Visual Navigation during Colony Emigration by the Ant Temnothorax rugatulus

Many ants rely on both visual cues and self-generated chemical signals for navigation, but their relative importance varies across species and context. We evaluated the roles of both modalities during colony emigration by Temnothorax rugatulus. Colonies were induced to move from an old nest in the center of an arena to a new nest at the arena edge. In the midst of the emigration the arena floor was rotated 60°around the old nest entrance, thus displacing any substrate-bound odor cues while leaving visual cues unchanged. This manipulation had no effect on orientation, suggesting little influence of substrate cues on navigation. When this rotation was accompanied by the blocking of most visual cues, the ants became highly disoriented, suggesting that they did not fall back on substrate cues even when deprived of visual information. Finally, when the substrate was left in place but the visual surround was rotated, the ants'' subsequent headings were strongly rotated in the same direction, showing a clear role for visual navigation. Combined with earlier studies, these results suggest that chemical signals deposited by Temnothorax ants serve more for marking of familiar territory than for orientation. The ants instead navigate visually, showing the importance of this modality even for species with small eyes and coarse visual acuity.     

Homing pigeons develop local route stereotypy

The mechanisms used by homing pigeons (Columba livia) to navigate homeward from distant sites have been well studied, yet the mechanisms underlying navigation within, and mapping of, the local familiar area have been largely neglected. In the local area pigeons pote ntially have access to a powerful navigational aid--a memorized landscape map. Current opinion suggests that landmarks are used only to recognize a familiar start position and that the goalward route is then achieved solely using compass orientation. We used high-resolution global positioning system (GPS) loggers to track homing pigeons as they became progressively familiar with a local homing task. Here, we demonstrate that birds develop highly stereotyped yet individually distinctive routes over the landscape, which remain substantially inefficient. Precise aerial route recapitulation implies close control by localized geocentric cues. Magnetic cues are unlikely to have been used, since recapitulation remains despite magnetic disruption treatment, and olfactory cues would have been positionally unstable under the variable wind conditions, making visual landmarks the most likely cues used.     

Homing pigeons only navigate in air with intact environmental odours: a test of the olfactory activation hypothesis with GPS data loggers

A large body of evidence has shown that anosmic pigeons are impaired in their navigation. However, the role of odours in navigation is still subject to debate. While according to the olfactory navigation hypothesis homing pigeons possess a navigational map based on the distribution of environmental odours, the olfactory activation hypothesis proposes that odour perception is only needed to activate a navigational mechanism based on cues of another nature. Here we tested experimentally whether the perception of artificial odours is sufficient to allow pigeons to navigate, as expected from the olfactory activation hypothesis. We transported three groups of pigeons in air-tight containers to release sites 53 and 61 km from home in three different olfactory conditions. The Control group received natural environmental air; both the Pure Air and the Artificial Odour groups received pure air filtered through an active charcoal filter. Only the Artificial Odour group received additional puffs of artificial odours until release. We then released pigeons while recording their tracks with 1 Hz GPS data loggers. We also followed non-homing pigeons using an aerial data readout to a Cessna plane, allowing, for the first time, the tracking of non-homing homing pigeons. Within the first hour after release, the pigeons in both the Artificial Odour and the Pure Air group (receiving no environmental odours) showed impaired navigational performances at each release site. Our data provide evidence against an activation role of odours in navigation, and document that pigeons only navigate well when they perceive environmental odours.     

