Orientation and navigation in bats: known unknowns or unknown unknowns?

Bats have been extensively studied with regard to their ability to orient, navigate and hunt prey by means of echolocation, but almost nothing is known about how they orient and navigate in situations such as migration and homing outside the range of their echolocation system. As volant animals, bats face many of the same problems and challenges as birds. Migrating bats must relocate summer and winter home ranges over distances as far as 2,000 km. Foraging bats must be able to relocate their home roost if they range beyond a familiar area, and indeed circumstantial evidence suggests that these animals can home from more than 600 km. However, an extensive research program on homing and navigation in bats halted in the early 1970s. The field of bird navigation has advanced greatly since that time and many of the mechanisms that birds are known to use for navigation were not known or widely accepted at this time. In this paper I discuss what is known about orientation and navigation in bats and use bird navigation as a model for future research in bat navigation. Technology is advancing such that previous difficulties in studying orientation in bats in the field can be overcome and so that the mechanisms of navigation in this highly mobile animal can finally be elucidated.     

Behaviour that influences dispersal and connectivity in the small,young larvae of a reef fish

Determining the scale of larval dispersal and population connectivity in demersal fishes is a major challenge in marine ecology. Historically, considerations of larval dispersal have ignored the possible contributions of larval behaviour, but we show here that even young, small larvae have swimming, orientation and vertical positioning capabilities that can strongly influence dispersal outcomes. Using young (11–15 days), relatively poorly developed (8–10 mm), larvae of the pomacentrid damselfish, Amblyglyphidodon curacao (identified using mitochondrial DNA), we studied behaviour relevant to dispersal in the laboratory and sea on windward and leeward sides of Lizard Island, Great Barrier Reef. Behaviour varied little with size over the narrow size range examined. Critical speed was 27.5 ± 1.0 cm s⁻¹ (30.9 BL s⁻¹), and in situ speed was 13.6 ± 0.6 cm s⁻¹. Fastest individuals were 44.6 and 25.0 cm s⁻¹, for critical and in situ speeds, respectively. In situ speed was about 50% of critical speed and equalled mean current speed. Unfed larvae swam 172 ± 29 h at 8–10 cm s⁻¹ (52.0 ± 8.6 km), and lost 25% wet weight over that time. Vertical distribution differed between locations: modal depth was 2.5–5.0 and 10.0–12.5 m at leeward and windward sites, respectively. Over 80% of 71 larvae observed in situ had directional swimming trajectories. Larvae avoided NW bearings, with an overall mean SE swimming direction, regardless of the direction to nearest settlement habitat. Larvae made smaller changes between sequential bearings of swimming direction when swimming SE than in other directions, making it more likely they would continue to swim SE. When swimming NW, 62% of turns were left (more than in other directions), which would quickly result in swimming direction changing away from NW. This demonstrates the larvae knew the direction in which they were swimming and provides insight into how they achieved SE swimming direction. Although the cues used for orientation are unclear, some possibilities seemingly can be eliminated. Thus, A. curacao larvae near Lizard Island, on average swam into the average current at a speed equivalent to it, could do this for many hours, and chose different depths in different locations. These behaviours will strongly influence dispersal, and are similar to behaviour of other settlement-stage pomacentrid larvae that are older and larger.     

Does the financing of extended producer responsibility influence economic growth?

The question of how the financing of Extended Producer Responsibility (EPR) affects the overall performance of the economy is important as products covered by EPR comprise an increasing part of the economy. In this paper, an Overlapping Generations (OLG) model with endogenous growth is applied to the case and a comparison between two financing schemes, an insurance solution and a pay-as-you-go (PAYG) solution, is made with respect to the effect on the level of production, the growth rate, the impact of a productivity shock and the risk exposure. It is found that in the case of a funded solution, both the level of production and the growth rate in production is higher than in the PAYG case, and the short-run effect of productivity shock is bigger. The policy indication is clear: EPR should be attached to a financing scheme if welfare is to be maximised.     

