Landmark Panorama Research Articles

Nest excavators’ learning walks in the Australian desert ant Melophorus bagoti

The Australian red honey ant, Melophorus bagoti, stands out as the most thermophilic ant in Australia, engaging in all outdoor activities during the hottest periods of the day during summer months. This species of desert ants often navigates by means of path integration and learning landmark cues around the nest. In our study, we observed the outdoor activities of M. bagoti workers engaged in nest excavation, the maintenance of the nest structure, primarily by taking excess sand out of the nest. Before undertaking nest excavation, the ants conducted a single exploratory walk. Following their initial learning expedition, these ants then engaged in nest excavation activities. Consistent with previous findings on pre-foraging learning walks, after just one learning walk, the desert ants in our study demonstrated the ability to return home from locations 2 m away from the nest, although not from locations 4 m away. These findings indicate that even for activities like dumping excavated sand within a range of 5–10 cm outside the nest, these ants learn and utilize the visual landmark panorama around the nest.

Learning walks in an Australian desert ant, Melophorus bagoti.

ABSTRACTThe central Australian ant Melophorus bagoti is the most thermophilic ant in Australia and forages solitarily in the summer months during the hottest period of the day. For successful navigation, desert ants of many species are known to integrate a path and learn landmark cues around the nest. Ants perform a series of exploratory walks around the nest before their first foraging trip, during which they are presumed to learn about their landmark panorama. Here, we studied 15 naive M. bagoti ants transitioning from indoor work to foraging outside the nest. In 3–4 consecutive days, they performed 3–7 exploratory walks before heading off to forage. Naive ants increased the area of exploration around the nest and the duration of trips over successive learning walks. In their first foraging walk, the majority of the ants followed a direction explored on their last learning walk. During learning walks, the ants stopped and performed stereotypical orientation behaviours called pirouettes. They performed complete body rotations with stopping phases as well as small circular walks without stops known as voltes. After just one learning walk, these desert ants could head in the home direction from locations 2 m from the nest, although not from locations 4 m from the nest. These results suggest gradual learning of the visual landmark panorama around the foragers’ nest. Our observations show that M. bagoti exhibit similar characteristics in their learning walks to other desert ants of the genera Ocymyrmex and Cataglyphis.

Landmark learning, cue conflict, and outbound view sequence in navigating desert ants.

Mobile animals need to reliably find goal locations and animal navigators acquire and use multiple cue sets within their environment designating direction and distance estimates of these locations. Foraging ants use multiple navigational tools including path integration and the learning of the landmark panorama. During landmark-based navigation, foragers first acquire the landmark cues around the nest through preforaging learning walks, and then learn non-nest site cues along their foraging routes. Here, we explore both foragers' ability to extrapolate views from around the nest to local displacement sites and landmark learning during the first foraging trips away from the nest area. During Experiment 1, foragers were given variable amounts of exposure to the nest area before being displaced 8 m away where their return trips were recorded. In Experiment 2, foragers' return trips from a site 8 m from the nest were recorded with the surrounding landmarks during either the outbound or inbound trip obstructed from view and with/without the aid of a homeward vector. Foragers were unable to correctly orient or return home efficiently regardless of the exposure level to the nest panorama, suggesting an inability to extrapolate views from learning walks and supporting recognition-based navigation. Foragers were able to use experience of either the outbound- or inbound-view sequence to initially orient home, yet were unable to quickly return to the nest when only exposed to the inbound route. Our results suggest that exposure to the outbound foraging path is critical for efficient homeward route formation. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

The Role of Celestial Compass Information in Cataglyphis Ants during Learning Walks and for Neuroplasticity in the Central Complex and Mushroom Bodies.

Central place foragers are faced with the challenge to learn the position of their nest entrance in its surroundings, in order to find their way back home every time they go out to search for food. To acquire navigational information at the beginning of their foraging career, Cataglyphis noda performs learning walks during the transition from interior worker to forager. These small loops around the nest entrance are repeatedly interrupted by strikingly accurate back turns during which the ants stop and precisely gaze back to the nest entrance—presumably to learn the landmark panorama of the nest surroundings. However, as at this point the complete navigational toolkit is not yet available, the ants are in need of a reference system for the compass component of the path integrator to align their nest entrance-directed gazes. In order to find this directional reference system, we systematically manipulated the skylight information received by ants during learning walks in their natural habitat, as it has been previously suggested that the celestial compass, as part of the path integrator, might provide such a reference system. High-speed video analyses of distinct learning walk elements revealed that even exclusion from the skylight polarization pattern, UV-light spectrum and the position of the sun did not alter the accuracy of the look back to the nest behavior. We therefore conclude that C. noda uses a different reference system to initially align their gaze directions. However, a comparison of neuroanatomical changes in the central complex and the mushroom bodies before and after learning walks revealed that exposure to UV light together with a naturally changing polarization pattern was essential to induce neuroplasticity in these high-order sensory integration centers of the ant brain. This suggests a crucial role of celestial information, in particular a changing polarization pattern, in initially calibrating the celestial compass system.

