Hoppin’ and Froggin’ Through the Rainforest
I spent my summer X-Sig experience with Professor Caldwell in Panama studying red-eyed treefrogs’ territorial behaviors and how they influence mating success.
Agalychnis callidryas, more commonly known as red-eyed treefrogs, are abundant in Neotropics. Males of this species tend to be found within the vegetation surrounding a given pond. From within these areas, they call for mates, and will fight off other male frogs of the same species using aggressive signals and even wrestling (Pyburn, 1970). These conflicts can last for many hours, sometimes stretching into the next day, which causes the frogs to miss the chance to mate (Caldwell et al., 2010). One likely reason that frogs may forgo mating during these long aggressive contests is that the calling site is held for an extended period of time. If this holds true, the frog loses one night of mating but gains a territory from which to court females on subsequent nights. The duration of time a male holds a territory has never been tested.
With this study I seek to answer two main questions: (1) Do red-eyed tree frog males hold their territories for multiple, consecutive nights, (2) Does the length of time they hold a territory influence mating success? I also wanted to determine whether the physical properties of males are correlated with their territorial behavior.
All of the field work and experimentation for this project is being performed at the Smithsonian Tropical Research Institute in Gamboa, Panama. Our main site is known as the “Experimental Pond” (“EP”). This is a large, concrete pond that is at the edge of the rainforest. It is full of various species of frog, caiman, and snakes, including the venomous fer de lance, the occasional anteater, basilisks, adorable kinkajous peering down from the trees, and every once and a while, an armadillo.
As my focus is on monitoring territoriality and mating success of male red-eyed treefrogs, tracking individual frogs is a necessity. To do this, I tag them with an 8 millimeter PIT tag right under their skin. Once a frog is tagged, I seal the wound with veterinary glue that becomes solid in water(perfect for frogs).
Before tagging a new male, I take some measurements. I weigh him and measure his snout vent length (nose to cloaca) and right tibulofibular length (a measure of limb length). This allows me to look at which physical factors may contribute to success in mating or holding territory.
Each night, I conduct my first census tat 8:30 PM, using a handheld PIT tag reader to scan each frog and record his unique identification number and the exact location from which he was calling.
The aim of this first check is to record the initial positions of males and any calling or aggressive behaviors as they first reach the pond. Any previously unmarked frogs are collected and tagged. At 11 PM, I conduct a second census, as calling activity is dying down, and most females have already selected a mate. So, across nights I have a record of where males are, who they are fighting with, and who gets to mate. With these data, I should be able to answer some important questions about what determines mating success in red-eyed treefrogs.
My X-Sig Experience, Beyond Research:
Tucked into the rainforest about 40 minutes outside of Panama City is the beautiful and wonderful town of Gamboa. In this town you will find many creative and unique people ranging from canal workers to scientists to bed and breakfast owners. The people are incredibly interesting and each one is more friendly than the last. This helped me to never feel lonely or homesick.
Coupled with the amazing people is an amazing atmosphere, full of flora and fauna one would never see on the East Coast of the States. One gets breathtaking experiences such as, feeding tamarin monkeys, waking up to parrots and toucans, and getting to hold a basilisk.
I never run out of things to do in Gamboa. When I’m not conducting research at the pond, there is the Summit Zoo, the Panama Canal, Panama City, the glamorous pool, the Canopy Tower, numerous hiking trails, and, of course, the Smithsonian Tropical Research Institute. Within the Smithsonian there are many events held, some scientific and some purely social. There are weekly seminars from an international cast of researchers, smaller talks on animal behavior experiments, educational classes such as a Statistics in R course I attended, women in science meetings, countless potlucks and barbecues, and Chiva buses. All of these adventures are shared with other researchers, interns, and graduate students from all over the world. It truly is a biologist’s paradise.
There are also opportunities trips farther away. Gamboa is surrounded by many beaches. I got the opportunity to take a trip to Playa Blanca on the Atlantic side of Panama with 13 other researchers, some PhD students, some interns, and some volunteers. It was one of the most awesome days of my life. That is the beauty of Gamboa: it is full of hard working biologists, but when the work day is done everyone gets together and has a great time.
This year in Panama was exciting due to the nation being in the World Cup. The nation as a whole erupted in pride and celebration after scoring their first ever goal in the World Cup. The World Cup allowed for lots of fun outings to watch the game with friends in the city. We got to watch the finals in the beautiful Casco Viejo, one of my favorite areas in Panama.
Facts and Skills Learned
- How to work with a caiman in close proximity and staring at you
- PIT tagging
- Running is harder in the tropics
- Frog and snake identification
- Red-eyed treefrogs are adorable
- Deer can, at times, be more aggressive than crocodiles
- Identifying animals by the glow of their eyes in a headlamp
- Working at night instead of during the day
- Always look where you step
- Basic data analysis in R
- Tamarin monkeys love to be fed bananas
- Overcoming language barriers when I’ve never had any Spanish language training
- Moving away from everything I know to an unfamiliar place for 2 months is not as difficult as one would expect
- Panama is incredible!
Thank you, Panama! I will miss you greatly and always appreciate what you have taught me.
Caldwell, M. S., et al. (2010). “Vibrational signaling in the agonistic interactions of red- eyed treefrogs.” Current Biology 20(11): 1012-1017.
Pyburn, W. F. (1970). Breeding behavior of the leaf-frogs Phyllomedusa callidryas and Phyllomedusa dacnicolor in Mexico. Copeia, 209-218.