Research principles

We mostly run behavioural experiments when trying to answer the questions on the sensory and cognitive abilities of all our animals. For this purpose we use the principles of operant conditioning which is primarily based on the positive reinforcement of specific behaviours. If an animal shows a desired or correct behaviour the animal is being rewarded with food (primary reinforcer) which is preceded by a sharp whistle (secondary reinforcer).


This training principle forms the basis to conduct behavioural experiments that are mostly run either as detection or discrimination experiments.

In a detection experiment the experimental animal has to signal the presence or absence of a signal. A detection experiment was run e. g. to determine the detection threshold for dimethyl sulphide (DMS), an odorant that could guide seals to profitable foraging grounds (Kowalewsky et al. 2006). In this experiment the seal had to pull its snout out of an apparatus if it was smelling DMS and it had to remain stationary if it was not smelling DMS.

In a discrimination experiment the animal has to discriminate at least two stimuli. Such an experiment was run to measure the seals' visual acuity (Weiffen et al. 2006; Hanke & Dehnhardt 2009). Stripe patterns were presented to the seals pairwise: one horizontal, which was rewarded, and one vertical stripe pattern of the same stripe width. When the stripe width became too thin to be resolved they appeared as grey, and the seals answered randomly. Acuity was calculated with the stripe width that the seals could correctly choose with 75 %.

With the help of operant conditioning our seals are trained on many behaviours which are essential for the daily routine, husbandry, regular check-ups and the mental vitality of the animals.

Besides behavioural experiments we also apply physical and electrophysical measurements, histological and morphological methods up to theoretical modelling and bionic approaches.