A REALLY dangerous liaison: Male brown widow spiders prefer sex with older females who are more likely to eat them afterwards

  • A new study has found that male brown widow spiders prefer mature females
  • These older females are less fertile and 50% more likely to eat their mate
  • Researchers say it’s possible the older females manipulate the males’ selection
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Mating can be a dangerous game for male spiders – and, it appears some prefer it that way.

Scientists studying the mating habits of brown widow spiders have discovered that males often seek out older females, who are not only less fertile than their younger counterparts, but 50 percent more likely to cannibalize their partners.

Given the high stakes, experts say the baffling behaviour could be a result of manipulation by the older females, who may be using ‘strong signals’ to entice a younger mate.


Scientists studying the mating habits of brown widow spiders have discovered that males often seek out older females, who are not only less fertile than their younger counterparts, but 50 percent more likely to cannibalize their partners. File photo

The new research from Ben-Gurion University of the Negev, The Hebrew University of Jerusalem and The Volcani Center in Israel examined male and female brown widow spiders from central and southern Israel.

Researchers placed the females in a way that allowed males to choose which they could approach: immature or mature.

While the immature females are not yet adults, they are able to mate and store sperm, allowing them to produce eggs after they make the final molt to adulthood.

But, males still preferred the less fertile mature females.

‘We originally thought the males would prefer the sub-adult females, as they are more fertile and far less likely to cannibalize them, but we were surprised to discover that was not the case,’ the researchers said.

And, this wasn’t the only surprise the study uncovered.

Some male spiders are known to leave part of their own sexual organs inside the female to ‘plug’ the genital openings, discouraging her from mating with another male.

The researchers suspected that the males may be better able to do this with the older females, which could help to explain their selections.


Given the high stakes, experts say the baffling behaviour could be a result of manipulation by the older females, who may be using ‘strong signals’ to entice a younger mate. File photo

WHY ARE SOME SPIDERS CANNIBALISTIC?

In some species of spider, the females are considerably larger than the males. 

This visible difference is called sexual dimorphism. 

As females can be cannibalistic post-copulation, male spiders have developed gruesome tactics to ensure successful fertilisation of a female, and secure paternity.

They may orally lubricate the female’s genitals or prolong courtship to deter being eaten. 

Older females tend to be more likely to eat their mating partner.  

Spiders have man other unique mating methods to ensure reproductive success. 

Some have been known to guard the female after copulation, or manipulate her appeal through chemical substances.

They’ve even been observed using a ‘mating plug’ to block the reproductive opening. 

Some types of orb-weaving spider have been observed to mutilate the genitalia of females after sex.

Mutilation thus establishes monandry, in which the female has just one mating partner during the reproductive period 

But, they found this was not the case.

The bizarre findings have perplexed scientists, as the males appear to be behaving in a way that goes against their own chances of survival and successful reproduction.

‘Males don’t seem to be behaving in their own self-interest and suffer a twofold cost – fewer offspring and no opportunity to mate with another female,’ the researchers say.

‘One possible explanation is that older females are manipulating the males by using strong signals to attract them, a hypothesis that remains to be tested.’

 

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