The Effects of Zinc Sulphate Anosmia on Homing Pigeons,Columba livia,in a Homing and a Non-homing Experiment

There is debate over whether homing pigeons, Columba livia, use olfactory information as part of their navigational map. Antagonists of the theory argue that homing deficits noted in anosmic pigeons may be due to a non-specific impairment in general information processing. In Experiment I, we present data from a modest investigation describing the typical navigational deficits that occur following zinc sulphate-mediated anosmia. Our results are consistent with previous experiments that noted impairments in homing performance from unfamiliar locations of anosmic pigeons. Experiment II is a critical experiment that involved a spatial working memory paradigm; this paradigm consisted of testing zinc sulphate-treated birds in a forced-choice alternation task in a T-maze. This experiment allowed us to determine whether anosmic pigeons were impaired in memory performance, a robust measure of general information processing. There were no differences between the last day of training and a subsequent-test day when pigeons received an intranasal injection of zinc sulphate. This experiment suggests that zinc sulphate anosmia does not impair general information processing, supporting the hypothesis that homing pigeons use olfactory cues when homing from unfamiliar locations.     

Multi-modal Orientation Cues in Homing Pigeons

How homing pigeons displaced into unfamiliar territory findtheir way home has been the subject of extensive experimentationand debate. One reason for the controversy is that pigeons seemto use multiple cues. Clock-shifting experiments show that experiencedpigeons use the sun as a preferred compass; when it is not availablethey rely on magnetic cues. That pigeons can home successfullywhile wearing frosted lenses suggests that landmarks, whilenot an essential navigational cue, are important in the finalstages. The sensory basis of the "map" or position finding systemis probably equally or even more complicated. When conditionsaround the loft are suitable, pigeons may use olfactory cuesto find their way or might use some feature of the earth's magneticfield for their navigation. The Wiltschkos (1989) showed thatpigeons raised without free access to ambient odors are notdisoriented when anosmic while their siblings raised with freeaccess to the prevailing wind were disoriented. Similarly, siblingpigeons from two lofts in Lincoln, Massachusetts. were welloriented or totally disoriented when released at magnetic anomaliesunder sunny skies depending upon which of the two lofts theyhad been reared in. All of these experiments and many more suggestthat pigeons use multiple and redundant cues to find their wayhome. Further, there is the suggestion that which cues theyadopt may well be influenced by the characteristics of the areaaround the home loft in which they were reared.     

Brieftauben

Homing pigeons Homing pigeons are well known for their excellent homing abilities which allow them to return to their lofts from unknown releasing sites more than hundreds of kilometres away. Several orientation mechanisms – sun compass, earth's magnetic field, olfactory cues, visual cues – are known to be involved in homing performance as well as parameters such as motivation and experience. New technology give an insight in their homing behaviour and track preferences and it is shown that homing pigeons physiology and neurobiology seem to be functionally adapted to homing. Pigeons races are still common and it is shown how the pigeon breeder tries to maximize the success of his pigeons.     

Comparison of visual and olfactory reversal learning in pigeons

Pigeons trained to discriminate between either two differentodors or two different colored lights acquired their discriminationsat the same rate. When the discrimination problems were reversedwithin a modality, however, the birds using visual cues acquirednew discriminations more rapidly than in original learning (positivetransfer), whereas the birds using olfactory cues acquired thediscrimination reversal less rapidly. On subsequent reversals,pigeons in the visual task condition developed a successivediscrimination reversal set with repeated reversals of the stimuli,while those in the olfactory condition did not. In a secondexperiment designed to assess the acquisition of redundant cues,birds received additional training with visual and olfactorycues in compound as discriminative stimuli, and were then testedwith only visual or olfactory cues. Birds previously trainedwith odor attended to visual cues in the compound, whereas birdspreviously trained to discriminate between lights did not attendto odor cues until they were presented alone. These resultsdemonstrate that the selection of stimuli may play a crucialrole in the performance of successive discrimination reversalsand suggest that, in contrast to rats, birds selectively attendto visual over olfactory cues in discrimination learning.     

