4 Aug 2017

Not Actually Prince Charming…but Close

A few years ago, I wrote a similar article devoted to these Barro Colorado visitors. The topic of the month at Biomuseo is amphibians. Now that it is raining almost daily, it is appropriate to collect more information about them. The visitors I am talking about are slippery when wet, they dwell in both the forest and urban areas. This newsletter is about toads and frogs.

They usually share the same bad reputation as snakes, bats, spiders, and others. Few individuals would try to kiss one expecting it to transform into a prince or a princess. Knowing more about these ever-present, interesting animals is necessary.

We talk about toads (“sapos”) and frogs (“ranas”) based on the texture of their skin, but they are almost the same. There are no substantial differences. Not all species are nocturnal, and few of them are poisonous. Panama is host to a total 185 amphibian species, 157 out of which are toads. We can find 30 different species of toads in Barro Colorado Island alone. After the last count (from the late 60’s), there is one more species. The Hyla microcephala succeeded in settling itself on the island.

In water, out of it, on land, underground, on bushes or tall trees. Some of these creatures never come down from treetops, never touch the soil.

Unlike mammals or birds, toads are not seed dispersion or pollination agents. They have a prominent role in regulating insect population numbers. In turn, birds and carnivorous bats feed on them. For some snakes, toads are the only food there is.

With so many researchers in Barro Colorado, we would think that toads are a constant subject of study. Actually, no. Except for the túngara frog, which is everywhere (both in cities and rural areas of the country). It has a particular call, its name is an onomatopoeia of its sound in Spanish.

What we know about the biology and role of these animals is not enough. Biologists Rand and Myers published a herpetology (amphibians and reptiles) study in 1990. They ended it by saying  “…we find it impossible to visualize the chain reactions that would occur if the herpetofauna were suddenly to disappear”.  That is how little we know.

Now, I want to introduce you to three different toads which may live very close to you. You may have heard them croak, I am sure:

Physalaemus pustulosus. Foto por: Brian Gratwicke (CC BY 2.0)

Physalaemus pustulosus.  The túngara frog. It grows to a length of 2.5 to 3.5 cm. It is found in Mexico, Central America and the northern regions of South America. It has rough, brown skin. This frog feeds on insects. On the other hand, snakes, bats, opossums, and larger frogs feed on them. Beware!

They prefer to lay their eggs during rainy season. This is when male frogs sing along the many ponds and brooks around. Sometimes male túngara frogs gather in large numbers. At a 10x20 mt pond made for attracting them in Barro Colorado, up to 450 males were counted, all singing at the same time. 

César Jaramillo is a fellow biologist. He specializes in amphibians and is a member of the Círculo Herpetológico de Panamá (Herpetology Circle of Panama). He informed me that the population of túngara frog is the largest of all frogs in Panama City.

 
Rhinella marina. Photo by: Brian Gratwicke (CC BY 2.0)
 

Rhinella marina. The “common toad” or cane toad. I grew up calling this toad as Bufo marinus, but this name was changed by zoologists a few years ago. I need to get used to this new name.

It is a rather large and abundant toad. People may recognize it for its size. Females are usually larger than males. They are nocturnal and hide during daylight. They feed on insects but they eat whatever comes in an appropriate size. Even cat and dog’s dry food is part of their menu. I know that for a fact. Around the house, there is one that learned how to climb 15 steps to Perla’s (our cat) plate.

Due to its insect-eating abilities, this species has been used for pest control in crops, particularly in sugarcane plantations. Introducing it to a different habitat has created a major problem in some cases. Like in Australia, to where it was taken in 1935, and now there are millions of them. They are extending their range at a rate of approximately 40 km per year. With a negative impact on several native animal populations.

Dendrobates auratus. Photo by: Marcus (CC BY-NC 2.0)

Dendrobates auratus. Here we have a funny little black and brown fellow with green spots. The pattern of these spots is variable: polymorphic. We can find these in the forest and in urban areas. They are very common in Cerro Ancón and Taboga Island. They have diurnal habits and are medium in size (4 cm; females are somewhat larger).

They feed on ants. Males are territorial, and females compete for them. They lay their eggs on fallen leaves, and males take care of them. When tadpoles are born, males carry them on their backs, one by one. They take them to a different location with water (a hole on a tree, a plant somewhat higher than the soil, a can with water).

One last thing, the Golden Frog Festival (Festival de la Rana Dorada) is in August. It is worth checking out. The golden frog is almost a national symbol.

The following links will help us appreciate the differences in the calls of the three species mentioned above:

Túngara: www.youtube.com/watch?v=5S-RAgudnww

Rhinella marina: http://amphibiaweb.org/sounds/Rhinella_marina.mp3

Dendrobates auratus: www.youtube.com/watch?v=CbshtQ9yaj4