Sperm Shows a New Trait: Teamwork It works together to keep rival male's sperm out of the picture By Harry Kimball, Newser Staff Posted Jan 21, 2010 10:58 AM CST 15 comments Comments Sperm. (Flickr) (Newser) – The sperm’s pursuit of the egg is not the free-for-all we might think it is, but rather a test of teamwork—at least in deer mice. The female of the species tends to have multiple partners, and a new study shows that sperm from one male tend to cooperate in the battle against rival sperm to inseminate the egg. By clumping together, the little swimmers can move faster. The researcher took contributions from two mice, died one set green and the other red, and then mixed them together in a petri dish. “What we found more often than not is that red sperm tend to clump more so together,” she tells NPR, “and green sperm tend to clump more so together.” She has no idea how they do it, but surmises it is the product of evolution.