The hoots and grunts of the spiny toadfish may communicate complex information, according to a new study in the Proceedings of the Royal Society B. It is the first time complex harmonics, called nonlinearities, have been observed in fish, though fish do make a wide variety of sounds. Bottom-feeding toadfish produce sounds by vibrating the muscles of their swim bladders, air-filled sacs that control their buoyancy, reports Wired. Researchers at Cornell University analyzed spectrograms of the toadfish's hoots to show that the fish generate complex, nonlinear calls like those produced by frogs, birds, and primates. Experimental silencing of the fish swim bladders demonstrated that the complex signals vanish when one of the bladders is paralyzed.
World's largest whale shark gathering
In August 2009, scientists observed the largest gathering of whale sharks ever reported. Described April 29th in PLoS One, researchers documented up to 420 of these behemoths off the northern coast of the Yucatan Peninsula, where they feasted on dense patches of fish eggs. "It’s one of the most incredible gatherings of animals that’s ever been recorded. It’s mind-blowing,” marine biologist Al Dove of the Georgia Aquarium told Wired. Whale sharks are often perceived as solitary animals, but accumulating evidence suggests the animals are "gregarious," the authors write, and may regularly gather in coastal waters.
Humans may walk upright because the posture helps men beat on each other, according to new research published May 18th in PLoS One. Measuring the forces of male boxers and martial artists hitting in different directions and from different postures, researchers at the University of Utah concluded that men hit best when standing tall and hit twice as hard downwards as upwards. The authors suggest that this fighting advantage may explain why our ancestors adopted a bipedal posture and why women tend to prefer tall men.
Cats target mockingbirds
There is no rest for the weary mockingbird—not even in cities, once thought to be refuges for the species. A new study published in the May issue of Biological Conservation found that domestic cats are a major predator of mockingbird eggs and nestlings in urban areas. Studying video recordings of urban nests from 2007 to 2009, researchers at the University of Florida found that cats are responsible for more than 70 percent of attacks on nesting mockingbirds. Snakes were the second-most dominant predator. Watch the predation videos here.
Social lizards with faithful families
The great desert burrowing skink, a lizard from the sandy plains of Central Australia, constructs a long-term home for its family, a behavior never before attributed to a lizard species. Published in PLoS One, researchers from Macquarie University in Sydney, observed skinks constructing elaborate tunneled burrows that a family occupies for up to seven years. Multiple generations participate in construction and maintenance of the burrows, the authors found. In addition, adult pairs of skinks are faithful, breeding together over multiple seasons—fidelity that is not common in lizards, and may explain the skink's unusual social behavior.