Synergistic effects of olfactory and tactile cues in short‐range mate finding of Ophraella communa

Sensory signals between individuals are important in short‐range mate finding. The purpose of our experiments was to verify the roles of different sensory cues in mate orientation and discrimination in Ophraella communa LeSage (Coleoptera: Chrysomelidae) adults. Sex discrimination and sensory deprivation tests (i.e., depriving the olfactory and/or visual senses of either or both sexes by coating with paint) were conducted in the laboratory. Male O. communa were able to locate and recognize conspecifics using olfactory cues prior to physical contact, but could not discriminate the opposite sex prior to physical contact. When the olfaction of male O. communa was deprived by painting antennae, males spent significantly longer times seeking mates in the arena. Copulation duration did not differ significantly among treatments. Thus, the mating process of O. communa adults was mediated by contact cues, but not by olfactory cues. The percentages of successful mating, searching duration, and copulation duration were all unaffected by visual deprivation, i.e., when the eyes of either or both sexes were covered by black paint. The function of visual cues was thus negligible in the mate‐finding process of O. communa adults. Overall, these results suggested that orientation and discrimination of the opposite sex by O. communa is dependent on the synergy between olfactory and tactile cues.     

Olfaction and homing in pigeons: Nerve-section experiments,critique, hypotheses

Summary At four sites in the cardinal directions from the home loft in about 180 km distance, 135 experimental pigeons (EPs) and 171 control pigeons (CPs) were released. The EPs had been made anosmic by bilateral olfactory nerve section. All birds were completely inexperienced in homing.Homeward orientation was clearly established in the CPs of which 19% returned to the loft. The performances of the EPs were significantly worse in (a) initial orientation, (b) vanishing intervals, (c) distribution of recoveries, and (d) homing success (none of them homed).The EPs still showed the loft-specific preferred compass direction (PCD).The recoveries of the EPs are much more widely scattered in direction than those of the rather well homeward oriented CPs, even if the distances from the release site are the same in both groups. It is concluded that the navigational capability rather than the motivation to fly or to return home is affected by olfactory deprivation. It is further concluded that homing of pigeons depends on olfactory stimuli perceived at the remote sites even at distances as large as 180km.In the data of the anosmic pigeons a non-olfactory component of homeward orientation persists which is much more pronounced on the W-E axis than on the N-S axis. This component alone appears to be insufficient for a return to the loft.Earlier results and conclusions that gave rise to some controversy are critically examined.The present as well as earlier findings are discussed with respect to two alternative hypotheses of olfactory navigation, the mosaic hypothesis (favoured by Papi) and the gradient hypothesis (favoured by the author).Abbreviations EP experimental pigeon(s) - CP control pigeon(s) - CLCP cueless transported control pigeon(s) (see p. 210) - PCD preferred compass direction I gratefully acknowledge the possibility to maintain our pigeon loft in a building that belongs to the Zoological Institute (Prof. M. Lindauer) of the University of Würzburg. I thank B. and K. Brendle, E. Thiele, and K. Wielander for the releasing of pigeons and for other technical assistance.     

Memory of Location and Site Recognition in the Ant Formica uralensis (Hymenoptera: Formicidae)

Spatial recognition cues used in site fidelity in the ant Formica uralensis Ruzsky were studied using outdoor and laboratory arenas. Ant workers visiting symmetrically spaced feeders were colour-marked corresponding to the initial feeder visited during sampling. The effect of manipulating environmental cues on the mean 'spatial specialization' of the population was measured. Site recognition appears to be based on visual landmark/canopy cues. However, ants maintained some fidelity when shielded from these cues, suggesting the involvement of additional cues. When ridding our experimental device of olfactory deposits and shielding visual cues, site fidelity was lost. Idiothetic and/or geomagnetic cues are thought to provide spatial references to visual or olfactory landmarks. Altering nest position relative to the arena and changing the geomagnetic field within the arena in our study, however, did nothing to the site fidelity of visually deprived and non-deprived foragers.
We conclude that site fidelity is developed in a visually structured environment but supplemented by an olfactory backup system that is probably based on discrete home range markings rather than radial odour trails. We demonstrate furthermore that the visual component involved in site location can be stored in the memory of individual F. uralensis foragers during a 6-month hibernation period.     

Pigeon Homing: Does Early Experience Determine what Cues are Used to Navigate?

