Radiata2010(4)e

Dieter Gramentz Leaps

Dieter Gramentz Leaps are executed from a virtual standstill or a resting position (Figs. 2A, B; 4A, B). As becomes clear from Fig. 2C, the leap begins with lifting the entire body on all four legs slightly, but even so completely, from the ground. Head and neck will largely be retracted prior to the leap (Figs. 2A, B; 4A, B) and maintained thus into the leap (Figs. 2C, D, E; 4C, D). This keeps the head and neck near the centre of gravity of the body. The leap begins with placing the hind legs under the plastron as far forward as possible (Fig. 2C), in order to optimise the angle for propelling the body in a vertical direction. The hind legs will then simultaneously press backwards, propelling the body forward and up. During the course of the leap, the front legs will also jerk down suddenly, but the main thrust comes from the hind legs and is enough to launch the turtle off the ground. The body will thus be catapulted into an almost vertical position (Figs. 2F; 4E), and the turtle will not rarely lose contact with the ground completely (Fig. 4E). The head will be kept retracted to the level of the eyes. After the stretched hind legs have lost contact with the ground as a function of their propelling kick, they will be jerked forward (Figs. 2F; 4E) in preparation for the landing. In most of the cases, the turtle will touch down with the outermost ventral margin of the carapace and flip down forward into a normal body position (Fig. 2G). Sometimes, however, the landing will fail in that the first point of contact on landing will be the dorsal margin of the carapace (Fig. 4F). Once this happens, the turtle will be unable to control its landing and inevitably flip over on its back (Fig. 4G). Immediately on impact and once the body has come to rest in its upside down position, the turtle will use its head and neck as a lever, dig its claws into the ground, and push with the hind leg on the side it has fallen to until it has turned itself over into a normal position (Figs. 4H, I, J). The turtle will then instantly retract the extended neck and slowly reposition its hind legs forward once more (Fig. 4K). Eventually, the turtle will thus be in the same position as before the leap, only that the vertical flip-over has placed it pointing in the opposite direction (Fig. 4L). It will now prepare for another leap by pushing its body backwards so that the hind legs are near the middle of the shell and therefore near centre of gravity of the body. Out of the 38 leaps that were recorded on film, the male landed in a normal position thirty-one times (81.6 %) and upside down seven times (18.4%). In a sequence of three leaps in rapid succession, he always landed upside down. It was interesting to note that the turtle clearly showed a preferred body side from which to turn back over into a normal position (laterality): He turned back over into a normal position from his right body side in all seven instances of landing upside down (100%). 30 RADIATA 19 (4), 2010

Florida Soft-shelled Turtle, Apalone ferox Specimen Carapace length (cm) Leap distance (cm) Leap distance in % of carapace length n= x „ s (cm) male 1 23.8 12.3-20.2 16.70 „ 2.45 14 70.2 male 2 13.4 7.0-12.0 9.05 „ 1.36 10 67.5 female 1 20.1 10.5-20.5 15.75 „ 3.32 12 78.4 Tab. 1. Carapace lengths (straight line) of the three tested Apalone ferox and leap parameters. A leap that ends with landing in a normal position takes about 1.7-1.8 seconds, whereas a leap that ends with the turtle in a flippedover position takes 5-6 seconds, including the time it needs for rightening itself. Discussion A number of animals are known to predate upon Apalone ferox. To defend itself against attacks from these predators and probably others more, it had to develop strategies that are effective enough to protect itself in the case of a hostile encounter at least most of the time. Ernst et al. (1994) list fish, other chelonians (Chelydra serpentina), snakes, wading birds such as herons (Ardeidae) and mammals such as armadillos (Dasypus) and otters (Lutra) as predators of juveniles. A juvenile Apalone ferox was found in the stomach of a cottonmouth (Agkistrodon piscivorus; Wright & Funkhouser 1915). The latter authors presumed that juvenile Florida soft-shelled turtles made up a certain part in the diet of larger snakes and other animals inhabiting the Okefenokee Swamp. Snail kite (Rostrhamus sociabilis; Beissinger 1990), sea eagle (Haliaeetus) and other birds of prey would also predate on smaller turtles. Alligators (Alligator mississippiensis) are likely to take all size classes, even though it would appear that this does not happen too often: According to Delany et al. (1999), only three out of 219 stomach content analyses of alligators yielded remains of Apalone ferox. The study presented here shows that if it is on land and faced with a potentially dangerous situation, Apalone ferox responds in a very active and flexible manner for a chelonian. While the raising of the shell towards the stimulus, i.e., towards the predator, will enlarge the body area visible to the predator (presumably to make the turtle look larger), it is likely to primarily reduce the risk of being turned upside down. Although these turtles are able to righten themselves from an upside-down body position relatively quickly, their ventral side with the even more reduced armour and exposed legs is more vulnerable than their dorsal side. Furthermore, the turtle can only defend itself from, or react to, a predator by threat displays, bites, leaps and flight if it is in a normal body position. Many defensive behavioural strategies involve that turtles use their shells to try and protect the head and limbs, which necessitates adjusting the position of the body in relation to the predator and so adapt to relative changes in a confrontation. Apalone ferox also occasionally defends itself by chemical means in that it discharges a deterrent substance, but this has actually been observed in only a third of the tested turtles (the female). The forward leap that covered distances of 2 / 3 to 3 / 4 of the carapace length in cases of normal landings, may come as a major surprise to a moderately sized predator and be rather impressive. RADIATA 19 (4), 2010 31