The Lizard Project

Our second week at Palo Verde was independent projects, take two. This time, I worked with Becca, who is a junior at Bowdoin College in Maine. After researching and planning for a few days, we decided to study the use of color vision in the recognition of fruit ripeness by Ctenosaura similis. Ctenosaurs are a species of iguana that are abundant at Palo Verde. It has been shown that they use both color vision and scent in making foraging decisions, but the importance and interaction of these senses in recognizing fruit ripeness was unstudied.

Questions

Our initial questions were:
I: Does Ctenosaura similis use color vision to differentiate fruits based on ripeness?
II: When equal “I’m yummy” olfactory cues are present, does C. similis differentiate between ripe and non-ripe colors?
III: When color cues contradict olfactory cues, does color preference prevail?

Thus, the final paragraph of my final paper's introduction was as follows:

In this study, (1) we examine the ability of Ctenosaura similis to differentiate between ripe and unripe fruits using color vision. Here, we predict that C. similis will show preference for ripe-colored fruits in the absence of olfactory cues. (2) We then assess whether C. similis differentiates between ripe and unripe fruit colors in the presence of equally attractive olfactory cues. By comparing preferences shown in (1) and (2), we determine whether the role of color vision changes when chemosensory cues are available. Finally, (3) we examine the relationship between color cues and scent in the foraging decisions of C. similis, with the goal of assessing the relative importance of each cue and by what factors is it influenced.

Methods

To examine the first question, (I) we made fruit models by covering pebbles with colored plasticine (nontoxic clay). Sets of three ripe-colored and three green fruit models were placed in areas frequented by ctenosaurs, and the number of bites on each color was recorded after approximately eight hours.

(II) In the second phase, we presented ctenosaurs with a choice between a ripe-colored and green banana slice (dyed with food coloring) and recorded which banana was eaten first.

(III) In the third phase, we presented ctenosaurs with a choice between a red fruit model and green banana and scored which was (a) approached first and (b) bitten first.

Data collection for our project was fun, hilarious, and very successful (unlike my last project!). Setting out the plasticine fruits took forever, but we got a lot better at knowing where to put the fruits so as to get the most data. Collecting the banana data was highly entertaining - we would first find a ctenosaur, then sneak toward it and set a piece of cardboard with fruits on it as close as possible without the ctenosaur running away. We would then wait and watch from a far-away vantage point and record what the iguana did. Repeat, repeat, repeat. We often named our test subjects after the place where we found them - for instance, we had dock lizard, log lizard, dining hall lizard, gift shop lizard, library lizard, field lizard, and about twenty woodshed lizards. Data collection continued for five days, and on the sixth began data analysis, presentation-making, and paper-writing.

Results & Conclusions

Our results actually turned out to be really interesting and pretty cool.

(I) In the first phase, ctenosaurs strongly preferred red, yellow, and orange over green, but showed no preference for light green over dark green. None of our seventeen brown vs. green fruit model setups received bites. From this we concluded that lizards do, indeed, use color vision to forage selectively on ripe fruits.

(II) In the first phase, lizards strongly preferred red, yellow, orange, and brown dyed bananas over green, but showed no preference for light green over dark green. From this we concluded that because brown is a common color in the forest (rocks, dirt, feces, etc.), brown is not recognized as a ripe color unless coupled with positive olfactory cues. (We nicknamed this the "Don't Eat Poop" theory.) We also concluded that light green probably represents an unripe or ripening fruit, and thus an unprofitable or only marginally profitable food item.

(III) In the third phase, no difference was observed in whether the red clay fruit model or green banana was approached first, but lizards consistently ate the green banana before biting the red clay. We thus concluded that from a distance, olfactory cues and color vision interact to determine fruit ripeness, but that olfactory cues prevail at close range.

Palo Verde

Our last field station was Palo Verde, in northwestern Costa Rica. We stayed there for three weeks, an hour's drive from civilization (most of us never left the station). The OTS-owned station is in Palo Verde National Park, and is located next to a large marsh. Palo Verde is a tropical dry forest, and we arrived about four days before the dry season started. Although hot, the weather was nice and it pretty much didn't rain after the rainy season officially ended. The first week consisted of lectures, faculty-led projects, and planning for our second independent projects, which took place during the second week (more to come on that in another post). The third week was presenting and writing up our IP's, studying for final exams, taking final exams, and finishing up loose-end assignments.

