Why does the cassowary have a helmet?

Scientists have not determined what the cassowary's helmet is used for, but there are several theories. It has long been thought that the helmet is used to protect the bird's head as it moves through the thick undergrowth of the rainforest and bushland in which it lives. However, the most likely theory is that, because the helmet continues to grow throughout the cassowary's life, it could be a sign of dominance. Recent scientific research has suggested the helmet may even assist cassowaries in detecting the low vibrating sound made by other cassowaries.