Archive for the ‘Trachycephala venulosus’ Tag

Pluvial Songs   6 comments

Philip Davison Nature Diaries. Bosque del Cabo Rain Forest Lodge.

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. Felipe del Bosque. Osa Peninsula. Costa Rica.

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. Philip Davison.

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. Sauria. Felipe del Bosque.

Green Iguana, (Iguana iguana)

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


Milk Is Not the Solution   4 comments

Felipe del Bosque Blog April 24th 2011

The last few weeks have been so busy that it has been almost impossible for me to sit down and write up my daily nature diaries in the form of a blog.  Now, with spring break and Easter over, I should be able to get back to normal.  This blog is the summary of all that has happened in the natural world forming my immediate surroundings over the last three weeks and so the species lists and total rainfall figures may seem somewhat inflated compared with my recent weekly summaries.

Curious Cats and Kinkajous

Over the past three weeks, there have been several Puma, (Puma concolor), sightings at various locations around the grounds.  Leaving the hotel one night after work, the restaurant employees saw a young male Puma on the main driveway by Casa Miramar.  He stood in the middle of the road and then headed into the undergrowth and watched the departing staff from the safety of the dense low growing vegetation.  Some visitors saw a Puma on the Titi Trail and yet another one, or perhaps the same individual, was spotted in the Citrus Garden behind the restaurant.

Kinkajou, (Potos flavus), activity has started to increase; their noisy whistles and honks adding to the nightly rustlings in the trees above your head.  After dinner, if you hear the sound of something moving in the vegetation above you, and you then direct the beam of your flashlight upwards, invariably a curious Kinkajou will run down the branch to take a look before disappearing quickly into the tree tops again.

Several mammals tend to be seen following the sunset rather than during the day.  The commonest of these are the Nine-banded Armadillo, (Dasypus novemcinctus), and the Virginia Opossum, (Didelphis virginiana), both of which I regularly observe on nightly outings with people on the Sunset Tour or when undertaking my nocturnal amphibian counts.

One morning, a noise which I had heard on many previous instances, was coming from outside my cabin, an arrhythmic thump, thump thump.  I went outside to find the cause of the sound which I knew, in fact, would be a large caviomorph rodent, the Agouti, (Dasyprocta punctata).  When danger threatens, in the same fashion as frightened rabbits, the Agouti thumps its foot against the ground.  On most other occasions this has revealed, upon closer scrutiny of the area around the disturbed rodent, a snake, generally a Boa of greater or smaller dimensions.  This time I could not find the subject of the Agoutis consternation but I am sure it was going to be around somewhere.

After The Deluge

The past three weeks has experienced some of the first heavy downpours of the impending rainy season.  There were several nights when we were subjected to some early evening deluges.

Milky Frog

The resulting reaction to this saturating stimulus is an explosion in amphibian numbers, both in respect to individuals and species.  We had two particularly intense drenchings separated by a week or so.  Both occasions drew the same response, a huge number of Milky Frogs, (Trachycephala venulosus), which seemingly arrive from nowhere, their numbers been very limited on normal count nights.  Following the heavy rain, they appear in dozens, the surface of the pond hosting a dreadful cacophony of calling males whose sole intention is to quickly find a single available female with whom to mate.  Many of them obviously succeed because the following morning the pond and floating aquatic vegetation is covered with their small black eggs.

Most frog eggs in the tropics hatch after a period of about a week, but not so the Milky Frog.  Their eggs are remarkable in as much as they hatch within 24 hours, after which the pond will be filled with small black tadpoles.  Following a further 6 – 8 weeks, the newly metamorphosed golden green colored froglets emerge from the pond.

Last year we had the first time appearance of Olive Tree Frogs, (Scinax elaeochroa), at the pond.  Their presence was of brief duration, but enough to fox me for several nights with the new calls I could not recognize until seeing one out in the open calling with gusto.  Their temporary occupation of the pond must have been successful as I have just seen a juvenile in amongst all the other pond regulars.

