Wednesday, February 3, 2010

Palo Verde National Park

For about the last ten days, I’ve been staying at Palo Verde National Park in Guanacaste Province, Costa Rica, one of the country’s 26 national parks. This is the first stop on our voyage (a Tropical Biology course offered through the Organization for Tropical Studies) through the country, and we stay here longer than any other site, save one. But our time here is nearly up.

When most people imagine tropical forests, they picture the lush jungles of the Amazon rainforest. There are some areas in Costa Rica that superficially resemble these jungles, and we’ll be visiting some later (with their yards of annual rainfall). But not all tropical areas receive a lot of rain (think deserts). Forests in these areas are called tropical dry forests, and they’re one of the most endangered habitat types in the world. Typified by deciduous trees, much of the tropical dry forests in Central America have been converted to agriculture or land for cattle grazing; it’s thought less than 1% of its original extent remains. Palo Verde National Park contains one of the last chunks.

Afternoons are oppressively hot, the tropical sun beats down on us relentlessly. If you want to spend any time outside, suntan lotion isn’t a luxury, it’s a necessity. Since it’s now the dry season, many of the trees have dropped their leaves; so even when in the forest it is very hot and dry with little shade. The brittle leaves on the ground crack with each step, making it difficult to sneak up on wildlife.

Mornings and nights are surprisingly comfortable, the sun sets quickly closer to the equator, and soon after dinner it is as dark as it will be all night. Cool and refreshing winds bombard you, though any physical activity is still sure to result in considerable sweating.

Ironically, though an extremely hot and dry area, Palo Verde contains one of the most important wetlands in this part of the world.

The Rio Tempisque (where I previously spotted the monster crocs) runs through the park, and where it seasonally overflows (not this time of year), vast marshes form. Over the following months, the water level in the marsh will slowly dissipate and evaporate until the marsh is eventually is reduced to isolated puddles.
Many have remarked the water seems scarcer each day we’re here. But in the meantime, migratory waterbirds congregate by the thousands, including large wading birds like Roseate Spoonbills and Wood Storks. So many Black-bellied Whistling Ducks depend on this wetland that both environmental and hunting organizations consider this a priority area for conservation.

The marsh has been overrun with dense cattails that reduce its appeal to waterfowl, in decades past these cattails were controlled through burning and cattle grazing, but neither is a feasible option now. Burning is not advisable due to the dry nature of the surrounding forest, it hasn’t been adapted to fire and if the flames escape from the marsh it could be catastrophic. On the other hand, so many cattle would be required to maintain the open marsh that the place would be overrun with them. As it is there are a limited amount of cows that are kept in the park, in the hopes they at least help keep the cattail in check. Though not a particularly effective strategy, allowing some cows to graze here allows the park to maintain good public relations with some of the nearby residents.

For the last few days, I’ve spent most of the daylight hours attending lectures here, conducting some small research projects, and writing up the results; but nights are generally free to explore. This is when I’ve made some of the more exciting discoveries. If you spent any time on my blog here, you know I have a passion for reptiles, but no self respecting wildlife biologist doesn’t get excited at the prospect of finding charismatic or large mammals.

A few days ago, while helping another student catch insects for their project, I looked up within a tangle of branches and noticed what initially appeared to be a medium-sized rodent. Closer and more intent inspection revealed the animal appeared to be a marsupial.

Later confirmed as a Mexican Mouse Opossum, I am pleased with my attempt to immortalize it in a photograph. I proudly exclaimed to have found the most attractive opossum in the region. Later that same night, I found the ugliest.

A few snakes, brought to the lecture room earlier so we could learn how to identify them, had to be released. Hoping I could get a few natural shots of these animals, I volunteered to let them go. Being nocturnal animals though, the responsible thing was to release them at night. So, I trudged down the dark road to the area where they had been captured the night before, peering into the surrounding woods with my flashlight at every snapped branch, real or imagined. As is typical of when I take dark walks in the jungle, my thoughts quickly drifted to large predators. On my way back from the release site, as I was imagining if I would be killed instantly during a jaguar attack or if I’d be alive as it dragged me back to a secluded area to eat me, I was suddenly confronted by a pair of eyes reflected back at me in the road. At the distant end of the area illuminated by my fading flashlight, the rational part of my brain reassured me that this animal was too small to be a jaguar capable of killing me. But, the insane part of my membrane wondered whether this was perhaps a cub serving to distract me while mom snuck forward menacingly.

The little creature and I stood frozen in the road, looking at each other for several seconds while we sized each other up. When I had collected my thoughts and settled down I recognized it as a common opossum. Picture one of our Virginia Opossums back home and then imagine one that really needs a bath, and you’ll have a pretty good idea of the dirty little creature that stood before me. It eventually realized it had had enough of looking at my mug, and it scurried away into the underbrush.

A nearby spring in the surrounding limestone outcrops is also a good place to see wildlife; the various species congregate at these water sources at night, especially during the dry season. I’ve seen White-tailed Deer and Raccoons, the same species we have in the States, in the general vicinity of the spring. But I’ve also spotted some more exotic species including Coatis, Collared Peccaries, Paca, and my personal favorite, a Tamandua, a yellow and black arboreal anteater.

Collared Peccaries

Bats cruise through the trees, their wings seem to flap in slow motion as they hunt the insects attracted to my headlamp. You could reach out and touch one, though I'm not sure why you'd want to.


Sean said...

Costa Rican Mouse Opossum.

Anonymous said...

If you're visiting the Tempisque marsh keep your eye peeled for a Jabiru Stork. I saw one there 20 years ago.
Dale (of the giant Georgia rattler)

David Steen said...


I've heard that Jabiru Storks were once common here, but the invasion of the cattails have made the marsh unattractive to these massive birds. None have been spotted this trip. I did see one once in Brazil though, an impressive animal.