashing lights, and use this information in a free-foraging task. Bees were trained to associate either the long or short-duration stimulus with a sugar reward versus an unpalatable solution until reaching a criterion, and then tested without sucrose solution with the same stimuli. In Experiment 1, we tested the ability to discriminate between a long stimulus (2.5 or 5 seconds) vs a short stimulus (0.5 or 1 second). The bees learned to discriminate between the two stimuli. To check whether bees solve the task without using the absolute difference in proximal stimulation as a cue, we ran a second experiment. In Experiment 2, the flashing stimuli were presented for the same total amount of time in a cycle. Bees could discriminate between durations even when the overall amount of stimulation in each presentation cycle was the same. This shows general learning abilities in bumblebees, that can discriminate seconds/subseconds intervals in visual flashing stimuli. This reveals an insects ability to use non-naturalistic stimuli and temporal cues in free foraging.

animal behavior and cognition↗

bioRxiv2024

Does bumblebee preference of continuous over interrupted strings in string-pulling tasks indicate means-end comprehension?

Bumblebees (Bombus terrestris) have been shown to engage in string-pulling behavior to access rewards. The objective of this study was to elucidate whether bumblebees display means-end comprehension in a string-pulling task. We presented bumblebees with two options: one where a string is connected to an artificial flower containing a reward and the other presenting an interrupted string. Bumblebees displayed a consistent preference for pulling connected strings over interrupted ones after training with a stepwise pulling technique. When exposed to novel string colors, bees continued to exhibit a bias towards pulling the connected string. This suggests that bumblebees engage in featural generalization of the visual display of the string connected to the flower in this task. If the view of the string connected to the flower was restricted during the training phase, the proportion of bumblebees choosing the connected strings significantly decreased. Similarly, when the bumblebees were confronted with coiled connected strings during the testing phase, they failed to identify and reject the interrupted strings. This finding underscores the significance of visual consistency in enabling the bumblebees to perform the task successfully. Our results suggest that bumblebees ability to distinguish between continuous strings and interrupted strings relies on a combination of image matching and associative learning, rather than means-end understanding. These insights contribute to a deeper understanding of the cognitive processes employed by bumblebees when tackling complex spatial tasks.

ecology↗

bioRxiv2024

Noxious stimulation induces self-protective behaviour in bumblebees

Self-grooming directed towards a noxiously-stimulated body part is one indicator that an animal may feel pain. In insects, the lack of evidence for such behaviour has been widely argued to reflect the absence of pain experiences. Here, we tested whether bumblebees (Bombus terrestris) selectively groom one of their antennae that was touched with a noxiously-heated (65 {square}C) probe. In the first two minutes after being touched with the noxiously-heated probe, bees groomed their touched antenna a) more than their untouched antenna, b) more than bees that were touched on the antenna with an unheated probe, and c) more than control (untouched) bees groomed either of their antennae. Our results clearly show that bumblebees can direct grooming towards a site of noxious stimulation. Our findings thus refute arguments that claim that insects do not feel pain because of their lack of displaying this behaviour.

animal behavior and cognition↗

bioRxiv2023

Social learning of a challenging two-step action sequence fulfils key criteria of cumulative culture in an insect

Culture in non-human animals refers to behaviour that is socially learned and persists within a population over time. Human culture is notable in that it is cumulative: new innovations have built on previous ones over thousands of years. As a result, what is acquired via social learning often goes far beyond the capacity of any individual to independently discover it during their lifetime1-3. To date, no previous study has convincingly demonstrated this phenomenon in a non-human animal. Here, we show that bumblebees can learn from a trained demonstrator to open a novel, 3D-printed two-step puzzle box to obtain food rewards, even though they fail to do so independently. Experimenters were unable to train demonstrators to perform the unrewarded first step of the behaviour without providing a temporary reward linked to this action: the reward then being removed during later stages of training. However, a third of naive observers learned to open the two-step box from these demonstrators, without ever having been rewarded after the first step. This suggested that social learning might permit the acquisition of behaviours too complex to "re-innovate" via individual learning. Furthermore, naive bees failed to open the box despite extended exposure over the course of 12 days. The temporal and spatial distance of the unrewarded first step from the reward appeared to inhibit acquisition of two-step box-opening via individual associative learning, but this limitation was overcome by the presence of a trained conspecific. To our knowledge, these results make bumblebees the first animal to demonstrate the ability to socially learn a behaviour that is beyond their ability to innovate individually. This finding challenges the prevailing opinion of the field, which generally considers cumulative culture, which is built on this capacity, to be unique to humans.