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

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.

Mapping the navigational knowledge of individually foraging ants,Myrmecia croslandi

Ants are efficient navigators, guided by path integration and visual landmarks. Path integration is the primary strategy in landmark-poor habitats, but landmarks are readily used when available. The landmark panorama provides reliable information about heading direction, routes and specific location. Visual memories for guidance are often acquired along routes or near to significant places. Over what area can such locally acquired memories provide information for reaching a place? This question is unusually approachable in the solitary foraging Australian jack jumper ant, since individual foragers typically travel to one or two nest-specific foraging trees. We find that within 10 m from the nest, ants both with and without home vector information available from path integration return directly to the nest from all compass directions, after briefly scanning the panorama. By reconstructing panoramic views within the successful homing range, we show that in the open woodland habitat of these ants, snapshot memories acquired close to the nest provide sufficient navigational information to determine nest-directed heading direction over a surprisingly large area, including areas that animals may have not visited previously.

Homing abilities of the Australian intertidal ant, Polyrhachis sokolova

The pressure of returning to and locating the nest after a successful foraging trip is immense in ants. To find their way back home, ants use a number of different strategies (e.g. path integration, trail following) and rely on a range of cues (e.g. pattern of polarised skylight, landmark panorama) available in their environment. How ants weigh different cues has been a question of great interest and has primarily been addressed in the desert ants from Africa and Australia. We here identify the navigational abilities of an intertidal ant, Polyrhachis sokolova, that lives on mudflats where nests and foraging areas are frequently inundated with tidal water. We find that these solitary foraging ants rely heavily on visual landmark information for navigation, but they are also capable of path integration. By displacing ants with and without vector information at different locations within the local familiar territory, we created conflicts between information from the landmarks and information from the path integrator. The homing success of full-vector ants, compared with the zero-vector ants, when displaced 5 m behind the feeder, indicate that vector information had to be coupled with landmark information for successful homing. To explain the differences in the homing abilities of ants from different locations we determined the navigational information content at each release station and compared it with that available at the feeder location. We report here the interaction of multiple navigation strategies in the context of the information content in the environment.

Mapping the navigational knowledge in Australian jack jumper ants, Myrmecia croslandi

Event Abstract Back to Event Mapping the navigational knowledge in Australian jack jumper ants, Myrmecia croslandi Ajay Narendra1*, Sarah Gourmaud1 and Jochen Zeil1 1 The Australian National University, Australia Ants are efficient navigators, guided by path integration and visual landmarks. The landmark panorama in visually rich habitats, provides reliable information on heading direction, on routes and on location. Landmark memories are route- and place-dependent and are therefore thought to provide ants with navigational knowledge that is limited to areas in the environment they have visited before. The Australian jack jumper ant are individually foraging animals that typically travel to one or two nest-specific foraging trees. They make occasional forays in other directions for short distances in search of prey. This naturally restricted foraging corridor allows us to systematically analyse the extent of navigational knowledge in individual animals. We find that within 10 m from the nest, ants both with and without vector information return directly to the nest from all compass directions (Figure 1). Full vector ants displaced between distances of 10-30 m from the nest either return directly to the nest, or travel briefly in the direction indicated by their home vector, before beginning to search or correcting their heading to reach the nest. However, when displaced 100 m from the nest, ants walk in the direction of their home vector, but only travel a short distance. By reconstructing panoramic views at the successful and unsuccessful homing locations, we show that in the open woodland habitat of these ants, snapshot memories acquired close to the nest provide sufficient information to determine nest-directed heading direction over a surprisingly large area, including areas that animals are unlikely to have visited before. Figure 1 Keywords: Myrmecia, navigation, landmark-guidnace, path integration, Ants Conference: International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013. Presentation Type: Poster presentation preferred Topic: Navigation and orientation Citation: Narendra A, Gourmaud S and Zeil J (2019). Mapping the navigational knowledge in Australian jack jumper ants, Myrmecia croslandi. Front. Physiol. Conference Abstract: International Conference on Invertebrate Vision. doi: 10.3389/conf.fphys.2013.25.00096 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Feb 2013; Published Online: 09 Dec 2019. * Correspondence: Dr. Ajay Narendra, The Australian National University, Canberra, Australia, ajay.narendra@mq.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ajay Narendra Sarah Gourmaud Jochen Zeil Google Ajay Narendra Sarah Gourmaud Jochen Zeil Google Scholar Ajay Narendra Sarah Gourmaud Jochen Zeil PubMed Ajay Narendra Sarah Gourmaud Jochen Zeil Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Navigational knowledge of homebound Australian sugar ants, Camponotus consobrinus.

