A list of valid, reliable and feasible welfare indicators in domestic horses will be one of the outcomes of the 7th FP of the European Commission „“AWIN““. The Equine behaviour research team of the Institute of Animal Science Prague participates in this project and will spread the results among the Czech stakeholders and breeders. Behaviour and welfare are closely related. We present two examples of natural selection based principles still playing role in behaviour of the mares with key impact on breeding and reproduction in domestic horses. 1) Common practice of transporting the mare for mating and then bringing her back to an environment with stallions or geldings is the main cause of high percentages of pregnancy disruption in domestic horses due to risk of male infanticide perceived by the mare. 2) Pregnant mares cope with parallel investment into a nursed foal and a foetus through enhancing nursing behaviour in early stages of pregnancy before the initially low requirements of the foetus increase.