Pluvial Songs

After four months of continual sun and no rain the weather briefly changed.  Over the course of the last week the clouds had been gathering, a portent of what was about to happen.  There were several nights with a brief light drizzle, not enough to dampen the ground but just enough to wash the layer of dirt covering the plant leaves.  Then one night the sky grew dark and a heavy shower dropped enough water to soften the hard, dry ground.  Finally, one afternoon a really heavy deluge poured out of the heavens, two and a half inches is as many hours.  Immediately the Fitzinger’s Rain Frogs, (Craugastor fitzingeri), started calling.  This was to herald a sudden coming to life of several amphibian species.

Fitzinger’s Rain Frog, (Craugastor fitzingeri)

Over the next few hours the calls of the Milky Frog, (Trachycephalus venulosus), began increasing in number and intensity.  The sun was setting, the daily environmental trigger that stimulates the frogs into emerging from their daytime hiding places, but over the dry season only one or two individuals of few species.  Now, however, a greater number of participants was joining the choral gathering.

Milky Frog, (Trachycephalus venulosus)

The Banana Frogs, (Dendropsophus ebreccatus), which for the past four months had been restricted to a solo, forlorn crooner was now accompanied by many more to form a backing group.  The loud nasally calls of the Masked Smiliscas, (Smilisca phaeota), entered to swell the ever-increasing cacophony.  All semblance of rhythm, cadence and orchestration disappeared as more and more frogs entered into what was becoming a free for all, each male trying to drown out his neighbor.  Up in the tree tops the Red-eyed Green Tree Frogs, (Agalychnis callydryas), were chirping from all quarters.  Down on the ground boomed the loud whooping of Savage’s Thin-fingered Frogs, (Leptodactylus savagei).  The sound of a mini jackhammer that is the mating call of the Marine Toad, (Chaunus marinus) along with the chucking calls of the rain frogs completed the din.

As the evening progressed, it was however, the calls of the Milky Frogs that became so intense that they could be heard from some distance away.  The ruckus continued well into the night.  The next morning the surface of the pond was covered in a gelatinous film containing the eggs of the milky frogs.  These are some of the fastest developing amphibian eggs I have ever encountered.  Within 24 hours the tadpoles have hatched and entered the water where they can be observed as wriggling black swarms just beneath the surface.  After several weeks they will be seen everywhere as tiny, newly emerged froglets sitting on the vegetation surrounding the pond.

Sadly for the amphibians, that one wet night was all they got.  The next day it was back to normal dry season conditions.  It won’t be long before the rains truly arrive though.  One other creature to be seen around the pond at night, sleeping on top of the vegetation are the juvenile Green Iguanas,  (Iguana iguana), newly hatched.  Their comatose, lime-green bodies can be found at the ends of the long branches but a lingering flashlight beam will soon stir them into a state of semi-consciousness ready to jump off and run away at the slightest disturbance.  If you are lucky you will also catch sight of the newly emerged Common Basilisks, (Basiliscus basiliscus).  They are harder to see as they sleep vertically and are more muted in coloration.  The hind legs sticking out sideways from the stems where they sleep is quite often a giveaway as to their presence.

Green Iguana, (Iguana iguana)

Philip Davison Is a Biologist, Writer and Photographer Based in Costa Rica