Barro Colorado Island, or BCI, as it’s commonly known, is one of the world’s most famous biological reserves. Part of what makes it exceptional is that it’s been left alone so long: It was declared a protected area in 1923, when such reserves in the neotropics were almost unheard of. Since then its flora and fauna have been more intensely studied than that of any other tropical area of comparable size.
The island is administered by the Smithsonian Tropical Research Institute (STRI, tel. 212-8951, fax 212-8026, www.stri.org ), which is based in Panama.
Barro Colorado Island was actually a hill until 1914, when the damming of the [nodr:40001 link Chagres River] to create Lago Gatún  made that hill an island. The flooding of the lake left only 15 square kilometers of tropical forest on the island, but they contain 480 species of trees (more than in all of Europe), 70 species of bats, 384 species of birds, 30 species of frogs, 47 species of snakes, and on and on.
Just accounting for the insects on the island is an overwhelming task. Take ants, for instance: More than 200 species have been identified so far.
Day visitors, as opposed to research scientists, can walk on only some trails, usually an interpretive loop that takes 2–3 hours to walk at an easy clip. It’s fairly flat most of the way, but it does get muddy at times. There’s a short side trail off the main loop that’s well worth taking. It leads to the aptly named “Big Tree,” a kapok (Ceiba pentandra) so huge other trees are growing on its branches.
Visitors are not allowed on the trails without an authorized guide. But consider buying A Day on Barro Colorado Island (Smithsonian), by Marina Wong and Jorge Ventocilla, anyway. It contains a trail guide and information on the island’s flora and fauna that will help you get much more out of your visit. It’s sold in a few places in Panama, including the little bookshop at STRI’s main office in Panama City . The Gamboa Rainforest Resort  may have it as well.
Note: Barro Colorado Island has the kind of wildlife many visitors come to the tropics to see, including tapirs, coatimundis, sloths, ocelots, anteaters, collared peccaries, and three species of monkeys. But as STRI personnel will be the first to tell you, day visitors expecting a jungle crawling with creatures will likely be disappointed. One may see almost no animal life during a short visit to BCI.
The only mammals one is likely to encounter are agoutis and howler monkeys. It’s actually hard not to stumble upon howlers. A 1977 census found 65 troops on the island, each with about 19 monkeys. Do the math. Their numbers haven’t changed much since.
Access to Barro Colorado Island is strictly controlled. Visitors must arrange a tour through STRI or an STRI-approved tour operator, and the few spaces get booked up early. Cancellations are not uncommon, however, so last-minute trips are sometimes possible. Some tour operators offer trips to Barro Colorado Nature Monument, which includes the surrounding mainland as well as the island itself. Make sure the tour actually goes to the island if that’s important to you.
The STRI offers tours (tel. 212-8951, fax 212-8026, www.stri.org , Tues., Wed. and Fri. at 7:15 A.M.; Sat. and Sun. at 8 A.M.; US$70 pp, US$40 students). The cost includes the launch from Gamboa  to Barro Colorado Island, a 2–3-hour hike with a naturalist guide, a tour of the visitors center, and lunch at the field-research station (vegetarian food is available). It may be possible to chat up a research scientist over lunch. Reservations should be made as far ahead of time as possible.
The launch to the island leaves from a pier in Gamboa, about an hour’s drive from Panama City  (if there’s no traffic). It’s imperative that visitors arrive early, as the launch to the island, about a 45-minute ride away, leaves on the dot and there’s no other way to get there. Visitors are responsible for their own transportation to Gamboa. A taxi from Panama City costs around US$20. The STRI website now has detailed information about the trip and a schematic map explaining how to get to the pier.