Directional escape strategy by the striped plateau lizard (Sceloporus virgatus): turning to direct escape away from predators at variable escape angles

A prey’s orientation to a predator’s approach path affects risk of fleeing straight ahead. By turning to flee closer to straight away from the predator before fleeing, prey can reduce risk. Laboratory studies suggest that escape angles should lead away from predators and be unpredictable. I studied orientation, turn, and escape angles and in a study of striped plateau lizards,Sceloporus virgatus. Lizards fled away from a predator, but often not straight away. Escape angles were variable and bimodally distributed: one mode was straight away for distancing prey from predator and one was near 90°, which maintains ability to monitor the predator or requires turning by the predator. Turn angles increased as orientation shifted toward the predator. Escape angle was closer to straight away when turn angle was larger, but turning did not fully compensate for degree of orientation toward the predator. Directional escape strategies of diverse prey are compared.

Escape strategy of Schreiber’s green lizards (Lacerta schreiberi) is determined by environment but not season or sex

Antipredator escape behaviour varies with several well-established sources of variation ranging from the physical environment to reproductive status. However, the relative roles of these sources are rarely assessed together. We measured (i) the distance to the nearest refuge that Schreiber’s green lizards, Lacerta schreiberi, maintained before an attack (refuge distance) and (ii) the distance lizards allowed a simulated predator to approach before fleeing (flight initiation distance, FID). Refuge distance was unaffected by studied variables. However, FID was positively related to refuge distance on grassy, but not on rocky substrates. Furthermore, refuge distance and escape angle interacted in a substrate-independent manner: lizards allowed predators close when refuges were close or when lizards had to flee towards the predator. In contrast, neither mating season nor sex affected FID. We suggest that the escape strategy of L. schreiberi is determined more by the physical environment than by sex or reproductive condition.

Fracture mechanism of copper micro-crystals by diamond single crystal

ABSTRACTCopper micro-crystal fracture mechanisms were discussed with the machining precisions under the several cutting conditions, such as cutting speed, cutting depth and width of grove formation by the diamond single crystal cutting tool which the scoop face of (100) crystal face. For the cutting test, the copper single at the size of 10 mm in diameter and 5 mm in height as the test piece which cut by single crystal diamond cutting tool with silicon oil on the shaper type ultra-precision cutting machine. Before groves cutting, the specimen surface was cut as flat by cutting-off tool (corner diameter; 50 mm, cutting width; 3.0 mm, scooping angle; 0 degree, and escape angle; 7.0 degree) at the work speed as 4000 mm/min and cutting depth of 5 μm. For the V-shape grove cutting, the flat copper surface was cut with the diamond-point cutting tool (V angle = 90 degree, scooping angle = 0 degree, and escape angle = 7.0 degree) at the work speed as 4-4000 m m/min and cutting depth of 0.1-10 μm for finishing machining. The cut machined surface was observed by optical microscope comparing the grove shapes. The diamond-point tool was also observed by optical microscope. As results of the cutting test of copper single crystal, the machining precision was better for the crystallographic direction of $[01\bar 1]$ than the direction of $[00\bar 1]$ under the deeper cutting profiles. The mechanisms of this fracture results considered that the slip plane of (111). On the other hand, shallow grove under 1.0 μm was better tracks scratched for the crystallographic direction of $[00\bar 1]$ than the direction of $[01\bar 1]$. This result was also considered that the slip plane related to the fracture behavior. For copper crystal cutting in nanometric scale, the crystallographic direction was quite important.

The Kinematics and Performance of the Escape Response in the Angelfish (Pterophyllum Eimekei)

The kinematics of turning manoeuvres and the distance-time performance in escape responses of startled angelfish (Pterophyllum eimekei) are investigated employing high-speed cinematography (400 Hz). All escape responses observed are C-type fast-starts, in which the fish assumes a C shape at the end of the initial body contraction (stage 1). Kinematic analysis of the subsequent stage (stage 2) allows the response to be classified into two types: single bend (SB), in which the tail does not recoil completely after the formation of the C, and double bend (DB), in which it does. The two types of response have different total escape angles (measured from the subsequent positions of the centre of mass, SB 120.0°; DB 73.3°, P<0.005), different stage 2 turning angles (in the same direction as stage 1 for SB, 11.0°; in the direction opposite to stage 1 for DB, −21.9°: P<0.0005) and different maximum angular velocities in the direction opposite to the initial one (SB −8.08 rad s−1; DB −56.62 rad s−1: P<0.001). There are no significant differences in stage 1 kinematics for the two types of escape. Stage 1 turning angle is linearly correlated to stage 2 turning angle for DB only (P<0.01; r2=0.60) and to total escape angle for both types of response (P<0.0001; r2=0.80). Stage 1 duration is linearly correlated to stage 1 turning angle (P<0.0001; r2=0.83) and to total escape angle (P<0.0001; r2=0.72) for both types of escape. Distance-time performance is also different in the two response types, mainly because of differences in stage 2 (maximum velocity for SB 0.99 ms−1; maximum velocity for DB 1.53 ms−1: maximum acceleration for SB 34.1 ms−2; maximum acceleration for DB 74.7 ms−2: P<0.0001 in both cases). As a result, there are significant differences in the performance throughout the whole response (maximum velocity 1.02 ms−1 and 1.53 ms−1 for SB and DB fast-starts, respectively; maximum acceleration 63.2 ms−2 and 91.9 ms−2 for SB and DB fast-starts, respectively) as well as within a fixed time (0.03 s). Overall, higher distance-time performances associated with smaller angles of turn are found in DB than in SB responses. Comparison with previous studies reveals that angelfish have a good fast-start performance despite specializations for low-speed swimming. In addition, the angelfish turning radius (0.065±0.0063 L, where L is body length; mean±2 S.E.) is lower than that previously reported for any fish.