According to this article a study has proved that chimpanzees expand their territory by attacking and killing their neighbours. According to the study groups of aggressive chimpanzees will invade their neighbours territory to obtain more resources or mates. The study was carried out in Uganda over a ten year period. During this time scientists recorded 18 attacks and found signs of three others. The attacks were carried out by a large male dominated community of chimps at Ngogo in Kibale National Park. In one case the aggressive males attacked a group of females from another group killing an infant that one of them was carrying and trying to take another from its mother. It is not clear whether the behaviour is an effort to acquire land or mates, however, the aggressive chimpanzees eventually began to occupy the area where most of the attacks had taken place expanding their territory by more than a fifth.