Contribution of olfactory navigation and non-olfactory pilotage to pigeon homing

Summary By means of training flights (mostly flock releases), two groups of young homing pigeons were made familar with a larger area asymmetrically extending from the loft toward SW and NE, respectively. Thereafter, birds of both groups were released within each of the training areas with which one sort of birds was familiar (F⁺), the other unfamiliar (F^-). Even the F⁺ pigeons had never been released at the test site itself (nearest previous release 10 km apart). Half of each group was allowed to smell environmental odors (O⁺); the other half breathed charcoal-filtered air during transportation and at the release site until a few minutes before release when they were deprived of olfaction by intranasal application of Xylocain (O^-). The two test sites were 53 km distant from home. There was little difference in initial orientation as well as in homing performance between pigeons that were allowed to smell natural air and were familiar with the area (F⁺O⁺) and those that were privileged in only one respect (F⁺O^- and F^-O⁺). Yet if none of the preconditions was met (F^-O^-), performances were drastically reduced. The findings show that pigeons make use of two independent homing methods, olfactory navigation (presumably based on a navigational map) and non-olfactory pilotage (presumably based on a topographical map). The latter method is restricted to a more or less familiar area determined by individual experience. Its boundaries are poorly defined and can be estimated by the experimenter only in rough approximation. Within this area, the homing system takes advantage of more or less redundant inputs. Outside of it, olfactory information seems indispensable.     

Pigeon homing: Different effects of olfactory deprivation in different countries

Summary This study compares the orientation of untreated pigeons and pigeons subjected to olfactory deprivation at two lofts near Pisa, Italy, at a loft at Ithaca, New York, USA, and at a loft at Frankfurt a.M., FRG. The experimental birds were rendered anosmic by nasal plugs until Gingicain, a local anaesthetic, was applied shortly before release. The Italian and American control pigeons appeared to orient towards home equally well, while the control pigeons in Germany frequently preferred directions that deviated significantly from the home direction. The effect of olfactory deprivation was small in the USA and in Germany; it was significantly larger in Italy, indicating that Italian pigeons depend on olfactory information to a much greater extent. These findings suggest that there are important regional differences in the strategies and cues pigeons use to navigate. The varied roles of olfactory information, and the reasons for these differences are discussed.     

Pigeon navigation: Charcoal filter removes relevant information from environmental air

Summary Homing pigeons were displaced and kept until they were released in airtight containers ventilated with environmental air that could be passed through: (a) a filter made of fiberglass paper retaining large portions of the solid and liquid aerosol particles, (b) an additional filter consisting of activated charcoal, or (c) no filter (controls). Before its release, each bird was taken out of the container, and its olfactory epithelium was immediately anesthetized by lidocaine (Xylocaine). Thus, neither experimentals nor controls were able to smell while their initial orientation behavior was being observed.The controls' initial bearings were better homeward-oriented than those of pigeons ventilated with charcoal-filtered air in 14 of 17 releases conducted in Italy and Germany, at distances of 24–155 km. In the final analysis, the bearings of the charcoal-filter birds did not show any relation to the direction toward home, whereas those of the controls did. Pigeons ventilated with air that had passed through only the paper filter did not behave noticeably differently from control pigeons.It is concluded that the material bases of olfactory navigation in pigeons are substances dispersed in the atmosphere, most probably in a molecular state.     

Young convict cichlids use visual information to update olfactory homing cues

In this study, we tested the tendency of young cichlids to orient towards their parents using chemical cues. Convict cichlids have biparental defence of their free-swimming young. If young become separated from their family they must rejoin their family within minutes to have any chance of survival. Here, we used a dichotomous Y-maze to test if displaced convict cichlid young can use chemical cues to orient to their family. First, we showed that young preferentially orient toward water taken from their home tank versus blank water taken from a tank that contained no fish. Second, we showed that young prefer home tank water to water from a tank containing another family of convict cichlids. In a third experiment, we placed young convict cichlids in a small aquarium inserted within a larger aquarium. The large aquarium contained either their parents or no fish. The small insert aquarium contained blank water from a tank that had never contained fish. After 20 min in the insert tank, young convict cichlids were placed in the Y-maze and given a choice between either their home tank water or water from the insert tank. Convict cichlids that did not see their parents during the 20-min conditioning period oriented strongly toward chemical cues of their home tank water. Young that saw their parents during the 20-min conditioning period oriented strongly toward the chemical cues of the insert tank. These data indicate that young convict cichlids use visual cues to learn and reset the smell of “home” in less than 20 min.     

