Archive for the ‘Papers from 2017’ Category

December Catch-up

Happy New Year to everybody. The first post of 2018 is a catch-up of the papers I didn’t find time to cover in December. Normal service resumed shortly.

The desert ant Cataglyphis fortis inhabits the salt pans of Tunisia. Individual ants leave the nest for foraging trips that can cover distances of more than 1,500 m. Homing ants use path integration, but they also rely on visual and olfactory nest-defining cues to locate the nest entrance. However, nest cues can become ambiguous when they are ubiquitous in the environment. Here we show how ants behave during the nest search when the same cues occur at the nest and along the route. Homing ants focused their search narrowly around a visual or olfactory cue that in training they had experienced only at the nest. However, when ants were trained to the same cue not only at the nest but also repeatedly along the foraging route, they later exhibited a less focused search around the cue. This uncertainty was eliminated when ants had a composite cue at the nest that consisted of two components, one unique to the nest and another that also occurred along the route. Here, the ants focused their search on that part of the binary blend that was presented only at the nest and ignored the other, ubiquitous component. Ants thus not only seem to be able to pinpoint their nest by following learned visual and olfactory cues, but also take into account which cues uniquely specify the nest and which, due to their ubiquity, are less informative and so less reliable.

Huber, R., & Knaden, M. (2017). Homing Ants Get Confused When Nest Cues Are Also Route Cues. Current Biology.

Animals that visit multiple foraging sites face a problem, analogous to the Travelling Salesman Problem, of finding an efcient route. We explored bumblebees’ route development on an array of fve artifcial fowers in which minimising travel distances between individual feeders conficted with minimising overall distance. No previous study of bee spatial navigation has been able to follow animals’ movement during learning; we tracked bumblebee foragers continuously, using harmonic radar, and examined the process of route formation in detail for a small number of selected individuals. On our array, bees did not settle on visit sequences that gave the shortest overall path, but prioritised movements to nearby feeders. Nonetheless, fight distance and duration reduced with experience. This increased efciency was attributable mainly to experienced bees reducing exploration beyond the feeder array and fights becoming straighter with experience, rather than improvements in the sequence of feeder visits. Flight paths of all legs of a fight stabilised at similar rates, whereas the frst few feeder visits became fxed early while bees continued to experiment with the order of later visits. Stabilising early sections of a route and prioritising travel between nearby destinations may reduce the search space, allowing rapid adoption of efcient routes.

Woodgate, J. L., Makinson, J. C., Lim, K. S., Reynolds, A. M., & Chittka, L. (2017). Continuous Radar Tracking Illustrates the Development of Multi-destination Routes of Bumblebees. Scientific reports, 7(1), 17323.

Desert ants that forage solitarily continually update their position relative to the nest through path integration. This is accomplished by combining information from their celestial compass and pedometer. The path integration system can adapt when memories of previous inbound routes do not coincide with the outbound route, through vector calibration. Here, we test the speed and limit of vector calibration in the desert ant Melophorus bagoti by creating directional conflicts between the inbound and outbound routes (45°, 90°, 135°, 180°). The homeward vector appears to calibrate rapidly after training with shifts occurring after three foraging trips, yet the limit of the vector’s plasticity appears to be a maximum of 45°. At 45° conflicts, the vector calibrates the full 45°, suggesting dominance of the previous inbound memories over the outbound cues of the current trip. Yet at larger directional conflicts, vector shifts after training diminish, with foragers in the 90° and 135° conditions showing smaller intermediate shifts between the inbound memories and the current outbound vector. When the conflict is at its maximum (180°), foragers show no calibration, suggesting the outbound vector is dominant. Panorama exposure during training appears to aid foragers orienting to the true nest, but this also appears limited to about a 45° shift and does not improve with training.

Freas, C. A., & Cheng, K. (2017). Limits of vector calibration in the Australian desert ant, Melophorus bagoti. Insectes Sociaux, 1-12.

Categories: Papers from 2017

A batch of JEB papers

We’ve had a nice batch of JEB papers all appear recently. So here they are all together.

Firstly, Barron and Plath discuss how the waggle dance of honeybees might be controlled in the neural circuits of the bee brain. This is fascinating stuff as it is one of the great mysteries in insect behaviour how bees can move information between different frames of reference. Secondly, Lobecke et al. look at the learning flights of bumblebees via an analysis of the fine-grain motor motifs. They find that learning flights don’t show the expected consistency of structure that might have been assumed to be useful for learning the location of the nest entrance. This variability leads the authors to suggest that the bee is acquiring a dynamic snapshot, as presumably a static snapshot would require more consistency across the views ‘acquired’ during the learning flight. Finally, a paper from us at Sussex. We investigated the relationship between Path Integration and visual information after first describing how PI controlled paths show a systematic speed variation, with higher speeds shown at greater distances from the next. We found that at lower speeds (i.e. nearer the nest) visual cues (either familiar or novel) have a greater impact on ants paths.

Barron, A. B., & Plath, J. A. (2017). The evolution of honey bee dance communication: a mechanistic perspective. Journal of Experimental Biology, 220(23), 4339-4346.

Lobecke, A., Kern, R., & Egelhaaf, M. (2017). Taking a goal-centred dynamic snapshot as a possibility for local homing in initially naïve bumblebees. Journal of Experimental Biology, jeb-168674.

Buehlmann, C., Fernandes, A. S. D., & Graham, P. (2017). The interaction of path integration and terrestrial visual cues in navigating desert ants: what can we learn from path characteristics?. Journal of Experimental Biology, jeb-167304.

