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Getting blown away and then getting back

Many animals have to try and recover from unintended displacements caused by wind. Many flying insects have super fast optic flow mechanisms that are used to ensure that flight direction is as intended. For an ant that is caught by a sudden gust and then tumbles across the surface, an immediate and accurate correction is impossible. What’s more the tumbling will ensure that calculating the unintended displacement from the experienced optic flow would also be almost impossible. However, we know that ants can make sensible corrections from such displacements. Wystrach and Schwarz have demonstrated this by blowing ants away from a feeder and then releasing them from an unfamiliar location. From these locations, ants adopted a direction that was opposite to the direction of displacement. As ants were blown away it was noted that they respond to wind by lowering their centre of mass and ‘clutching’ the substrate. Ants that ‘clutched’ but were not blown away would still take a direction opposite to the wind when released on unfamiliar ground; Whereas ants denied a view of the sky whilst clutching did not show purposeful headings on release. From these elegant manipulations we learn that ants are able to integrate their current facing direction – information acquired from a geocentric compass – with the egocentric perception of the wind. This multi-modal calculation gives ants the geocentric direction of the wind and allows them to counter this when the displacement is over. Neat.

A. Wystrach, S. Schwarz (2013) Ants use a predictive mechanism to compensate for passive displacements by wind Current Biology – 16 December 2013 (Vol. 23, Issue 24, pp. R1083-R1085)

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Categories: Papers from 2013

How do ants integrate information sources?

The problem of integrating conflicting information is at the heart of how animals deal adaptively with their environment. One accessible behaviour within which to ask questions about cue-integration is the compass system of a navigating insect. We know that multiple redundant sources of information input to the celestial compass systems of ants and bees. Here, Lebhardt and Ronacher investigate conflicts within this set of cues.

Abstract: Desert ants, Cataglyphis fortis, perform large-scale foraging trips in their featureless habitat using path integration as their main navigation tool. To determine their walking direction they use primarily celestial cues, the sky’s polarization pattern and the sun position. To examine the relative importance of these two celestial cues, we performed cue conflict experiments. We manipulated the polarization pattern experienced by the ants during their outbound foraging excursions, reducing it to a single electric field (e-)vector direction with a linear polarization filter. The simultaneous view of the sun created situations in which the directional information of the sun and the polarization compass disagreed. The heading directions of the homebound runs recorded on a test field with full view of the natural sky demonstrate that none of both compasses completely dominated over the other. Rather the ants seemed to compute an intermediate homing direction to which both compass systems contributed roughly equally. Direct sunlight and polarized light are detected in different regions of the ant’s compound eye, suggesting two separate pathways for obtaining directional information. In the experimental paradigm applied here, these two pathways seem to feed into the path integrator with similar weights.

 

Lebhardt, F., & Ronacher, B. (2013). Interactions of the polarization and the sun compass in path integration of desert ants. Journal of Comparative Physiology A, 1-10.

Categories: Papers from 2013

Meta-cognition?

It is well understood that more efficient decision making can be achieved if an agent holds estimates of uncertainty alongside the primary-information used to make a decision. Incorporating uncertainty into decision making would seem to be a sensible thing for insects to do, however there is little evidence to point to this. Perry and Barron address this issue by looking at the choices of bees in an opt-out paradigm. In this style of  experiment, bees are rewarded for correct choices and punished for incorrect choices. Therefore, when the decision is difficult, an opportunity to opt-out may be adaptive. This paper reports that individual bees do indeed take the opt-out option in trials when a choice is difficult, thus suggesting that they are capable of monitoring uncertainty.

The exact mechanisms which lead to this behaviour are unclear. The authors discuss that it is hard to “[determine] whether simple invertebrates monitor uncertainty in decision making—or simply appear to do so”. This dichotomy seems to be questioning whether bees are using a cognitive strategy or not – which is of course an interesting question. But in some situations, “simply appearing to do something” is just the same as “doing something”. Understanding how apparent meta-cognition might emerge from the implementation of associative sensori-motor learning would be a valuable outcome and perhaps highlight the value of “bottom-up”  approaches to animal cognition.

