When the male Australian redback spider finally locates a mate, the thrill is short-lived. And so is the spider. During copulation, the male flips himself onto the female’s fangs so that she can devour him.
While this cannibalistic behaviour seems bizarre, it’s actually an effective reproductive strategy. Male redbacks can keep transferring sperm while they’re being consumed, and the length of time it takes to be eaten can help ensure successful fertilization.

The strange ways of the redback spider have fascinated Dr. Maydianne Andrade for over a decade. Dr. Andrade, an evolutionary biologist at the University of Toronto Scarborough Campus, is interested in the evolution of mating systems, and the redback’s mating practices make it an ideal research subject. “If you’re dealing with a species that has many mating opportunities,” she explains, “that really complicates testing some theories about reproduction because it’s difficult to anticipate all the mating conditions the species is going to encounter. But we know that the redback only gets one shot.”

With some of the variables removed from the mating equation, Andrade and her colleagues can get a clearer look at how reproductive strategies and adaptations emerge. In a recent study, for example, they discovered that redback males become sexually mature more quickly when females are nearby. This comes at the sacrifice of body mass and strength, but as Dr. Andrade points out, “the reason for getting big is to survive the trip to the female. If you smell one near by, you don’t need to pack on the pounds.”

Observing spiders is painstaking work, even in the controlled confines of a lab. That’s why an investment by the Ontario Innovation Trust has been essential to Dr. Andrade’s research. The funding helped provide holding facilities for thousands of spiders—“It has to be Australia in the basement,” she explains—as well as video equipment and sophisticated image analysis software that lets researchers track and analyze the activity of multiple spiders on screen.

“They’re endlessly fascinating,” Dr. Andrade says of her eight-legged subjects. “I’ve been working on these guys now for a little over 10 years, and everything we find out just raises more questions.”
Why even bother asking questions about the mating habits of an Australian spider?

“We’re exploring sexual selection theory,” Dr. Andrade replies, “which can tell us about things like fertility and mating success that apply to other species. If we can understand the factors affecting sperm production and sperm use as an evolutionary strategy, we may be able to apply that knowledge more broadly to farm animals and perhaps even human fertility some day. Basic research, like the kind I’m doing, is critical for laying down our understanding of how the theory works.

“In fact,” she continues, “sperm competition theory has been applied to humans.” She pauses and smiles. ”Though not in the case of cannibalistic behaviour.”