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!

My pond and the cycle of life

Undergoing cardiology exams can bring up thoughts of mortality and a life lived; perhaps they also made me more attentive to the cycle of life in my yard, particularly in the vicinity of my backyard pond.

Several years ago, a local garden center went out of business and they had a 175-gallon black plastic pond for sale. It was a good deal, so I invested in it and then had to dig a large hole in the rocky Piedmont clay ground of my backyard (with a bit of help from a neighbor teen). At a certain point, the ground was so hard we couldn’t penetrate it with shovels so the pond now sits a bit above ground level; the rocks I piled up around it have offered a home to Eastern chipmunks (Tamias striatus).

 

I transferred some of my beautiful koi and goldfish from a smaller pond, only to have a great blue heron (Ardea herodias) come by to clean them all out.

On the recommendation of the garden center staff, I had positioned a heron statue by the pond – they said herons don’t like competition, so the intruder would keep flying when s/he saw the one by the pond. It didn’t take long for the bird to figure out the stationary bird was not real, however.

After the heron had eaten all the koi and goldfish, I still had some tiny baby fish. At first, I thought they were from my now deceased koi but apparently the intruder heron had had fish eggs on its feet from a nearby natural pond and left them behind. So for a time, I had unidentified native fish in the pond. They were extremely shy, however, and I only got a brief look at them when they surfaced early in the morning; as soon as I came near, they dove down under the water plants (no good photos).

Then some green frogs (Lithobates clamitus) moved in this past summer and ended up being extremely prolific reproducers. Before I realized it, there were at least 500 tadpoles in the pond!! They were eating the fish food and at the same time I noticed that I wasn’t seeing the fish at all anymore. Going online, I found out that tadpoles will eat fish – their sheer numbers had to have spelled doom for the fish.

 

 

I collected lots of the tadpoles, gave some to a friend for her water feature and released hundreds into the local creek (they are native animals after all). A few of the tadpoles grew into frogs and the pond became a residence for some very loud croakers.

 

  

The next chapter in the story came a couple days ago. I had seen a pair of red-shouldered hawks (Buteo lineatus) visiting my yard recently. I thought they were after the chipmunks, numerous squirrels and songbirds populating the area. The other day, however, one hawk took up a position in the crepe myrtle tree next to the pond and just sat there calmly not bothering with any of those creatures. Numerous Northern cardinals (Cardinalis cardinalis) perched in the tree above her and many other species of birds were at the nearby feeders;  none of them were concerned at all with the hawk’s presence. The squirrels didn’t seem perturbed either.

She sat fairly still and I took some photos through my kitchen window. Then I ventured out into the backyard, sure she would take off as I left the porch steps. But Ms. Hawk just sat there, sometimes stretching a leg or engaging in a little grooming.

     

   

Occasionally, she looked up but often her gaze was fixed on the area around the pond.

She would stare intently down at the ground – I thought she might have spotted one of the pond chipmunks.

Then after a while, I noticed her shifting her stance – suddenly she plopped down into the pond with spread wings. It happened too fast for me to get out from behind dried plants to get a good photo, so I watched as she climbed out of the pond. Then it became apparent what she had been hunting – she had caught one of the green frogs.

  

It looked like she bit its head to kill it as soon as she got on dry land; the frog wasn’t moving.

Then she spent time ruffling and shaking out her feathers which had gotten a good soaking.

She spent a little time looking around and then abruptly took off with her prize, closely followed by another red-shouldered hawk who suddenly swooped in.

He chased her but she got away with her meal and he ended up sitting in a neighbor’s tree, somewhat disgruntled with his failed thievery attempt.

  

Ms. Hawk returned yesterday and spent quite a bit of time in a high tree surveying the yard and gazing down at the ground. Red-shouldered hawks sometimes eat birds, such as sparrows, doves and starlings (which are all numerous around my feeders) but more often they go after snakes, mice, toads, frogs, lizards and small mammals such as voles and chipmunks. They will also eat insects and earthworms. Since I’m leaving the leaf litter, there are undoubtedly more insects hiding there than in neighboring yards. I’m not sure what Ms. Hawk is seeking in my yard, but I hope she doesn’t get all the pond frogs. In any event, I’m sure new ones will find the water in the spring and in the meantime, I have a beautiful bird of prey to watch this winter.