This study investigated the influence of density and floor area on stress and the adaptation process of cats in animal shelters and boarding catteries. Sixty-three rescued cats were observed on 113 days in a shelter at group densities of 0.3-0.9 animals m−2. In addition, 49 rescued cats were observed during their first week after being admitted to a control group housed at a density of 0.5 or 0.8 animals m−2, and 44 boarding cats were observed in single cages of either 0.7 or 1.0 m2 floor area during their first week in a cattery.

Group density was highly correlated with the stress level of animals housed in groups. A stress level of ‘weakly tense ‘ was reached when the group density reached 0.6 animals m−2. During the first week of their stay, stress levels among cats which had been newly admitted to groups housed at 0.5 or 0.8 animals m−2 did not differ significantly. On days 1, 2 and 6 after admission, boarding cats housed in single cages with a floor area of 1.0m2 had significantly lower stress levels than animals in cages with a floor area of 0.7m2.

Group density was clearly shown to influence the adaptation process of cats which were housed for several weeks in groups. In order to avoid high stress levels, a group density of 0.6 animals m−2 should not be exceeded. However, the minimum spatial requirement for singly housed cats remains unknown.