To test the hypothesis that early experience might determine the nature of the cues used to navigate, homing pigeons were made anosmic by nerve section before they could experience the natural odours in the region of the loft. They were allowed to make free flights and trained by flock releases with intact controls. Next they were tested and compared with intact controls as well as birds made temporarily anosmic just before the experiment. Initial orientation and homing performance of the experimental birds were very poor and showed that the pigeons were unable to acquire an alternative mechanism of navigation.     

Orientation by pigeons deprived of olfaction by nasal tubes

Summary In an effort to avoid the trauma and other nonolfactory effects produced by surgical sectioning of pigeons' olfactory nerves, and to avoid the interference with breathing produced by nostril plugs, a way of making pigeons anosmic by inserting plastic tubes in their nostrils was developed. A total of 16 experimental releases were conducted from unfamiliar sites to compare the homing behavior of birds wearing a tube in each nostril with controls wearing a tube in only one nostril. In five short-distance releases (less than 25 km), no convincing differences in initial orientation, vanishing intervals, or homing success were observed. In eleven releases from longer distances (more than 76 km), the experimental birds were random in three cases and the controls were random in two. In no case were the differences in the distributions of the bearings of experimental and control birds statistically significant, nor were there ever significant differences in vanishing intervals. However, experimental birds had much poorer homing success from these long-distance releases. It is concluded, in view of the anosmic pigeons' good orientation at distant unfamiliar sites, that olfaction is not necessary for homeward orientation and hence that it cannot be the basis of the birds' navigational map. Poor homing success from long distances is probably a consequence of the physical irritation and interference with breathing unfortunately produced by the nasal tubes.We thank our colleagues, Irene Brown, Timothy Larkin, and André Gobert for their help in conducting the releases. This research was supported by Grant BMS 75 18905 AO2 from the National Science Foundation.     

Long-term Retention of Many Visual Patterns by Pigeons

Using a simultaneous discrimination procedure it was shown that pigeons were capable of learning to discriminate 100 different black and white visual patterns from a further 625 similar stimuli, where responses to the former were rewarded and responses to the latter were not rewarded. Tests in which novel stimuli replaced either the rewarded or nonrewarded stimuli showed that the pigeons had not only learned about the 100 positive stimuli but also about the 625 negative stimuli. The fact that novel stimuli enhanced discrimination performance when they replaced the many negative stimuli indicated that the pigeons had categorized the stimuli into two classes, familiar and less familiar. Long-term retention was examined after a 6-month interval. To begin with it seemed poor but a recognition test performed after the subjects had been retrained with a subset of the stimuli after an interval of 7 months confirmed that pigeons are capable of retaining in memory several 100 visual items over an extended period. It is proposed that the initial retrieval weakness was due to a forgetting of the contingencies between stimulus categories and response outcomes. Further tests involving variously modified stimuli indicated that while stimulus size variations had a negative effect on performance, orientation changes did not interfere with recognition, supporting the view that small visual stimuli are memorized by pigeons largely free of orientation labels. The experiment generally confirms that pigeons have the capacity of storing information about a large number of visual stimuli over long periods of time.     

Orientation behaviour of toads (Bufo bufo) displaced from the breeding site

Summary The sensory basis and spatial range of orientation to the breeding site were studied in the toadBufo bufo, during two breeding seasons. Toads were displaced passively from their breeding pond and fitted with a tracking device to record the path of migration in individuals. The directional choice and the straightness of trails after release were used to quantify the effect of experimental treatments. In both years, control (untreated): toads headed to the breeding site with the same precision at all release sites. The initial orientation of toads blinded by opaque tape over their eyes. did not differ from controls, but the return paths were not as direct. The directional choice of anosmic toads was apparently random, however, individuals followed a straight path in a chosen direction. Anosmic toads also blinded were completely disoriented, moving in cycloid trails. Bar magnets glued to the head caused an increase in dispersion of toads. However, in some individual releases a directional bias without increased dispersion was observed. Sky conditions (clear or overcast) did not influence the initial orientation or the dispersion of toads. Nevertheless, the breeding site component was significantly correlated with wind direction in relation to the breeding site. Wind blowing from the breeding site improved the initial orientation, whereas wind from the opposite direction reduced the breeding site component. The spatial range for the ability to relocate the breeding pond after displacement exceeded 3 km, but the time taken to select the correct direction increased with the displacement distance. The results indicate that after displacement the initial orientation ofB. bufo is based mainly on olfactory and magnetic cues, with visual control of straightness.     

