Rainforest Cafe but in Real Life

Welcome to the Caldwell Lab!

About the Caldwell Lab

In the Caldwell lab, we primarily focus on communication via bimodal acoustic calls, which are a way that sounds and vibrations work together to send information from one animal to another. An emphasis in our research this summer has been testing whether vibrations made by calling frogs attract predatory snakes.

Hello! I have been part of the Caldwell lab since my first year and am now a rising senior Biology major. This year, I traveled with Dr. Caldwell to conduct my X-SIG project in the Panamanian rainforest. I really love seeing and hearing so many types of tropical animals that I’ve never encountered before. Experiencing the intense rain and thunder here, though, has probably been one of the most exciting things – aside from being under a moving troop of howler monkeys – and it all reminds me of Rainforest cafe (a chain restaurant that is rainforest themed with rainforest sound effects)!

Research in Gamboa, Panama

In Panama, we are working at the Gamboa laboratory facilities of the Smithsonian Tropical Research Institute (STRI). The Trillo Lab, also from Gettysburg College, is working here this summer (see their X-SIG blog!). Gamboa is a town bordered by the Chagres River and the Panama Canal. The Panama Canal, which was completed in 1914, allows ships to travel between the Atlantic and Pacific oceans. The Smithsonian began conducting studies here in 1910 that looked at the environmental impact the Panama Canal would create on the flora and fauna of the tropics that surround the area. Now, STRI facilities are a base for scientists from around the world to conduct research on the tropical rainforest and marine ecosystems. STRI provides many facilities such as butterfly insectaries, growth chambers, flight cages for bats, and an experimental pond. We work at Experimental Pond, which is man-made, surrounded by vegetation, and adjacent to Soberanía National Park. This site gives us quick access to great diversity of forest creatures, all with a space nearby sheltered from rain and wired with electricity. Dr. Caldwell has been conducting research at STRI for nearly 20 years, and at Experimental Pond for more than 15 years.

Snake Vibrotaxis

My main project this summer builds on research from an earlier X-SIG project, in 2019. We have two related research questions: 1) Do snakes use vibrations produced by calling frogs to find these prey?, and 2) Can snakes tell which direction plant vibrations are coming from?

To answer these questions, we first must train non-venomous wild tree snakes to forage in our experimental arena. This is done by offering them frog egg clutches. I put a snake in the arena and check on it every half-hour to see if it has eaten. In total, we have collected three snakes: Nimbus (Leptophis), Sunshine (Leptodeira), and Tigo (Leptodeira) for the project.

Nimbus, named after the model of the bathroom vent found in our apartment, was released after we realized they had no interest in the all-you-can-eat-buffet of egg clutches.

Sunshine, which is the first snake I caught, has been very cooperative. It went up and ate a clutch on the first night of training! I was so excited that I sang “Walking on Sunshine,” hence the name.

The picture I took when I got Sunshine

We also recently caught Tigo, named after a phone service here in Panama, who is as nice as Sunshine. As Tigo is still going through training, I’m getting to know their personality and have noted that Tigo likes to go swimming in their water bowl.

Once trained, we play snake pre-recorded sound and vibration from the calls of hourglass treefrogs (Dendropsophus ebraccatus). Sound is played from a speaker overhead, while vibrations are filtered using MATLAB to ensure they are played with realistic spectral and amplitude properties, and then played through one of two Y-shaped branches in the arena using an electrodynamic shaker. During trials, if snakes forage more often on the branch vibrating with frog calls, we will conclude these vibrations are used to find prey. If snakes travel to the side of the vibrating branch from which call vibrations are played, we will conclude that snakes can extract localization information from these vibrations.

Other Projects

In addition to the snake vibrotaxis work, I am also spending time working on other projects. One of them looks at the Dear Enemy Effect in red-eyed treefrogs (Agalychnis callidryas). In that experiment, I’m trying to determine whether the frogs are less aggressive to neighboring frogs that they are already familiar with. I’ve also been conducting censuses at Experimental Pond of red-eyed treefrogs and another frog, Hyla rosenbergi. Many of these frogs were tagged in 2021, and we would like to know which frogs return to the pond and if they reclaim the same territories in subsequent rainy seasons.

Experiencing Panama

When we are not doing research, we try and make time to explore much of our surroundings. Sometimes this includes Sunday hikes, where we get to see monkeys and other critters. We’ve also made trips to Panama City, where I got to celebrate my birthday, and grooved our way out of restaurants. I’ve enjoyed my time here and all the animals I’ve seen!

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