Do you have other needs? Come and gather together!

Self-protection, working together to prey, breeding are the three main aims for marine animals to gather together, however, there are some other factors make the animals loving gathering together. Some of them can not match the definition of “colony” in ecology, but the cluster behavior still induce great curiosity of people.

In the army chasing for sardines are lots of predators with big size and fast swimming speed, such as tuna and sailfish. Its interesting that the fishes dont only act in cluster when preying ,but also immigrate in orderly queue in ordinary time. The scientists found in research that when the fishes line in an orderly queue the eddy in the water caused by the front fishes may reduce the resistance of the rear fishes, so the fish group will swim in higher efficiency.

Some unique physiological mechanism of the animals may also cause the colonization. For instance, on the palau islands in the east of Philippines, there is a salt water lake, living in many jellyfishes. For lack of natural enemies, the jellyfishes gradually lost the terrible nematocysts which their same kinds exist, they dont bite people anymore. But for losing the hunting tools, their feeding habits change from meat to vegan——more precisely, they keep some alga in their bodies, and feed on the organics made by the alga. Therefore, there is a unique view attracting travelers all over the world: everyday, as the sunshine crosses the bank and project on the surface of the lade, large quantities of jellyfishes gather to the surface carrying the inorganic salt absorbed in the deep lake water, and swim slowly from the west to the east, let the algae in their bodies to accept the sunshine for photosynthesis. In the afternoon, the jellyfishes swim back to the west, and sink under the lake again after the sunset, finishing the one days “sunbath”.