Attempts to Determine the Roles of Visual and Olfactory Inputs in Initial Orientation and Homing of Pigeons over Familiar Terrain

The role of familiar visual landmarks in pigeon homing is still unsettled. If they are involved, they must be thought to be utilized in parallel with olfactory signals. In order to recognize the effectiveness of either one of the input channels separately, vision and olfaction, it is therefore necessary to interfere with both of them. Pigeons were temporarily deprived of image vision by spectacles made of translucent white paper, producing a condition called V^- as compared with the largely unimpaired condition V⁺. Access to olfactory signals was temporarily prohibited by charcoal filters before release and nasal anaesthesia upon release, resulting in condition O^- versus unimpaired smelling of natural air in O⁺. Prior to the test releases, all the participating pigeons had been made familiar with the two or four test sites (and with other sites in the area) by training flights. According to decreasing levels of initial homeward orientation and homing performance, the four combinations of treatments are to be arranged in the following order: V⁺O⁺, V⁺O^-, V^-O⁺, V^-O^-. In the last type, no trace of initial homeward orientation remained, indicating that at least one of the two input channels need be functional to enable home-related orientation. Over well known terrain, either alone seems to be more or less sufficient. The results are indicative but not definitely conclusive. Effects of visual impairment on behavioural activities in general cannot clearly be separated from orientation-specific effects. Therefore, and because many pigeons refuse to fly in V^- condition or fail to provide useful data, we stopped applying this method.     

Differential magnetic field effects on heart rate and nociception in anosmic pigeons

Several studies have shown that exposure to altered magnetic fields affects nociception by suppressing stress‐induced hypoalgesia, and that this effect is reduced or abolished if the treatment is performed in the absence of light. This raises the question as to whether other sources of sensory stimuli may also modulate these magnetic effects. We investigated the possible role of olfaction in the magnetically induced effects on sensitivity to nociceptive stimuli and heart rate (HR) in restraint‐stressed homing pigeons exposed to an Earth‐strength, irregularly varying (<1 Hz) magnetic field. The magnetic treatment decreased the nociceptive threshold in normally smelling birds and an opposite effect was observed in birds made anosmic by nostril plugging. Conversely, no differential effect of olfactory deprivation was observed on HR, which was reduced by the magnetic treatment both in smelling and anosmic pigeons. The findings highlight an important role of olfactory environmental information in the mediation of magnetic effects on nociception, although the data cannot be interpreted unambiguously because of the lack of an additional control group of olfactory‐deprived, non‐magnetically exposed pigeons. The differential effects on a pigeon's sensitivity to nociceptive stimulus and HR additionally indicate that the magnetic stimuli affect nociception and the cardiovascular system in different ways. Bioelectromagnetics 33:309–319, 2012. © 2011 Wiley Periodicals, Inc.     

