The echolocation and hunting behavior of Daubenton's bat,Myotis daubentoni

Summary The echolocation and hunting behavior of Daubenton's bat (Myotis daubentoni) were studied in the field under completely natural conditions using a multiflash photographic system synchronized with high-speed tape recordings. The hunting behavior of M. daubentoni is separated into four stages. In the search flight stage Daubenton's bat flies with an average speed of 3.4±0.6 m/s SD usually within 30 cm over water surfaces searching for insects. After the detection of potential prey, the approach flight stage occurs, during which the bat approaches the target in a goal-directed flight. The stage tail down indicates that M. daubentoni is close to the potential prey (approximately 10–22 cm) and is preparing for the catch. The insects are caught with the interfemoral membrane, the feet, and sometimes with the additional aid of a wing. In the stage head down, the bat seizes the prey during flight. Immediately afterwards, Daubenton's bat returns to search flight. M. daubentoni shows the typical echolocation behavior of a vespertilionid bat, emitting frequency-modulated (FM) echolocation signals. The three behavioral stages search, approach, and terminal phase (Griffin et al. 1960) are used to describe the pulse pattern of foraging M. daubentoni in the field. The terminal phase (or buzz) of Daubenton's bat is separated into two parts: buzz I and buzz II. Buzz II is distinguished from buzz I by the following characteristics: a sharp drop in terminal frequency, a distinct reduction in the bandwidth of the first harmonic, a continuous high repetition rate throughout the phase in the range 155–210 Hz, very short pulses (0,25–0.3 ms) and interpulse intervals (4.5–5.0 ms) at the end of the phase, and a distinct decrease in duty cycle. A pause in echolocation separates the end of the terminal phase from the ongoing search phase. The reduction in sound duration after the detection of a target and during pursuits with successfull or attempted catches is discussed in relation to the actual distance of the bat to the target at each stage. It is likely that Daubenton's bat reduces sound duration during approach and terminal phase in order to prevent an overlap of an outgoing pulse with the returning echo from the target. It is argued that the minimum detection distance can be estimated from the sound duration during search flight. Estimates of detection and reaction distances of M. daubentoni based upon synchronized photos and echolocation sequences are given to corroborate this hypothesis. An average detection distance of 128 cm and an average reaction distance of 112 cm were determined. Each behavioral stage of foraging M. daubentoni is characterized by a distinct pattern of echolocation signals and a distinct stage in hunting behavior. The approach flight in hunting behavior coincides with the approach phase and with buzz I in echolocation behavior. The stage tail down corresponds to buzz II. The stage head down is correlated with a pause in echolocation. Immediately afterwards, the bat returns into search flight and into the search phase, emitting search signals.     

Application of a stochastic, Weibull probability generator for replacing missing data on ambient concentrations of gaseous pollutants

A stochastic, three-parameter, Weibull frequency distribution, probability generator was tested by using theoretical data. Subsequently, it was applied to replace missing values of hourly atmospheric concentrations of trace gases that were continuously monitored at three study sites, for 2 years. The results were highly accurate and realistic. The cumulative means and the medians calculated by the Weibull method were intermediate between corresponding values calculated by uniform substitution of missing values with 'zero' or with half of the minimum detection limit of the appropriate measurement instrument used. Furthermore, the Weibull method allowed the replacement of as many as 100 missing values on either side of a measured data sub-set, without altering the overall characteristics of the true frequency distribution of the entire data set.     

Determination and characterization of chloroguaiacol conjugates in fish bile by HPLC

In this study a small-scale technique for direct analysis of metabolic conjugates of 4,5,6-trichloro- (CG-3) and tetrachloroguaiacols (CG-4) in fish bile by RP-HPLC is presented. Only one metabolite, glucuronic acid conjugate, was demonstrated in two Lake Baikal fishes (Leuciscus leuciscus baikalensis and Cottus kessleri) exposed to CG-3 or CG-4 at 6 degrees C for 1-2 days. In Leuciscus the ratio between free CG-4 in the ambient water and conjugated CG-4 in the bile averaged 264,000. Intraperitoneal injections of tetrachloroveratrol (CV-4) into Thymallus arcticus baikalensis did not reveal any traces of free CV-4 or CG-4 glucuronide in the bile in 2 days at 5 degrees C. We therefore suggest that CV-4 was not demethylated and subsequently conjugated with glucuronic acid in the liver of this fish species.     

Photolysis of atrazine and ametryne herbicides in Barbados sugar cane plantation soils and water

The photodegradation kinetics of atrazine (2-chloro-6-(ethylamino)-4-isopropylamino-1,3,5-triazine) and ametryne (2-methylthio-4-ethylamino-6-isopropylamino-s-triazine), in fresh and coastal salt water from Barbados, were measured under irradiation with artificial solar and UV254-radiation. The first-order rate constants were greater for ametryne than for atrazine, and the rates were reduced in seawater relative to fresh water, and in soil slurries relative to fresh water. However, rates were accelerated in the presence of iron(III) at pH 3 due to photo-Fenton type processes. This rate enhancement was reduced at ambient pH values (pH 7-7.5) representative of surface water in Barbados. These results have important implications for the relative persistence of these contaminants in aquatic environments in tropical areas.     

