Breeding Season Cheats Today

Consider the superb fairy-wren. The male has brilliant blue plumage—but females leave his territory to mate with males in other groups. Why? Two reasons. First, . A clutch of eggs with mixed paternity reduces the chance of inbreeding or inheriting two copies of a bad gene. Second, sperm competition . By mating with multiple males, females force sperm to race. The winner’s offspring may inherit faster, more competitive sperm themselves.

Females risk nest abandonment, infanticide (males of some species kill unrelated young), or social punishment. In a famous study of house sparrows, females caught cheating were harassed so relentlessly by their social mate that they laid smaller clutches the following year. breeding season cheats

plays a subtler game. In horseshoe crabs and some frogs, a satellite male positions himself next to a calling male. Females approach the caller—but mate with the silent satellite first. The caller does the advertising; the satellite does the copulating. It’s the biological equivalent of a fake storefront. Consider the superb fairy-wren

So the next time you hear a male blackbird singing his heart out from a cattail, remember: he’s not just singing to attract a mate. He’s singing to keep his neighbor’s sperm out of his nest. And somewhere in the reeds, a small, dull-colored male is listening—waiting for his nine-second window. Two reasons

is small, unornamented, and fast. In salmon, bluegill sunfish, and many frogs, “jack” males don’t grow large or develop bright breeding colors. They hide near spawning grounds, then dart in to release sperm just as the female spawns with a dominant male. The dominant male invests in fighting; the Sneaker invests in timing . One study found that 40% of female salmon’s eggs were fertilized by sneakers they never saw.