Washington: Look, if any of these male nursery web spiders out there want to get busy and perpetuate their lineage, they better not show up empty-handed. Because they could get eaten. Alive.
“Nuptial gift-giving” has long been observed in nursery web spiders (Pisaura mirabilis). Basically, male spiders offer female spiders insects wrapped up in silk (yes, a snack packaged in high-end material).
There’s been a fair amount of interest in this unique mating ritual, and a new study published this week in Biology Letters sheds further light on it. Researchers found male spiders without gifts were six times more likely to be eaten by female spiders before mating. And that happened “independent of female hunger.”
“We propose that the nuptial gift trait has evolved partly as a counteradaptation to female aggression in this spider species,” they wrote.
As the American Association for the Advancement of Science’s magazine notes, 15 male spiders in the study that courted without gifts were eaten before mating, compared with just one male spider with a gift. And that gift-bearing spider was eaten after copulation, so from an evolutionary standpoint, he really had nothing to complain about.
Females store sperm in an organ and then release it when there are eggs available to be fertilized. Previous research has shown female spiders prefer males that offer gifts. A 2013 study published in Proceedings of the Royal Society B by researchers from Aarhus University in Denmark found that females stored more sperm from gift-giving males and had a higher rate of egg-hatching success.
“The gift facilitates longer copulations and increased sperm transfer, providing two different types of advantage to gift-giving in males,” those authors wrote.
The gift-giving could also be an indicator of mate quality to females, the researchers noted. The signal: This guy is a keeper, the kind of spider that can catch prey – and pass on superior hunting skills to his offspring.
But lest you feel bad for these male spiders (and you shouldn’t because these are spiders, and not people, but anyway), keep in mind that they can be deceitful little creatures. Some males actually bring fake gifts – inedible plant seeds or the remains of an insect they’ve already eaten – and try to pass off these packages as legit meals.
A 2011 study in BMC Evolutionary Biology found that females responded to worthless gifts by ending mating sooner than if the gift had been good.
Oh, and how do males respond to females that cut mating short and try to run away with the gift? Males pretend to be dead (a practice known as thanatosis). Feigned death took place in half of the matings involving edible gifts, but just once with a fake gift, the 2011 study found. And sometimes female spiders eat those dead-playing dudes.
“The evolution of male deceit involves a complex equation of costs and benefits,” lead author of the 2011 study, Maria Albo, said in a release. “It costs the males to find and wrap a gift, but these costs can be reduced if the male does not have to first catch his gift, or gives one that has already been eaten.” Albo continued: “The benefit of the gift is longer mating, which leads to more sperm being transferred, and potentially a higher number of offspring. However, the females are wise to deception and terminate mating early for worthless gifts.”
The Washington Post