Michael H. Robinson, a spider expert who long sought to make zoos places where the public could learn about animals and their environments, is planning to retire next April as director of the Smithsonian's National Zoological Park.

Robinson, an animal behaviorist and tropical biologist who studied the courtship behavior of arachnids, became director of the zoo in 1984. For most of his professional life, Robinson has worked for the facility or the Smithsonian's Tropical Research Institute in Panama. He will turn 71 in January.

During his tenure, the zoo changed from being a collection of pens and cages filled with monkeys, tigers and giraffes to more of a park where many animals are presented in settings that bear some resemblance to their natural habitats. In recent years, some of the animals received new habitats, such as the sandy pond for the prairie dogs and an elaborate system of towers and cables for the orangutans.

The zoo itself has 5,000 animals of 500 different species, living at the 163-acre park on Connecticut Avenue and at a conservation and research center in Front Royal, Va. They range from the giant panda Hsing-Hsing, perhaps the zoo's best-known resident, to fennec foxes from the deserts of the Middle East (one of Robinson's favorite species).

McKinley Hudson, the zoo's deputy director, said Robinson took a "holistic" approach. "He looked at his role not only to teach about the animals but to increase awareness that we have species that are leaving the Earth. He believed in backyard biology and that we should talk about things around the animals," Hudson said.

His view of a "biopark" was not universally accepted, drawing criticism from traditionalists who believe giving the public a good view of a majestic elephant or sea lion is a zoo's primary task. Yet facilities that have been updated, such as New York's Bronx Zoo, are enormously popular attractions.

At Washington's zoo, a federal park since 1889, Robinson installed the controversial Think Tank, an exhibit on animal thinking that looked at orangutan language acquisition and tool use. He also helped open the Amazonia building, the largest exhibit to be added to the zoo in 50 years. It is a lush habitat filled with colorful birds, running water and tropical plants of the rain forest. There is also a new Pollinarium, where visitors can study plants and the animals that pollinate them. An exhibit on water is in the planning stages.

Robinson, who was out of the country yesterday, issued a short statement through a spokesman: "Zoos are powerful forces of biological education, places where people can be moved by the wonder and glory of real living things."

He has long argued that a biopark should use animals along with the best that natural history museums, botanical gardens, aquariums and even art galleries have to offer to illustrate "the splendor of all living things."

J. Dennis O'Connor, the provost of the Smithsonian, said Robinson was extremely comfortable in his role as a behavioral field biologist. He recalled spending a night with Robinson watching bats fly in and out of caves in Panama. Robinson's vision of what a zoo could be was gaining acceptance in many places, including the Smithsonian, O'Connor said. "There's still some work to do, but he has succeeded in getting the concept of a biological park firmly present in the consciousness of the Smithsonian," he said.

Robinson was born in Preston, Lancashire, England, and earned his doctorate at Oxford University under Nobel laureate Niko Tinbergen. He also has degrees from the University of Liverpool and the University of Wales and taught school for seven years in the United Kingdom. He joined the Smithsonian as a predoctoral scholar in 1965. He has written 150 papers and articles, and a book on the courtship and mating of spiders.

Robinson, who has a shock of white hair, made colorful presentations before the House appropriations subcommittee when it was chaired by then-Rep. Sidney Yates. He used animals from the zoo as props during his presentations, once taking a rare Komodo dragon to the Capitol in pursuit of appropriations. "Mike was wonderful at persuading Congress, and some of us on the Mall were jealous. We didn't have the cute little monkeys and such," said Donald Ortner, a curator of anthropology at the National Museum of Natural History. The zoo receives a federal appropriation of $22 million for operating costs, and is supported by the 30,000 members of the Friends of the National Zoo.

But Ortner also pointed out that Robinson was committed to research on endangered species. Animal nutritionists at the zoo have headed a study of the feeding behavior of endangered desert tortoises in Nevada. In another lab, a pathologist is developing a snake-specific virus that is designed to eliminate the brown tree snake that is threatening to overrun Guam and wipe out the Pacific island's rare birds.

In April Robinson plans to go to Panama to spend a year studying reef squid and orb-weaving spiders at the Smithsonian's Tropical Research Institute.

Staff writer D'Vera Cohn contributed to this report.