One of the highlights of our stay at Palo Verde ended up being Thanksgiving, which we all expected to be completely depressing. We had been told that nothing special would happen for Thanksgiving, since it isn't celebrated in Costa Rica. It fell during IP week, so we spent the day collecting data as planned. We had been banned from the dining hall for the day as it was being fumigated (or so we thought). Turns out the whole thing was a cover-up for an absolutely delicious turkey dinner, complete with mashed potatoes, cranberry sauce, pumpkin pie, and the like. On a day when a lot of us were sad not to be with our families, it was exactly what we needed.

To escape all the academic craziness, a few friends and I made it a habit to play soccer before dinner every day with a few guys at the station. Although I'm absolutely terrible at soccer, it became something I looked forward to every day. Our Tico friends were also pretty amused at our attempts to yell soccer-related things in Spanish. The only downside was that the absolute worst time for mosquitoes at Palo Verde is at about 5:30, and despite my constant self-dousings with DEET, my legs were completely mutilated by the end of our stay. Oh well - it was worth it.

A few of my favorite memories from Palo Verde involve the various creatures that inhabit the area around our bunk rooms. There are men's and women's bathrooms at the station, which are next to each other. The wall between them doesn't go all the way up to the ceiling - as in, there's a space between the top of the wall and the ceiling. One night, a few girls and I were in the bathroom brushing our teeth and getting ready for bed. Suddenly, we hear one of the guys in the other bathroom telling us to back up away from the wall. "Why?!" we asked. The reply was something like, "Just do it!" (so we did) and suddenly a scorpion flew over the wall and into our bathroom. After the obligatory screaming and laughing, Becca carefully picked up the scorpion with a paper towel and attempted to throw it back over the wall. Paper towels, however, are not at all aerodynamic and the scorpion instead slammed into the wall. Attempt two, and repeat. That was the end of the scorpion, but the event has become one of our favorite jungle stories.

Another hilarious occurence occurred during the last week, right in the middle of IP and finals stress. Two of my roommates (Claire and Becca) and I were sleeping peacefully when suddenly we were awakened by our third roommate (Courtney) whispering in a very panicked voice. It was about 1:00 AM, so it took me a minute to become conscious, but when I did I realized that Courtney was informing us all that there was a rat in our room. Sure enough, we turned on our headlamps and saw a rat (probably about five inches in length without the tail) digging around in some ziploc bags in the middle of the room. Upon being spotted, it quickly ran and hid under Courtney's bed. I was exhausted, and thus decided to just go back to sleep, but it quickly became obvious that Courtney was not about to let us all sleep when there was a rat living under her bed. Thus, Plan B: I put on my shoes and ran out to the classroom to get one of the insect-catching nets. Back in the room, I crouched down and the floor and somehow (miraculously) managed to swipe the rat into the net on my first try. Laughing hysterically (although trying not to wake everyone), we put the rat outside, thinking that was the end of that.

Wrong. The next night, I was again awaked by Courtney's frantically whispering voice. This time, though, she was saying, "Hilary! Hilary!" When I woke up, she informed me not only had ANOTHER rat found its way into our room, but this time it had climbed into my bed. This, of course, set me flipping my sheets everywhere thinking the rat was going to come flying into my face at any second. Neither of us knows where this second rat went, but it didn't seem to actually be in my bed although Courtney had watched it crawl up towards me. The general consensus is that the rat (thankfully) never actually made it inside my mosquito net. I always knew that thing protected me from things besides mosquitoes; I just never knew from exactly what until then.

Luckily, the next night was our last, and we spent most of it in the classroom revising our papers - thus, no more rat incidents. Good times.

^My, Courtney's, Claire's, and Becca's room at Palo Verde. My bunk, into which the rat climbed on our second-to-last night, is on the bottom right.

^Cows and birds in the Palo Verde marsh. Cows are grazed in the marsh to control invasive cattails.

^View of the sunset over the marsh from the soccer field.

^Tarantula we found during a faculty-led project.

^Measuring scorpions during a faculty-led project.

^White-faced monkey with a baby on its back.

^View from an overlook to which we hiked during the first week.

^Sunset over the marsh - Tim is in the birdwatching stand.

