Insect Navigation: How Do Wasps Get Home? Collett, Thomas S.; Philippides, Andy; Hempel de Ibarra, Natalie
Current biology,
02/2016, Letnik:
26, Številka:
4
Journal Article
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Bees and wasps are famous for many things, including elaborate flights to learn where their nest is. A new study provides precise, three-dimensional details of a wasp’s head and body movements during ...such flights and reconstructs what the wasp sees.
Bees and wasps are famous for many things, including elaborate flights to learn where their nest is. A new study provides precise, three-dimensional details of a wasp’s head and body movements during such flights and reconstructs what the wasp sees.
Bumblebees tend to face their nest over a limited range of compass directions when learning the nest's location on departure and finding it on their approach after foraging. They thus obtain similar ...views of the nest and its surroundings on their learning and return flights. How do bees coordinate their flights relative to nest-based and compass-based reference frames to get such similar views? We show, first, that learning and return flights contain straight segments that are directed along particular compass bearings, which are independent of the orientation of a bee's body. Bees are thus free within limits to adjust their viewing direction relative to the nest, without disturbing flight direction. Second, we examine the coordination of nest-based and compass-based control during likely information gathering segments of these flights: loops during learning flights and zigzags on return flights. We find that bees tend to start a loop or zigzag when flying within a restricted range of compass directions and to fly towards the nest and face it after a fixed change in compass direction, without continuous interactions between their nest-based and compass-based directions of flight. A preferred trajectory of compass-based flight over the course of a motif, combined with the tendency of the bees to keep their body oriented towards the nest automatically narrows the range of compass directions over which bees view the nest. Additionally, the absence of interactions between the two reference frames allows loops and zigzags to have a stereotyped form that can generate informative visual feedback.
The directional responses of turtles to simulated magnetic coordinates of positions in the sea have given insight into the turtles' route-like and map-like behaviour.
ABSTRACT
We investigate the ability of human ‘expert’ classifiers to identify strong gravitational lens candidates in Dark Energy Survey like imaging. We recruited a total of 55 people that completed ...more than 25 per cent of the project. During the classification task, we present to the participants 1489 images. The sample contains a variety of data including lens simulations, real lenses, non-lens examples, and unlabelled data. We find that experts are extremely good at finding bright, well-resolved Einstein rings, while arcs with g-band signal to noise less than ∼25 or Einstein radii less than ∼1.2 times the seeing are rarely recovered. Very few non-lenses are scored highly. There is substantial variation in the performance of individual classifiers, but they do not appear to depend on the classifier’s experience, confidence or academic position. These variations can be mitigated with a team of 6 or more independent classifiers. Our results give confidence that humans are a reliable pruning step for lens candidates, providing pure and quantifiably complete samples for follow-up studies.
The desert ant Cataglyphis fortis has at least three types of navigational strategy that can guide it between its nest and a familiar food site. The initial strategy after first finding a food site ...is based on a path integration memory of the position of the food site with respect to the nest. A second strategy is based on visual snapshot memories of features viewed from near or on the way to the food site. A third strategy uses local vector memories of the direction and length of habitual route segments. We show here that while such local vectors encode sufficient information to guide an individual along both the direction and distance of a route segment, its acquisition and long-term maintenance requires support from the other two strategies. We trained ants along an L-shaped route, designed to show that ants can learn local vectors on the way to a food site. The sharp turn appears to present particular difficulties for the ants. When low bushes 20-30 m from the route were removed, local vectors were briefly unaffected, but then deteriorated. The vectors improved again once the missing bushes were replaced by artificial landmarks. The fragility of local vector memories may permit an ant the flexibility to adapt its route to fluctuations in the distribution of its resources.
Animals typically have several navigational strategies available to them. Interactions between these strategies can reduce navigational errors and may lead to the emergence of new capacities.
