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Animals navigate a wide range of distances, from a few millimeters to globe-spanning journeys of thousands of kilometers. Despite this array of navigational challenges, similar principles underlie these behaviors across species. Here, we focus on the navigational strategies and supporting mechanisms in four well-known systems: the large-scale migratory behaviors of sea turtles and lepidopterans as well as navigation on a smaller scale by rats and solitarily foraging ants. In lepidopterans, rats, and ants we also discuss the current understanding of the neural architecture which supports navigation. The orientation and navigational behaviors of these animals are defined in terms of behavioral error-reduction strategies reliant on multiple goal-directed servomechanisms. We conclude by proposing to incorporate an additional component into this system: the observation that servomechanisms operate on oscillatory systems of cycling behavior. These oscillators and servomechanisms comprise the basis for directed orientation and navigational behaviors.

Animals employ compasses during navigation, but little attention has been paid to how accuracy is maintained in the face of compass error, which is inevitable in biological systems. The use of multiple landmarks may minimize the effect of compass error. We allowed Clark's nutcrackers to cache seeds in an outdoor aviary with either one or four landmarks present, and subsequently subjected them to small clock-shifts mimicking the effects of compass error. As predicted, the results showed a significant decrease in search accuracy following the clock-shift when one landmark was present but not when four landmarks were present. These results support that nutcrackers encode information from the sun as well as terrestrial landmarks, and these spatial cues are used in a flexible manner. Overall, our results are important as they support the hypothesis that multiple landmarks may be used during situations where the sun compass has even a small amount of error., (© 2018 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.)

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).

Rüdiger Wehner's work on insect orientation and navigation has influenced many scientists studying navigation, not only in ants and bees, but in other animals as well. We review the scientific legacy of six topics arising from Wehner's work on navigation. The polarisation compass is a chapter with a lot of behavioural and neurobiological detail. It has influenced the study of polarisation vision in other systems, and led Wehner to formulate the concept of a matched filter. The matched filter has probably had earlier formulations, but Wehner's paper on it has been much cited in studies on navigation and in other fields. The polarisation compass serves the task of path integration in insects. Work on path integration took off in the 1980s with work on desert ants and rodents. The use of terrestrial visual cues, landmarks or the panorama in view-based matching is another major theme of navigational research today. Search strategies were also well described in desert ants, and this line of research helped to launch theoretical and empirical developments in searching behaviour, now a lively area of research. Finally, robotic work has often drawn inspiration from work on insect navigation. We end with some discussion of current research directions.

The Central Australian desert ant Melophorus bagoti is known to use celestial cues for compass orientation. We manipulated the available celestial cues for compass orientation for ants that had arrived at a feeder, were captured and then released at a distant test site that had no useful terrestrial panoramic cues. When tested in an enclosed transparent box that blocked some or most of the ultraviolet light, the ants were still well oriented homewards. The ants were again significantly oriented homewards when most of the ultraviolet light as well as the sun was blocked, or when the box was covered with tracing paper that eliminated the pattern of polarised light, although in the latter case, their headings were more scattered than in control (full-cue) conditions. When the position of the sun was reflected 180° by a mirror, the ants headed off in an intermediate direction between the dictates of the sun and the dictates of unrotated cues. We conclude that M. bagoti uses all available celestial compass cues, including the pattern of polarised light, the position of the sun, and spectral and intensity gradients. They average multiple cues in a weighted fashion when these cues conflict.