Not long after the vocal manifestation of the Rain Frogs heralded the approaching rainy season, the first actual rains encouraged out of hiding for the first time in five months the nightly sound of little ringing metal bells, that particular sound created by the Tink Frog.  Noticeable by their absence during the dry period, we will now have seven months of dusk till dawn chiming, their calls infinitely preferable to the dreadful din of the Milky Frogs, which thankfully only occurs once or twice at the onset of the rains.  In Spanish the Tink Frog is known as the Martallito, the little metal hammer, because its call closely resembles the tinny ring of a small hammer hitting an anvil.

One other frog to emerge in rain induced numbers are the Banana Frogs which will now be present in greater or smaller numbers at least until December.

Mating Banana Frogs

Fading Beauty

The butterfly season is on the downturn now.  Most numbers of individuals and species occur throughout February and March.  The start of the rains can severely deplete numbers seen but extended periods of sun between the showers will see the numbers rise once again but not to the peaks of the dry season.

One thing that I will notice though is the frequency at which I will encounter a few species of butterfly that I will only see maybe once or twice during the course of the year.  It is always nice to renew this re-acquaintance as well as recording species that I have previously not monitored on the grounds of Bosque del Cabo.

The swirling and frenzied clouds of Green Urania Moths are now diminishing in numbers too.  They will have mated, laid eggs, the adults are dying and the resulting new offspring upon emergence will fly off is search  of new Omphalia vine hence continuing that verdant migration back and forward throughout Central America.

One particular moth has been capturing the attention of some of the visitors walking the trails if only for its initial shock value, the Bird Wing Moth, (Thysania agrippina).  When disturbed it vacates its perch on the side of a tree trunk, taking to flight some enormous floppy bat flying away from you down the forest path only to suddenly disappear from in front of your eyes as quickly as it appeared.  If you approach slowly, you will see the moth has alighted on the trunk of the tree, its wings aligned up to down, its body horizontal.  The wings are patterned with a series of wavy lines that look to all intents and purposes like the bark of the tree.  Only the visually acute will spot them in this position.

Broken Blossoms

There is a constantly changing flux of plants flowering and fruiting.  The recent blooms of Lady of the Night Orchid have momentarily faded.  Walking through the forest you will happen upon many fallen blooms and fruits from vines, trees and their associated epiphytes.

Minute white flowers of the Hobo or Hog Plum, (Spondias mombin), carpet the forest floor like confetti from a secretive woodland wedding ceremony.  The Legato Negro is also in flower, its blooms appear to a rich prize for the Leaf-cutter Ants which harvest them from the tops of the tree crown, descend and carry them over large distances, finally returning to the nest where they will be processed into compost along with any other plant material that enters the subterranean Attine domain.

In recent weeks I have seen the bases of Ajo trees, (Caryocar costaricense), littered with their fallen green fruits.  The fruits have an oily nutritious pulp that the rodents enjoy eating.  The presence of high rodent numbers can attract in another, less welcome by some, visitor to the base of the trees, snakes, in particular, the Terciopelo, (Bothrops asper).  These large pit vipers are ambush predators that sit and wait, sometimes for days on end, for a meal in the form of a small furry creature to pass by.  It is one reason why you should check the base of trees before complacently stepping in to have your photograph taken against some of the giant buttresses.

Two species of Nutmeg Trees have recently been producing the “Golden Fruits” that give the trees their name, Fruta Dorada.  The golden fruits are the hard shelled nuts that upon ripening and splitting reveal the seed that is the nutmeg and the bright red membranous aril that surrounds it.

Philip is a biologist, writer and photographer as well as the onsite naturalist guide at Bosque del Cabo Rainforest lodge on the Osa Peninsula, Costa Rica.

 Photo Feature

The shorted and stuttered rain induced breeding frenzy of the Milky Frogs was witnessed by many of the visitors to Bosque, some of whom could not contain their curiosity and simply had to go and investigate what was causing the unfaltering ruckus they were hearing over the course of their dinner.  For one young boy the effect was overwhelming, reducing him to tears, seriously disturbed by a sight he, (as far as he is concerned), hopefully will never witness again.

