Some spiders have a clever way of attracting and mating with females: they wrap prey items in silk and offer them as gifts. This behavior, known as nuptial gift-giving, is a form of sexual selection, a theory that explains how some animals use traits or behaviors to increase their chances of reproducing.
But not all spider gifts are what they seem. Some males cheat by offering worthless or inedible gifts, such as empty exoskeletons, plant seeds, or silk balls. This is called deceitful gift-giving, and it may have evolved as a way to reduce the costs of producing or finding valuable gifts, and to avoid being eaten by the females after mating.
One example of a deceitful gift-giver is the nursery web spider, which is found in Europe, Asia, and North America. The male spider wraps his gift in silk and offers it to the female. If she accepts it, he climbs on her back and mates with her. Sometimes, he makes a quick getaway once the deed is done. Other times, he hangs around for a bit, but always runs off with his gift at some point.
Researchers have found that males that offered worthless gifts mated for a shorter time than those that offered genuine prey. However, they still managed to transfer a similar number of sperm, suggesting that they can achieve comparable reproductive success with lower costs.
The researchers also found that males that offered genuine gifts were more likely to mate again with the same female, while those that offered worthless gifts were rejected. This indicates that females can discriminate between gift types and adjust their mating behavior accordingly.
Another example of a deceitful gift-giver is the dark fishing spider, which is found in North America. The male spider also wraps his gift in silk, but instead of offering it to the female, he uses it as a lure. He places the gift on a web and waits for the female to approach. When she does, he grabs her and mates with her. He then tries to retrieve his gift and escape before she can eat him.
The use of worthless gifts by males is not just a matter of saving energy or time. It also has a life-or-death implication: males that offer genuine gifts are more likely to be eaten by females after mating than those that offer worthless gifts.
Nuptial gift-giving is a method through which sexual selection influences animal behavior and evolution. It illustrates how males and females may possess distinct interests and strategies in terms of reproduction, and how they can impact each other’s decisions and results.
Relevant articles:
– TIL Theory of sexual selection says giving gifts increases male’s chances of mating amongst heavy competition. Some species of spiders continue to hold the gift between their legs even after sex starts, refusing to give it up and running away with it as soon as the process is over, Reddit, 6 minutes ago
– Here goes nothing: Male spiders found giving females silk-wrapped zilch, Mongabay, 22 February 2021
– Spiders use silk to lure and trap their mates, ScienceDaily, 23 February 2021
– The spider that wraps its prey in silk and gives it to females as a gift, The Conversation, 24 February 2021