Breeding Behavior of a Lacustrine Population of Threespine Sticklebacks (Gasterosteus Aculeatus L.)

The breeding behavior of threespine sticklebacks from Wapato Lake, Washington, U.S.A., was investigated using the ethological approach. Much of the breeding effort of males was synchronized and there were 3 peaks of abundance during the 100 day period of major breeding. In June, a male's cycle lasted 13 to 14 days during which an average male collected 1000 eggs from about 10 females. Superior reproductive success of males was associated with nesting early in the season, in vegetated littoral areas of the lake, in deep water, and in shelter habitat. A male's level of aggression, body color, boldness toward predators, nest concealment behavior, and egg stealing behavior changed during his reproductive cycle. The changes in body color and behavior seemed related to a decreasing emphasis on stealing eggs from a rival's nest and an increasing emphasis on parental care. Most nest offspring were cannibalised within 2 days after fertilization. Neighboring males in all stages of breeding used solitary sneaking behavior to steal eggs from a rival's nest and most eggs were stolen by parental males. Raider packs, composed of hundreds of non-breeding male and female adults, also raided nests causing a total loss of the nest and its contents. Raiding of nests by breeding males seemed related to a shortage of food resources. Females often courted males prior to spawning. The incidence of this behavior seemed related to an excess of females.