Time-courses of memory decay in vector-based and landmark-based systems of navigation in desert ants, Cataglyphis fortis

We use a genetic algorithm to evolve neural models of path integration, with particular emphasis on reproducing the homing behaviour of Cataglyphis fortis ants. This is done within the context of a complete model system, including an explicit representation of the animal's movements within its environment. We show that it is possible to produce a neural network without imposing a priori any particular system for the internal representation of the animal's home vector. The best evolved network obtained is analysed in detail and is found to resemble the bicomponent model of Mittelstaedt.Because of the presence of leaky integration, the model can reproduce the systematic navigation errors found in desert ants. The model also naturally mimics the searching behaviour that ants perform once they have reached their estimate of the nest location. The results support possible roles for leaky integration and cosine-shaped compass response functions in path integration.

Section: Search Patternsmentioning

confidence: 99%

Evolving neural models of path integration

Vickerstaff

Paolo

2005

“…After undertaking tasks within the nest for about 4 weeks, the ants forage outside the nest only for less than a week (Cataglyphis bicolor: Schmid-Hempel and Schmid-Hempel, 1984). The life expectancy of C. fortis outside the nest has not been systematically determined yet, but Ziegler and Wehner (1997) mention 7.3 days (for a short survey comparing the forager survival frequencies of different desert ant species, see fig. 39.1 in Wehner and Rössler, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the ants may link so-called 'local vectors' to specific landmarks (Bisch- Knaden and Wehner, 2001;Collett et al, 1998Collett et al, , 2001. In general, the visual landmark memories of C. fortis are very stable and long lasting for up to the entire foraging life span (Ziegler and Wehner, 1997). A landmark memory is most robust when acquired close to the nest entrance (Bisch- Knaden and Wehner, 2003b).…”

Section: Introductionmentioning

confidence: 99%

Ontogeny of learning walks and the acquisition of landmark information in desert ants,Cataglyphis fortis

Fleischmann

Christian

Müller

et al. 2016

131

At the beginning of their foraging lives, desert ants (Cataglyphis fortis) are for the first time exposed to the visual world within which they henceforth must accomplish their navigational tasks. Their habitat, North African salt pans, is barren, and the nest entrance, a tiny hole in the ground, is almost invisible. Although natural landmarks are scarce and the ants mainly depend on path integration for returning to the starting point, they can also learn and use landmarks successfully to navigate through their largely featureless habitat. Here, we studied how the ants acquire this information at the beginning of their outdoor lives within a nest-surrounding array of three artificial black cylinders. Individually marked 'newcomers' exhibit a characteristic sequence of learning walks. The meandering learning walks covering all directions of the compass first occur only within a few centimeters of the nest entrance, but then increasingly widen, until after three to seven learning walks, foraging starts. When displaced to a distant test field in which an identical array of landmarks has been installed, the ants shift their search density peaks more closely to the fictive goal position, the more learning walks they have performed. These results suggest that learning of a visual landmark panorama around a goal is a gradual rather than an instantaneous process.

“…With the aid of PI, on its outward journey the ant combines the distances and directions that it travels into a vector of its current distance and direction from the nest. The value of this 'home vector' can be remembered, at least for a short period (Ziegler and Wehner, 1997;Cheng et al, 2006;Narendra et al, 2007). Once an ant has expressed its home vector and reached its nest, its current PI state has dropped to zero, but it still retains a longer-term memory of its PI state at the feeding site.…”

Section: Introductionmentioning

confidence: 99%

The acquisition and expression of memories of distance and direction in navigating wood ants

Fernandes

Philippides

Collett

et al. 2015

Wood ants, like other central place foragers, rely on route memories to guide them to and from a reliable food source. They use visual memories of the surrounding scene and probably compass information to control their direction. Do they also remember the length of their route and do they link memories of direction and distance? To answer these questions, we trained wood ant (Formica rufa) foragers in a channel to perform either a single short foraging route or two foraging routes in opposite directions. By shifting the starting position of the route within the channel, but keeping the direction and distance fixed, we tried to ensure that the ants would rely upon vector memories rather than visual memories to decide when to stop. The homeward memories that the ants formed were revealed by placing fed or unfed ants directly into a channel and assessing the direction and distance that they walked without prior performance of the food-ward leg of the journey. This procedure prevented the distance and direction walked being affected by a home vector derived from path integration. Ants that were unfed walked in the feeder direction. Fed ants walked in the opposite direction for a distance related to the separation between start and feeder. Vector memories of a return route can thus be primed by the ants' feeding state and expressed even when the ants have not performed the food-ward route. Tests on ants that have acquired two routes indicate that memories of the direction and distance of the return routes are linked, suggesting that they may be encoded by a common neural population within the ant brain.