by Lauren Reynolds

Created on: May 23, 2008

Animals need to be able to find resources in order to survive and reproduce. However, wondering around randomly is inefficient and can't provide any sure means of survival. For this reason, most animals have evolved strategies to orient themselves towards goals in their environment. When this orientation is towards where the animal lives, it's referred to as homing. If an animal is displaced far enough from it's home, the new goal becomes to find a habitat. Although the goal has changed, the principle remains the same: find a place to live or die.

The suggest mechanisms for turtles to locate the nearest habitat included geotaxis (movement either up or down an incline), olfaction, use of light characteristics (movement towards or away from light, orientation using gradients of light polarity or wavelength), use of local topographic landmarks, use of a sun compass, and use of a magnetic compass. The first three (geotaxis, olfaction, and use of light characteristics) can be considered water-finding mechanisms. The final three mechanisms (use of topographic landmarks, a sun compass, and a magnetic compass) can be used to locate water, but only if the animal has a knowledge of its surroundings (ex: mental map). Each of the orientation mechanisms operates within a certain distance from the goal. Beyond these distances, the direction of the goal is unknown and the animal must begin a search for the resources it needs to survive. Presumably, if turtles are placed where they can no longer detect water, they will begin searching and use a straight-line search strategy.

There were two objectives in this study. The first was to figure out whether the eastern painted turtles used an orientation mechanism when placed in an unfamiliar territory. The second was to determine if turtles navigate towards the nearest body of water in an unfamiliar area. These both connected to the key casual question- What causes turtles to find their way in unfamiliar territory?

For the experiment, turtles were captured and brought to foreign lakes, far enough away from their own habitats so that homing would not be possible. Each turtle was released individually in remote areas so that human and other turtles interference was minimized. Each turtle was attached to thread (tied to a stake at the release point) so that the turtle's path could be tracked later. Approximately 24 hours after release, the turtles were recaptured, and returned to their home lake. Upon returning to collect data, the thread

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