Despite all the exciting recent discoveries about great apes, many dangers still threaten these amazing animals. The greatest threat to apes, as well as to all other tropical creatures, is deforestation, the destruction of their forest habitats. Faced with the intense pressure of a rapidly growing human population, many developing countries are doing little to protect what remains of their natural forests. People need land for farms and villages, and governments and companies want profits from timber sales.

All wild great apes live in poor nations—some of them among the poorest on Earth—where the populations are growing rapidly and governments have little incentive to protect wildlife or its habitats. For example, primatologist Carel van Schaik from Duke University in Durham, North Carolina, and his colleagues have estimated that since the early 1990's, timber-cutting operations have destroyed up to 80 percent of the orangutan habitat on Sumatra.

The trade in bushmeat (meat from wild animals) poses a second major threat to the survival of apes. People have been hunting and eating wild animals for hundreds of thousands of years. In Africa, the meat of chimpanzees, gorillas, and bonobos is considered a delicacy. This may sound gruesome, but it is no more strange than the popularity of turkey, lobster, or frogs' legs as food in many cultures. In March 2001, the United Nations Food and Agriculture Organization reported that the bushmeat trade was becoming an increasingly profitable industry. As logging roads are cut into the forests, local businesspeople capitalize on the frequent truck traffic by setting up hunting businesses. Hunters ship the ape carcasses on trucks to nearby towns, where they are sold in the market at prices up to five times as high as that for beef. In addition, the logging companies sometimes provide their workers with shotguns to hunt for meat for themselves rather than supplying them with food.

In forests all across Africa, people set snares (leg traps) to catch antelope, wild pigs, and other animals for food. These snares also entrap great apes as they walk across the forest floor. Poachers used to make snares from natural fibers. If a chimpanzee stepped into one, the material usually rotted quickly and the snare would fall off, causing no major damage. However, metal wires have replaced fiber snares. These tighten around the ape's limb and continue to cut into the flesh until the hand or foot develops gangrene (a condition in which body tissues die from lack of oxygen), which can kill or maim the ape. More than one-third of all the chimpanzees living in some forests today, including Uganda's Budongo Forest, are either amputees or carry severe injuries from snares. In some parks, rangers collect snares—sometimes finding hundreds in a given area—but in unprotected areas, the danger from these traps is extremely high.

Because of their genetic similarity to us, great apes can catch nearly all infectious human diseases. And like us, apes lack any immunity (resistance) to diseases to which they have never been exposed. So when a chimpanzee contracts the common cold or other respiratory infection, the disease is often fatal. In particular danger are apes that come in contact with people, for example, in areas where farms and forests sit side by side.

Primatologists believe that thousands of gorillas and chimpanzees have died across Africa since the early 2000's in epidemics of the deadly Ebola virus, which may be transmitted between apes and human beings. A study published in 2004 by Eric M. Leroy of the Research Institute for Development in Gabon, Africa, linked five Ebola outbreaks in central Africa in the early 2000's to a 60-percent drop in gorilla populations and a 90-percent drop in chimpanzee populations. In 2004, Heinz Ellerbrock of the Robert Koch Institute in Berlin and Fabian Leendertz of the Max Planck Institute for Evolutionary Anthropology in Leipzig announced that they had discovered anthrax bacteria in chimpanzees that had died at Tai National Park in Côte d'Ivoire. Their findings represent the first time the disease had been identified in a wild ape population.