Black widow spiders 'twerk' to find mates

A team of Metro Vancouver-based researchers has uncovered the dating secrets of male black widow spiders — specifically, how they avoid being eaten by their mates.

By shaking their abdomens, males help distinguish themselves from prey

Think Miley Cyrus, but with a few more legs: Simon Fraser University researchers have observed that male black widow spiders shake their abdomens in a "twerking" shimmy to create vibrations so that females do not confuse them for prey. (Shutterstock, Canadian Press)

Black widow spiders use jittery, abdominal movements not unlike twerking — the hip-shaking dance move made infamous by Miley Cyrus — to navigate the dangerous world of arachnid mating, according to a newly published study from a team of British Columbia researchers.

In the paper, published in Frontiers in Zoology, the researchers say the vibrations from a "twerking" male black widow tell a female perched on her web that she's being approached by a potential mate, rather than dinner.

"What the male does, it has very subtle abdominal tremulations, so very subtle lateral movements of the abdomen that may be comparable to the twerks, absolutely," Prof. Gerhard Gries of Simon Fraser University said in an interview Friday.

"These very subtle twerks cause these very subtle vibrations of the web, and that is what the female spider will respond to in a very friendly, rather than aggressive, nature."

For male spiders, mating can be a treacherous endeavour in which an innocent attempt at courtship can end with — and this is the scientific term — sexual cannibalism.

Cannibalism is a common danger facing male spiders attempting to approach females, since most spiders are predatory and extremely aggressive. One wrong move can be fatal.

Male black widow spiders, like the one on the right, shake their abdomens to produce distinct vibrations to indicate they are a potential mate, and not dinner. In contrast, house flies and crickets produce short, high-pitched vibrations, which signal to the female spider (on the left) that food is waiting. (Sean McCann/Simon Fraser University/CP Images)

Two of Gries' graduate students, Samantha Vibert and Catherine Scott, set out to determine how male black widows approach females on the web without being mistaken for prey.

The researchers used sophisticated equipment to measure the vibrations produced by males approaching females on a web and then compared those to the vibrations from house flies and crickets.

The males could be seen shaking their abdomens, producing long, low-amplitude vibrations on the web that the researchers compare to "whispers."

While the short, percussive vibrations of the flies and crickets triggered a predatory response from the female black widows, the male spiders' distinct whispers did not.

Gries said the male spider has a delicate task: get the female's attention without provoking an attack.

"Envision you are on a date, and your date, the female, is much bigger than yourself," said Gries.

"So when you start this date on the wrong foot, make a wrong move, give the wrong signal, what could happen to you is that not only will the date be over, but you will become the dinner. So the male has to really try everything to avoid that."

Female black widows, as their name suggests, have a reputation in pop culture for eating male spiders after they're finished mating. While that can happen, Gries said it's relatively uncommon.

The vibrations are in addition to other strategies male spiders use to protect themselves from aggressive females, including cutting the threads of the females' web to limit her movement or attempting to mate with a moulting female.

Gries' broader research specializes in the communication among animals such as insects. He was practically giddy while chatting about the black widow research, which he described as "absolutely mind-boggling."

"It opens our minds to the intricate communication systems that are happening, not only in the spider world but in the animal kingdom," he said.

"When you take a closer look, a more careful look, there are so many fascinating things to discover."

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