Dietary exposure to polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls of the French population: Results of the second French Total Diet Study

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) bioaccumulate through the food chain and are therefore of public health concern. Exposure to these compounds was assessed in the second French Total Diet Study (TDS). Food samples (n=583) were collected to be representative of the whole diet of the population, prepared as consumed, and analyzed. Contamination data were combined with national individual food consumption data. Mean exposure (95th percentile) to PCDD/F+DL-PCBs was assessed to be 0.57 (1.29) pg TEQ(WHO-98) (kg bw)(-1) d(-1) in the adult population and 0.89 (2.02) pg TEQ(WHO-98) (kg bw)(-1) d(-1) in the child and teenager population. Less than 4% of the population exceeded the health-based guidance value for PCDD/F+DL-PCBs. Mean exposure (95th percentile) to the six indicator PCBs (PCB 28, 52, 101, 138, 153, 180) was estimated at 2.71 (7.90) ng (kg bw)(-1) d(-1) in the adult population and 3.77 (11.7) ng (kg bw)(-1) d(-1) in the child and teenager population. Only 2.6% of the adults [CI(95%): 1.9; 3.3] and 6.5% of the children and teenagers [5.2; 7.8] exceeded the health-based guidance value for total PCBs. These results show that the contamination levels in food and therefore the exposure of the general French population to PCDD/Fs and PCBs have declined (by a factor of 3.2 for PCDD/F+DL-PCBs and about three for total PCBs) since the last evaluation, which was conducted using another methodology in 2005 and 2007, and show the efficiency of the European risk management measures which came into force after these evaluations.     

Physiological recovery from episodic acid stress does not mean population recovery of Gammarus fossarum

The physiological responses of the acid-sensitive amphipod Gammarus fossarum exposed in situ to acid stress (pH4.5 and 5.5) and then transferred back to neutral water were investigated. Survival rate and haemolymph [Cl(-)] and [Na(+)] were assessed after 24, 48 and 72h of exposure in acidic streams and after a recovery period of 12, 24, 36, 48 and 60h. After 24h, exposure to slightly acidic (pH5.5) and strongly acidic water (pH4.5) led to a severe and significant depletion in haemolymph [Na(+)] and [Cl(-)] compared to organisms exposed in circumneutral water (pH7.3). However, after only a 12h-period of transfer back in neutral water and whatever the previous exposure time (24, 48 and 72h) in both slightly and strongly acidic water, haemolymph [Na(+)] and [Cl(-)] were equal or superior to the control level without associated mortality. In spite of this fast physiological recovery capacity, populations of G. fossarum living in streams undergoing episodic acid stresses were drastically affected thus, demonstrating the high acid-sensitivity of this species. We discuss the possible reasons of population regression and the absence of population recovery.     

Prediction of the vertical profile of ozone based on ground-level ozone observations and cloud cover

A number of statistical techniques have been used to develop models to predict high-elevation ozone (O3) concentrations for each discrete hour of day as a function of elevation based on ground-level O3 observations. The analyses evaluated the effect of exclusion/inclusion of cloud cover as a variable. It was found that a simple model, using the current maximum ground-level O3 concentration and no effect of cloud cover provided a reasonable prediction of the vertical profile of O3, based on data analyzed from O3 sites located in North Carolina and Tennessee. The simple model provided an approach that estimates the concentration of O3 as a function of elevation (up to 1800 m) based on the statistical results with a +/- 13.5 ppb prediction error, an R2 of 0.56, and an index of agreement, d1, of 0.66. The inclusion of cloud cover resulted in a slight improvement in the model over the simple regression model. The developed models, which consist of two matrices of 24 equations (one for each hour of day for clear to partly cloudy conditions and one for cloudy conditions), can be used to estimate the vertical O3 profile based on the inputs of the current day's 1-hr maximum ground-level O3 concentration and the level of cloud cover.     

An automated overlying water-renewal system for sediment toxicity studies

An automated water-renewal toxicity test system is described for exposing benthic invertebrates to whole sediments. The system will intermittently deliver laboratory or on-site water for overlying water replacement in sediment exposures. A range of cycle rates can be used to produce different volume additions of overlying water per day to exposure chambers. The system can be used with six different treatments and eight replicates per treatment producing 48 exposure chambers. Three formulated sediments with variable organic carbon (1.5%, 7.5%) and sand (14%, 63%) content were prepared to test the system exposing amphipods, Hyalella azteca and midges, Chironomus tentans in 10 day whole sediment tests. Intermittent water flow was used with a 90 min cycle time to create two volume additions of laboratory water per 24 h in exposure chambers (180 ml sediment, 320 ml water). Overlying water quality conditions, and survival and growth of both species were consistent and within acceptable limits for the testing requirements of the U.S. EPA guidelines for sediments with freshwater invertebrates.