Samenvatting

Due to their high adaptability and opportunistic predation behaviour feral cats have a great impact on worldwide bird biodiversity in particular on islands. However not much is known about their actual behaviour and time budget, as direct behavioural observations often are difficult regarding free-ranging animals that live in remote areas. Since knowledge of behaviour is essential for effective management this study aimed to get insight into feral cat behaviour and behavioural time budgets. On the island Schiermonnikoog in the Dutch Wadden Sea, which represents an important area for breeding birds, nine feral cats were collared with tri-axial accelerometers, which measured acceleration for a period of three months during the breeding season of ground nesting birds in 2014. In order to link the recorded acceleration data to actual behaviour supervised classification was used. In October and November 2014 video footage of the feral cats was obtained and linked to the acceleration data. In total this training dataset comprised 5805 seconds containing fixed 1 s segments of single feral cat behaviour. By means of a Random Forest model using 15 summary statistics and executed with the web-based application AcceleRater feral cat behaviour was labelled to acceleration data. The model was validated by a 10-fold cross-validation. In total 10 behaviours were classified with an overall performance of 84 %. Regarding the circadian cycle, the feral cats were most active during 22:00 - 01:00 h. Lying occurred mostly from 04:00 - 10:00 h, being highest (63 %) from 07:00 - 08:00 h. Throughout the breeding season no striking changes in the activity patterns could be observed, except for lying and walking, which decreased and increased respectively. The found behavioural time budget largely coincided with findings of other studies on (feral) cat behaviour. Six out of the 10 behaviours e.g. sitting or lying showed a high classification (84-94 %), whereas some behaviours such as standing with head down or trot had a recall of 18-67 %, thus were considerably misclassified as other behaviours. The obtained knowledge of feral cat behaviour can be used further to complement other research. It may then contribute to a possible future assessment of the impact of feral cats on the breeding birds of Schiermonnikoog.