In a synthetic approach to studying navigational abilities in desert ants, we review recent work comparing ants living in different visual ecologies. Those living in a visually rich habitat strewn with tussocks, bushes, and trees are compared to those living in visually barren salt pans, as exemplified by the Central Australian Melophorus bagoti and the North African Cataglyphis fortis, respectively. In bare habitats the navigator must rely primarily on path integration, keeping track of the distance and direction in which it has travelled, while in visually rich habitats the navigator can rely more on guidance by the visual panorama. Consistent with these expectations, C. fortis performs better than M. bagoti on various measures of precision at path integration. In contrast, M. bagoti learned a visually based associative task better than C. fortis, the latter generally failing at the task. Both these ants, however, exhibit a similar pattern of systematic search as a 'back up' strategy when other navigational strategies fail. A newly investigated salt-pan species of Melophorus (as yet unnamed) resembles C. fortis more, and its congener M. bagoti less, in its path integration. The synthetic approach would benefit from comparing more species chosen to address evolutionary questions. This article is part of a Special Issue entitled: CO3 2013., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The purpose of this article is to review and evaluate the range of theories proposed to explain findings on the use of geometry in reorientation. We consider five key approaches and models associated with them and, in the course of reviewing each approach, five key issues. First, we take up modularity theory itself, as recently revised by Lee and Spelke (Cognitive Psychology, 61, 152-176, 2010a; Experimental Brain Research, 206, 179-188, 2010b). In this context, we discuss issues concerning the basic distinction between geometry and features. Second, we review the view-matching approach (Stürzl, Cheung, Cheng, & Zeil, Journal of Experimental Psychology: Animal Behavior Processes, 34, 1-14, 2008). In this context, we highlight the possibility of cross-species differences, as well as commonalities. Third, we review an associative theory (Miller & Shettleworth, Journal of Experimental Psychology: Animal Behavior Processes, 33, 191-212, 2007; Journal of Experimental Psychology: Animal Behavior Processes, 34, 419-422, 2008). In this context, we focus on phenomena of cue competition. Fourth, we take up adaptive combination theory (Newcombe & Huttenlocher, 2006). In this context, we focus on discussing development and the effects of experience. Fifth, we examine various neurally based approaches, including frameworks proposed by Doeller and Burgess (Proceedings of the National Academy of Sciences of the United States of America, 105, 5909-5914, 2008; Doeller, King, & Burgess, Proceedings of the National Academy of Sciences of the United States of America, 105, 5915-5920, 2008) and by Sheynikhovich, Chavarriaga, Strösslin, Arleo, and Gerstner (Psychological Review, 116, 540-566, 2009). In this context, we examine the issue of the neural substrates of spatial navigation. We conclude that none of these approaches can account for all of the known phenomena concerning the use of geometry in reorientation and clarify what the challenges are for each approach.

Many animal species, including some social hymenoptera, use the visual system for navigation. Although the insect compound eyes have been well studied, less is known about the second visual system in some insects, the ocelli. Here we demonstrate navigational functions of the ocelli in the visually guided Australian desert ant Melophorus bagoti. These ants are known to rely on both visual landmark learning and path integration. We conducted experiments to reveal the role of ocelli in the perception and use of celestial compass information and landmark guidance. Ants with directional information from their path integration system were tested with covered compound eyes and open ocelli on an unfamiliar test field where only celestial compass cues were available for homing. These full-vector ants, using only their ocelli for visual information, oriented significantly towards the fictive nest on the test field, indicating the use of celestial compass information that is presumably based on polarised skylight, the sun's position or the colour gradient of the sky. Ants without any directional information from their path-integration system (zero-vector) were tested, also with covered compound eyes and open ocelli, on a familiar training field where they have to use the surrounding panorama to home. These ants failed to orient significantly in the homeward direction. Together, our results demonstrated that M. bagoti could perceive and process celestial compass information for directional orientation with their ocelli. In contrast, the ocelli do not seem to contribute to terrestrial landmark-based navigation in M. bagoti.

Many species have been shown to encode multiple sources of information to orient. To examine what kinds of information animals use to locate a goal we manipulated cue rotation, cue availability, and inertial orientation when the food-storing Clark's nutcracker (Nucifraga columbiana) was searching for a hidden goal in a circular arena. Three groups of birds were used, each with a different goal-landmark distance. As the distance between the goal and the landmark increased, nutcrackers were less accurate in finding the correct direction to the goal than they were at estimating the distance (Experiment 1). To further examine what cues the birds were using to calculate direction, the featural cues within the environment were rotated by 90 degrees and the birds were either oriented when searching (Experiments 2 and 3) or disoriented (Experiment 3). In Experiment 4, all distinctive visual cues were removed (both internal and external to the environment), a novel point of entry was used and the birds were either oriented or disoriented. We found that disorienting the nutcrackers so that they could not use inertial cues did not influence the birds' total search error. The birds relied heavily but not completely on cues within the environment, as rotating available cues caused them to systematically shift their search behavior. In addition, the birds also relied to some extent on Earth-based cues. These results show the flexible nature of cue use by the Clark's nutcracker. Our study shows how multiple sources of spatial information may be important for extracting multiple bearings for navigation.

