Frogs and Compases.

It is well known now in the scientific community that many species of animals use the Geographic magnetic field to direct where they are going. Studies have been done on several species of birds and reptiles testing this hypothesis and trying to prove it. Franciso j. Diego-Rasilla and John B. Phillips had an Idea to test this very theory in a new way. They wanted to find out if animals are able to use the geomagnetic field for orientation wanted to find out whether the environment that they developed played a larger role than the simple genetics of the creature. To test this theory, they used Iberian green frog tadpoles. Many amphibians have been tested in labs to have magnetic orientation so using frogs was a great start.

They collected a group of Iberian frog tadpoles from a stream in northern Spain. All of the tadpoles were collected from the same side of the same stream to insure no experimental error. They immediately divided these tadpoles into two testing tanks. One testing tank was aligned along the magnetic north south axis where the shore was facing south and the deeper end facing north. The other was configured so that it was facing the east-west direction with the shore on the east and the deeper end on the west. Both tanks were identical in every way besides their alignment. The deeper ends were dark, the water was constantly filtered (to resemble an actual stream) and the shore was approximately 1 cm in depth. They again made the experiment consistent on both groups to ensure no experimental error.

The Tadpoles were left in the Tanks for five days. These five days acted as a teaching mechanism for to learn the y axis direction (direction of the shore) before testing them. During this time tadpoles in both tanks were fed lettuce placed at shore on a daily basis. No other interactions were made between the tadpoles and the outside forces.

After the five day learning period was done, the actual testing began. The tadpoles were taken out individually and put into a small plastic container with 1 cm of water depth that was aligned relative to the tank the tadpole had just been removed from. For example if the tadpole had been removed from the north/south tanks, the container he would be put into was aligned north to south. The individual tadpoles were left for 5 min in this individual isolation tank. From there the tadpole was placed into the testing tank and given on minute to calm down from human handling. After that 1 minute passed, the tadpoles were released into a symmetrical container that had no shores. The experimenters watch the tadpoles swim to one part of the testing container and marked which direction they hit first. Some tad poles were given a geographical magnetic field and others were tested in lab engineered magnetic fields. The experimenters used a device that can rotate the geographic north to either, south, west, or east. An equal number of tadpoles were tested on each of the magnetic fields. For testing purposes, tadpoles that responded in less than 10s were disqualified from the results and greater than 10m were also disqualified due to the exhibition of randomly oriented escapes these tadpoles showed.

The results were rather remarkable. Tad poles that had been held in the north-south tanks showed a bimodal magnetic compass orientation which means they showed orientation along the shore/deep water axis (x axis). Contrary to the tadpoles that had been held in the east-west tanks that showed orientation towards the shore (y axis). This notable difference is enough to infer that Tadpoles learn their magnetic compass response to orientate themselves.