Question: Is alpha the average number of mates? What if my mean alpha value is less than 1? Alpha values less than one just mean many of the broods can be explained by a single mating. The alpha value is not the mean number of mates, although it governs that number. Alpha is the parameter for a truncated poisson distribution, where the truncation removes zero values. Unlike the regular poisson distribution, the mean number of mates is not alpha but alpha/(1-exp{-alpha}). This number is greater than one, as long as alpha >0.