Milky Frog

It is almost impossible for me to give the spoken part of the Sunset Tour over the top of such a din, and I often have to retire to the quieter confines of the garage across the road before I can make myself heard.

Milky Frogs are the largest of the Costa Rican Tree Frogs.  They are sometimes referred to as Marbled Tree Frogs because of the handsome mottled browns and beige of the body color.  As documented above it is an explosive breeder.  I only count it in small numbers, if at all around the pond, but they are obviously there because as I have mentioned, with the first torrential rain, they come out in force, up to 50 or 60 individuals.  It is another frog that has the ability to glide from the tree tops to ground level using widely spread and heavily webbed fingers and toes.  This allows the frog to take advantage of perfect breeding conditions very rapidly.  Significantly other frogs such as the Smoky Jungle Frog were present in much smaller numbers than normal while the one off Milky Frog invasion occurred.  The males grab anything that moves and I think that overzealous behavior may have kept other amphibians at bay.

Milky Frog

When disturbed, the Milky Frog gives off from glands in its skin, a thick white secretion that can prove to be highly irritating especially if making contact with mucus membranes such as mouth, nose and eyes.  In fact it can cause temporary blindness.

It occurred to me that I should go along after dinner and photograph the event.  So after I finished up in the office, I returned to the pond at 11:00 pm.  Just as I arrived, an incredible thing happened, as one all of the frogs stopped calling.  It was so simultaneous that it seemed like an off switch had been hit.  Not only that, but as I tried to compose some exposures, the frogs made a mass exit from the water and ran up the side of the trees like small mice on amphetamine sulphate.  Within a matter of minutes the pond have had been vacated with the same alarming rapidity with which it was occupied only a few hours earlier.

Red-eyed Green Tree Frog Spawning     Red-eyed Green Tree Frog Spawn     Red-eyed Green Tree Frog Spawn

It was while I stood marveling at the truly amazing scene unfolding in front of my eyes that I noticed a pair of amplected Red-eyed Green Tree Frogs that had made their way, despite their boisterous co-inhabitants, under a low lying leaf and they were beginning to lay eggs.  I couldn’t quite get in at a good angle to record the event but managed to get at least several shots.

Text and Photographs are taken from the forthcoming book:

The Natural History of Bosque del Cabo by Philip Davison

Temperature and Rainfall

Average Daily Temp High 86°F.  Average Daily Temp Low 74°F.

Average Daily Rainfall 0.32 ins.  Total Weekly Rainfall 6.73 ins

Average Daily Temp High 31.2 °C.  Average Daily Temp Low 23.0 °C.

Average Daily Rainfall 7.9 mm.  Total Weekly Rainfall 166.4 mm

Species List for the Week


  • Howler Monkey
  • Spider Monkey
  • White-faced Monkey
  • Central American Squirrel Monkey
  • Alfaro’s Pygmy Squirrel
  • Red-tailed Squirrel
  • Agouti
  • Nine-banded Armadillo
  • Kinkajou
  • Tayra
  • Puma
  • Collared Peccaries


  • Orange-chinned Parakeet
  • Red-lored Amazon
  • Scarlet Macaws
  • Grey-necked Woodrail
  • Great Currasow
  • Pale-billed Woodpecker
  • Crested Caracara
  • Laughing Falcon
  • Mangrove Black Hawk
  • Roadside Hawk
  • White Hawk
  • Magnificent Frigatebird
  • Stripe-throated Hummingbird
  • Wedge-billed Woodcreeper
  • Chestnut-backed Antbirds
  • Black-hooded Antshrike
  • Common Paureque
  • Spectacled Owls
  • Rufus Piha
  • Short-billed Pigeon
  • White-tipped Dove
  • Blue-crowned Manakin
  • Red-capped Manakin
  • Chestnut-mandibled Toucan
  • Fiery-billed Aracari
  • Cherrie’s Tanager
  • Grey-headed Tanager
  • Bright-rumped Atilla
  • Great Kiskadee
  • Masked Tityra
  • Great Tinamou
  • Black-throated Trogon
  • Slaty-tailed Trogon
  • Black Vulture
  • King Vulture
  • Turkey Vulture