Perry, C. J., & Barron, A. B. (2013). Honey bees selectively avoid difficult choices. Proceedings of the National Academy of Sciences, 110(47), 19155-19159.

Categories: Papers from 2013

Wiggle while you walk!

From behavioural studies we have been able to determine some of the general properties of how vision is used by navigating insects. However, the fine-grained sensori-motor implementation of visual strategies is less clear. Visual navigation presents interesting problems for walking ants in particular because their viewing direction is fixed relative to their long axis and therefore walking direction. Consequently, the characteristic wiggly path of an ant will lead to large changes in the ant’s view of the world, even if the ant’s path is direct overall. Lent et al. have looked at the fine details of this situation for wood ants navigating towards a visually defined goal. The wiggly/zigzag paths that the ants take toward the goal results in the ant reliably (but briefly) facing in the goal direction at the points of the zigzag where ants change turning direction.  They find that the rapid saccade-like-turns (Lent et al. 2010, PNAS) that ants use to correct for errors in visually defined direction, are usually found in the same phase of the zigzag cycle as when ants would expect to be facing in the goal direction. Such phase-dependent use of vision shows how ants have organised their sensori-motor behaviour in such a way that they can still use a simple path control strategy.

Lent, D. D., Graham, P., & Collett, T. S. (2013). Phase-Dependent Visual Control of the Zigzag Paths of Navigating Wood Ants. Current Biology.

Categories: Papers from 2013

The ontogeny of exploration

With radar technology we are able to track bees over reasonable distances and with that we can investigate how naive bees explore their environment prior to a foraging career. We have long know that in the vicinity of a goal bees will perform learning flights (aka turn back and look flights) whereby they inspect the surroundings of the goal. In addition to this bees perform orientation/survey flights where they inspect the environment over reasonable distances (but don’t forage). Data regarding these larger flights is rare and so any new data is invaluable. Here, Osborne et al. look at naive bumblebees and show path development with experience and discuss the similarities and differences with equivalent honeybee behaviour.

 Osborne JL, Smith A, Clark SJ, Reynolds DR, Barron MC, et al. (2013) The Ontogeny of Bumblebee Flight Trajectories: From Naïve Explorers to Experienced Foragers. PLoS ONE 8(11): e78681. doi:10.1371/journal.pone.0078681
Categories: Papers from 2013

A universal landing strategy

Studies of visually guided behaviour in insects have a long tradition of elucidating elegant computational strategies that demonstrate how task specific visual parameters can be directly extracted from the visual scene. Continuing in that tradition, Baird et al. show how bees use the apparent rate of expansion within a scene to reduce speed on approach to a landing event. Importantly, this strategy does not require knowledge of the speed of the bee or the distance to the surface. It also works without the bee having to stabilise orientation. As the authors also point out, this represents a universal strategy suitable for any flying agent landing on any surface.

Baird, E., Boeddeker, N., Ibbotson, M. R., & Srinivasan, M. V. (2013). A universal strategy for visually guided landing. Proceedings of the National Academy of Sciences, 201314311.

Categories: Papers from 2013

The foraging patterns of the jack jumper

One of the benefits of ants as a study system is that we can relate our understanding of natural foraging behaviour to our contrived experimental situations. Therefore as we seek to understand the computational mechanisms that underpin insect navigation, we have to ground our theories in basic behavioural ecology. To this end, Jayatilaka et al. describe the foraging patterns of individual jack jumpers. Interestingly, with respect to navigation studies, they find that individuals do not have fixed idiosyncratic routes between places, and that individuals have different foraging patterns when hunting live prey to when foraging for nectar. These results, combined with the long life-span of foragers, have very real implications for the navigational knowledge we might expect individuals to hold.

JAYATILAKA, P., RADERSCHALL, C. A., NARENDRA, A., & ZEIL, J. Individual foraging patterns of the jack jumper ant Myrmecia croslandi (Hymenoptera: Formicidae). Myrmecological News.

Categories: Papers from 2013