Watch: Male spiders catapult themselves away after sex
Cannibalism is an unfortunate fact of life if you’re a male spider in the dating game - but one species has a unique tactic to survive after mating.
After males of the orb-weaving spider Philoponella prominens mate with a female, they spring away at enormous speed - before the female can tuck in.
Lead author Shichang Zhang of Hubei University in Wuhan, China said: "We found that mating was always ended by a catapulting, which is so fast that common cameras could not record the details clearly.”
The researchers found that the male spiders use a joint in their first pair of legs to pull off a split-second catapult action, flinging themselves away from their partners at impressive speeds clocked at up to 88 centimetres per second (cm/s).
The researchers say that failing to pull off the athletic feat usually results in death.
The few males the researchers saw that didn't catapult were promptly captured, killed, and consumed by their female partners.
When the researchers prevented males from catapulting, they met the same fate.
Zhang and colleagues made this discovery while studying sexual selection in this spider, which lives in communal groups of up to 300 individuals in a web complex with many individual webs within it.
Of 155 successful matings, they report that 152 ended with the male catapulting.
All those catapulting males survived their sexual encounters - and the three males that didn't catapult were killed.
Another 30 prevented by the researchers from catapulting also got killed and eaten by the female.
With high-resolution video cameras, the researchers calculated an average peak speed of catapulting spiders of about 65 cm/s.
Speeds ranged from about 30 cm/s to almost 90 cm/s.
As they soar through the air, the males also spin around 175 times per second on average.
The males manage to catapult at these speeds by folding their tibia-metatarsus joint against the female. When released, hydraulic pressure allows for rapid expansion. The joint in question lacks extensor muscles in spiders, they explain.
"We observed that males that could not perform the catapulting were cannibalised by the female," Zhang says.
"It suggests that this behaviour evolved to fight against female's sexual cannibalism under strong predation pressure of females.
"Females may use this behaviour to judge the quality of a male during mating. If a male could not perform catapulting, then kill it, and if a male could perform it multiple times, then accept its sperm."