Magnetic sense test facility

The magnetic sense test facility was specially built out of non-ferrous material and located away from any possible magnetic interference. The building consists of two rooms: one for testing and the other for observation. Saltwater is pumped directly from the sea and supplies both the test tank and outside training tanks. Prior to testing, eels are placed for several days in a training tank, where the magnetic field can be manipulated. Experiments are carried out inside a tank, surrounded by a cube surface coil (see Kirschvink 1992), which allows the observer to set magnetic north at geographic north, south, east or west. The inclination and/or intensity of the magnetic field can also be manipulated. A wooden platform (non-magnetic material) was built around the tank (but physically uncoupled), for easier access. Observations can be made from the adjacent room via a camera placed over the tank and coil. During testing, one eel is placed in the “net release device” which is lowered once the observer has left the test room. The eel then tries to escape by swimming over the edge of the insert, and is caught in one of the nets attached around the insert. The test tank (diameter: 140 cm) has been fitted with a polyethylene insert. Once the eel is placed in the center of the insert, its natural behavior is to try and escape. Its movements up against one of the 6 slopes of the insert are recorded under infra-red lighting via a camera located above the coil. All electronic equipment is in the observation room. Electrical power is filtered to minimize radio frequency interference. Magnetic field measurements are carried out using a 3-axis flux gate magnetometer. The facility was designed in cooperation with Professor John Phillips, a world leader in the study of the magnetic sense.