Pigeon homing: A repetition of the deflector loft experiment

Summary Pigeons brought up in closed cages deflecting the winds to the left or to the right show, on release, a bias of the mean vanishing directions to the left or right of the mean direction of untreated control birds. The results are in full accord with the findings of Baldaccini et al. (1975).Supported by the Deutsche Forschungsgemeinschaft     

Pigeon homing: sun compass use in the southern hemisphere

Although the sun compass of birds is based on learning the sun's arc during development, it was unclear whether birds can use the sun when its apparent movement is reversed, in particular, whether northern birds that have been introduced into the southern hemisphere can use the southern sun. To answer this question, clock-shift experiments were performed with local homing pigeons in Auckland, New Zealand (37°S). In three fast-shift tests and two slow-shift tests, the experimental birds showed deflections from the untreated controls that were the mirror images of those observed in the northern hemisphere. These results clearly show that homing pigeons in New Zealand use a sun compass that is adapted to the situation in the southern hemisphere. The learning processes establishing the compensation mechanisms thus appear to be free of constraints concerning the direction of the sun's movement. Differences from recent findings with migratory birds, where the direction of celestial rotation proved of crucial importance for establishing the migratory direction, are discussed: the differences may arise from the different orientation tasks, in particular, from the involvement of innate information in establishing the migratory direction. Received: 13 November 1997 / Accepted after revision: 28 February 1998     

Pigeon homing: the effect of a clock-shift is often smaller than predicted

This analysis is based on 103 releases with 6-h clock-shifted pigeons of various ages and experiences. Resetting the internal clock normally leads to a significant change in initial orientation; however, in half of the cases, the induced deflections are significantly smaller than predicted by the sun compass hypothesis. The relative size of the deflections decreases with increasing age and experience (Fig. 3). Only young pigeons with limited experience respond as expected, while old birds show deflections which are, on the average, only slightly more than half of the predicted size, except at extremely familiar sites (Table 2). There is no difference between fast and slow shifts (Fig. 4). It is not possible to clearly specify under what circumstances smaller deflections occur; previous clock-shifts (Fig. 5), familiarity with the release site (Table 4) and duration of the shifting procedure (Table 5) do not seem to be the reasons. Clock-shifting also tends to decrease the vector lengths and has a marked effect on homing performance (Table 7). Nevertheless, considerable numbers of clock-shifted birds return on the day of release before their internal clock has begun to be reset back to normal. The general role of the sun compass in bird orientation is considered and theoretical implications of our findings are discussed in view of the map and compass-model and the possibility that an alternative, non-time-compensating compass is used in parallel with the sun compass.     

Detour experiments with homing pigeons: information obtained during the outward journey is included in the navigational process

Summary To test the hypothesis that information on the route of the outward journey is involved in the orientation of displaced homing pigeons, we compared the behavior of control pigeons that had been displaced by the most direct route with that of experimental pigeons that had been transported along detours to the same release sites. At distances of 40 km we found no consistent effect. At distances between 75 and 130 km, however, deviations to the left of the direct route induced deflections to the left, while deviations to the right induced deflections to the right, i.e. the deflections of the vanishing bearings tended to compensate for the initial detour of the outward journey. The deflections were smaller than the deviations of the routes; they were not related to the routes themselves or the location of the release sites. A significant correlation emerged with the vector length of the controls, as longer vectors were associated with smaller deflections. This suggests that information on the route of the outward journey is used together with local map information in the navigational process, the significance of the route-specific information apparently depending on quality and reliability of the available local information. The nature of factors controlling the detour effect is still open.Correspondence to: R. Wiltschko     

Ultrastructure of olfactory mucosa in the homing baltic sea trout Salmo trutta trutta

Scanning and transmission electron microscopy techniques have been used to study the olfactory organs of adult fresh-water adapted Baltic sea trout Salmo trutta trutta L. homing back to the River Umeälven in Västerbotten, Sweden. Parr and smolt show only minor differences in comparison to the adult mucosa. All fish have polymorphism of receptors, supporting cells and basal cells, and a dynamic cell population with primary cells basally. These mature and die, and are either extruded or phagocytized. The mucosa has a remarkably large population of loose connective tissue cells (plasma cells, macrophages and lymphoid wandering cells) as well as all types of leucocytes. The olfactory organs of sea trout have labyrinth cells, a cell type unique for vertebrates. These cells probably help to maintain an optimal ion balance, which is of great ecological importance for this migrating species. The mucosa cilia have small tubercles arranged in a spiral pattern and correlated with transitional filaments from the 9 peripheral fibrils. A hypothesis on the relationship of primary supporting cells, primary nonsensory cells, immature fibroblasts and Schwann cells is presented.     

