Malawi

In Lake Malawi, fish build sandcastles to attract a mate.

Males of around 200 cichlid species shape large structures directly in the sand on the lake floor.

They scoop sand into their mouths, swim a short distance and spit it out somewhere else. Again and again, sometimes hundreds of times an hour and over several days.

Some species dig crater-like pits. Others build tall, volcano-shaped sandcastles.

Females move between the construction sites and assess both the male and his structure. The size, shape and position of the sand construction can influence mate choice.