Estimation of distance travelled (odometry) forms a vital part of navigation for solitarily foraging ants. In this study we investigated the properties of odometric memory in the Australian desert ant Melophorus bagoti. Ants were trained to travel in linear channels to a feeder placed at 6 m or 12 m from the nest. We determined if the ability to estimate distances accurately increased with experience. We also determined the delay at which the odometric memory started to decay at both these distances. Ants with six trials of experience did not get better at estimating distances and the odometric memory decayed after a 24 h delay. We then determined if ants integrated their latest odometric memory with their previous memories. We did this by training two groups of ants for five trials, one group to 6 m and another to 12 m, and then halving or doubling the outbound distance on their sixth trip, respectively. The ant's estimate was noted when the ants were released either immediately or after a 24 h delay. Ants always estimated their last outbound distance when released immediately. However, they switched to route-based navigation rather than estimating distances after a 24 h delay (at which time their odometric memory would have decayed).

Roberts and Van Veldhuizen's [Roberts, W.A., Van Veldhuizen, N., 1985. Spatial memory in pigeons on the radial maze. J. Exp. Psychol.: Anim. Behav. Proc. 11, 241-260] study on pigeons in the radial maze sparked research on landmark use by pigeons in lab-based tasks as well as variants of the radial-maze task. Pigeons perform well on open-field versions of the radial maze, with feeders scattered on the laboratory floor. Pigeons can also be trained to search precisely for buried food. The search can be based on multiple landmarks, but is sometimes controlled by just one or two landmarks, with the preferred landmarks varying across individuals. Findings are similar in landmark-based searching on a computer monitor and on a lab floor, despite many differences between the two kinds of tasks. A number of general learning principles are found in landmark-based searching, such as cue competition, generalization and peak shift, and selective attention. Pigeons also learn the geometry of the environment in which they are searching. Neurophysiological studies have implicated the hippocampal formation (HF) in avian spatial cognition, with the right hippocampus hypothesized to play a more important role in the spatial recognition of goal locations. Most recently, single-cell recording from the pigeon's hippocampal formation has revealed cells with different properties from the classic 'place' cells of rats, as well as differences in the two sides of the hippocampus.

There is evidence, beginning with Cheng (1986), that mobile animals may use the geometry of surrounding areas to reorient following disorientation. Gallistel (1990) proposed that geometry is used to compute the major or minor axes of space and suggested that such information might form an encapsulated cognitive module. Research reviewed here, conducted on a wide variety of species since the initial discovery of the use of geometry and the formulation of the modularity claim, has supported some aspects of the approach, while casting doubt on others. Three possible processing models are presented that vary in the way in which (and the extent to which) they instantiate the modularity claim. The extant data do not permit us to discriminate among them. We propose a modified concept of modularity for which an empirical program of research is more tractable.

Ants use the panoramic skyline in part to determine a direction of travel. A theoretically elegant way to define where terrestrial objects meet the sky is to use an opponent-process channel contrasting green wavelengths of light with ultraviolet (UV) wavelengths. Compared with the sky, terrestrial objects reflect relatively more green wavelengths. Using such an opponent-process channel gains constancy in the face of changes in overall illumination level. We tested the use of UV wavelengths in desert ants by using a plastic that filtered out most of the energy below 400 nm. Ants, Melophorus bagoti , were trained to home with an artificial skyline provided by an arena (experiment 1) or with the natural panorama (experiment 2). On a test, a homing ant was captured just before she entered her nest, and then brought back to a replicate arena (experiment 1) or the starting point (the feeder, experiment 2) and released. Blocking UV light led to deteriorations in orientation in both experiments. When the artificial skyline was changed from opaque to transparent UV-blocking plastic (experiment 3) on the other hand, the ants were still oriented. We conclude that UV wavelengths play a crucial role in determining direction based on the terrestrial surround. [ABSTRACT FROM AUTHOR]