Sneaky little giraffe weevils beat big rivals

A little stealth helps smaller males compete with big ones to mate with a female

giraffe weevils

STEATH MOVE  Big male giraffe weevils (top) can lose out to smaller males (middle) that sneak underneath to mate with females (bottom). Dots of paint help researchers identify individual weevils.

Courtesy of C. Painting/Univ. of Auckland

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You might think a male giraffe weevil, or a male anything for that matter, would object to a rival creeping between his legs when he’s mating.

But creeping sneaks get away with outrageous stunts among New Zealand’s giraffe weevils (Lasiorhynchus barbicornis). Christina Painting at the University of Auckland remembers the first big male weevil she watched, an 80-millimeter bruiser standing possessively over a female for more than an hour. “He moved away — I guess to have a rest — and I realized the whole time there had been a tiny, tiny male underneath him waiting for the opportunity to mate.”

A sneaker can hide even while he mates. “He’ll rotate himself around and tuck his long [snout] underneath the female,” Painting says. “Often they quite happily keep mating” when a big male arrives and repeatedly fumbles to get into position himself. “The big male can’t figure out what’s going on,” she says.

Only small guys resort to funny business, but they don’t have much choice. Male giraffe weevils joust with fishing-pole–like snouts that can grow as long as the rest of their bodies. In a fair fight, a 40-millimeter-plus weapon would leave the smallest males’ 7 millimeters ridiculously out-snouted.

Underendowed males of a variety of species, from dung beetles to salmon, procreate via sneakery. But biologists usually treat them as “these subordinate little things,” Painting says. Among giraffe weevils, however, “I found very quickly that males of all sizes — it doesn’t matter how small you are — will fight.” Little weevils just don’t pick dumb fights with giants.

Overall, guile can compensate for lack of size. Sneakers mate about as often as big jousters do, Painting and Gregory Holwell, also at Auckland, report August 24 in Behavioral Ecology.

All this fighting and male drama fails to stir an obvious reaction from female weevils. Even while mating, the female’s attention seems focused on boring into a tree’s bark with her tiny, sharp jaws to create a hole for her egg. “There’s no courtship,” Painting says, and females hardly ever reject a male’s advances.

But the female’s role in giraffe weevil sex shouldn’t be overlooked. Females stow incoming sperm in a hard-cased storage organ. Whether sperm  from sneaky or super-snouted males ends up actually fertilizing her eggs remains to be seen. And so does whether the females are making that final choice themselves.

IN ON THE ACTION  On trees where female giraffe weevils go to drill holes for eggs, males keep busy jousting, sneaking and interrupting each other while mating. Credit: Images and video by Christina Painting; adapted by Ashley Yeager

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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