Sperm competition games: inter- and intra-species results of a continuous external fertilization model

We investigate the relationship between sperm competition intensity and sperm expenditure, both across species and within a species, using a two sperm competition models. In model 1, the males cannot assess the number of competitors, and their ejaculate effort is shaped by the average number of competitors. In model 2, males can assess the number Ni of competitors at each spawning exactly. Males can vary the mass m of their sperm and the number si at a spawning. The aim is to find the evolutionarily stable strategies and hence the way that m and si vary with Ni. A continuous fertilization model in which the sperm have to swim in order to fertilize an egg is described. This is used to find simultaneous equations describing m and si. These are solved numerically.