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Do grey seals (Halichoerus grypus) use above water stimuli in foraging?

Magdalena Beszczyńska


Increasing population of the Baltic Halichoerus grypus causes conflicts with the fishery. Damages to the fishing gears and loss of catch caused by the seals increased seriously in the last two decades. To mitigate results of this conflict, new proactive approaches must be considered and new fishing strategies developed. Therefore, it is highly important to learn more about seals’ foraging behaviour, in particular in localising fishing nets.

Most research has been dedicated to vision, audition and the vibrissae organs. Data referring to chemoreceptive senses (e.g. olfaction) is quite limited. Almost no information exists on how seals use their olfactory abilities in foraging and navigation.

This experiment investigated the possible use of sense of smell in the foraging behaviour of the Baltic Halichoerus grypus. The study was performed in the Bothnian Sea by using baited buoys with olfactory cues (repellent, attractive and neutral). The frequency of positive response would indicate possible use of above water stimuli by the seals.

The analysis of the relative frequency of taken baits showed nearly the same number of taken baits between treatments.

During the experiment 96 underwater cameras with mechanical trigger arms were installed to confirm that baits were taken by the seals. In five, successfully taken photos positive identification of seals was possible.

The effect on the frequency of taken baits of the environmental factors: light intensity, wind direction and wind speed was the most significant.

The results of this experiment clearly indicate that smell is of minor importance in seals foraging behaviour.

Key words: foraging behaviour, Halichoerus grypus, olfaction.


Magdalena Beszczyńska


Responsible for this page: Agneta Johansson
Last updated: 05/31/05