^A few of us decided to dress up for dinner one night, just to be ridiculous (and to make ourselves feel a little bit less disgusting)

After finishing our final exams at Palo Verde, we spent two days essentially vacationing at a touristy place called Buena Vista Lodge. This gave our professors time to grade our exams and us time to unwind from a pretty intense week. During one of our days there, a group of us took a bus to a nearby national park and hiked almost 7 miles round-trip to a waterfall. We spent a while swimming in the water beneath it, which I found absolutely freezing but of course was the only one who thought so.

^Swimming beneath the waterfall.

^We saw lots of cactus-like bromeliads on our hike to the waterfall.

^Hanging out with three of my favorites at Buena Vista Lodge. From the left: Becca, Jess, Courtney, and me.

Nicaragua... and FIRE

Upon leaving Monteverde, we set off on a seven-hour bus ride for Nicaragua. We arrived, ate lunch, cleared Costa Rican customs, and loaded our backpacks and ourselves into a strange bus-like boat on the San Juan River. From there we traveled three hours downriver to the west, stopping at one point to clear Nicaraguan customs. We arrived at our station at Refugia Bartola around 7:30, unloaded the boat, and moved into our three-person rooms. Refugia Bartola was an interesting combination between a tourist lodge and a biological station. While the rooms were rustic and bare (bunk beds with mosquito nets), the dining and common area was a beautiful paved area with hammocks, a long rectangular table with a white tablecloth, and a high thatch roof. Unlike at the other stations, the meals at Refugia Bartola were served to us, complete with different courses! Temporarily, we felt like we were living in luxury.

^The boat that took us down the San Juan River to Refugia Bartola.

^View from the boatride.

^The dining and common area at Refugia Bartola.

We spent the day after our arrival doing the usual new-station business - learning about the area and going on orientation walks. We also began preparing for the two faculty-led projects that were supposed to take place that week, which involved catching fish in the river and wandering through the woods looking for bat tents under big leaves. After dinner, we caught bats and nets and examined them in the thatch-roof common area, which was really neat. The professor that was handling the bats got bitten at one point, and we've been teasing him ever since that he now has rabies. We went to bed that night tired and happy, but were rudely awakened in the middle of the night... I'm going to just paste the story of what happened that I e-mailed to a few of my friends.

^Cool tree in the forest near the lodge.

^One of the bats we netted and examined.

First, a quick description of the place where we were staying - the main part of the building was a wide, really tall circular open area with a thatch roof that served as the dining room, common area, etc. To this was attached the kitchen, and to the kitchen a row of eight small bunk rooms with 3-4 beds in each room - I was staying in room 7.

On Tuesday night my two roommates and I went to bed at 11:11 (I know this because it was 11/11 so we decided to stay up and make a wish). We woke up sometime after midnight to our professor yelling from outside and other loud noises - a fire had started in the kitchen and the huge thatch roof was completely consumed in flames that were probably three or four stories high. I ran out my door, looked to my right, and was (seriously) temporarily frozen with fear. I remember wondering how in the world the fire had gotten so huge before anyone woke up - it was terrifying. After a second I realized that some other students were standing outside their rooms looked dazed, so (in true form) I started yelling my head off... something like, "WAKE UP EVERYONE IN YOUR ROOM! GET YOUR PASSPORT, GET A LIGHT, PUT YOUR SHOES ON, AND GET OUUUUTTTT!" My classmates later joked that for once, my painfully loud voice had come in handy. We quickly made our way out of the building for fear that the gasoline in the kitchen would explode, but it turned out that had already happened while we were still sleeping. With the help of the guys at the station, we managed to get everyone's stuff out of their rooms, because the wind was blowing away from the bunk rooms and the fire was actually moving slowly. Amazingly, the guys at the station managed to put the fire out by tearing out the roof above the first bunk room and spraying it with a hose - in the end, the fire only reached the first bunk room. The only thing I lost was my watch, and my only injury was an absolutely huge and disgusting bruise on my leg- I probably ran into something in the initial panic, but I strangely have no recollection of doing so. We left Nicaragua the next morning the same way we had come and stayed in San Jose until the following Saturday, when we traveled to Palo Verde in the northwest of Costa Rica. Thinking back to the whole thing seems pretty surreal -none of us like to think of how bad things could have been if our professor hadn't heard the fire and woken up (there were, of course, no fire alarms). We were also extremely lucky that the wind was blowing away from our rooms - we were completely in the middle of nowhere and would have been in major trouble had the fire made its way into the adjoining forest.

