Ants Can Learn to Forage on One-Way Trails (original) (raw)
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Context-dependent navigation in a collectively foraging species of ant, Messor cephalotes [2013]
More than 100 years of scientific research has provided evidence for sophisticated navigational mechanisms in social insects. One key role for navigation in ants is the orientation of workers between food sources and the nest. The focus of recent work has been restricted to navigation in individually foraging ant species, yet many species do not forage entirely independently, instead relying on collectively maintained information such as persistent trail networks and/or pheromones. Harvester ants use such networks, but additionally, foragers often search individually for food either side of trails. In the absence of a trail, these 'off-trail' foragers must navigate independently to relocate the trail and return to the nest. To investigate the strategies used by ants on and off the main trails, we conducted field experiments with a harvester ant species, Messor cephalotes, by transferring on-trail and off-trail foragers to an experimental arena. We employed custom-built software to track and analyse ant trajectories in the arena and to quantitatively compare behaviour. Our results indicate that foragers navigate using different cues depending on whether they are travelling on or off the main trails. We argue that navigation in collectively foraging ants deserves more attention due to the potential for behavioural flexibility arising from the relative complexity of journeys between food and the nest.
Context-dependent navigation in a collectively foraging species of ant, Messor cephalotes
More than 100 years of scientific research has provided evidence for sophisticated navigational mechanisms in social insects. One key role for navigation in ants is the orientation of workers between food sources and the nest. The focus of recent work has been restricted to navigation in individually foraging ant species, yet many species do not forage entirely independently, instead relying on collectively maintained information such as persistent trail networks and/or pheromones. Harvester ants use such networks, but additionally, foragers often search individually for food either side of trails. In the absence of a trail, these 'off-trail' foragers must navigate independently to relocate the trail and return to the nest. To investigate the strategies used by ants on and off the main trails, we conducted field experiments with a harvester ant species, Messor cephalotes, by transferring on-trail and off-trail foragers to an experimental arena. We employed custom-built software to track and analyse ant trajectories in the arena and to quantitatively compare behaviour. Our results indicate that foragers navigate using different cues depending on whether they are travelling on or off the main trails. We argue that navigation in collectively foraging ants deserves more attention due to the potential for behavioural flexibility arising from the relative complexity of journeys between food and the nest.
Route following by one-eyed ants suggests a revised model of normal route following
2020
SummaryThe prevailing account of visually controlled routes is that an ant learns views as it follows a route, while guided by other path-setting mechanisms. Once a set of route views is memorised, the insect follows the route by turning and moving forwards when the view on the retina matches a stored view. We have engineered a situation in which this account cannot suffice in order to discover whether there may be additional components to the performance of routes. One-eyed wood ants were trained to navigate a short route in the laboratory guided by a single black, vertical bar placed in the blinded visual field. Ants thus had to turn away from the route to see the bar. They often turned to look at or beyond the bar and then turned to face in the direction of the goal. Tests in which the bar was shifted to be more peripheral or more frontal than in training produced a corresponding change in the ants’ paths, demonstrating that they were guided by the bar, presumably obtaining infor...
Views, landmarks, and routes: how do desert ants negotiate an obstacle course?
Journal of Comparative Physiology A, 2011
The Australian desert ant Melophorus bagoti often follows stereotypical routes through a cluttered landscape containing both distant panoramic views and obstacles (plants) to navigate around. We created an artificial obstacle course for the ants between a feeder and their nest. Landmarks comprised natural objects in the landscape such as logs, branches, and tussocks. Many ants travelled stereotypical routes home through the obstacle course in training, threading repeatedly the same gaps in the landmarks. Manipulations altering the relations between the landmarks and the surrounding panorama, however, affected the routes in two major ways. Both interchanging the positions of landmarks (transpositions) and displacing the entire landmark set along with the starting position of the ants (translations) (1) reduced the stereotypicality of the route, and (2) increased turns and meanders during travel. The ants might have used the entire panorama in view-based travel, or the distal panorama might prime the identification and use of landmarks en route. Despite the large data set, both options (not mutually exclusive) remain viable.
Memory and chemical communication in the orientation of two mass-recruiting ant species
Insectes Sociaux, 1993
The relative contribution of visual and chemical components in the orientation of Lasius niger and Iridomyrmex humilis (Argentine ant) workers during mass recruitment to newly discovered food sources is analyzed over short time intervals. While both species orient in response to the trail pheromone, a large number of L. niger foragers rapidly switch to a more individual orientation, based on their memory of environmental cues. L humilis workers, on the other hand, predominantly use collective chemical cues. The effect of the number of reinforcements on visual learning and its interference with chemical communication show that olfactory cues always prevail in the Argentine ant. In L. niger, the proportion of ants orienting to visual cues is independent of the trail concentration. Detailed observations of the trail-laying behavior of individually marked foragers show that nearly all the L humilis workers initially lay a trail, whereas only half the L. nige~ foragers do so. This proportion decreases considerably with the number of trips performed by L. niger workers, while remaining constant for the Argentine ants. These results are interpreted with respect to the species' behavioral ecology.
Ecological Entomology, 2012
1. Ants using trails to forage have to select between two alternative routes at bifurcations, using two, potentially conflicting, sources of information to make their decision: individual experience to return to a previous successful foraging site (i.e. fidelity) and ant traffic. In the field, we investigated which of these two types of information individuals of the leaf-cutting ant Acromyrmex lobicornis Emery use to decide which foraging route to take.
How desert ants cope with enforced detours on their way home
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1992
We ask whether desert ants (Cataglyphis fortis) perform path integration on their homeward as well as on their outward journey. If path integration does occur on the return journey, then, after an enforced detour, the ant's trajectory should point directly at its nest. To test whether this is so, ants were trained to forage at a spot 25 m from
Path integration in desert ants, Cataglyphis: how to make a homing ant run away from home
Proceedings of The Royal Society B: Biological Sciences, 2004
Path integration is an ant's lifeline on any of its foraging journeys. It results in a homebound global vector that continually informs the animal about its position relative to its starting point. Here, we use a particular (repeated training and displacement) paradigm, in which homebound ants are made to follow a familiar landmark route repeatedly from the feeder to the nest, even after they have arrived at the nest. The results show that during the repeated landmark-guided home runs the ant's path integrator runs continually, so that the current state of the homebound vector increasingly exceeds the reference state. The dramatic result is that the homing ants run away from home. This finding implies that the ants do not rely on cartographic information about the locations of nest and feeder (e.g. that the nest is always south of the feeder), but just behave according to what the state of their egocentric path integrator tells them.