Satellite tracking of a fin whale (Balaenoptera physalus) in the north-western Mediterranean Sea and fractal analysis of its trajectory

Satellite tracking of whales was the aim of the ARGOCET program in the west ern Mediterranean Sea. With the tracking technology and the development of telemetry, we can study large mammals under natural conditions. In 1991, a satellite tracking during 42 days on a fin whale (Balaenoptera physalus) wa s obtained. The Argos system allowed us to know the location of this tagged fin whale 263 times. In this study, we can distinguish two kinds of moveme nts: linear segments and tortuous segments with loops drawn in a clockwise direction. Such loops may be superficial oscillations of inertia due to the inertia of the water mass combined with earth's rotation. With this trial study, which is the best we have obtained, we can estimate the fractal dime nsion d of this trajectory at different observation scales. These d values seem to be scale-independent, so the fin whale path is fractal-like or scal e-independent. Fractal dimension, which is a scale-independent measure, sum marizes interactions between an organism and its ecosystem and depends on t he heterogeneity of the whale's environment (exogeneous factors) and the wh ale's ability to perceive it (endogeneous factors). For the fin whale traje ctory we calculated d = 1.03 +/-0.01 with the divider method. The aggregate d distribution of available resources for the fin whale in the western Medi terranean Sea can explain this result close to 1. The heterogeneity of this food resources is not a `measured heterogeneity' but is a `functional hete rogeneity'. The low fractal dimension also points to the low probability th at the tagged fin whale and the zooplankton aggregates will meet in the wes tern Mediterranean Sea so the fin whale must cover long straight lines from one patch of available zooplankton to another.