This morning’s activity was an excursion to Tortuguero National Park. Over 77,000 acres was declared a National Park in 1970 after being protected as a turtle nesting sanctuary since 1963. The park has great biological diversity and ecosystems including tidal mangrove swamps, rainforest, beaches, and lagoons, with more than 400 species of trees and about 2,200 species of other plants. The trees here are shorter than those of non-flooded forest because of the instability caused by the wet, poorly drained soils. Along the coast the forests grade into mangrove forests, and estuary, beach and marine habitats.
The only way to tour the Park is in a boat, and we had to stop at the Park Office first to pay the entrance fee. While Gustavo was doing that, we looked at some of the floating aquatic plants, including water lettuce (Pistia stratiotes), water pennywort (Hydrocotyle sp.), and something else none of us knew that had interesting sausage-shaped air bladders underneath to keep it afloat.
After Gustavo purchased our entrance tickets, our boat captain Hancy took us across the river to enter the systems of natural and a few man-made canals that form a network through the area to look for plants and wildlife. One of the first things we encountered was Pachira aquatic. This is one of the most conspicuous trees along the Tortuguero canals, but it occurs in many other wet areas from southern Mexico to Peru and Brazil, as well as being cultivated in some other regions in the world—with many common names including malabar chestnut, provision tree, and money tree. It has a buttressed trunk, growing up to 60 feet tall, with palmate leaves on long petioles, and dramatic flowers with white, strap-like petals and numerous long red stamens. We only saw a couple of the flowers, but many of the rounded, reddish-brown fruits which can grow up to 12 inches long and 2.5 inches in diameter. Monkeys and other animals eat the seeds.
Most of this area is well-matured secondary growth. Huge trees towered over a very thick understory of small trees, palms, and shrubs. Some of the other plants we focused on included raffia palm, Raphia taedigera, that we also saw lots of on the boat ride here. This is one of about 20 species of palms in the genus Raphia (the others are native to tropical Madagascar and Africa) that are a source of raffia fibers, produced from the membrane on the underside of each individual frond leaf, used in twine, rope, baskets and textiles. The plants have very long, arching leaves that create dense shade that limit the growth of other plants. They occur in dense stands along the edges of the canals in Tortuguero National Park, as well as in other swampy areas of the country. The other very common and distinctive tree here is gavilán (Pentaclethra macroloba). This tall tree in the pea family (Fabaceae) has pinnate leaves that are twice compound, arranged in a spiral on the stems, with 15-20 paired leaflets. Erect, arching racemes of up to 200 small white flowers each produce a single fruit. The hard, curved, brown pods split open to release the seeds at maturity. This is common in the wet Atlantic lowlands, and in many parts of Tortuguero where the other hardwood trees had been harvested in the past, leaving these less useful (for timber, at least) trees behind.
Our boat pilot skillfully navigated through the shallows and fallen trees while Gustavo pointed out plants and birds and insects and mammals and reptiles.
We got good views of sloths and caimans, iguanas, emerald basilisks and turtles.
Colorful butterflies fluttered around and dragonflies flitted here and there. Howler monkeys let us know that they knew we were near, but they didn’t allow us to get a look. The sun shone brightly through breaks in the canopy, but also we were in deep shade in some areas. We saw numerous birds, some widespread and also seen in the US, but others unfamiliar to the group.
In the late afternoon we went for a walk in the forest adjacent to the lodge, looking at a diversity of birds and plants and insects. We learned about the cecropia tree (Cecropia spp.), a very fast-growing tree with a distinctive ringed trunk, open canopy and large, palmate leaves. It is an early succession plant in disturbed areas or when land is allowed to revert back to native forest. This tree has a symbiotic relationship with Azteca spp. ants which protect its foliage from other animals that try to eat it. Sloths are about the only mammal that is unfazed by the ants, so they are often seen in these trees. The unusual fruits on the female trees are eaten by many birds and other animals. We watched a Montezuma orenpenola feeding on one, and later found a small troop of howler monkeys that were foraging in the cecropia trees. They would break off the fruits, but sometimes were being chased off by the ants, so often retreated to other nearby trees to eat the fruits.
When we returned to the lodge we encountered a small planting of black pepper (Piper nigra) growing on a trellis. Gustavo told the group about this exotic plant, then we tasted one of the spicy fruits!
The wildlife wasn’t restricted to the forest – many birds visited or were living on the lodge property, too. Someof the many birds we saw here included oropendolas nesting in one of the tall trees, a flock of twelve green macaws flying overhead, and keel-billed toucans came to eat the fruits off a palm near the swimming pool.