Categories: Papers from 2017

The birds and the bees

Well, I’ve been waiting for a good while to use that BLOG title and now the perfect paper has come along. Pritchard et al. discuss the similarities in foraging ecology between bees and hummingbirds, which are strong enough to suggest that we may see convergent evolution in the cognitive adaptations for foraging and spatial behaviour. Furthermore, and particularly nice to see for us, the authors discuss the ways in which conceptual and technical advances from insect navigation research are now, finally, having traction in studies of birds.

Pritchard, D. J., Ramos, M. T., Muth, F., & Healy, S. D. (2017). Treating hummingbirds as feathered bees: a case of ethological cross-pollination. Biology letters, 13(12), 20170610.

Categories: Papers from 2017

Ant-bots and compass sensors

A fundamental principle behind this BLOG is that the study of insect spatial behaviour is inherently interesting to roboticists. This is because the sensors and behaviours are tuned for navigation and little else. Following conference season, we have a bumper crop of such biorobotic projects. Two papers from the Marseille team detail the development of a hexapod robot and then the deployment of a compass sensor inspired by the specialised ommatidia in the dorsal rim area of insect eyes. Wolfgang Stürzl also presents the development of a new compass sensor. In this case inspired by the ocelli of insects, which are 3 simple dorsally facing ‘eyes’.

Julien Dupeyroux, Julien Diperi, Marc Boyron, Stéphane Viollet, Julien Serres. A novel insect-inspired optical compass sensor for a hexapod walking robot. IROS 2017 – IEEE/RSJ International Conference on Intelligent Robots and Systems, Sep 2017, Vancouver, Canada.

Dupeyroux, J., Passault, G., Ruffier, F., Viollet, S., & Serres, J. (2017). Hexabot: a small 3D-printed six-legged walking robot designed for desert ant-like navigation tasks. In IFAC Word Congress 2017.

W. Stürzl (2017). A Lightweight Single-Camera Polarization Compass With Covariance Estimation. In Proceedings of the IEEE International Conference on Computer Vision (ICCV), pp. 5353-5361

Categories: Papers from 2017

From the field to VR (and back again?)

The last month has seen the publication of a pair of papers describing open-source tools solving two key problems faced by field experimentalists. Firstly, at the recent ICCV2017 workshop on animal tracking, Risse et al presented Habitracks – an open-source software to automatically track small animals in videos recorded in natural habitats. Fully automatic and highly accurate tracking was shown for a number of species including ants, bees, and dung-beetles in video recording from field experiments. In the second work, the same team present Habitat3D, a software tool that automatically integrates multiple laser scans of natural environments into a single photorealistic mesh. This then allows easy reconstruction of animal views using standard graphics packages or the presentation of realistic VR worlds to insects in track-ball experiments. Combined these tools bring us a step closer to realising the goal of reconstructing the actual visual perspective of animals allowing validation of hypothesis in realistic environments.

Risse, B., Mangan, M., Del Pero, L., & Webb, B. (2017). Visual Tracking of Small Animals in Cluttered Natural Environments Using a Freely Moving Camera. The IEEE International Conference on Computer Vision (ICCV)(pp. 2840-2849).

Risse, B., Mangan, M., Stürzl, W., & Webb, B. (2018). Software to convert terrestrial LiDAR scans of natural environments into photorealistic meshes. Environmental Modelling & Software, 99, 88-100.

Categories: Papers from 2017

Learning about sky compasses

The early days of an ant forager’s life present a succession of learning challenges. Ants must learn about the ephemeris function for their part of the world and the current time of year. They also have to learn about the visual surrounds of their nest. Learning walks with specific structure are key to this. A key part of learning walks in desert ant species from visually rich environments is that ants fixate the nest at specific points. Here, Grob et al look at how these precise fixations might depend on celestial information. Interestingly, the precision of fixations is maintained even when polarisation and sun position information is removed. However, natural polarization information via the UV channel is necessary for the triggering of brain changes in these new foragers. Learning walks with natural polarisation and UV lead to brain changes in both central complex and the visual input region of the mushroom body. This gives some clues as to the neural underpinning of early ‘career’ learning in new foragers.

Grob R, Fleischmann PN, Grübel K, Wehner R and Rössler W (2017) The Role of Celestial Compass Information in Cataglyphis Ants during Learning Walks and for Neuroplasticity in the Central Complex and Mushroom Bodies. Front. Behav. Neurosci. 11:226. doi: 10.3389/fnbeh.2017.00226

Categories: Papers from 2017

Neural control of flight

With each passing month, we learn more about the neural underpinnings of navigation and orientation behaviours. Here is another piece in the jigsaw:

Abstract: The impressive repertoire of honeybee visually guided behaviors, and their ability to learn has made them an important tool for elucidating the visual basis of behavior. Like other insects, bees perform optomotor course correction to optic flow, a response that is dependent on the spatial structure of the visual environment. However, bees can also distinguish the speed of image motion during forward flight and landing, as well as estimate flight distances (odometry), irrespective of the visual scene. The neural pathways underlying these abilities are unknown. Here we report on a cluster of descending neurons (DNIIIs) that are shown to have the directional tuning properties necessary for detecting image motion during forward flight and landing on vertical surfaces. They have stable firing rates during prolonged periods of stimulation and respond to a wide range of image speeds, making them suitable to detect image flow during flight behaviors. While their responses are not strictly speed tuned, the shape and amplitudes of their speed tuning functions are resistant to large changes in spatial frequency. These cells are prime candidates not only for the control of flight speed and landing, but also the basis of a neural ‘front end’ of the honeybee’s visual odometer.

Ibbotson, M. R., Hung, Y. S., Meffin, H., Boeddeker, N., & Srinivasan, M. V. (2017). Neural basis of forward flight control and landing in honeybees. Scientific Reports (Nature Publisher Group), 7, 1-15.

Categories: Papers from 2017