animal behavior and cognition↗

bioRxiv2023

An insect's view of a numerosity illusion: a simple strategy may explain complex numerical performance in bumblebees

Despite some similarities in numerical abilities among vertebrates, animals seem to differ with respect to the perceptual factors underlying numerical estimation. This is particularly evident in the case of numerosity illusions, a type of illusory phenomena elicited by the spatial arrangement of the elements that compose it. We investigated whether an insect experiences the most famous numerosity illusion, the Solitaire Illusion. Bumblebees (Bombus terrestris audax) presented with two mixed arrays containing magenta and yellow dots were trained to select the array containing the larger number of a target colour (either magenta or yellow). In the test phases, bumblebees were presented with sets of stimuli differing in the numerical ratio, including the illusory arrays: in one array, magenta dots were centrally located (yellow dots in the perimeter), whereas in the other one, magenta dots were located in the perimeter (yellow dots in the centre). Bees discriminated up to a ratio of 0.78 (14 vs. 18). Video analyses showed that bumblebees sequentially scanned the stimuli before making a choice. Bumblebees required longer scanning time for patterns with smaller numbers of reinforced colour dots, suggesting that bumblebees spent longer time on searching for more information or finding a reinforced arrangement of spatial dots before making an accurate decision. In the presence of the "illusion arrangement", bees behaved in a manner consistent with misperception of numerosity, overestimating the number of centrally located dots. The spatial configuration of the stimuli influenced how the patterns were assessed: bees examined the clustered reinforced colour dots longer. Flying paths analysis suggested that bumblebees followed the paths formed by similar colour dots rather than counting each dot to make a numerical discrimination. These results challenge the notion that visual illusions can be inferred simply from evaluating choices of different visual patterns and reinforce the idea that multiple strategies can potentially be used to achieve seemingly similar cognitive outcomes. Detailed analyses of decision-making processes are essential to deduce the cognitive strategies underpinning discrimination tasks, whether they are numerical or other visual tasks.

animal behavior and cognition↗

bioRxiv2023

A neuromorphic model of active vision shows spatio-temporal encoding in lobula neurons can aid pattern recognition in bees

Bees' remarkable visual learning abilities make them ideal for studying active information acquisition and representation. Here, we develop a biologically inspired model to examine how flight behaviours during visual scanning shape neural representation in the insect brain, exploring the interplay between scanning behaviour, neural connectivity, and visual encoding efficiency. Incorporating non-associative learning, adaptive changes without reinforcement, and exposing the model to sequential natural images during scanning, we obtain results that closely match neurobiological observations. Active scanning and non-associative learning dynamically shape neural activity, optimising information flow and representation. Lobula neurons, crucial for visual integration, self-organise into orientation-selective cells with sparse, decorrelated responses to orthogonal bar movements. They encode a range of orientations, biased by input speed and contrast, suggesting co-evolution with scanning behaviour to enhance visual representation and support efficient coding. To assess the significance of this spatiotemporal coding, we extend the model with circuitry analogous to the mushroom body, a region linked to associative learning. The model demonstrates robust performance in pattern recognition, implying a similar encoding mechanism in insects. Integrating behavioural, neurobiological, and computational insights, this study highlights how spatiotemporal coding in the lobula efficiently compresses visual features, offering broader insights into active vision strategies and bio-inspired automation.

neuroscience↗

bioRxiv2022

The establishment and transmission of novel foraging techniques indicates a capacity for culture in bumblebees (Bombus terrestris).

The astonishing behavioural repertoires of social insects have been thought largely innate, but these insects have repeatedly demonstrated remarkable capacities for both individual and social learning. Using the bumblebee Bombus terrestris as a model, we developed a two-option puzzle box task and used open diffusion paradigms to observe the transmission of novel, non-natural foraging behaviours through populations. Box-opening behaviour spread through colonies seeded with a demonstrator trained to perform one of the two possible behavioural variants, and the observers acquired the demonstrated variant. This preference persisted among observers even when the alternative technique was discovered. In control diffusion experiments that lacked a demonstrator, some bees spontaneously opened the puzzle boxes but were significantly less proficient than those that learned in the presence of a demonstrator. This suggested that social learning was crucial to proper acquisition of box-opening. Additional open diffusion experiments where two behavioural variants were initially present in similar proportions ended with a single variant becoming dominant, due to stochastic processes. This could lead to the emergence and maintenance of local cultural variation. These results suggest that bumblebees, like mammals and birds, may have the capacity for culture and to sustain cultural variation.

animal behavior and cognition↗

bioRxiv2022

Placement of new comb cells built by honeybees is guided by sub-cell scale features to align with the existing layout

