One day when Tu-ariki was fishing in his canoe, he caught a young shark. Tu-ariki decided to keep this shark as a pet, and he took him back to his village and placed him in a pool in a river near his home. He called him Tutae-poroporo, and every day he would visit him and bring him food.
Tutae-poroporo grew very quickly, and soon he was as large as a whale. At the same time he began to change his appearance. He had been grey and silver, but now he became black. His skin became hard and spiky, wings like those of a bat sprouted from his back, and his tail changed to resemble that of a lizard. His fins grew longer and stiffened into legs, with feet that were webbed and had claws like those of a hawk. He still had the teeth of a shark, but his head was now like a bird’s head, except that it was featherless and bare. Tu-ariki saw that his pet was no longer a shark, but a taniwha, a dragon.
Tutae-poroporo remained friendly towards his master, and he and Tuariki lived together for some time. Then one day some warriors from Whanganui attacked the village and killed Tu-ariki, carrying his body home with them for food. For several days Tutae-poroporo waited, but Tu-ariki no longer came in his accustomed way to visit him. So the taniwha left his pool and travelled through the forest, seeking everywhere for his master. But when he did not find him, he knew that Tu-ariki was dead. Then Tutae-poroporo wept for Tu-ariki, and after this he set out to avenge him.
He swam down the river until he came to the sea, and there he smelled the wind. He smelled the wind from the east and the wind from the west and the wind from the south and found no sign of his master. But when he turned to the north, Tutae-poroporo smelled the smell of human flesh being cooked in an oven, and he knew that the north wind came from the home of the men who had killed Tu-ariki.
Then Tutae-poroporo uttered a great roar, and swam north to take his revenge. When he came to the mouth of the Whanganui River the scent of his master became stronger, and he entered the river. Under a high cliff there is a cave in which he made his home, and there he lay in wait for his enemies.
He had not been there long when he saw some canoes being paddled down the river. As they passed him he charged out of his cave, raising great waves like the sea and spouting like a whale. The people fled in terror, but they could not escape; Tutae-poroporo swallowed them all, and their canoes as well.
Now that he had tasted human flesh, Tutae-poroporo found it much to his liking, and he seized and devoured all the people who came in canoes down the river.
At first the tribes who lived higher up the river did not know what was happening; they thought that their friends must long ago have reached their destinations. But after a time, when their friends did not return and they could hear no news of them, the people became alarmed. They joined together, loaded their canoes, and started off down the river, but they so arranged things that some canoes went ahead of the others. They did this so that if the first canoes got into trouble, the rest could either escape or go to their assistance. Soon they drew near to the place where the taniwha lived. He saw them and made for them, bellowing hideously. The men in the first canoes could not escape; they were caught and eaten. But those behind them paddled to the bank, abandoned their canoes, and fled to their homes. Thus it became known that a taniwha held possession of the river, and all the people who lived in the lower reaches of the river left their villages and fled inland into the hills.
Then the tribes began to consider how they could rid themselves of the monster. They held many meetings, and did much talking. But for a long time they could think of no solution, because all feared to do battle with such a mighty monster. At last Tama, an old chief, rose up and said to the assembled people.
‘I have heard of a man named Ao-Kehu, who lives at Wai-totara. He is a great warrior, and he has been victorious over many monsters. Perhaps he will be willing to help us.’
Then all the people said, ‘Go and ask him if he will do this, for our need is great’. So Tama departed, and went to Wai-totara, and was welcomed by the people there. Then Tama said to Ao-kehu, the slayer of taniwhas.
‘I have come to you because all our people have been consumed by the taniwha Tutae-poroporo. Our land is desolate and our homes are abandoned, for our people are scattered abroad through fear of this monster’.
‘We have heard of this taniwha’, Ao-kehu said then, ‘and of how he preys upon your people. Rise up, and go, for tomorrow we will come to do battle with the monster’.
So Tama returned to his home. Early next morning Ao-kehu set off for Whanganui, accompanied by seventy of his warriors. He took with him two famous weapons, which were shaped something like a saw, with sharks’ teeth along both edges. When he arrived at Whanganui he was met by Tama and his people, and the customary greetings were exchanged.
Then Ao-kehu ordered his people to find a log and cut out of it a box long enough to hold a man, and also to make a close-fitting lid for it. Soon the box was completed, and the warrior lay inside it, taking with him his two weapons. The lid was bound down securely, the holes were filled with clay to make it watertight, and Ao-Kehu was set afloat. Then all the people climbed to the top of the high cliffs over the river, so that they could see what would happen.
Soon the box drifted down near the taniwha’s lair, and Tutae-poroporo, smelling the sweet smell of human food, rushed from his hiding-place and swallowed both the box and Ao-kehu. Then Ao-kehu, inside the monster, recited magic incantations and cut away the lashings which held down the lid of the box. Then that brave fighter began to battle with Tutae-poroporo, and with his saw-toothed weapons he slashed at the interior of the monster, fighting so fiercely that Tutae-poroporo bellowed with pain and reared up in agony in the water. But the taniwha had no means of attacking his enemy, and soon he was dead.
As soon as the great body of the taniwha drifted to the shore, the people came down from the cliffs above. They cut a hole in the side of the body, and released Ao-kehu from his prison. Inside, they found the bones of all the people whom the taniwha had devoured—men, women and children. There were canoes as well, and all the weapons, the tools, and the greenstone jewellery which these victims had possessed. Then the people took the bones of their kinsfolk and laid them to rest in the tribal burial ground, but the body of the taniwha they left as food for the birds of the air and the fish of the sea. After this they went rejoicing back to their homes, from which Tutae-poroporo in his anger had driven them.