Harbour seal spatial distribution estimated from Argos satellite telemetry: overcoming positioning errors

A limiting factor of satellite telemetry in the context of habitat use by marine mammals is the low accuracy of the received positions. A novel statistical analysis to overcome the low accuracy was developed in the context of processing data on harbour seals Phoca vitulina for the atlas of Dan- ish mammals. Ten harbour seals were caught in the Danish Wadden Sea and tracked with satellite transmitters. The statistical analysis reversed the problem of positioning: Instead of attempting to cor- rectly assign each individual position to a single grid cell, our approach considers the combined prob- ability that at least one position originated in each grid cell. Thus, all satellite-derived positions, including positions of poor precision, can contribute to the evaluation. The method is an alternative to other methods describing spatial use, such as kernel home range, and constitutes a viable approach for inclusion of satellite-derived positional data into spatial modeling of animal distribution and habitat use.