Nature Notebook – Mates

Sometimes it’s hard for a girl to find a man…in the animal world. Species with large home ranges may use a lot of energy trying to locate a mate. The shorter lifespan of some males can make it difficult for a female to find a mate. So what’s a girl to do?

She stores the sperm from any breeding encounter until she is ready to be pregnant. Sperm storage is an adaptation that allows a female to retain viable sperm inside her reproductive tract for an extended period (weeks to years). It can be used to produce one or more broods. When the female enters estrus, if suitors are nowhere to be found or she deems it too dangerous (or too much work) to search for mates, the stored sperm are used to fertilize the eggs.

The practice is common in invertebrates. Queen honeybees and termites mate once. They are then lay fertilized eggs for several years.

Some vertebrates are also capable of sperm storage. Reptiles, including turtles, lizards, crocodiles and some snakes retain sperm in storage tubules. One of our garter snakes gave birth after being in captivity for three years. Some birds and a few mammals also store sperm.