Determinants of Reproductive Success of Male Sticklebacks in the Field and in the Laboratory

Abstract

Several determinants of reproductive success of male three-spined sticklebacks, Gasterosteus aculeatus L., have been identified in the laboratory under semi-natural conditions. The impact of these determinants in natural populations is largely unknown. Here we analyse some determinants of reproductive success in natural Dutch stickleback populations and compare them with those obtained in a laboratory study of VAN DEN ASSEN (1967). Although we fail to affirm a positive correlation between territory size and aggression, the determinants of reproductive success revealed in VAN DEN ASSEM'S study are shown also to be of importance under natural conditions. Superior reproductive success is associated with large territory size and males with large territories suffer less egg raiding. An enhanced likelihood of nest entering by ripe females occurs right after creeping through and this male behaviour is observed more frequently in males with relatively large territories. Further, ripe females are more apt to enter a nest that already contains eggs, and this is not a result of changes in the male's courtship through the presence of eggs in its nest. The functional significance of some behavioural patterns like creeping through, sneaking and egg-raiding is discussed.