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Summary1. Daubenton's Bats (Myotis daubentonii) foraging over a stream concentrated their activity over calm surfaces, avoiding an adjacent area with small ripples (< 3 cm high). Aerial insects were most abundant over the ripples, so insect distribution could not explain why the bats avoided this area. 2. The bats flew low over water and always (N = 22) directed the head forwards, presumably emitting the echolocation beam parallel to the surface, thus minimizing clutter. At an angle of incidence of 30°there was significantly more clutter from the rippled water. 3. The ripples produced ultrasonic noises in the form of transient pulses at an average rate of 6·2 per second. In the present case, such pulses were common enough potentially to interfere with target detection by the bats. Transient noises and echo clutter from moving ripples may be the principal reason why bats generally avoid foraging low over turbulent water. 4. The target strength of a potential insect prey at the water surface and the source levels of the bats' searching signals were measured to use in estimating the echo level at the bat when it detects the prey. The echo level at detection (+ 38 dB sound pressure level) was about the same as the clutter level extrapolated to the detection distance. This suggests that Daubenton's Bat operates at very low signal-to-noise ratios when foraging for insects near the water surface. Key-words: Echo clutter, noise, predation, source levels, ultrasoundFunctional Ecology (1999) 13, 247-255 247 Materials and methods DESCRIPTION OF THE STUDY SITEThe study was made at the upper reach of the Tidan river system in southern Sweden (57°53'N; 13°38'E) 24 July to 31 August 1996. The study site was a small (5-10 m wide, about 0·5 m deep) stream, ≈ 200 m long, connecting two oligotrophic lakes and surrounded by deciduous woodland and pasture (the site has been described in more detail earlier; Rydell 1986). The observations and experiments were made within 50 m along the stream; in a 15-m section of gently turbulent water and along adjacent sections of calm, slow-flowing water upstream and downstream. The bank of the upstream calm water section consisted of stone walls (about 1 m high) and this section also had an old stone bridge crossing it. The rippled section and the downstream calm water section had lower banks, naturally covered by herbaceous vegetation and a few rocks. All sections of the stream were bordered by old deciduous trees and thus partly shaded by the overhanging branches. The largest ripples in the middle of the turbulent section had amplitudes of 2-3 cm (measured with a ruler) with distances of 5-10 cm between the tops. RECORDING BAT ACTIVITYThe flight activity of Myotis daubentonii was estimated at the three sites (calm water upstream, ripples and calm water downstream, respectively), by counting bat passes, using a D-960 bat detector (Pettersson Elektronik AB, Uppsala, Sweden), directed out over the water. A small torch light was also aimed across the stream, to facilitate visual observations in ca...

SUMMARY We investigated the echolocating bat's use of an acoustic landmark for orientation in a complex environment with no visual information. Three bats of the species Eptesicus fuscus were trained to fly through a hole in a mist net to receive a food reward on the other side. In all experiments, the vocal behavior of the bats was recorded simultaneously using a high-speed video recording system, allowing for a 3D reconstruction of the flight path. We ran three types of experiments, with different spatial relations between the landmark and net hole. In the first experiment, the bat's behavior was studied in test trials with the landmark placed 10 cm to the left of the net opening; between test trials, the positions of the net opening and landmark were moved, but the spatial relationship between the two remained fixed. With the landmark adjacent to the net opening, the bats quickly found the hole. In the second experiment, bats were tested in control trials in which the landmark was moved independently of the hole, breaking the established spatial relationship between the two. In control trials the bats repeatedly crashed into the net next to the landmark, and inspected the area around it. In the final experiment, the landmark was removed altogether from the set-up. Here the bats spent more time per trial searching for the net opening with an increased number of inspections as well as crashes into the net. However, over the course of a test day without the landmark, bats reduced the time spent per trial and focused inspections and crashes around the hole. The behavioral data show for the first time that the echolocating bat can learn to rely on an acoustic landmark to guide spatial orientation.

Currently the most prevalent format for mobile gaming is the single-player variety, where users interact with the game's artificial intelligence within a number of genres such as sports, action, racing, and puzzle games, etc. The users install the game and play it for entertainment and to pass the time until repetitiveness and boredom prompts them to stop playing that game and switch to another one. We would like to suggest the incorporation of socializing elements into mobile game concepts, in order to enrich the user experience and allow users to share this experience with other members of their readily available social networks. Empirical studies with Malaysian and Thai youths were conducted to gain insights on behavior in playing videogames in general and playing mobile games to be specific. These studies identified socializing as one of the key drivers in playing these games. The results were shared and resulted in a jointly collaborated interface design project to explore the theme of 'socializing in mobile games'. Interface design students created new game concepts incorporating elements of socializing. Two of these mobile design projects were shown as examples to illustrate the mobile game concepts and also to identify the common themes in the context of socializing within mobile games.