When Does the Male Stickleback Turn Red?
The male stickleback’s belly turns red at the start of the breeding season in spring. This shade helps to attract females and is due to carotenoids that are present in the bodies of these fish. Females use the intensity of the coloring to determine how healthy a male fish is.
Those that are more brightly colored are less likely to be infested by parasites. This means that they will probably live longer and are more likely to be around to help with taking care of their young. Researchers have shown that the females will even pick a male with artificial coloring over one that does not have much color.
Normally the belly of this small fish is silver colored, the rest of its varying from brown to green. But when the time comes for him to mate he becomes very active in attracting females with his bright new color.
In building the home and rearing the family the male stickleback performs many of the functions usually associated with a female fish. He chooses the place for the nest, collects the stems of various aquatic plants and binds them together using a threadlike web secreted from his kidney.
Once the female has been enticed into his nest, she will lay her eggs and depart, leaving him on guard. He watches over the eggs with great care and even looks after the baby fish.
It is very important for females to pick a male that will live for a long time, since most of the responsibility for protecting the young will lie with them. Males court females with distended abdomens and if they are successful with one of them, they lead them back to their nest. There, spawning and fertilization of the eggs takes place. Males collect eggs for several days and then they switch to the role of father.
Male stickleback fish use visual clues to help them determine which female fish would be a good mate. Although male fish will be stimulated to begin courtship activity by the sight of a suitable female, they do not simply go with the first one they see.
If they have a selection of females to choose from, they will opt for the one that has the most distended abdomen. The male fish interpret the level of fullness in the abdomen as a sign of the female’s readiness for spawning.