Share this:

Parachuting into an Orgy

The past week has been a mixture of sun and rain.  The days have been gloomy with heavy, brooding overcast skies.  Occasionally the clouds part and the sun has shone down to light up the shadows.  But the menacing grey blanket that covering the area from north to south and east to west always threatened to unleash a downpour.  Sometimes the drizzle filled the air from dawn to dusk but you knew there was more to come.  By late afternoon the light rain would turn to heavy and by the time the sun had set below the horizon then the heavens would open drenching one and all.

The amphibians have been enjoying the onset of the rainy season, their numbers increasing over the last month but these more persistent nightly deluges have had the frogs collecting in huge numbers and rejoicing in a reproductive frenzy.  One frog that responds to torrential rain is the Parachuting Red-eyed Green Tree Frog, (Agalychnis spurrelli).

Parachuting Red-eyed Green Tree Frog, (Agalychnis spurrelli)

One evening, just after sunset it started to rain heavily and by next morning we had experienced 11 inches of rain.  That was the trigger that stimulated hundreds of Parachuting Red-eyed Green Tree Frogs to leave the canopy, which is where they reside out of view, and launch themselves into the air.  This frog has a uniformly colored dark mossy green upper side.  Its flanks are a pale lemon yellow.  It has large heavily webbed hands and feet of the same buttery hue and, of course, it has the large red eyes.  As they leap out of the canopy they spread the fingers and toes so the webbing is stretched tight, quite literally into a parachute of living tissue, which allows the frogs to glide down to the vegetation surrounding the pond without ill effect.

Each male quickly establishes a territorial perch from which he begins to call in an attempt to entice an egg-laden female his way.  The call is a short, soft, almost electronically-sounding sound.  Selecting a male on the quality of his call, the deeper the sound the better, the female makes her way over to the chosen chorister, he jumps on her back and they set off to visit the pond.  The female absorbs water through her skin and fills her bladder.  Now the female, not only with a body full of eggs but also carrying the male on her back, makes her way to a deposition site.  She chooses a broad leaf overhanging the surface of the pond and she commences to lay a sheet of eggs across the leaf.  At the same time as she releases the eggs from her body the male fertilizes them.  This normally take place just before daylight.

Parachuting Red-eyed Green Tree Frog Eggs.

As dawn breaks and the sun rises, the frogs have to get out of the light and into the dark as quickly as possible.  They don’t have time to get back to the canopy, parachuting down was a quick descent but the ascent involves a 100 foot climb and there is little time.  The sun continues to steadfastly climb in the sky.  Hundreds of frogs are now scrambling desperately to escape the skin-drying effects of its harsh rays.  This was the point at which I arrived, just in time to see countless small green goblinesque figures running along branches in a desperate effort to find a not already fully accommodated shelter.  I was not the only one.  A Bare-throated Tiger Heron had found itself an early morning breakfast bonanza and was picking off the unfortunate amphibians one after the other.

The larvae will develop in the eggs for about 7 or 8 days before the gelatinous mass liquidizes and the wiggling tadpoles drop into the pond water.  There they will complete the tadpole stage and if they make it through the aquatic stage will finally emerge after 7 or 8 weeks as a tiny froglet which will eventually have to make its way to the tree tops.  The Parachuting Red-eyed Green Tree Frog is an explosive breeder and these episodes can only be witnessed following those biblical-like rain storms.

Parachuting Red-eyed Green Tree Frogs After Sunrise

Showing Off in the Green Room

The forest flora can be flamboyant and gaudy or subtle and subdued.  The blooms may appear abruptly in a visual feast or occur in small numbers isolated and hidden in the dark green depths the subcanopy.  Some plants flower but once a year, a spectacular show drawing the eye like a beacon which is setting the tree tops ablaze and illuminating the forest canopy in a patchwork of color on natures silvian canvas.  It is no wonder that the largest percentage of insect life resides and thrives at the tree tops.  Here you will find a kaleidoscope of dancing butterflies waltzing from bloom to bloom in search of the energy rich nectar, so vital in allowing these ephemeral beauties to complete the final stage of their short adult lives.  Other plants may flower continuously throughout the year but only producing one or two blooms at a time.

It is not just the butterflies that rely upon the flowers.  Many other insects are attracted by their rich colors and evocative scents.  The plants will sometimes target birds or mammals to do their bidding.  The plants offer the animals rewards but there is method to their bribery.  These are windless forests; a zephyr is the strongest a current of air that will move through the trees.  Pollen needs to be transported from one plant to another in order for the plants to reproduce.  It helps if the plant can target and reward a specific agent to enable its pollen to be deposited in the flower of the same species.