^Nobody really got much in the way of pictures of the fire, but here's one Becca took- the flames you can see are rising high above the bunk rooms, which are between the camera and the fire.

^The dining area the morning after the fire.

^Sorting through all of our stuff the morning after the fire was a bit of a nightmare as everything had been thrown in a giant pile in the rush to get it out of the building, but obviously we were just grateful not to have lost all of it.

Thankfully, our professors gave us a lot of free time during our couple of days in San Jose, so we were all able to calm down and chill out a little bit. We're now staying at an OTS station in Palo Verde, but more on that to come later.

^Claire and I dying Tim's hair blue on one of our free nights in San Jose... good times.

Monteverde

After midterm break ended, we returned to San Jose to pack for the most rustic two weeks of the semester. We would spend one week in the Monteverde cloud forest and one in Nicaragua, and because we had to hike in to the station in Monteverde, we had to pack all our belongings for the two weeks into one backpack. On the Monday after break ended, we set off for Monteverde. On the way, we stopped to visit one of the strangest ecosystems I have seen: mangroves. For a few hours, we hiked (trudged) in our rubber boots through the most disgusting-smelling, deep, and sticky mud I have ever seen. To make things worse, a common characteristic of mangrove tree species is pneumatophores, which are roots that grow up and out of the ground to get oxygen from the air. As we walked through these upward-pointing roots, they flung mud absolutely everywhere, with the end result that we left the mangrove completely drenched in mud that smelled like sewage. Of course, after this, we had to ride in the bus for a few more hours with a stop for lunch at a restaurant before we arrived in Monteverde. Ewwwww.

^Mangroves with pneumatophores... ewwwww.

After a terrifying (for me, anyway, as I am terrified of driving anywhere near cliffs) drive through the mountains to an altitude of 1200 m in north-central Costa Rica, we left our bus and hiked to the Monteverde station with our backpacks. The first half of the hike was on a road (impassable for the bus), and the other half was through the woods. It was steeply downhill the entire way, and after about an hour we arrived at San Geraldo station in El Bosque de los Niños. The station was rustic, with generator power for only about four hours each night and no hot water (and by this I mean FREEZING cold water to go along with the cold mountain temperatures). From our rooms we had a beautiful view of Arenal Volcano, and a few nights we even saw red lava glowing as it flowed down the volcano.

^View of Arenal Volano from the porch of the station.

^Hanging out on the porch outside our rooms at night :)

We had a pretty full week at Monteverde, which included a visit from two local biologists - one a bird specialist and the other an amphibian specialist. We spent one very early morning netting birds, which was really fun as we each got to learn how to hold, examine, and identify the birds we caught. We also went on a night hike with Mark Wainwright, the amphibian specialist. He's a pretty famous guy here, having written and illustrated about a zillion books and guides on the fauna of Costa Rica. We also had our second plant exam (ewww) and somehow found the time for some epic games of ultimate frisbee, charades, ping pong, and the like.

^One of the birds we caught in the mist nets.


^Cool herbivory we saw on the night hike - something ate part of the Heliconia leaf while it was young and still rolled up.

Towards the end of the week, we got some entertainment from the removal of a botfly from Jess's head (the fifth one she had). If you're not familiar with botflies, basically what happens is that a mosquito that has a botfly egg inside it bites you and inserts it under your skin. The egg then hatches and a larva grows under your skin - it turns into a bump that apparently gets pretty painful as the larva grows. If you leave it alone, it will eventually (after up to two months) crawl out on its own. Jess had her previous four botflies (three on her shoulder and one on her head) removed by a doctor while we were in San Jose, but as we were completely isolated in Monteverde, our professors elected to stick a small tub of Vaseline on top of the botfly to cut off its oxygen source, forcing it to crawl out. This worked pretty well, but getting the larva completely out was pretty disgusting (see photo).

^Botfly larva coming out of Jess's head... ewww.

