I always end up writing these blogs in a place I never expected. Currently, I am relaxing in my bathing suit in an aquamarine-colored chair, looking out at the Atlantic Ocean, the beach at my feet. We’ve come a long way from Costa Rica. To get here took a lot of work and sweat. So I’m going to take you back two weeks ago, to our re-emergence to the modern world and its amenities (internet) from El Campanario.
We arrived at Las Cruces two Saturdays ago, well-weathered but missing the beach. This was to be our “relaxation period,” as we caught up on work in an intensive few days at what I would call the most beautiful conference center at least in Costa Rica, maybe in the world. There was a laundry service (which I, personally, desperately needed, as I had already gone through all my underwear and had to handwash many pairs twice) and great food, and, most thrillingly, no projects for a few days. On our first morning, Rodo, one of the resident biologists at Las Cruces Biological Station, took us on a tour of the plant life. Las Cruces is known for its extensive botanical garden, inhabited by plants from Namibia as well as Costa Rica. We paid close attention to alternate versus opposite branching, simple versus compound leaves, how to differentiate between cycads and palms, all out of interest as well as preparation for our “Botany Practicum” in a few days. Similar to our “Vertebrate Practicum” in Palo Verde, this was a quiz where we took our answers from the field.
Also at Las Cruces, we took up the less thrilling but more fulfilling work of finishing up manuscripts of previous projects, putting the final touches on our work from Cuerici and writing the entirety of our hermit crab manuscript from El Campanario. Unfortunately, my personal mood had turned since we resurfaced to reality, which made me, in all honesty, not the most helpful group member. The process had depressed many of us. We were hitting the halfway mark of the trip, and while we were all relieved to see our families, it reminded us how much we missed them. I personally also had a lot of trouble sleeping. Perhaps it was the rickety bunk beds or the possibility of snakes on bathroom runs, but I was not my best. Las Cruces therefore brought out the cranky in many of us, but we got our work done, all while staring out the window at exotic plants (and once a katydid the size of my fist). On the last day, we found ourselves confronted with the Botany Practicum. Many of us spent the majority of the day studying, forming massage trains and shouting out confusing plant names and distinguishing characteristics. Braden, our TA and practicing plant biologist, gave us our quiz a few hours later, which I vaguely remember causing me to literally scratch my head with confusion. I passed, but it was not my best hour. Plants are harder than you would think (or, potentially, I’m just particularly bad at them). Try keying one out sometime, and experience the confusion. Studying them does open one’s eyes to the world around them, though. Never will I look at a palm tree the same way again.
Midweek, after a short few days in Las Cruces, we packed up our bags and took a long bus ride to La Selva. La Selva Biological Field Station is probably the most well known and oldest of the stations we visited in Costa Rica. There were several other scientists and tourist groups there when we visited, and it had a dining room three times the size of the others. Our first morning there, Alberto and Kenneth (resident naturalist tour guides) took us on a slow hike around the area. We stopped for keel-billed toucans that looked just like the ones off the cereal boxes, with beaks so large in proportion to their body it is a wonder they don’t keel over. Another guide lifted a leaf (from a Heliconia plant, as I learned in the Botany Practicum) to show us rare white bats that looked like tufts of cotton, one of two white species of bats in the world. And, most miraculous of all, our guides spotted two wooly spheres in the treetops: sloths. For anyone older than 40 (and maybe 30), sloths are an obsession among my generation. I have no idea where the thousands of memes began, but sloths have become a reigning symbol, perhaps representing the teenage need to show the world they don’t care. Sloths and their stereotypically lackadaisical attitudes seem to fit this mold. In any case, there was genuine awe and excitement among our group that might have been unmatched by anyone older. One student had been so excited about seeing sloths that he had bought a sloth hat, and his face when we finally did – it was maybe the most joy I’ve ever seen in a person. His face lit up, and he smiled so much he produced lines that had never been there before. This is the kind of joy a sloth can bring in a person, especially one of my generation. And, though I may not have shared quite this level of elation, I found the question of sloths an interesting one, and eventually wound up in the sloth group, studying them.
