Pura Vida 3: Swamp Froggin

Amphibians are intrinsically linked to water. When reproducing, amphibians lay eggs in water or moist microhabitats to prevent them from drying out. After a period of development, the eggs hatch out into the surrounding water as free swimming, gilled larvae. However, many amphibians circumvent this pattern in some unusual but fantastic ways. Amphibians also have moist skin that passively transports water in and out of their body. In particular, a highly vascularized patch ventral to the pelvis is important in the osmotic regulation of amphibians.

Because the wet tropical forests of La Selva Biological Station receive around 4 meters of annual rainfall, they harbor an impressive diversity of amphibian life with at least 48 species documented. On rainy or humid nights, many amphibians can be found out in the forest or breeding in areas with standing water. These swamps provide excellent grounds for amphibians to reproduce as they lack some predators, such as fish.

On my first night at La Selva, a few students and I trekked out into the rain to investigate the swamp near our rooms. This “suampo” is called the “cantarana,” which literally means “singing frog.” It has a wonderful boardwalk that cuts directly through the swamp, which is excellent for viewing animals that would otherwise be difficult to see. It was raining steadily, and we were amazed by the number of animals we saw and heard. I became captivated with the swamp herpetofauna and explored numerous swamps spread across the property. The Cantarana, Suampo Experimental, and Chanchera became my nightly stomping grounds.

Common in and around the swamps is the Smokey mountain jungle frog (Leptodactylus pentadactylus). This is a large frog found perched near the water’s edge on the ground or on logs. These voracious predators (eat anything smaller than themselves) can often be spotted at night by their red eye shin in the light of a headlamp. This species lays its egg in large foam nests in dry cavities. Subsequent rain then fills up the cavities, releasing the tadpoles to ephemeral water sources. Although I never experienced it, I hear that if you pick an adult L. pentadactylus up they sometime will emit a large squeak/squeal sound. Unfortunately, I did make the mistake of rubbing my eye after holding a particularly large individual. I proceeded to feel immense discomfort and pain in that eye for the next hour. Looking back, this was a foolish thing to do, knowing that all amphibians have toxic skin secretions to some degree.

Leptodactylus pentadactylus

Another extremely common swamp frog is Lithobates vaillanti. This large green or brown member of the family Ranidae will perch on logs or mud banks. Seems like a likely food source of the resident caiman….

Lithobates vaillanti

On rainy nights, many frogs of the family Hylidae breed in the swamps. Hourglass tree frogs (Dendropsophus ebraccatus) can be found perched among various understory plants. These are beautiful hylids with a highly variable pattern on their back that can resemble an hourglass in shape. Similarly, Dendropsophus phlebodes can be found breeding during rainy nights. In my experience, this species is less common, as I found only two in ten weeks, as opposed to many D. ebraccatus (>50). A friend of mine was studying the ecological differences between these two sympatric congeneric species. He found interesting differences in the insects they consume and the structures they perch on.

Dendropsophus ebraccatus

Dendropsophus phlebodes

One charismatic species that I became exceptionally fond of was the Scarlet-webbed tree frog (Hypsiboas rufitellus). This gorgeous swamp hylid is unique for having bright red webbing between its toes. Calling males can have a blue throat which is quite pretty. I have seen yellow, green, and grey individuals.

Hypsiboas rufitellus

Two species of the genus Scinax can be found in the swamps of LSBS. Scinax elaeochrous is a beautiful yellow hylid. It is readily identified by its visibly green bones. It is a fairly common frog found breeding in numbers during rainstorms or out to a lesser degree on a nightly basis. When held, this species emits a foul stench. On the other hand, Scinax boulengeri is more elusive, only showing itself during breeding events. This species has large tubercles distributed across the body, creating an interesting contour, and an elongate snout. Although primarily a drab brown/grey coloration, there are bold spots of yellow, orange, and green on the groin and the back of the thigh.

Scinax elaeochrous

Scinax boulengeri

Another species that I did not see often was Tlalacohyla loquax. On my first night, I observed and photographed an amplectic breeding pair. I did not identify another until one of my last nights in La Selva; unfortunately, this individual evaded photographs. This species is larger than most of the other hylids, yellow, and lacking bold patterns.