Propagation of olfactory information within the honeybee hive

Transfer of information about food source characteristics within insect societies is essential to colony-foraging success. The food odor communicated within honeybee hives has been shown to be important for food source exploitation. When successful foragers return to the nest and transfer the collected nectar to hive mates through mouth-to-mouth contacts (trophallaxis), potential recruits receiving these samples learn the food odor by associative learning. The food then becomes rapidly distributed among colony members, which is mainly a consequence of the numerous trophallaxes between hive-mates of all ages during food processing. We tested whether the distribution of food among hive mates causes a propagation of olfactory information within the hive. Using the proboscis extension response paradigm, we show that large proportions of bees of the age groups representing the main worker castes, 4 to 9-day-old bees (nurse-aged bees), 12 to 16-day-old bees (food processor-aged bees), and actual foragers (about 17+ day old bees) associatively learn the food odor in the course of processing food that has been collected by only a few foragers. Results further suggest that the information is shared more or less equally between bees of the three age groups. This shows that olfactory information about the flower species exploited by foragers is distributed within the entire colony and is acquired by bees of all age groups, which may influence many behaviors inside and outside the hive.     

Application to the Port of Sines of a new tool for risk assessment in port navigation

This paper describes a first approach on the risk assessment in port navigation using GUIOMAR, an integrated system for port and coastal engineering modelling developed at the National Civil Engineering Laboratory (LNEC), Portugal, using a GIS software environment. A set of automatic procedures was designed to include a new methodology based on the amplitude of the wave-induced vertical movement of a ship along its trajectory. In this methodology, the risk in port navigation is assessed on the basis of a combination of the probability of exceedance of a pre-set threshold for the ship??s vertical movements and its consequences. To test the new procedures, a set of sea wave records obtained at the Sines wave-buoy from 1988 to 2002 was transferred into Sines Port using two numerical models of sea wave propagation and deformation (SWAN and DREAMS), included in the GUIOMAR system. The numerical model WAMIT was used for estimating the wave-induced ship??s vertical movements inside the port. By applying the new procedures, automatic generation of risk maps was carried out for navigation in the vicinity of the West breakwater of the Port of Sines. The recent developments contribute towards a more versatile and efficient GUIOMAR system, which results in a more adequate tool to support decision-making processes in port and coastal management.     

The role of trail following in the homing of intertidal chitons: A comparison between threeAcanthopleura spp.

Three species of intertidal tropical chitons observed between 1984 and 1986, exhibit different movement patterns:Acanthopleura gemmata (Indian and Pacific Ocean) is a strict homer;A. granulata (Caribbean Sea) is mostly a ranger but sometimes shows homing behaviour;A. brevispinosa (Western Indian Ocean) alternates homing and ranging for different excursions. The three species have been studied in the field using a motographic technique to assess the importance of intra-individual trail following in homing. The fraction of the path which overlaps with earlier segments of an individual's trail is different in the three species: when returning from feeding groundsA. gemmata follows almost the whole of the outgoing path; inA. granulata the path coincidence is minimal, whileA. brevispinosa shows intermediate trail following values. InA. gemmata andA. brevispinosa trail overlap rises rapidly just after feeding, and trail following is mostly backward along the outgoing path. On the other hand,A. granulata shows a linear increase in trail coincidence with increasing path covered and the proportion of forward trail following is relatively higher. Nevertheless, all specimens of the three species which show a high homing performance invariably show a large trail following also. These findings confirm that, despite the interspecific difference in ecology and the related variation in spatial organization of foraging excursions, trail following is the basic mechanism for homing in intertidal chitons.     