The plants cannot rely on wind for seed dispersal either.  Once more they have evolved the means by which to encourage animals into becoming innocent vectors of transfer and movement of the seeds that will potentially give rise to the next generation.

Over the last week as I was walking along the paths through the forest I could see some of those secretive flowers blooming in the shadows as well as some bright vivid forms, their colorful flower heads breaking up the somber borders of the trails.  One of the more subtle blooms was that of the Spiral Ginger,  (Costus scaber).  The flowering head is a rather stout, deep red spike composed of bracts, each of which will produce a bloom.

Spiral Ginger, (Costus scaber)

The fiery orange, yellow-tipped flower sticking out of the bract attracts in hummingbirds which are the principal pollinator of this species.  The colors red, orange and yellow are commonly used by plants to attract hummingbirds, these being the colors in the spectrum that are complementary to the background green of the leaves.  These are also very hot colors whereas green is a cool color and so they readily stand out, particularly to animals that have keen color vision such as birds.  The hummingbirds hover in front of the flowers and probe within searching for the nectaries.  As they do so, the head and bill pick up pollen from the anthers which is transferred to the stigma of the next flower it visits thereby effectively pollinating the plant.

The family Costaceae is closely related to the ginger family: Zingerberaceae.  Most gingers are Asian but there are some gingers native to the Neotropics.  Most costas are American but there are some costas that are native to Asia.  There are 23 species of costa native to Costa Rica, 14 of which are found on the Osa Peninsula.  As they all look similar it is not too hard to identify them as costas but it is a little more difficult to identify them to species level.

Queen of Pain

Insects are fascinating creatures to photograph.  Once you have downloaded the image and zoom in, as long as the picture is in sharp focus, then the body form and colors become compelling.  All of the joints, the body plates and the detail of the head and wings will keep the naturalist mesmerized.  You can conjecture as to the function of all those different hairs and how the body parts articulate.  Not only that but how does the creature live, what is life history and what are the multitudinous, complex interconnected threads that tie it into the ecosystem of its habitat.  Insects complete their lives in almost as many ways as there are species.  Many insect’s lives are a mystery to us, we simply have no idea how they get from egg to adult.  That is not surprising as there are more species of insect on the planet than any other group of animals.  Because we don’t know, then that makes us more eager to study and discover more information to unravel those mysteries.

One groups of animals, the Hymenoptera, bees, wasps and ants, provide an endless source of material for research.  Many of them have well documented life histories and they work to a general pattern but there are variations.  I saw this wasp guarding its brood in a nest under a leaf in the tropical garden.

Although the wasp appeared to be alone, it was one of the social wasps belonging to the family: Vespidae.  The nest is made of carton which is a chewed up fibrous vegetable material, quite often wood, which forms the cells into which the eggs are laid.  The egg hatches and the larva develops, growing rapidly on a diet of chewed up insect prey captured by the queen.  The queen only uses her sting for defense, the prey is caught and chewed-up in the mandibles.  A pale larva lacking in pigment, can be seen in one of the cells.   When the larva pupates, the entrance of the cell is capped by a carton lid from which a new adult will emerge sometime later.

Paper Wasp Queen on Nest, (Polistinae sp)

There were, in fact, two wasps sitting on the nest.  This suggests that they belong to the subfamily: Polistinae.  These colonies consist of one or two queens both of which are responsible for the construction of the nest and raising the offspring without the aid of other workers.

Even if nobody told you, then you would learn very quickly from painful experience to leave wasps alone.  The black and yellow coloration of bees, wasps and hornets is the most visible of all color combinations.  As I have already mentioned, the wasp does not use its sting to subdue prey but rather uses it to defend itself.  But, as in many cases, it is better to use a deterrent rather than become involved in a physical battle where even though you may win, the probability is that you will sustain some damage yourself.  To ward off any potential threat, the wasps use threatening coloration.  It does not take too many painful encounters before most creatures would learn to avoid anything sporting that vividly distinctive black and yellow.

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

Share this:

After a five week period away from the Osa Peninsula I am back to carry out another year of research.  For the past sixteen years I have been monitoring populations of both butterflies and amphibians in the forests of Cabo Matapalo on the tip of the Osa Peninsula in South West Costa Rica.  I collect the daily weather data and compare changes in amphibian populations against precipitation and butterflies populations against temperature in an effort to evaluate how or whether climate change effects the fauna of a tropical rain forest.

