A species of small fish, Parakneria thysi, has been observed by thousands of individuals climbing a vertical waterfall in the Democratic Republic of Congo, Luvilombo Falls. The researchers documented this behaviour and found that it illustrates the ingenious ways animals can adapt to extreme environments. The fish, which can reach about 9.8 centimetres (3.9 inches) long, scaled the Luvilom Falls in the upper Congo Basin, a vast river system spanning Central Africa and home to the world's second-largest rainforest. They may take nearly 10 hours to complete the climb, moving in short bursts and resting frequently. The discovery highlights the complexity of fish behaviour in the Congo Basin and suggests other fish species may also be capable of overcoming similar vertical obstacles. The main threats to the species are illegal fishing using fine-mesh mosquito nets and water extraction for irrigation.