  • Barred Ameiva
  • Four-lined Ameiva
  • Central American Whiptail
  • Green Iguana
  • Golfo Dulce Anolis
  • Central American Smooth Gecko
  • Clawless Gecko
  • Mediterranean House Gecko
  • Boa constrictor
  • Cat-eyed Snake
  • Litter Snake
  • Salmon-bellied Racer
  • Terciopelo
  • Tropical Bird-eating Snake


  • Marine Toad
  • Red-eyed Green Tree Frog
  • Banana Frog
  • Masked Smilisca
  • Milky Frog
  • Smokey Jungle Frog
  • Black and Green Poison Arrow Frog
  • Golfo Dulce Poison Arrow Frog
  • Fitzinger’s Rain Frog
  • Stejneger’s Dirt Frog
  • Tink Frog


  • Adelpha cytherea
  • Adelpha heraclera
  • Adelpha serpa
  • Aeria euromedia
  • Anartia Fatima
  • Anartia jatrophae
  • Anastrus naearis
  • Anatrytone potosiensis
  • Anthoptus Epictetus
  • Antirrhea philoctetes
  • Arawacus lincoides
  • Archaeoprepona demophon
  • Astraptes egregious
  • Astraptes fulgerator
  • Battus polydamus
  • Caligo eurilochus
  • Callicore lyca
  • Callimormus radiola
  • Calycopis isobeon
  • Catonephele numilia
  • Cissia confusa
  • Colobura dirce
  • Copaeodes minima
  • Dione juno
  • Dryas iulia
  • Eueides aliphera
  • Eueides lybia
  • Euphyes vestris
  • Eurema albula
  • Eurema daira
  • Glutophrissa Drusilla
  • Heliconius cydno
  • Heliconius erato
  • Heliconius hecale
  • Heliconius ismenius
  • Heliconius sapho
  • Heraclides cresphontes
  • Hermeuptychia hermes
  • Hyalyris excelsa
  • Junonia everete
  • Laparus doris
  • Magneuptychia libye
  • Marpesia berania
  • Mechanitis lysimnia
  • Mechanitis polymnia
  • Melinaea scylax
  • Mesosemia zonalis
  • Metacharis victrix
  • Morpho helenor
  • Morpho Menelaus
  • Morys valerius
  • Nastra Julia
  • Panoquina evansi
  • Pareuptychia ocirrhoe
  • Parides erithalion
  • Philaethria dido
  • Phoebis agarithe
  • Phoebis argante
  • Phoebis sennae
  • Pierella luna
  • Polites vibex
  • Pompeius pompeius
  • Pseudolycaena damo
  • Pyrgus oileus
  • Pyrrhogyra crameri
  • Quasimellena balsa
  • Rhetus arcius
  • Saliana fusta
  • Siproeta stelenes
  • Temenis laothoe
  • Tigridia acesta
  • Urbanus proteus
  • Urbanus simplicius
  • Urbanus tanna


  • Almendra Fruiting
  • Balsa Fruiting
  • Barrigón Fruiting
  • Black Alligator Tree Flowering and Fruiting
  • Cashew Flowering and Fruiting
  • Calabash flowering and fruiting
  • Clusia Vine Fruiting
  • Monkey Comb Tree Flowering and Fruiting
  • Garlic Tree Fruiting
  • Candlestick Plant Flowering.
  • Cannonball Tree Fruiting
  • Figs Fruiting
  • Guanacaste Tree Fruiting
  • Gustavia Flowering
  • Hog Plum Flowering
  • Inga Fruiting
  • Lady of the Night Orchid Flowering
  • May Tree Flowering
  • Manglillo Fruiting
  • Nutmeg Fruiting
  • Passion Vine Flowering
  • Pochote Tree Flowering
  • Psychotria Fruiting
  • Rubber Tree Flowering and Fruiting
  • Santa Maria Flowering
  • Sombrerito Fruiting
  • Stinky Toe Fruiting
  • Ylang ylang Flowering
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