The world's smallest owl, the 14 cm (5 1/2 in) high elf owl, also is a resident of the American desert. This tiny predator uses the hollowed-out nests of woodlocated in cactuses, as its home.

The desert also has its reptiles, including many speof lizards, plus two of the four poisonous snakes of North America — the rattlesnake and coral snake.

Rattlesnakes are pit vipers, a group of reptiles which also includes the fer-de-lance, bushmaster, water moc-casin, and the copperhead The pit is an opening below the snake's eyes which contains a heat-sensing organ.

Only two of North America's lizards are poisonous — the gila monster and Mexican beaded lizard. Unlike poisonous snakes which inject their venom through hollow fangs, these lizards bite their victims, hold on, and allow poison to flow into the open wound from fangs which are grooved at the rear.

The coastlands and adjacent lands of the United States are the habitat of a wide variety of reptiles, birds and mammals. Water moccasins and copperheads are found in the warmer portions, and the largest of all North American reptiles, the alligator, lives in the riv-ers and bayous of the southeast.

Alligators can be distinguished from the closely re-lated crocodiles by their broader heads and the lower teeth which are out of sight when the mouth is closed. A crocodile's teeth are visible at all times.

There are no authenticated cases of wild alligators attacking humans. Crocodiles, on the other hand, can attack people.

Many species of shorebirds live in North America. One of them, the brown pelican, came close to extinc-tion on the continent because of DOT. The pesticide was sprayed and dusted on croplands, then percolated into the ground water and was carried to sea where it entered the ocean's food chain. The pelicans, being ultimate consumers, got heavy doses. Although the chemical didn't kill them, it did weaken the shells of their eggs. The result was few pelican hatchlings. After DDT was banned the pelican population began to grow again. In 1979, 1,200 nests were counted in California, a remarkable comeback.

Marine mammals of the U.S. Pacific coast include four species of pinnipeds — members of the seal group. They are elephant seals, harbor seals, Steller sea lions and California sea lions.

South of the United States and northern Mexico, the character of the land and its wildlife changes. Desert, chaparral, and plains give way to tropical forest. In places rainfall exceeds 500 cm (200 in) annually, and a mild average temperature of 27°C (81°F) prevails.

As in most rain forests, primates dominate. In America they consist of dozens of species of monkeys and marmosets. New World monkeys are only distantly related to those of the Old World. Many species have prehensile tails, a feaure lacking in the Old World monkeys. This "fifth hand" is especially well develin the spider monkey.

Not all of the rain forest's primates have prehensile tails. Marmosets of the forests of Panama and the Amabasin lack it. And the uakari has a mere stub of a tail, making it the only short-tailed New World monkey.

South America is home to approximately 40 percent of the world's birds, and most of them live in its rain forest. Two groups of rain forest birds are among the most colorful in the world — the hummingbirds and parrots.

Known as "living jewels," hummingbirds are found only in the New World, where they live from southern Alaska to Tierra del Fuego. However, they are primartropical birds. There are 319 known species which range in size from the world's smallest bird, the 57 mm (2 1/2 in) long Cuban bee hummer, to the giant hummingbird of the high Andes, measuring 216 mm (8 1/2 in) in length.

A second group of colorful rain forest birds, the parrots, are distributed worldwide in the tropics and on all lands in the southern hemisphere excepting the southern tip of Africa and some of the more remote Pacific islands. In the New World, they reach northinto southern Arizona and New Mexico, where they are represented by occasional visits of the enthick-billed parrot.

The only parrot native to the United States is now extinct. In the early 19th century, the Carolina parakeet ranged from North Dakota and central New York south to eastern Texas and Florida. It was especially abunin the Mississippi River bottoms and along the Atlantic seaboard The little bird was slaughtered for sport and to control its depredations on fruit crops The last one was sighted m the Florida Everglades m the early 1920 s

In addition to its wealth of birds, the South Amen can rain forest is the home of a wide variety of other animals The world s slowest mammal, the sloth which spends long periods hanging upside down from tree branches, is a forest dweller So are opossums, anteaters,