Male Brown Widow Spiders Prefer Older Females
May 2, 2018
Gizmodo – Ben-Gurion University, in collaboration with Hebrew University and The Volcani Center in Israel have found that male brown widow spiders prefer to have sex with older females even though they’re less likely to bear offspring and the older female spiders are 50 percent more inclined than young females to devour their partners after mating. The research was published in Animal Behavior.
To test this theory the scientists collected males and females from central and southern Israel. In a laboratory setting, the spiders were arranged such that the male had his choice of which prospective mate to approach: either subadult females, young mature females or older mature females. The researchers fully expected the males to avoid the older females for three reasons: less time and energy for courtship displays, a greater chance of reproductive success and self-preservation.
But the observations didn’t bear this out. The males, to their apparent detriment, consistently preferred the older females.
“[W]hen given a choice, males preferred mature over subadult females and older females over young mature females,” says Prof. (Emeritus) Yael Lubin, of BGU’s Marco and Louise Mitrani Department of Desert Ecology.
This result caused quite the confusion.“We found no benefit for males in mating with the females of their choice,” says Prof. Lubin.
One possible explanation is that older females are manipulating the males by using larger quantities of pheromones. In other words, the older females may be producing a kind of irresistible perfume that the males cannot resist, and at greater amounts compared to younger spiders. “It’s a hypothesis that remains to be tested,” says Prof. Lubin.
The pheromone theory makes sense, but clearly more work needs to be done in this area.