The comb of honeybees has long been the subject of curiosity and admiration. Its noteworthy features include the even hexagonal layout and the sharing of walls, both side walls and bases, that provide a maximum storage volume while using a minimum of wax for its construction. The efficiency of its structure relies on a regular layout where cells are positioned correctly relative to each other. Each new cell should be placed exactly between two previously constructed cells, a task made more difficult by the incomplete nature of cells at the edge of comb where the new ones are to be built. By offering bees shaped wax stimuli we have identified sub-cell scale shapes that trigger certain patterns of behaviour by honeycomb construction workers. These behaviours, we found, cause the creation of a new cell to be aligned to small concavities and for cell walls to be built mid-way between two such stimuli. We show that by responding to the form of partially constructed comb, the bees build the next iteration of cells and walls at the locations necessary for the repeated pattern of cells to continue.

animal behavior and cognition↗

bioRxiv2022

Honeycomb cell walls are plastic; initially built as curves the walls are reformed by bees during subsequent construction

Honeybee comb comprises recognisable hexagons, each with straight sides. Not only are the cell side-walls flat, but so too are those that form the base of cells; base faces which are shared with cells on the opposite face of the comb. The mechanism by which bees build cells with flat sides has been the subject of speculation for centuries, but it has been conjectured by Kepler, Darwin as well as more recent researchers that bees build cylindrical cells that are transformed into flat sided prisms, without consensus as to the process by which this is achieved. By offering bees shaped wax stimuli and observing the comb that was built upon them, we have shown that under certain conditions walls will be curved and others where walls are reformed to be flat. A wall of a cell, be it a side-wall or a face of the base, with no other cell beyond it will be built as a convex curve whereas a wall with a cell to both sides will be formed flat. Furthermore, we show that these walls are plastic; walls that were initially built curved were re-shaped to be flat once a second adjacent cell had been built.

animal behavior and cognition↗

bioRxiv2022

Early-stage honeycomb contains non-uniform cells which are subsequently optimised

The hexagonal structure of honeycomb maximises storage volume while minimising the amount of wax required for its construction. How honeybee builders achieve this geometry, however, remains unclear. Previously, our group identified behavioural patterns that were triggered in builders when they encountered certain sub-scale features associated with partially constructed comb, which resulted in the alignment of new cells to small concavities and the construction of cell walls between two of these stimuli. This caused new cells to be built in the proper locations without the need for explicit instructions . Here, we investigated whether the hexagonal geometry of honeycomb cells resulted from the dense packing of cells that would otherwise have been circular tubes. We hypothesised that the reaction of a builder to a cell that is not fully enclosed by other cells would be an attempt to maximise the internal space by excavating and re-forming the surrounding walls to create a cylindrical interior. However, the creation of a cylindrical cell would be thwarted by the activities of workers within adjacent cells also acting according to these rules. Eventually an equilibrium will emerge with walls that meet at a junction arranged so that the available angular range (360{degrees}) is sub- divided equally between the cells that meet at the junction (typically, internal angles of 120{degrees} when three cells meet). To test this hypothesis, we offered wax stimuli to comb-building honeybees, shaped to encourage or to constrain the construction of comb cells, recording the bees progress. We found that at an early stage cells could be an irregular shape with curved walls and unequal wall lengths and corner angles, however, when allowed further time and unconstrained access the workers reshaped the cells achieving significantly greater regularity.

animal behavior and cognition↗

bioRxiv2022

Bumblebees retrieve only the ordinal ranking of foraging options when comparing memories obtained in distinct settings

Are animals preferences determined by absolute memories for options (e.g., reward sizes) or by their remembered ranking (better/worse)? The only studies examining this question suggest humans and starlings utilize memories for both absolute and relative information. We show that bumblebees make decisions using only memories of ordinal comparisons. After learning to discriminate pairs of different flowers by sucrose concentration, bumblebees preferred flowers (in novel pairings) with 1) higher ranking over equal absolute reward, 2) higher ranking over higher absolute reward, and 3) identical qualitative ranking but different quantitative ranking equally. Despite these suboptimal choices, bumblebees found the optimal option in an ecologically relevant foraging task. Our results illuminate a divergent mechanism of learned preferences that may have arisen from adaptations to bumblebees natural environment.

