Several studies have used behavioural tests to characterise sows regarding their maternal performance. These studies have always chosen a selection of behavioural tests and the combination of tests varied between the studies. In the present study, 47 sows were tested in week 2 and 4 of lactation in five successive maternal tests, which were conducted in their home pens and in a test arena. The sows' reaction to piglet stress signals, separation from and reunion with their piglets were tested. The behavioural parameters observed in these maternal tests were examined by means of a factor analysis to identify redundancies in behavioural parameters. Five factors were extracted, explaining together 89.2 % of the total variance, of which Factor 1 explains 33.5 %, Factor 2 18.4 %, Factor 3 14.5 %, Factor 4 12.6 % and Factor 5 10.2 %. The interpretation of the factor loadings revealed four underlying maternal factors: communication, care, contact and local attachment. Communication, thus vocalisation, was extracted by the factor analysis as the most important maternal factor and is used in sows to call their piglets in threatening situations as in the separation test and the piglet scream test. Furthermore, communication plays a role for the maternal contact and care factors. Sows used vocalisation to contact their piglets using nose-to-nose contacts, which were observed in the reunion test and also in the piglet scream test. With regard to the care factor, sows use vocalisation to call their piglets for nursing and to synchronise nursing with other sows. The willingness to stay with their piglets, thus local attachment to their piglets, was shown by sows in the separation and reunion test in the test arena and the piglet scream test. Furthermore, the factor analysis proves that single maternal tests can also combine more than one maternal factor and that the experimental environment in which the tests are placed influences the significance of the tests. The present results demonstrate the complexity and diversity of maternal behaviour. (C) 2017 Elsevier B.V. All rights reserved.