Evidence for EvolutionSperm competition in 13 lined ground squirrelsHere's number seven in my series. It's about sperm competition and male mate choice in 13 lined ground squirrels. As I have said before, each post is just the summary of some current paper published in a mainstream peer reviewed journal. This shows that evolutionary biology is a valid. productive branch of science and is recognized as such by the scientific community as a whole. No article is meant as a capsule proof of evolution. In most species, females choose the males they wish to mate with. This is not the case in the thirteen lined ground squirrel, Spermophilus tridecemlineatus. In this system, oestrous females mate with any male that approaches them. On average a female will have two matings. The first male to mate will sire more of the offspring than the second (this is due to sperm competition). The ratio of first male offspring to second male offspring is modulated by two factors: delay between matings and duration of second mating. The longer the delay between the first and
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