Folk Stories From Southern Nigeria, by Elphinstone Dayrell, [1910], at sacred-texts.com
XXIX. How the Tortoise overcame the Elephant and the Hippopotamus
THE elephant and the hippopotamus always used to feed together, and were good friends.
One day when they were both dining together, the tortoise appeared and said that although they were both big and strong, neither of them could pull him out of the water with a strong piece of tie-tie, and he offered the elephant ten thousand rods if he could draw him out of the river the next day. The elephant, seeing that the tortoise was very small, said, "If I cannot draw you out of the water, I will give you twenty thousand rods." So on the following morning the tortoise got some very strong tie-tie and made it fast to his leg, and went down to the river. When he got there, as he knew the place well, he made the tie-tie fast round a big rock, and left the other end on the shore for the elephant to pull by, then went down to the bottom of the river and hid himself. The elephant then came down and started pulling, and after a time he smashed the rope.
Directly this happened, the tortoise undid the rope from the rock and came to the land, showing all people that the rope was still fast to his leg, but that the elephant had failed to pull him out. The elephant was thus forced to admit that the tortoise was the winner, and paid to him the twenty thousand rods, as agreed. The tortoise then took the rods home to his wife, and they lived together very happily.
After three months had passed, the tortoise, seeing that the money was greatly reduced, thought he would make some more by the same trick, so he went to the hippopotamus and made the same bet with him. The hippopotamus said, "I will make the bet, but I shall take the water and you shall take the land; I will then pull you into the water."
To this the tortoise agreed, so they went down to the river as before, and having got some strong tie-tie, the tortoise made it fast to the hippopotamus' hind leg, and told him to go into the water. Directly the hippo had turned his back and disappeared, the tortoise took the rope twice round a strong palm-tree which was growing near, and then hid himself at the foot of the tree.
When the hippo was tired of pulling, he came up puffing and blowing water into the air from his nostrils. Directly the tortoise saw him coming up, he unwound the rope, and walked down towards the hippopotamus, showing him the tie-tie round his leg. The hippo had to acknowledge that the tortoise was too strong for him, and reluctantly handed over the twenty thousand rods.
The elephant and the hippo then agreed that they would take the tortoise as their friend, as he was so very strong; but he was not really so strong as they thought, and had won because he was so cunning.
He then told them that he would like to live with both of them, but that, as he could not be in two places at the same time, he said that he would leave his son to live with the elephant on the land, and that he himself would live with the hippopotamus in the water.
This explains why there are both tortoises on the land and tortoises who live in the water. The water tortoise is always much the bigger of the two, as there is plenty of fish for him to eat in the river, whereas the land tortoise is often very short of food.