How, I wondered while watching a light rainfall of sticks, does anyone get any work done here? Or, is thisthe work?

“Barro Colorado is the longest-studied piece of tropical real estate
in the world,” said Beth King, the institute’s science interpreter.
“It’s not a park; it’s a research island. It’s like walking through a
living lab.”

To be sure, the Smithsonian “lab” is neither sterile nor controlled.
It occupies a 3,707-acre island, part of the Barro Colorado Natural
Monument, and is an active petri dish of mammals (93 species), birds
(366), plants (1,368), amphibians and reptiles (90) and visiting
scientists (up to 300 a year). The humid tropical forest has been
barely touched by Homo sapiens; the man-made constructions
include a small dock, a weather tower and a smattering of simple
buildings. In this barely adulterated environment, international
scholars can pursue their life’s devotions: the foamy nests of tungara
frogs, the night vision of bees, the dreams of sloths. In addition, a
limited number of tourists (10 on weekdays, 20 on weekends) may visit,
to hike, lunch and observe the resident brains and beasts.

In the early morning, I went to Gamboa Pier, 45 minutes north of
Panama City, to catch the boat that carries workers and tour-takers to
the institute. I shared the commute with tanned, fit men and women
dressed in light khaki clothing, tall rubber boots and wide-brimmed
hats. The workhorse vessel sped along Gatun Lake, passing vibrant green
islands shaped like jigsaw-puzzle pieces. Where the land opened to the
sea, I glimpsed massive cargo ships drifting by, their black hulks
smudging the otherwise pristine landscape. About 30 minutes into the
ride, Barro Colorado loomed into view, its dock and red-roofed
structures making it look like a recluse’s private sanctuary.

The Smithsonian’s link to Barro Colorado dates to 1910, when
President William Howard Taft asked the institute to assist in an
environmental impact study concerning the construction of the Panama
Canal. The island, which was designated a biological reserve in 1923,
grew into a world-class field station for tropical research. Through
the years, high-profile scientists have come to this ecologically
diverse landmass to study evolution or disease-carrying mosquitoes, for
example, or to test the resilience of certain materials, such as Kodak
film, under extreme conditions. Congress designated the Smithsonian the
administrator of the reserve in 1946, and when Panama gained control of
the canal in 1999, the organization received permission to use the
facility through at least 2019.

“For a century, this has been the central place where people
studying the tropics go,” King said. “A lot of guidebook information,
like where do toucans make their home, was discovered on Barro
Colorado.”

My own biological training stopped after frog dissection. So I had
to take King at her word when she said, “I smell howler monkeys,” only
minutes into our walk. However, with a little guidance, I could now
clearly identify the monkeys’ chorus: a deep, throaty baritone that
reverberated through the forest. Yet, in this instance, scent plus
sound did not add up to a sighting.

In many cases, it took a sharp eye to spot the animals. The thick
forest, debris-strewn ground and pallid sunbeams create the perfect
camouflage for creatures of varied shapes and hues. I nearly mistook an
agouti tucking into lunch for a mound of dirt. Even the scientists
sometimes struggle to locate their specimens.

“She’s spent a lot of time sitting under trees looking for
anteaters,” King said as a young woman passed us, carrying a metal pole
with a looped end and a determined expression.

“I can find them, but I can’t catch them,” the woman retorted, en
route to a giant ceibo where an anteater recently had been detected.

Because the island is essentially an office, visitors are expected
to respect the scientists and not interfere with their work or bombard
them with questions. However, King said many of the researchers are
eager to share their experiments with layfolk. A young Dutchman with an
overstuffed backpack let us follow him into the brush to check on a
trap. Swishing through sharp branches, he explained that he was part of
a team studying the role agoutis play in forestation. So far, the team
has trapped 29 of the critters, but not this time. A guileless rat had
fallen for the coconut bait instead.

Before lunch, we tagged along with Meg Crofoot, a postdoctoral
fellow at the institute who specializes in capuchin monkeys. She took
us off-trail, into a thicket of trees many stories high. In the upper
levels, a handful of howler monkeys watched us watching them. It was
unnerving, as when a child or a dog stares intently at you. Crofoot
said that was normal monkey behavior: We were in their domain, and they
were simply checking us out. Forming a circle overhead, they scrunched
their faces into ugly masks and started tossing sticks. “They are much
less scared of you,” Crofoot says. I could only imagine what they’d
throw if they were frightened: an anteater?

On my way to the boat back to the mainland, I heard one last bellow
from a howler monkey. Maybe one day, because of the Smithsonian
scientists, I will read in a guidebook or magazine what it was saying.

The Smithsonian Tropical Research Institute runs its Day
Visit Program five times a week (no Mondays or Thursdays). The $70 fee
includes round-trip boat ride from Gamboa Pier; interpretive tour and
hike lasting up to three hours; and lunch. Reservations required. Info:
011-507-212-8951 or 011-507-212-8026, http://www.stri.org.