Guys having a hard time getting lucky, imagine this: you search for a mate; you rival for her attention; woo her into hooking up with you-only to be eaten during sex. You escape from her hungry grasp, but can’t help but go back for more.
Court, mate, sacrifice. Repeat until she swallows you entirely.
Welcome to the life of the male Australian redback spider.
Dr. Maydianne Andrade, an assistant professor of zoology at U of T Scarborough, studies the eccentric mating ritual of Latrodectus hasselti, a species of spider in which the female sets the mating rules, and males must adopt extreme strategies to mate successfully.
The female redback spider has two copulatory organs, two genital tracts and two sperm storage sacs-allowing for two sets of copulations, sometimes with different partners. To adapt, male redback spiders “somersault” into the mouth of the female redback, positioning their abdomen above the fangs of their mate and offering themselves as food. While the female lies still and slowly devours her partner, male redbacks transfer sperm. If the mating is long enough for the lucky male, he may even break off part of his copulatory organ in her genital tract, which acts as a plug that prevents future mating with competing males.
Redbacks often constrict their abdomen during courtship, allowing them to survive the female’s cannibalism during the first copulation and to try mating for a second time.
“Males don’t have many mating opportunities anyways,” Andrade pointed out. With over 80 per cent of males dying while trying to find a mate, “even if they are not cannibalized, the chance of finding a female because of their ecology is very low. Therefore, they invest everything in this one mating.”
Male redbacks spend between five and eight hours courting a potential mate, by moving around her web and creating vibrational signals, while competing with up to eight rival males. However, unlike other species, fatal fighting is hardly witnessed amongst the males.
By placing a pair of rival male redbacks on the same web, Andrade’s graduate student Jeff Stoltz and post-doc Dr. Damian Elias have recently discovered that female redbacks will punish males who are aggressive towards each other. When a pair of redback males approach each other and are about to exchange blows, the female redback will strike the web with her forelegs to stop the fight, sometimes with so much force that it flicks the males off.
Additionally, smaller redbacks who try to mate aggressively are often cannibalized by the female before the first shag even finishes, giving them no chance for a second shot.
One wonders why a female even allows smaller male redbacks a chance to mate. “Maybe some diversity in offspring is good,” Andrade suggested. For female redback spiders, who give birth to a large number of offspring that will disperse to unpredictable habitat, perhaps it is advantageous to have a diversity of genetic traits. Her group is now testing this idea.
For Andrade, the redback spiders’ bizarre and complicated mating behaviours provide the perfect system to study the factors that shape the evolution of male mating strategies.
“Unlike most other system, redback males only get one shot at mating,” she said. Whereas males of other species are concerned with mating as many females as possible, the redback male can only get one mating, and cannot force copulation.
“Now we can ask what happens when female interests are critical to mating success and how do male strategies evolve. What you end up with is the counter-intuitive: self-sacrifice is involved.”