Navigational knowledge of homebound Australian sugar ants, Camponotus consobrinus.

The properties of the visual system in the Australian desert ant Melophorus bagoti

The Australian desert ant Melophorus bagoti shows remarkable visual navigational skills relying on visual rather than on chemical cues during their foraging trips. M. bagoti ants travel individually through a visually cluttered environment guided by landmarks as well as by path integration. An examination of their visual system is hence of special interest and we address this here. Workers exhibit distinct size polymorphism and their eye and ocelli size increases with head size. The ants possess typical apposition eyes with about 420–590 ommatidia per eye, a horizontal visual field of approximately 150° and facet lens diameters between 8 and 19 μm, depending on body size, with frontal facets being largest. The average interommatidial angle Δϕ is 3.7°, the average acceptance angle of the rhabdom Δρrh is 2.9°, with average rhabdom diameter of 1.6 μm and the average lens blur at half-width Δρl is 2.3°. With a Δρrh/Δϕ ratio of much less than 2, the eyes undersample the visual scene but provide high contrast, and surprising detail of the landmark panorama that has been shown to be used for navigation.

Polarised skylight and the landmark panorama provide night-active bull ants with compass information during route following

Navigating animals are known to use a number of celestial and terrestrial compass cues that allow them to determine and control their direction of travel. Which of the cues dominate appears to depend on their salience. Here we show that night-active bull ants attend to both the pattern of polarised skylight and the landmark panorama in their familiar habitat. When the two directional cues are in conflict, ants choose a compromise direction. However, landmark guidance appears to be the primary mechanism of navigation used by forager ants, with those cues in the direction of heading having the greatest influence on navigation. Different colonies respond to the removal of these cues to different degrees, depending on the directional information provided by the local landmark panorama. Interestingly, other parts of the surrounding panorama also influence foraging speed and accuracy, suggesting that they too play a role in navigation.

Nest mark orientation in desert ants Cataglyphis: what does it do to the path integrator?

In desert ants, path integration is the fundamental system of long-distance navigation. Normally, the path integrator is reset to the zero state whenever the ant returns to the starting point of its foraging journey, the nest. We investigated whether the landmark panorama characterizing the nest entrance suffices to reset the path integrator. We designed an experimental paradigm in which the position where the ants’ path integrator was at the zero state (PI position) did not coincide with the position of the nest as marked by the familiar landmark panorama (LM position). Once the ants displaced from the training area to a distant test field had arrived at the PI position, the artificial landmark array defining the nest site was installed at the LM position. The ants immediately headed towards the LM position and searched there persistently. However, upon removal of the landmarks they returned to the PI position. Hence, they ignored information from their path integrator while they concentrated their search at the landmark-defined nest position, but they again relied on their continually updated path integrator as soon as the landmarks had been removed. Although their concentrated search at the LM position showed that the ants had used the landmarks as reliable cues for the position of their nest, this landmark-induced search for the nest entrance did not reset the ant’s path integrator. In general, this might mean that geocentric visual cues in themselves are not sufficient to recalibrate the egocentric path integrator.