Relevance of visual and olfactory cues for host location in the mustard leaf beetle Phaedon cochleariae

The relevance of visual and olfactory cues for host‐plant location is investigated in males and females of the oligophagous mustard leaf beetle Phaedon cochleariae Fabricius (Coleoptera: Chrysomelidae). Different objects are offered in a walking arena and the behaviour of beetles is observed. Beetles orient toward vertically or horizontally striped black and white pattern independent of stripe orientation. The results suggest that contrast facilitates orientation in the field, whereas the pattern itself may be less important for host location in dense vegetation. The response to green and yellow objects is tested to investigate discrimination abilities between young (green) and mature (yellow) leaves. Beetles prefer green over yellow independent of material (cardboard or leaves of Nasturtium officinale R. Br., Brassicaceae). Preference behaviour tested in a dual‐choice contact assay coincides with visual preferences, where adults prefer young, more nutritious leaves for feeding and oviposition. Furthermore, females discriminate between visual cues of green leaves and green cardboard, whereas males do not, indicating that females are more sensitive in colour discrimination. Differences in colour wavelength influence the choice of beetle behaviour more strongly than differences in intensity. Both sexes of P. cochleariae prefer volatiles of the host plant N. officinale, whereas only females respond to the main volatile compound 2‐phenylethyl isothiocyanate. Given a choice between visual and olfactory cues, males orientate towards the colour cues, whereas females do not show any preferences. In males, visual cues may thus override olfactory cues, whereas, in females, both are equally important, which may reflect different ecological requirements and/or physiological abilities.     

When Does Previewing the Landscape Affect Pigeon Homing?

The importance of visual landmarks during homing in pigeons (Columba livia) remains a contentious issue. Three experiments which explore the role of visual landmarks at release sites are reported here. The effects of releasing homing pigeons after a 5-minute period in either a clear or an opaque sided release box were investigated. In the clear sided box pigeons were able to observe local surroundings at a release site, but this view was obstructed in the opaque sided box. In experiment 1 pigeons were released from familiar locations close to home (between 2 and 5.6 km): being unable to view landmarks prior to release significantly slowed homing speeds. In experiment 2 pigeons were released at familiar locations further from home (between 8.4 and 10 km): being unable to view landmarks prior to release did not significantly affect homing speeds. In experiment 3 pigeons were trained to home from distant release sites but were tested at closer, unfamiliar sites located on the likely homing routes used by the pigeons in training. No significant difference in homing speeds were observed when pigeons were released from either the clear or opaque sided box. The significance of these results for understanding the role of visual landmarks within a pigeon's familiar area is discussed.     

Female effect in sheep. II. Role of volatile substances from the sexually receptive female; implication of the sense of smell

The importance of olfactory cues in inducing luteinizing hormone and testosterone secretion as a response to stimulation by sexually receptive ewes has been tested. In sexually experienced rams, olfactory stimulation with urine, wool and vaginal secretions from sexually receptive females placed in a mask did not induce an endocrine response. The female-induced secretion of LH and testosterone was similar in anosmic, sham-operated and in control rams. These results show that olfactory cues are not necessary in the mediation of interindividual stimulation of endocrine response in the sexually experienced ram.     

Which senses play a role in nonhuman primate food selection? A comparison between squirrel monkeys and spider monkeys

In order to optimize foraging efficiency and avoid toxicosis, animals must be able to detect, discriminate, and learn about the predictive signals of potential food. Primates are typically regarded as animals that rely mainly on their highly developed visual systems, and little is known about the role that the other senses may play in food selection. It was therefore the aim of the present study to assess which senses are involved in the evaluation of food by two species of New World primates: the squirrel monkey and the spider monkey. To this end, six animals per species were repeatedly presented with both familiar and novel food items, and their behavior was videotaped and analyzed. To obtain a further indication of the relative importance of visual and chemosensory cues, the animals were also presented with familiar food items that were experimentally modified in color, odor, or both color and odor. The results demonstrate that squirrel monkeys and spider monkeys use olfactory, gustatory, and tactile cues in addition to visual information to evaluate novel food, whereas they mainly inspect familiar food items visually prior to consumption. Our findings also show that in both species the use of nonvisual cues decreased rapidly with repeated presentations of novel food, suggesting a fast multimodal learning process. Further, the two species clearly differ in their relative use of nonvisual cues when evaluating novel or modified food, with spider monkeys relying more on olfactory cues than squirrel monkeys, and squirrel monkeys relying more on tactile cues compared to spider monkeys.