The aim of this thesis was to investigate impact of a nesting material enrichment for mice and foraging enrichment for rats and how that would affect the animals, with emphasis on anxiety, exploration behaviours and long term effect. In experiment I, 30 female mice of the strain NMRI were placed in either enriched housing system containing nesting material, or a control cages. Mice behaviour in the home cage was observed during two periods with one week in between to determine if the enrichment was still being used. Risk assessment and anxiety behaviours were observed in an open field test. During the second period the mice did climb and dig more while nesting, grooming, feeding and sleeping were performed more in the first period. Nesting was performed significantly more in the enriched cages, 18.63 % of the observations. The results obtained from the open field test were contradictive since mice in enriched housing showed more explorative and anxious related behaviours.

During experiment II, enrichment in the shape of a maze, was introduced to 36 male rats of the strain Sprague-Dawley. The observation procedure was performed in the same way as in experiment I. Food was placed in the corners of the maze for the rats to hoard or to eat at the spot, the control cages was provided food ad libitum. On average the rats did spend 75.38 ± 3.31 percentage of the observation in the maze and 52.30 ± 19.29 in the cage. In the open field test the rats without enrichment showed more anxiety related behaviours. Enrichment may increase the ability to perform species specific behaviours, hence enhance welfare.