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'Deceitful' male spiders offer gifts and 'play dead' to woo girls

Washington, Mon, 14 Nov 2011 ANI

Washington, Nov 14 (ANI): A new study has revealed that male nursery web spiders (Pisaura mirabilis) give silk-wrapped gifts to females to win them for mating, and also 'play dead' if the partner try to moves away and then attempt to re-establish mating.


Most gifts contain insects, but some gifts are inedible plant seeds or empty exoskeletons left after the prey has already been eaten (presumably by the male himself!).


The study examined the reproductive success of deceitful males and found that females are not impressed by worthless gifts.


It discovered that males that offered any gift were more likely to successfully mate than males without present.


However the length of time the females allowed males with worthless gifts to spend transferring sperm was shorter than those with edible gifts (and even shorter for those with no gift at all).


It appears that both male and female spiders are apparently able to assess the value of the gift and modify their behaviour accordingly.


Not only did the female spiders end mating sooner with an inedible gift, but male death feigning (thanatosis) - which is triggered by the female attempting to end mating and run away with the gift) - occurred in half of the matings involving an edible gift, but only once with a worthless gift.


"The evolution of male deceit involves a complex equation of costs and benefits. 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," Maria Albo who led the research explained.


"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 final results show that the number of eggs hatching was lower if the female had not received a gift, but there was little difference between females who had received an edible or inedible gift. The success of cheating probably explains why both strategies have co-evolved and are maintained in the population," she added.


The findings were published in BioMed Central's open access journal BMC Evolutionary Biology. (ANI)


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