Implementing a new model to measure and assess eco-effectiveness as an indicator of sustainability

A model able to measure eco-effectiveness, which was theoretically proposed and illustrated in a previous article, is here developed and implemented for three case studies (USA, EU-15 and Japan) in order to verify its potential usefulness in the natural resources field. The results obtained by the application of the 'loss function' – ability to measure the distance between a real and an ideal situation – show that the model can be seen as a fundamental basis to assess the exploitation intensity of resources among different countries/areas and/or over time, especially if new measures and best environmental practices are adopted to increase resource productivity and to reduce environmental burdens. Since a main issue in the model implementation is related to the subjective choice of weights to be given to the various resources in the loss function (materials, fossil fuels and biomass), a graphical approach based on a 'weighting triangle' is also proposed to overcome the problem of previous weight selection. This tool permits us to make a distinction between a 'non-sustainability' area and a 'sustainability' area, based on whether an increase or a decrease of the loss function is more plausible.     

Designs with a priori information for nonmarket valuation with choice experiments: A Monte Carlo study

Good practice in experimental design is essential for choice experiments used in nonmarket valuation. We review the practice of experimental design for choice experiments in environmental economics and we compare it with advances in experimental design. We then evaluate the statistical efficiency of four different designs by means of Monte Carlo experiments. Correct and incorrect specifications are investigated with gradually more precise information on the true parameter values. The data generating process (DGP) is based on estimates from data of a real study. Results indicate that D-efficient designs are promising, especially when based on Bayesian algorithms with informative prior. However, if good quality a priori information is lacking, and if there is strong uncertainty about the real DGP—conditions which are quite common in environmental valuation—then practitioners might be better off with shifted designs built from conventional fractional factorial designs for linear models.     

Evaluation of tests to assess the quality of mine-contaminated soils

An acid metal-contaminated soil from the Aljustrel mining area (a pyrite mine located in SW Portugal in the Iberian Pyrite Belt) was subjected to chemical characterisation and total metal quantification (Cd, Cr, Cu, Ni, Pb and Zn). Water-soluble metals were determined and a sequential extraction procedure was used to investigate metal speciation. Two bioavailable metal fractions were determined: a mobile fraction and a mobilisable fraction. Soil ecotoxicity was studied using a battery of bioassays: plant growth test and seed germination with cress (Lepidium sativum L.), earthworm (Eisenia fetida) mortality, E. fetida avoidance behaviour, luminescent inhibition of Vibrio fischeri and Daphnia magna immobilisation. Although the total content of Cu, Zn and Pb in the soil was large (362, 245 and 1,250 mg/kg dry matter, respectively), these metals were mostly structurally bound (87% for Cu, 81% for Zn and 89% for Pb) and, therefore, scarcely bioavailable. Nonetheless, the D. magna immobilization test using soil leachate showed an EC₅₀ (48 h) of 36.3% (v/v), and the luminescent inhibition of V. fischeri presented an EC₂₀ (15 min) of 45.2% and an EC₂₀ (30 min) of 10.7% (v/v), suggesting a considerable toxic effect. In the direct exposure bioassays, E. fetida avoided the mine soil at the highest concentrations (50%, 75% and 100% v/v). At the same soil concentrations, cress showed negligible growth. The results suggest the need to use a battery of toxicity tests, in conjunction with chemical methods, in order to assess the quality of mine-contaminated soils correctly.     

Nitrogen and phosphorus turnover in some benthic marine invertebrates: implications for the use of C:N ratios to assess food quality

The present study was designed to measure the relative turnover of nitrogen and phosphorus during a standard period of metabolism among several co-occurring species of benthic invertebrates: chitons (Poneroplax albida Blainville 1825); albalones (Haliotis roei Gray, 1826); gastropods [Turbo (ninella) torquatus Gmelin, 1791]; ascidians [Herdmania momus (Savigny)]; and sponges (Aplysina sp. and Iotrochata baculifera Ridley, 1884). Five of the six species (collected at Wreck Rock, Western Australia in 1985) exhibited a high turnover of phosphorus (P) relative to nitrogen (N). In contrast to N, P turnover was related to the concentration of P in body tissues. A relatively high demand for P in the diet is required to support the observed rapid turnover of P with respect to N. This observation suggests that the evaluation of potential foods would be better accomplished by the measurement of the C:P or the N:P ratio, rather than the commonly used C:N ratio.