Wild Things: Piranhas, Nazca Boobies, Glowing Millipedes

Among southern elephant seals, four-ton alpha males lord over harems ashore and block other males from mating with the hundreds of females. But P.J.N. de Bruyn of the University of Pretoria has found that the top seal’s control is not ironclad: The timing of pregnancy indicates some females mate at sea, possibly escaping the alpha.

Barks: When confronting another piranha face to face.
Drums: When circling another piranha for a fight, especially over food.
Snaps: Its jaws shut loudly when it tries to bite its prey or a foe. So says a study by researchers at the University of Liège in Belgium, the first to determine how the Amazonian freshwater fish makes sounds and what they signify. The barking and drumming come from an organ called the swim bladder; the snapping noise is done with a firm bite. The researchers studied piranha in a tank (and got their fingers nipped). Now they want to know whether piranha vocalize while mating.

Native to the Galápagos Islands, Nazca boobies nest in huge, crowded colonies, where adults frequently bite and peck their neighbors’ chicks. A Wake Forest University-led study shows that the birds more frequently abused as chicks are more likely to engage in such bullying as adults. Researchers are examining the role of early exposure to avian stress hormones in driving violent tendencies later in life.

Neanderthals had relatively short limbs, a common adaptation to cold climates. An analysis from Johns Hopkins University suggests stubby shins also made them well suited for their mountainous Eurasian terrain. Going uphill, Neanderthals didn’t have to raise their legs as high as people with longer shins. “For a given step,” says study leader Ryan Higgins, they “put in less effort.”

Nocturnal millipedes in the genus Motyxia glow in the dark. But why? Being blind, they’re not lighting up to impress one another. Scientists collected 164 millipedes from Giant Sequoia National Monument in California and painted half of them to conceal their light. They also created 300 clay millipedes, half painted with a luminescent pigment. They left the millipedes out overnight and found “carnage” the next day, says University of Arizona entomologist Paul Marek. Dark millipedes, whether real or fake, were attacked by rodents more than twice as often as their glowing counterparts. The greenish blue light appears to serve as a defense mechanism, warning predators away, like a skull and crossbones: These millipedes produce a cyanide toxin that predators do well to avoid.