Many bees and wasps learn about the immediate surroundings of their nest during learning flights, in which they look back towards the nest and acquire visual information that guides their subsequent ...returns. Visual guidance to the nest is simplified by the insects' tendency to adopt similar viewing directions during learning and return flights. To understand better the factors determining the particular viewing directions that insects choose, we have recorded the learning and return flights of a ground-nesting bumblebee in two visual environments--an enclosed garden with a partly open view between north and west, and a flat roof with a more open panorama. In both places, bees left and returned to an inconspicuous nest hole in the centre of a tabletop, with the hole marked by one or more nearby cylinders. In all experiments, bees adopted similar preferred orientations on their learning and return flights. Bees faced predominantly either north or south, suggesting the existence of two attractors. The bees' selection between attractors seems to be influenced both by the distribution of light, as determined by the shape of the skyline, and by the direction of wind. In the partly enclosed garden with little or no wind, bees tended to face north throughout the day, i.e. towards the pole in the brighter half of their surroundings. When white curtains, which distributed skylight more evenly, were placed around the table, bees faced both north and south. The bees on the roof tended to face south or north when the wind came from a wide arc of directions from the south or north, respectively. We suggest that bees switch facing orientation between north and south as a compromise between maintaining a single viewing direction for efficient view-based navigation and responding to the distribution of light for the easier detection of landmarks seen against the ground or to the direction of the wind for exploiting olfactory cues.
We report on SPT-CLJ2011-5228, a giant system of arcs created by a cluster at z = 1.06. The arc system is notable for the presence of a bright central image. The source is a Lyman break galaxy at zs ...= 2.39 and the mass enclosed within the Einstein ring of radius 14 arcsec is . We perform a full reconstruction of the light profile of the lensed images to precisely infer the parameters of the mass distribution. The brightness of the central image demands that the central total density profile of the lens be shallow. By fitting the dark matter as a generalized Navarro-Frenk-White profile-with a free parameter for the inner density slope-we find that the break radius is kpc, and that the inner density falls with radius to the power −0.38 0.04 at 68% confidence. Such a shallow profile is in strong tension with our understanding of relaxed cold dark matter halos; dark matter-only simulations predict that the inner density should fall as . The tension can be alleviated if this cluster is in fact a merger; a two-halo model can also reconstruct the data, with both clumps (density varying as and ) much more consistent with predictions from dark matter-only simulations. At the resolution of our Dark Energy Survey imaging, we are unable to choose between these two models, but we make predictions for forthcoming Hubble Space Telescope imaging that will decisively distinguish between them.
While foraging, the desert ant Cataglyphis fortis keeps track of its position with respect to its nest through a process of path integration (PI). Once it finds food, it can then follow a direct home ...vector to its nest. Furthermore, it remembers the coordinates of a food site, and uses these coordinates to return to the site. Previous studies suggest, however, that it does not associate any coordinates remembered from previous trips with familiar views such that it can produce a home vector when displaced to a familiar site. We ask here whether a desert ant uses any association between PI coordinates and familiar views to ensure consistent PI coordinates as it travels along a habitual route. We describe an experiment in which we manipulated the PI coordinates an ant has when reaching a distinctive point along a habitual route on the way to a feeder. The subsequent home vectors of the manipulated ants, when displaced from the food-site to a test ground, show that also when a route memory is evoked at a significant point on the way to a food site, C. fortis does not reset its PI coordinates to those it normally has at that point. We use this result to argue that local vector memories, which encode the metric properties of a segment of a habitual route, must be encoded in a route-based coordinate system that is separate from the nest-based global coordinates. We propose a model for PI-based guidance that can account for several puzzling observations, and that naturally produces the route-based coordinate system required for learning and following local vectors.
We explore the properties of lensing galaxies and lensed faint sources at redshifts between 1.5 and 3.0. Our sample consists of nine, carefully selected strongly lensed galaxies discovered by the ...CASSOWARY (Cambridge And Sloan Survey Of Wide ARcs in the skY) survey in the Sloan Digital Sky Survey (SDSS) data. We find that, despite some limitations of the original SDSS data, the homogeneous sample of lensing systems can provide a useful insight into lens and source properties. We also explore the limitations of using low-resolution data to model and analyse galaxy–galaxy lensing. We derive the relative alignment of mass and light in fitted lens profiles. The range of magnification extends above 5; hence, we are able to analyse potentially small and low-mass galaxies at high redshifts. We confirm the likely evolution of the size–luminosity relation for blue star-forming galaxies as a function of redshift.
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