Swimming in a river on the Osa Peninsula in Costa Rica, my son Matt was suddenly hit on the head by a hard-thrown fig. He stood up to look into the thick-leaved trees above - and was immediately smacked by several more flying fruits.
"Cut it out!" he called, but then spotting the troublemakers, he burst out laughing. A troop of white-faced monkeys was frolicking on the branches, snacking on the ripe fruit and eagerly tossing down the remainders.
"Come look!" Matt called, and the rest of our family waded back into the warm waters of Corcovado National Park. For close to an hour, we stood mesmerized as 30 or so intelligent and endlessly entertaining capuchin monkeys scrambled through trees, stared curiously at us, and stopped to groom one another.
At one point, a fight broke out when the monkeys objected to an anteater who was interfering with their territory. The sweet-looking monkeys turned aggressive, and the intruder left. But they didn't mind the howler monkey - larger and slower-paced than they were - whose loud cry sounded like an ambulance siren in the otherwise hushed forest.
The lush rain forest in the remote southwest corner of Costa Rica is home to more monkeys than people. On virtually any foray into the 108,000 acres of Corcovado National Park, you're likely to encounter one of the four species that know this land is their land - and those of us holding binoculars are just visitors.
After Matt's discovery, we continued on our hike and almost immediately came across a score of long-limbed spider monkeys swinging acrobatically above us.
We spotted one mother with a newborn on her back and two other females holding their babies under an arm. Since spider monkeys give birth only every two or three years, it was a welcome sight.
These nomadic primates need an expansive primary forest to thrive, and they find it in Corcovado, which gets about 200 inches of rain each year and has been protected from logging and gold mining since 1975.
Corcovado boasts some 230 species of mammals, more than 500 varieties of birds, and more reptiles, amphibians, and insects than anyone can count.
If the busy monkeys don't capture your attention, you might be fascinated by the two- and three-toed sloths, furry balls that hang from the trees not doing much at all. My older son was intrigued by the bright green-and-black-spotted poison dart frog he found hiding in the well of a tree and the red-necked lizards that offer a glorious display to scare off other males and attract mates.
Some 30 percent of the land in Costa Rica is protected, but nothing else is quite as untouched as Corcovado National Park. The area is difficult to reach - a nine-hour drive over bad roads or a one-hour flight in a shaky four-seater plane (the latter is preferable). Four ranger stations provide access to the park, but the only accommodations are in the few ecolodges on the periphery.
Our plane landed on the tiny Carate airstrip where an ox cart was waiting to transport our luggage to Corcovado Lodge. We accompanied it on foot, walking along the wide, empty beach at the edge of the jungle. Hawks and swallowtail kites swooped overhead, and we were constantly interrupted by the raucous songs of scarlet macaws perched in almond trees. These glorious colorful birds mate for life, but their calls suggest endless domestic dispute.
At Corcovado Lodge, platform tents directly on the beach are furnished with twin beds, candles (no electricity), and a small table. It's hard to feel as though you're roughing it, though, when the tents have cheerful bedspreads and curtains, and there are fresh hibiscus flowers on your pillow.
At night, a giant croaking bullfrog accompanied us up the outdoor stairs to the bathrooms, and one morning a boa constrictor was calmly wrapped around the railing on our tent's patio. (We didn't bother him and he returned the favor.)
Trails leading from the lodge wind into the rain forest, where we spotted coati (a relative of the raccoon), agouti, and, of course, monkeys - though the elusive squirrel monkey evaded us.
After climbing up one trail, we let strong local guides winch us 120 feet into the air, where we made a soft landing on the platform surrounding a 600-year-old guapinol tree.
The view across the top of the rain forest canopy was glorious but quiet, and at first we were disappointed. But remembering this was a natural habitat, not a zoo, we settled down with our binoculars and let the show slowly unfold.
Startlingly beautiful birds such as green honeycreepers and a red-bellied trogon flew to branches nearby, colorful show-offs including toucans and parrots preened in the trees, and a three-toed sloth lay quietly resting just a few feet away.
Walking through the jungle of Corcovado National Park was like being on a Hollywood set with no special effects needed - the curly monkey ladder vines twisted and turned in midair, and the leaves on the oversized banana plants were taller than a person.
We also discovered peppery citrus leaves, sour-tasting orange plants, creamy yellow flowers that smell like root beer, and a fruit that leaves a tattoolike stain on the skin that lasts a couple of weeks.
When it was time to leave Corcovado, we climbed back into a tiny plane, not even minding that the pilot tossed open the window as he taxied down the runway. By now we had seen enough to expect that in this distant corner of Costa Rica, the unusual was simply to be expected.