Table 1. Ethogram for the recording of home cage behaviour.

Category	Name	Definition
General activity	Inactive	Sitting or lying motionless throughout the 15 s interval, occasionally interrupted by brief single twitches lasting no longer than 5s.
	Active	All activities except the stereotypic activities listed below.
Stereotypic behaviour	Bar-mouthing	Chewing on a bar with the bar held in the gap between incisors and molars (diastema) while hanging on the cage lid (with all four paws or the forepaws only) or standing on the hind legs. Bar-mouthing may be performed on the spot or by moving along the bar while chewing.
	Circling	Running around the cage in circles.
	Cage-top twirling	Spinning around the longitudinal body axis while hanging on the cage lid with the forepaws.
	Back-flipping	Backward flip from one cage wall or the food rack towards the opposite cage wall, with or without touching the cage lid and/or the opposite cage wall during the flip.
	Route-tracing on the cage-lid	Moving along the same route on the cage lid with all four legs.

Behaviour patterns were considered as stereotypic if the same movement sequence was repeated continuously for at least 3 s (bar-mouthing) or at least three times in a row without pauses longer than 3 s between bouts (cage-top twirling, back-flipping, route-tracing, circling).