The swimming actions and performances of young green turtles (
Chelonia mydas
) and freshwater chelonians of similar size (
Mauremys caspica, Chrysemys scripta elegans
and
Kinosternon subrubrum
) were compared to evaluate the advantages conferred by the hypertrophied flapping forelimbs and streamlined form of the marine species. Evidence is presented to demonstrate that propulsive force is generated both on the upstroke and the downstroke of the green turtle’s foreflippers, and that the force is produced largely by hydrodynamic lift generated as the flippers move through the water at relatively modest angles of attack. The green turtle’s forelimbs therefore act like wings rather than as oars or paddles. Specimens of
Chelonia mydas
can generate twice the propulsive force, and swam six times as fast as
Mauremys caspica
. Much of this advantage stems from the efficiency of the swimming action (much less negative thrust is generated by
C. mydas
than by
M. caspica
) together with the streamlined shape, which also permits effective gliding. The swimming performance of young green turtles is similar in efficiency to that of streamlined fish such as mackerel.
The distribution of the koala (Phascolarctos cinereus) and the common brushtail possum (Trichosurus vulpecula) within the Prairie-Torrens Creek Alluvials province of the Desert Upland region of north-western Queensland was examined. The optimum habitat for each species as indicated by the occurrence of faecal pellet groups was found to be that associated with creek-lines. However, other land types were also used by each species to varying degrees. The relationship between various habitat variables and pellet group counts was investigated using Multiple regression and a Generalised linear model. Proximity to creek-bed, total basal area of trees, species richness and Acacia basal area (negative) best explained the occurrence of koalas. Proximity to creek-bed, Acacia basal area (negative), total basal area of trees, and available water (negative) best explained the occurrence of brushtail possums. In contrast to studies of arboreal species in the moist-south-eastern forests of Australia no relationship was found between foliar nutrient concentrations and the occurrence of koalas or brushtail possums. However, a significant relationship was found between leaf water concentration and the occurrence of koalas. It is suggested that water availability is the paramount factor defining preferred arboreal habitat in arid and semi-arid woodlands.
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