animal behavior and cognition↗

bioRxiv2022

Motivational trade-offs in bumblebees

Mammals can supress their nociceptive responses to prioritise other important responses via endogenous modulation from the brain. It is well established that insects display nociception, but not whether the insect brain can modulate nociceptive processing. To address this question, we investigated whether bumblebees (Bombus terrestris) attraction to higher sucrose solution concentrations reduces their avoidance of noxious heat. Bees were given the choice between either unheated or noxiously-heated (55{degrees}C) feeders with different sucrose concentrations. The feeders were associated with colour stimuli to act as conditioned cues. Bees fed more from higher sucrose concentration heated feeders than lower sucrose concentration unheated feeders. Further, bees "testing out" of feeders (landing but not feeding) reduced as the experiment progressed, demonstrating that conditioned colour cues informed the bees behaviour. Therefore, bees trade off competing conditioned motivational stimuli to modulate nocifensive behaviour, suggesting a form of pain perception.

animal behavior and cognition↗

bioRxiv2022

Discrimination of edge orientation by bumblebees

Simple feature detectors in the visual system, such as edge-detectors, are likely to underlie even the most complex visual processing, so understanding the limits of these systems is crucial for a fuller understanding of visual processing. We investigated the ability of bumblebees (Bombus terrestris) to discriminate between differently angled edges. In a multiple-choice, "meadow-like" scenario, bumblebees successfully discriminated between angled bars with 7{degrees} differences, significantly exceeding the previously reported performance of eastern honeybees (Apis cerana, limit: 15{degrees}). Neither the number of choices required to learn, nor the bees final discrimination performance were affected by the angular orientation of the training bars, indicating a uniform performance across the visual field. Previous work has found that, in dual-choice tests, eastern honeybees cannot reliably discriminate between angles with less than 25{degrees} difference, suggesting that performance in discrimination tasks is affected by the training regime, and doesnt simply reflect the perceptual limitations of the visual system. We used high resolution LCD monitors to investigate the limits of bumblebees angular resolution in dual-choice experiments. Bumblebee could still discriminate 7{degrees} angle differences under such conditions (exceeding the previously reported limit for Apis mellifera, of 10{degrees}, as well as that of A. cerana), eventually reaching similar levels of accuracy, but required longer learning periods than under multiple-choice conditions. Bumblebees show impressive abilities to discriminate between angled edges, performing better than two previously tested species of honeybee. This high performance may, in turn, support complex visual processing in the bumblebee brain.

animal behavior and cognition↗

bioRxiv2021

Genomic signatures of recent adaptation in a wild bumblebee

Behavioral experiments and analyses of observation records have shown that environmental changes threaten insect pollinators, creating risks for agriculture and ecosystem stability. Despite their importance, we know little about how wild insects or other animals can adapt in response to environmental pressures. To understand the genomic bases of adaptation in an ecologically important pollinator, we analyzed genomes of Bombus terrestris bumblebees collected across Great Britain. We reveal extensive genetic diversity within this population, and strong signatures of recent adaptation throughout the genome. More specifically, we find that selection recently affected key processes underpinning environmental interactions, including neurobiology, wing development, and response to xenobiotics. We also discover unusual features of the genome, including a 53-gene region that lacks genetic diversity in many bee species, and a horizontal gene transfer from a Wolbachia bacteria. The genetic diversity and gene flow we observe for this species could support its resilience to ongoing and future challenges. Overall, we provide important insight on the genetic health of an ecologically and economically important pollinator and reveal mechanisms by which it has recently adapted. The approach we used could help to understand how species differ in their adaptive potential, and to develop conservation strategies for those most at risk.

evolutionary biology↗

bioRxiv2021

Automated video tracking and flight analysis show how bumblebees solve a pattern discrimination task using active vision

Active vision, the ability of the visual system to actively sample and select relevant information out of a visual scene through eye and head movements, has been explored in a variety of animal species. Small-brained animals such as insects might rely even more on sequential acquisition of pattern features since there might be less parallel processing capacity in their brains than in vertebrates. To investigate how active vision strategies enable bees to solve visual tasks, here, we employed a simple visual discrimination task in which individual bees were presented with a multiplication symbol and a 45{degrees} rotated version of the same pattern ("plus sign"). High-speed videography of unrewarded tests and analysis of the bees flight paths shows that only a small region of the pattern is inspected before successfully accepting a target or rejecting a distractor. The bees scanning behaviour of the stimuli differed for plus signs and multiplication signs, but for each of these, the flight behaviour was consistent irrespective of whether the pattern was rewarding or unrewarding. Bees typically oriented themselves at ~{+/-}30{degrees} to the patterns such that only one eye had an unobscured view of stimuli. There was a significant preference for initially scanning the left side of the stimuli. Our results suggest that the bees movement may be an integral part of a strategy to efficiently analyse and encode their environment. Summary statementAutomated video tracking and flight analysis is proposed as the next milestone in understanding mechanisms underpinning active vision and cognitive visual abilities of bees.

animal behavior and cognition↗