A male cave weta's super-long hindlegs effectively shelter females from pesky bugs that scuttle around them as they wait in the darkness. Photo / Supplied
A male cave weta's super-long hindlegs effectively shelter females from pesky bugs that scuttle around them as they wait in the darkness. Photo / Supplied
Opening a car door or draping a warm coat over cold shoulders have long been part of gentlemanly chivalry.
But in New Zealand's dark and gloomy caves, weta go to a much greater length, and quite literally.
University of Auckland researchers have just shown how a male's super-long hindlegs effectively shelter females from pesky bugs that scuttle around them as they wait in the darkness.
"Adult male weta have extraordinarily elongated hind-legs, which can be over one and a half times as long as those of females or immature males," explained Murray Fea, who carried out a just-published study with Dr Greg Holwell.
"This suggests that they have an important role in helping males compete to pass on their genes."
The nocturnal native species gathered in caves during the day, forming a dense patch of individuals.
But sudden bursts of activity within that patch had high potential to disturb any pairs trying to get on with mating at the time.
A weta pair could stay together for a long time, but a rambunctious juvenile weta, a passing spider, or any other creepy-crawly that bumped into them in the dark was enough to send them running in fright.
A male cave weta is seen here shielding a female. Photo / Supplied
"Having a female flee due to contact with a nuisance can be fatal to the male's chances, as he may never find her again in the pitch darkness."
Using observation of behaviour in the weta's natural environment, the study determined that male weta's highly elongated limbs sheltered the female, reducing the chances of her being jostled by other creatures.
This was one of the only examples of a so-called "exaggerated structure" - think deer's antlers or elephant's tusks - being used to directly shield a mate, rather than functioning as a symbol of dominance or to fight off rivals.
It also raised an example of one way in which females may benefit from being guarded by males, a subject of ongoing debate about the costs and benefits of mating to males and females.
Fea said the study provided yet another example of something novel that New Zealand's unique animals could teach us about animal evolution.
"Despite their fascinating biology and behaviour, cave weta have hardly been studied since the 1960s."
More than 70 known species of weta are in New Zealand, of which 16 are at risk, and little is known about their past distribution.