Landmark memories are more robust when acquired at the nest site than en route: experiments in desert ants

Foraging desert ants, Cataglyphis fortis, encounter different sequences of visual landmarks while navigating by path integration. This paper explores the question whether the storage of landmark information depends on the context in which the landmarks are learned during an ant's foraging journey. Two experimental set-ups were designed in which the ants experienced an artificial landmark panorama that was placed either around the nest entrance (nest marks) or along the vector route leading straight towards the feeder (route marks). The two training paradigms resulted in pronounced differences in the storage characteristics of the acquired landmark information: memory traces of nest marks were much more robust against extinction and/or suppression than those of route marks. In functional terms, this result is in accord with the observation that desert ants encounter new route marks during every foraging run but always pass the same landmarks when approaching the nest entrance.

Tests for cognitive mapping in Clark's nutcrackers (Nucifraga columbiana).

In these experiments, the authors examined the nature of the spatial information that Clark's nutcrackers (Nucifraga columbiana) use during navigation and whether this information is represented in the form of a cognitive map. In Experiment 1, nutcrackers were able to use distal cues to locate a small hidden goal. In Experiments 2 and 3, nutcrackers were given the opportunity to develop a map of a room by viewing local subsets of the landmarks in the room at a goal during training. During transfer tests, nutcrackers were presented with a landmark panorama that was not previously seen at the goal. Of 3 nutcrackers that had learned the relationship between distal cues and the goal, 3 were able to locate the goal during transfer, indicating they may have developed a cognitive map. Experiments 4 and 5 suggest that the simpler mechanism of vector integration may have been used by some nutcrackers during the transfer tests.

Homing in wood ants, Formica japonica: use of the skyline panorama.

Homeward orientation was studied in wood ants Formica japonica that, while foraging, shuttled back and forth along a 7.9m route between the nest and a feeding site located on a wide terrace platform surrounded by a conspicuous landmark panorama. The return runs of the ants were amazingly straight, not only in the controls (starting at the feeding site) but also in ants displaced for various distances to the left and right of the feeding site. These courses, however, were oriented neither parallel to the predisplacement courses nor directly towards the nest. This result excludes the use of chemical cues and celestial compass cues. Furthermore, the nest itself, or some object close to it, could not have served as a beacon. The extensions of the homeward paths taken by ants that had been displaced to various release sites up to 11m sideways from the training route intersected at a point far (approximately 13m) behind the nest. This result suggests that the ants used distant landmarks seen by them in their frontal fields of view. To test this hypothesis, the distant landmark panorama was concealed by an opaque sheet mounted at right angles to the normal return route of the ants and extending up to different elevations. Shielding the lower part of the landmark panorama had no effect on the homeward paths. However, when the screen was mounted in such a way that the ants could only see the top skyline, represented by the upper edges of a line of trees, for part of their return run, it was only during these parts that their path was oriented in the homeward direction. When, during the course of displacement experiments, the ants were deprived of their familiar skyline panorama, they moved in their home direction only for an extremely short distance (0.1-0.4m rather than the usual 7.9m) and then started a systematic search programme. Hence, in the present context, skylight information is not used, at least not extensively. Instead, ants use the distant skyline as a navigational guidemark.

Optimizing distal landmarks: horizontal versus vertical structures and relation to background

During hoarding excursions, golden hamsters use distal landmarks and dead reckoning (updated signals derived from locomotion) to find their way back from a food source at the centre of a circular arena to their nest at the periphery. The preference for particular landmarks was assessed by setting landmark panoramas in conflict with dead reckoning. The hamsters tended to prefer horizontal landmarks to vertical ones when these landmarks were presented alone. However, in combination with a continuous background pattern including a single apex, vertical landmarks were more effective than horizontal ones. A panorama consisting of a vertical cylinder or bar and the background pattern was optimal provided the vertical landmark was aligned or superimposed on the apex of the background. The impact of a landmark panorama therefore depends on its particular components as well as on their mutual relationship.

Optimizing visual landmarks: two- and three-dimensional minimal landscapes

When hoarding food within a circular arena, golden hamsters, Mesocricetus auratus W., return along a direct path from the feeding place at the centre to their nest at the periphery. The homing direction depends on dead reckoning (updated internal signals derived from locomotion) and, if available, on landmarks outside the arena. This study was aimed at defining the conditions under which a landmark panorama predominates over dead reckoning during conflict situations. In agreement with previous results, this was found to be the case only when the panorama contained at least one prominent vertical feature aligned with the apex of a two-dimensional, continuous background pattern. The minimal landscape that controlled homing was a solid cylinder presented in front of the background pattern, or its two-dimensional projection on the pattern itself. Contrary to a previous hypothesis, depth did not appear to be a critical factor in an effective landmark panorama.