Tlalacohyla loquax

I’ll end this segment with the perhaps the most recognizable of anurans, the Red-eyed tree frogs (Agalychnis callidryas and A. saltator). These charismatic frogs are a national symbol of Costa Rica’s wonderful animals and forests. Active nocturnally, these canopy dwelling species descend down to the understory to breed explosively during the heaviest rain events of the rainy season. Unlike many frogs that lay eggs directly in water, these species oviposit onto leaves hanging over water. After a period of development, the tadpoles emerge and fall through the air into their new aquatic home. A. callidryas has a barred blue pattern on the flanks, while A. saltator has creamy blue flanks with no pattern.

Agalychnis callidryas

Agalychnis saltator

Pura Vida: 2, La Selva Biological Station

I was a little bit nervous as it was my first time flying solo, but everything went smoothly. My first flight left Cleveland Hopkins airport at 5:30 AM on June 13. After a brief layover in Atlanta, I eventually arrived in San Jose, Costa Rica at 1:00 PM (the Central American time zone is two hours behind Eastern Time in the USA). After a lengthy wait in customs ("aduenas"), I met up with the REU program coordinator, Jenny Stynoski, and another REU, Ramiro Mata, who would become one of my good buddies for the summer. He is a Mexican-American from southern Texas, who attends Brown University. She took us to a hotel in SE San Jose, El Sesteo, where we spent the night before heading on to La Selva. The place was very nice, and I had a blast meeting some of the others in my group. Ramiro, Seth Thompson, and I quickly became fast friends, enjoying Imperials, “La Cerveza de Costa Rica,” and talking soccer.

A view of the mountains south of San Jose from our hotel.

The following day, we made a pit stop at the OTS Headquarters to grab some gear. Seth and I volunteered to carry a heavy chest down to the cars. Instead of going down stairs, we obviously decided to take the elevator – no brainer, right? Well, the elevator got stuck, and we were locked inside it for an hour in complete darkness. Pretty funny looking back, but at the time I was sweating some serious bullets.

Organization for Tropical Studies HQ

We made the 1.5 hour drive from San Jose to Puerto Viejo de Sarapiqui, the town located near LSBS. Here, we stopped at El Colono, the hardware shop, to purchase rubber boots for those who needed them. After this quick stop, we FINALLY made it to the station.

La Selva Biological Station is an amazing place. It has over 1000 hectares of old growth forest, an extensive set of trails, and a nifty grid system that makes it very difficult to become lost. More can be read about it here. Suffice to say, I was eager to explore my new home.

First, I took my gear to my room in the River Station. The River Station is the original building constructed by Lisa Holdridge when she founded La Selva. It is situated high between the Rio Puerto Viejo and a smaller tributary, surrounded by primary forest. Throughout the summer, I saw many frogs, lizards, snakes, mammals (howler monkeys, kinkajous, armadillo, possums, rodents, jaguarundi), and birds (toucans, owls, off the top of my head) while making the trip from the lab clearing to the River Station (or vice-versa).

After getting situated a bit, we quickly ate lunch and then split into groups to get our first taste of the forest. The guides at La Selva are all locals who know a staggering amount of information about the natural history of an incredibly diverse rainforest flora and fauna. On this first tour, I was excited to see a wide variety of animals, including anoles, strawberry dart frogs, night lizards, white-faced capuchins, toucans, bullet ants ("balas"), peccaries, green basilisks, iguanas, and white bats.

An adult iguana, a common sight in trees above the Rio Puerto Viejo.

White-collared peccary, a ubiquitous artiodactylid of LSBS.

White bats (Ectophylla alba) sleeping in a tent.

After dinner and a few talks, it was raining outside, and I was eager to explore some more. A few of us enthusiasts went and checked out the swamp near the river station, called the “cantarana.” Although I didn’t realize it at the time, we were fortunate to observe the explosive breeding event of the Parachuting red-eyed tree frog (Agalychnis saltator). We also saw many hylid species and our first snake of the trip (Sibon annulatus).

Tired, we decided to return to the River Station and retire for the night. On our way up the steps toward the station, I spotted my first venomous snake of the trip, a juvenile fer-de-lance (Bothrops atrox). I took the opportunity to show it to some other students in our group. They had been hearing a lot about this infamous venomous denizen of the rainforest and were surprised to find it so calm and un-intimidating. All said, it was a great first day to what would be a great summer.

Bothrops asper

In future posts, I plan to detail the animals I encountered in various groups. I’ll first discuss the swamp herpetofauna, and then I’ll talk about animals found in other places, such as leaf-litter, primary forest, or roads.