Our last day in Monteverde was a rest day, and a bunch of us hiked out of the station to go to Selvatura, a local touristy place where we went ziplining through the forest and walked around on the canopy bridges. On the morning we left, we had to hike with our backpacks back out the way we had come - i.e., up the extremely steep hill we had mostly slid down on the way in. It took us about double the time, with everyone stopping periodically on the way to gasp for breath and gulp water. Despite the fact that we had all been convinced we would never make it back up the hill with all our stuff (we had half-jokingly discussed the possibility of throwing clothes, soap, books, etc into the road as we hiked), we eventually all made it back to the bus and were on the way to Nicaragua.

^Kiva ziplining through the Monteverde forest.

^Canopy bridges at Selvatura.

Nirvana Semana!

Semana = "week" in Spanish. Nirvana = "the perfect peace of the mind." Nirvana Semana = GLORIOUS.

For our week-long midterm break, fourteen of us rented a beach house on Playa Flamingo on the Pacific coast. Including an adjoining apartment, our house sleeps 18 and has a nice kitchen, TV, big boom box, hammocks, beautiful porch, pool, etc. A flight of stairs leads down to the beach, which is mostly deserted because it's the off-season. Other than dealing with scheduling classes for next semester and registration, we spent the week chilling on the beach, going deep-sea fishing and snorkeling, kayaking, swimming in the pool, playing the guitar, watching movies, and generally enjoying ourselves to the max. Most of us bought food on a group basis and we cooked a delicious dinner in-house every single night. The sunsets over the beach were absolutely gorgeous, and one night we cooked hot dogs and roasted marshmallows out on the beach. Tomorrow, we'll take the return 6-hour bus ride back to San Jose, and on Monday morning we're off to Monteverde and then Nicaragua. We won't have internet at either site, so I'll be out of touch until about November 17. ¡Hasta luego!

^Kiva, Tim, Whitney, and a random dog watching the sun set on the beach.

^On our second-to-last night, we were visited by an unusually bold anteater.

^In honor of Halloween, Courtney carved a watermelon. Fabulous.

^Deep-sea fishing! Unfortunately, Whitney caught the only fish of the entire day.

^View of the sunset from our porch.

^Billy decided to catch a giant iguana we found. He's probably going to have scars from its claws... no, seriously.

^Campfire on the beach! Tim is for some reason eating ketchup in this picture...

^Our house, Villa Martita. Wonderful :)

Weekend Fun

While living in San Pedro, we took full advantage of our weekends to enjoy ourselves and explore what Costa Rica has to offer. Here's a quick synopsis.

Whitewater Rafting

On the Saturday of our first weekend, 12 of the OTS students went on an all-day rafting trip on the Pacuare River. We left the language school a little after 6 AM and returned right before dinner, exhausted and somewhat sunburned. We were in six-person rafts with a guide in the back yelling instructions, of which my favorite was "GET DOWN!", which was when you dove to the center of the raft to avoid flipping over in a huge wave. My only previous whitewater rafting experiences had been in two-person rafts, so this was different and really fun. I was lucky enough to be in the front of the raft, too, which also meant that I got the most wet. The rapids were classes I - IV.

^Our raft - I'm in the front, on the right.

^Our raft, mostly underwater. ahhhh!

Cahuita
The second weekend, as I wrote before, began as soon as our midterm exams were over. I went with six friends straight to the bus station when we finished our exams, and about five hours later we were in the small, beautiful Caribbean beach town of Cahuita. We stayed in a cheap and sufficiently sketchy hostel and spent the weekend enjoying black sand beaches, Cahuita National Park, the small bars in town, and snorkeling on the coral reef. It was the perfect way to forget about our exams, and I was really glad that we took advantage of our only opporunity to visit the Caribbean coast.

^We decided to climb a fallen tree on the Playa Negra. (Picture by Becca)

^We met up with some friends who were also in Cahuita for the weekend - qué divertido! (Picture by Becca)

^Sunset on the beach in the National Park. (Picture by Becca)

Poas Volcano
During our last weekend in San Pedro, after our Spanish classes were finished and our midterm break was beginning, a few of us spent Saturday visiting Poas Volcano. First, we went to a viewpoint above the crater. There was steam pouring off of the hot water inside the crater, and the air smelled of sulfur. After that we hiked around to see a lagoon, and then headed to a nearby resort that had enclosures of birds, monkeys, and butterflies as well as a walkway along a series of waterfalls. We ate a delicious buffet lunch, and all in all it was a really cool day.

^The crater at Poas Volcano.

^Toucan! This was taken right after I attempted to take a picture with the bird and it attacked my head. Good times.