We ended up looking at sloth thermoregulation. Most people don’t realize that sloths are classified as facultative poikilotherms, meaning that their body temperature varies with ambient temperatures. Classically, they would be referred to as “cold-blooded,” but they have been rebranded with a less confusing word that is more fun to say. Various studies have shown that the sloth metabolism increases with higher temperatures (so they, for example, breathe faster when it’s warmer out). This is different from homeotherms like humans that have a constant internal temperature, and generally our metabolisms increase with lower temperatures (we might breathe faster in colder temperatures to help keep our body temperature up). We wanted to look at whether sloths would follow poikilothermic strategy in their activity level and behaviors. In other words, are they more active when it’s warmer, as poikilotherms would be. The general procedure for this basically involved us sitting outside in uneasy deck chairs, craning our necks up at the trees for hour-long periods, and writing down everything our sloths did. We eventually found 4 sloths (with the help of our guides). With each new data collection day (there were only three days), we had to scout for our sloths to see if they still occupied the same trees. And, though it may come as a surprise to some people, they were never in the same place, and we often lost them, for either a few hours or the rest of the data collection period. This was the case with Tina (all sloths were named by the previously described joyful sloth enthusiast), who seemed very trustworthy until she disappeared on us in our second day of data collection. Disappointing, disappointing Tina. Jeff, on the other hand, was a very interesting case. On our first morning scouting for sloths, before we began collecting any real data, we saw Jeff swinging through the trees like the mammal we know he is. No one seems to believe us, but I have three other witnesses who saw what I saw: a sloth moving from tree to tree faster than you would ever expect. We took one measurement in which Jeff moved nine body lengths in one minute. A sloth is several feet (even meters) long, so imagine a sloth going 27 feet/min, or 0.31 mph. When I put it like that, I suppose it doesn’t seem like very much, but for a sloth, that is very fast. When we began collecting data, Jeff, probably unsurprisingly after his marathon, slept for two whole days, and barely moved even to scratch himself. We also found two sloths on the Stone Bridge, which connects the field station over a river. One day I turned around, and there he (we randomly ascribed gender to the sloths, but in reality, we had no way of identifying sex, as researchers usually do this through genetic analysis) was, a big fur ball only a few meters from my face. We eventually named him Yung Wun (“young one”) because he appeared smaller than the other sloths, and was often the most active. A few hours later, a guide pointed out another sloth in the same tree (who would have thought?), who we named Carmen Sandiego for the spy character from an old computer game (“Where in the world is Carmen Sandiego?”) for the difficulty in spotting her. We proceeded to take data on every move each sloth made for various periods throughout the day for three days, and upon analysis, we noticed something very interesting. For both Jeff and Carmen Sandiego (we had to exclude Tina because there was so little data), we found no trend in the data. This is interesting in itself, because it goes against what we would expect with poikilotherms. Yung Wun, however, was even more interesting: his activity level had a negative relationship with temperature. In other words, as temperature decreased, he upped his activity. The takeaway from this data is basically that, though some aspects of sloths may be poikilothermic, they are behaviorally homeotherms. You might expect animals with constant body temperature to move more in colder temperatures to warm themselves up, and this seems to be the case with sloths. This is a pretty incredible discovery considering that most researchers consider sloths poikilotherms. If any sloth researchers are out there, they should consider studying the behavioral effects of temperature on sloths. They may be surprised.
Soon after we gave our presentation on sloths, we left Costa Rica. It was bittersweet, leaving the wildlife and the Stone Bridge (one morning I got sick and threw up over the side of it, in a very dramatic episode I will never stop recounting). We spent more time in Costa Rica than almost any other school or tourist group, or so we were informed. I think I soaked just as much as I could out of the experience as a student. Maybe one day I’ll return. As what, who can say just yet? For now, I find myself in Little Cayman after several days of travel, awaiting a new destiny in the surf of the Atlantic Ocean.