Q) Do any animals besides humans hold a grudge?
Sacha Denison, Cardiff, California
Ten years ago, a behavioral psychologist might have reacted to this notion with a sniff and quiet, anti-anthropomorphic rage. Today, thanks to new findings in neuropsychology, many concede that animals have humanlike personality traits, though some would argue that they're incapable of a sentiment as complex as a grudge. Sam Gosling, a psychologist at the University of Texas and director of the Animal Personality Institute, says grudgelike behavior has been spotted in creatures as diverse as cuttlefish and great cats. "Many social species, in order to maintain accountability, keep track of who's pulling their weight," he says. Lions develop a mistrust of lazy members of the pride. Cows, one study found, can maintain a beef for years with heifers who wrong them. And then there are African elephants, who appear to be suffering species-wide trauma after a century of habitat loss and poaching. A dramatic upswing in elephant violence in recent years, including unprovoked attacks on humans, may be their attempt at revenge.

Hit or Myth?

Is there really a giant plastic island in the Pacific? Actually, there are two, though they're not so much islands as floating clusters of plastic bits. Dubbed "the Great Garbage Patches," they're each roughly the size of Connecticut but can swell to Texas proportions in certain weather. (Other oceans have smaller clusters.) Once a piece of plastic ends up in the Pacific, it begins a six-year journey in the North Pacific Gyre, a clockwise current circling the ocean between the equator and 50 degrees north. Along the way, the sun-sensitive plastics break down, leaching chemicals into the sea, and some sink to the ocean floor. The surviving debris, as small as rice grains and as big as pickups, joins the two sub-gyres—one midway between Washington State and Hawaii and the other southeast of Japan. Sadly, according to Bill Macdonald, vice president of Long Beach, California's Algalita Marine Research Foundation, there's no way to clean them up. "Imagine vacuuming that much space," he says. "Except it's wet."

Q) Where's the best spot on earth to avoid natural disasters?
Evie Gagne, St. Andrews, New Brunswick
To erect your dream bungalow in the neighborhood with the least chance of cataclysm, Art Lerner-Lam, director of the Center for Hazards and Risk Research, at Columbia University, suggests pointing your contractor to the Upper Midwest of the U.S., the Baltics, or the steppes of northern Eurasia. In other words, places far away from seacoasts, mountains, fault lines, or other hot spots of geologic activity. "There is no absolutely safe area," he cautions. "The earth is dynamic, and there's lots of potential for disasters." As for the safest U.S. city, a recent report by the number crunchers at San Francisco–based SustainLane.com, a sustainable-living Web portal, concluded that Mesa, Arizona, and Milwaukee, Wisconsin, were the urban areas with the lowest risk of feeling the back of Mother Nature's hand. That is, if Milwaukee stops counting bratwurst shortages as natural disasters.

Q) What's the perfect shape for a skipping stone?
Luke Anders, Carlsbad, California
Last year, overfunded French scientists in Marseille built a robot arm to skim aluminum disks across a pool to investigate the physics of skipping stones. Early calculations led them to posit that a disk with a two- or four-inch diameter flung at 22 miles an hour would beat the record of 40 pitty-pats, set by Kurt Steiner on the Allegheny River during the 2002 Pennsylvania Qualifying Stone Skipping Tournament. But their research didn't delve into stone shape or weight, nor did it account for variables like choppy water and finger length. Jerdone Coleman-McGhee, founder of the North American Stone Skipping Association, says shape is less important than weight and thickness, and that irregular stones like triangles are best, since they're easier to spin. "Round stones don't skip a hoot," says Coleman-McGhee, who prefers the five-sided, 50- and 100-gram clay stones he crafts at home. He should know: His personal best is 38 skips. Franco-bot never got above 25.