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 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 〈N〉 of competitors. In model 2, males can assess the numberNiof competitors at each spawning exactly. Males can vary the massmof their sperm and the numbersiat a spawning. The aim is to find the evolutionarily stable strategies and hence the way thatmandsivary withNi. 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 describingm* andsi*. These are solved numerically.