Chimps More Hostile in Groups

There does appear to be strength in numbers, including among chimpanzees. New research has found that chimps in the wild tend to be more aggressive when they travel in large groups.

Chimps live in societies made up of groups of affiliated cliques. Periodically, some members of these groupings, mostly males, silently gather together and leave in an orderly, single-file line to patrol the boundary of their territory. These chimp patrols have long been known to attack, beat and sometimes even kill neighboring chimps they encounter. But the reasons for the attacks are unclear.

John C. Mitani of the University of Michigan and David P. Watts of Yale University collected data about a community of about 150 chimps in Ngogo, Kibale National Park, in Uganda between 1999 and 2003. On patrol days, researchers found that a larger number of males gathered together than on non-patrol days. The addition of each individual to the group increased the odds of a patrol by 17 percent, the researchers reported in an upcoming issue of the journal Animal Behavior.

"The take-home of all of this is that male numbers seem to matter, they find strength in numbers in doing this behavior, and they find strength in making these attacks," Mitani said.

Chimps are humans' closest living relatives, and it's rare for other mammals to attack their neighbors. But Mitani said he was hesitant to draw any analogies between human and chimp behavior:

"I think it is difficult to make any general conclusions about what this says about human behavior."

-- Rob Stein

Florida Panther Data Reassessed

When the U.S. Fish and Wildlife Service reached for the "best available science" to help the endangered Florida panther survive the condos encroaching on its forest habitat, it turned out the "best available" wasn't very good at all.

Among other things, efforts to define the nocturnal cats' habitat were all done during the daytime, says fisheries and wildlife scientist Michael Vaughan of Virginia Polytechnic Institute.

"Some of the data collected in the 1980s got into peer-reviewed literature and shouldn't have," he said. "Once that happens, it's like gospel and it gets perpetuated."

But officials wised up and hired Vaughan and three colleagues to review past studies and make recommendations. The 1980s studies had concluded that the panthers would not travel more than 100 yards from the forest, a finding that figured into decisions on how close to the woods developers could build.

"This seemed strange to us since, in the West, panthers are all over open country," Vaughan said. "Then we found that all the [early research] was done during the daytime, and panthers are nocturnal animals. Where they are during the day may have nothing to do with where they are at night."

"We didn't say the research was wrong," Vaughan continued. "We just said you need more data." Their results are slated to appear in the January edition of the Journal of Wildlife Management.

The "Florida panther" is the same as any other cougar, mountain lion, catamount, wildcat, puma, painter or panther elsewhere in the Americas, Vaughan said. The cats' population in Florida, which fell to between 40 and 50 animals 10 years ago, has probably risen to 80 today, he said, after imported Texas cougars gave the gene pool a much-needed jolt.

-- Guy Gugliotta

Amazon Ant Uses Herbicide

Scientists have found an ant species in the Amazon rain forest that makes its habitat more hospitable by using poison to control what plants grow there.

Megan Frederickson, a graduate student in biology at Stanford University, studied areas known as "devil's gardens," large stands of trees in the Amazon jungles of western Peru that are home to the ants.

These lemon ants are definitely not your regular, everyday ants. They live in the hollow, swollen stems of the lemon ant tree, but they are not content just to settle in the trees that happen to be there. The ants have glands that produce formic acid, a toxic compound they use to kill off the trees, vines, shrubs and wildflowers that compete with their favored trees.

Other ant species make small gardens of their host plants by weeding out other plants, but they weed by biting and chewing off bits of vegetation. What makes lemon ants different is that they weed using an herbicide. The ants take a small bite in a leaf and then inject the poison through the hole. The leaves begin to die within 24 hours of the injection.

In a phone interview, Frederickson, lead author of a paper in the Sept. 22 issue of the journal Nature, said it is the first known example of an ant using a herbicide to shape its surroundings.

Each devil's garden is tended by a single colony of as many as 3 million workers and 15,000 queens. Each queen can live 20 to 25 years, and a colony can persist as long as 800 years, Frederickson said.

-- Michael Zimmerman

Male chimpanzees form extra-large groups to patrol territory, as here in Kibale National Park in Uganda.