Do cod form spawning leks? Evidence from a Newfoundland spawning ground

Catch and acoustic telemetry data were used to test three predictions of lekking behaviour in Atlantic cod (Gadus morhua L.) at a small-scale spawning ground (∼25 km²) in Placentia Bay, Newfoundland: (1) that cod form male-skewed aggregations during spawning; (2) spawning arenas occur at consistent sites; and (3) on the arenas, there will be higher proportions of spawning fish. Forty-two fishing sets from 1998 to 2003 indicated male-skewed sets early in the spawning season (April) in 5 of 6 survey years. Male-skewed sets were consistently distributed at depths < 50 m and mostly in one part of the ground. The proportions of spawning females and spent males were significantly higher in male-skewed sets, whereas sets with equal sex ratios had significantly higher proportions of immature males and spent females. In addition, cod of both sexes were significantly larger in male-skewed sets. Telemetric tracking of 25 cod in 2002 and 2003 (12 males, 13 females) indicated that both males and females were highly mobile while present on the spawning ground. Overall, our results add support to the hypothesis that cod employ a lekking mating system.     

The effect of metal catalysts on the formation of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran precursors

The catalytic effects of copper and iron compounds were examined for their behavior in promoting formation of chlorine (Cl₂), the major chlorinating agent of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), in an environment simulating that of municipal waste fly ash. Formation of Cl₂ occurred as a result of a metal-catalyzed reaction of HCl with O₂. Catalytic activity was greatest at a temperature of approximately 400 °C, supporting a theory of de novo synthesis of PCDDs and PCDFs on fly ash particles downstream of waste combustion.     

Distribution of radionuclides among the main components of Lake Chervyanoe in the Eastern Ural Radioactive Trace

Radioecological conditions have been estimated in Lake Chervyanoe located on the central axis of the Eastern Ural Radioactive Trace (EURT) about 100–110 km northeast of the Mayak Production Association. Data on the ⁹⁰Sr and ¹³⁷Cs contents in the main components of the lake, the distribution of these radionuclides over the profile of bottom sediments, and their amounts in the lake are presented. The experimental data have been used to construct mathematical models for estimating changes in the radionuclide concentrations and amounts in the water and bottom sediments of the lake over a long period after the nuclear accident, as well as the tritium content of the lake water in different periods of time.     

Experiments comparing the use of kites and gas bangers to protect crops from woodpigeon damage

Woodpigeon damage to spring cabbage on two farms in different years was greatly reduced when a large kite was flown over the fields. Protection continued for over 3 months with no sign of habituation to the kite by pigeons. Woodpigeons avoided flying or settling within 250 m of the kite. Damage in fields with a gas banger exceeded that in fields with a kite, especially in severe winter weather. “Humming line” proved ineffectual in reducing damage. On these lowland farms it was necessary to launch the kite on most mornings, but if such launching can be carried out, kites can be effective in reducing damage by woodpigeons.     

Cadmium uptake by the water hyacinth: Effects of root mass,solution volume,complexers and other metal ions1

At a fixed Cd²⁺ concentration water hyacinth ($\text{Eichhornia crassipes}$) plants with greater root mass (dry weight) take up more metal ions as a function of time, and more metal ions are taken up by a plant as the solution volume is increased. Experiments in which several different metal ion complexers were present suggest that (1) the roots possess sites which initially reversibly bind free Cd²⁺, (2) some added complexers can compete with these root sites for free Cd²⁺, and (3) with time Cd²⁺ bound to the roots is translocated into into the root tissues effectively removing it from the equilibrium processes in solution. Many metal ions are taken up by the plant but only the micronutrient Zn²⁺ competes well with Cd²⁺ for uptake. Thus, there may be binding sites on the roots for specific metal ions.     

Structural-temporal organization of a rodent community in the Teletskaya Taiga,Altai Mountains

The structural-temporal organization of a murine rodent community in the taiga has been studied near Lake Teletskoe, Mountain Altai. The results show that the long-term dynamics of indices characterizing community diversity depend mainly on changes in the structure of dominance rather than on the population dynamics of species. The distribution of species in the factor space corresponds to their preference for certain biotopes, from dry to relatively moist. An analysis of relationships within the rodent community has revealed the synchronous dynamics of species abundance and antiphase pattern of changes in the structural indices of dominant species.