Awesome amphibians in Costa Rica

During my two trips to Costa Rica (so far?), it was my good fortune to see different kinds of animals besides the birds which were the focus of the trips. There are a lot of interesting amphibians and reptiles to see; in this blog, we’ll see some of the amphibians that I managed to photograph. I was ultimately able to identify almost all of them except the one to the right; if anyone can tell me which frog this is, it would be appreciated!

 

One of the most famous frogs in the country is the little (0.75-1 inch) strawberry poison dart frog (Oophaga pumilio), also known as the blue jeans frog because many individuals have a bright red upper body accented by a bright blue lower half. It turns out that the species has an estimated 15-30 color variations – in 2000, totally blue individuals were seen at the La Selva Field Station.

The female lays 3-5 eggs on a leaf and the male then keeps the eggs hydrated with water he transports in his cloaca. After the eggs hatch and tadpoles emerge, the female frog transports them on her back and deposits each one separately in a small pool formed in the crevice or hole of a tree or a large bromeliad. There, the tadpoles consume only unfertilized eggs that their mother feeds, a practice called obligatory oophagy,

 

The feeding habits of the adults (certain ant and mite species) are what makes them poisonous when touched or eaten. Their skin is toxic and humans should wash their hands vigorously after touching them.

A very tiny frog that we saw last year was the common tink frog (also called dink frog; Diasporus diastema). I’m not absolutely certain that the two shown below are tink frogs but think they are. These tiny frogs change color, having grayish brown skin with spots or bars during the day and a pale tan or pink color at night, when it is most active.

 

 

A somewhat larger amphibian that we saw at the same pond as the tink was the hourglass tree frog (Dendropsophus ebraccatus). Part of the species name comes from the Latin term ebraccata, which means “without trousers”. Some people call this frog the “pantless frog” because they think the smooth yellow thighs that contrast with its highly patterned back make it look as if it is not wearing pants. These individuals had patterns on their thighs, however!

The attractive hourglass frogs were in an amorous mood when we spotted them. The female chooses her mate and he mounts her to deposit his sperm. She then will seek out a suitable place for her eggs, either in the water or a leaf overhanging water. When the arboreal eggs hatch, the tadpoles roll off the leaf into the water below.

These frogs are of interest to scientists because their skin contains bioactive peptides which have anti-fungal and anti-bacterial properties and might even have therapeutic properties useful in treating diabetes.

 

The pond had quite a few frogs in residence and several brilliant forest frogs (Lithobates warszewitschii)were among them. They are slender-looking frogs with pointy heads. Their sides are apparently always darker in color than their backs.

 

 

Their coloring seems to vary somewhat, being browner in some individuals and featuring more green highlights in others. They tend to have yellow spots on their legs.

They do not have vocal sacs or slits but do make trilling sounds.

 

 

We were lucky to catch a glimpse of a red-eyed tree frog (Agalychnis callidryas) at the pond. Although some lodges will ask you to avoid using a flashlight during night-time walks to see amphibians, it’s very difficult to spot them without some use of a light. That’s how we managed to spot the tree frog.

We came across the Canal Zone tree frog (Boana rufitela) taking a daytime nap, right out in the open on a large leaf next to a walking path. This frog is also known as the red-webbed or scarlet-webbed treefrog. It used to have the scientific name Hypsiboas rufitelus, which was changed for a reason I couldn’t determine.

The smoky jungle frog (Leptodactylus pentadactylus) is Costa Rica’s largest frog species; males grow to as much as 7.3 inches (18.5 cm). The adults are so big that they can eat small mammals (e.g., bats), small birds and lizards. They have some interesting characteristics. In contrast to the little blue jeans frogs, who only lay 5 or fewer eggs, female smoky jungle frogs lay about 1000 eggs at a time! They can secrete copious amounts of mucus, which makes them difficult to hold for predators; in addition, these secretions are toxic. They can even vaporize the toxin, causing people to sneeze and get swollen eyes.

What has further contributed to making them famous is the alarm call that they emit when captured; some liken it to a human person screaming. It doesn’t sound like that to me; rather, what I heard in a video sounds to me like a sound that a distressed cat might make.

That brings us to Costa Rica’s largest amphibian, the cane toad, also known as the marine toad. They are not only this Central American’s biggest amphibian, though; they are the largest toad in the world, growing as long as 9 inches long (22.86 cm) and weighing up to 3.5 lbs (1.59 kg).

This animal has also gotten a new scientific name; while it used to be called the Bufo marinus, it is now known as the Rhinella marina. Like some of the frogs, this toad has toxic skin and they are especially dangerous for dogs.

They were introduced to different countries to control pests as they have voracious appetites. Now they are considered an invasive species and pests themselves.

In 2018, I came across these toads in different places. There are a few living around a fountain in the hotel in San José where our tour groups stayed; they enjoy taking a shower under the running water.

To end today’s offering, I’ll show you the frog that really fascinated me most — the reticulated glass frog (Hyalinobatrachium valerioi). Our guide, Cope (who showed us the awesome spectacled owls and bats shown in previous blogs), led us to this awesome amphibian. It has a green and yellow back but its ventral (abdominal) skin is completely transparent! The frog’s heart is covered by white tissue and its liver and digestive tract are also white. Here you see the male frog on a leaf guarding eggs – he actually looks pretty much like the egg masses!

Isn’t nature endlessly interesting? Next blog: Costa Rican reptiles!

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