Marine Toad, (Chaunus marinus)

As I live in the forest and can be found constantly walking the trail systems, camera in hand, it provides ample opportunity to photograph the diversity of life that surrounds me.  I am generally photographically prepared for small things so unless I am going out specifically to capture images of mammals or birds then my photographic galleries generally consist of reptiles, amphibians, all manner of arthropods as well as any plant and fungi features that catch my eye.

Savage’s Thin-fingered Frog, (Leptodactylus savegei)

This blog acts as an expanded form of my nature diaries which are simply daily recordings on Excel spreadsheets.  I enjoy sharing my experiences with those who read my blog and over the years the number of subscribers constantly increases.  If you are a first-time reader, then welcome and I hope you enjoy the content and the photos.  I am not a professional photographer but I do try and take the best composed shots I can.

Banana Frog, (Dendropsophus ebreccatus)

The blog also allows visitors to the area an insight of what they might expect to see in their absence or when they arrive as well as providing a small amount of information about the natural history of the organisms I feature.  I try to post one blog a week but sometimes time constraints means there may be occasions when this is not possible.

Small-headed Frog, (Dendropsophus micracephalus

For me the year does not begin on the January 1^st but rather on my return to the area in November.  At this time of year we should be moving out of the main rainy season, which is what caused me to leave for a month or so, and into the dry season.  There is no exact date and sometimes the rains hang on until December while other times the sun has started to shine constantly by mid-November.  Anyway, here we go with the opening blog of the 20016/17 season.

Olive-snouted Treefrog, (Scinax elaeochrous)

First things first.  November normally heralds the ending of the rainy season.  Sometimes the wet period may continue into December but by now we are looking towards a drying of the forest.  Not so this year.  This has been, without doubt, the wettest November I have recorded in 17 years, 185 inches of rain fell in that 30-day period.  The area was briefly closed down as bridges were not crossable, roads were not passable and the local town of Puerto Jimenez and its attendant landing strip were closed due to being under water.  This may bode well for the coming dry season when for 4/5 months the area receives little or no rain whatsoever but at the moment the forest floors have rivulets with running water everywhere.

Red-eyed Green Tree Frog, (Agalychnis callidryas)

The daily torrential downpour has made wildlife spotting rather difficult.  It is neither easy to see or hear anything in those conditions.  In the inter deluge periods I have been out searching for whatever I could find and it may come as no surprise that the amphibians most certainly have enjoyed the excess water.  All the usual members of the pond community have been out calling; Banana Frogs, Small-headed Frogs, Red-eyed Green Tree Frogs, Parachuting Red-eyed Green Tree Frogs, Savage’s Thin-fingered Frog, Marine Toads and Masked Smiliscas.  Even the largest tree frogs in Costa Rica, the Milky Frogs have been coming out, which is unusual this time of year.  Away from the pond the Tink Frogs and Fitzinger’s Rain Frogs call as soon as the sun sets.  Here are some photographs of the amphibians you may be lucky enough to see if you visit the Osa Peninsula now.

Parachuting Red-eyed Green Tree Frog (Agalychnis spurrelli)

Tink Frog, (Diasporus diastema)

Gladiator Frog, (Hypsiboas rosenbergi).

Bolivian Frog, (Leptodactylus bolivianus)

Masked Smilisca, (Smilisca phaeota)

Philip Davison is a Biologist, Photographer and Writer based in Costa Rica.

Share this:

 

Orgy of Frenzied Frog Sex

Today has been a reasonably quiet day, overcast with no sun or rain, but with a gentle breeze constantly blowing.  The subdued atmosphere was briefly interrupted by some visitors who had been up and out walking before breakfast.  They had been over to the tropical garden area where there is a large pond.  Just before sunrise they had witnessed a frog orgy, an explosive breeding episode of the Parachuting Red-eyed Green Treefrog, (Agalychnis spurrelli).

The previous night, they had emerged on mass; throwing themselves from the tops of the trees they use the large, heavily webbed bright yellow hands and feet as parachutes to glide down to the ground level vegetation.  What the visitors had then come across were hundreds of paired up males and females laying sheets of eggs on the upper surfaces of the leaves around the pond.  For those who went a little later to see the spectacle, it was too late.  As the sun rises, the frogs make their way higher into the bushes and shrubs and then they tuck themselves up under the leaves to avoid the potentially desiccating effects of the sun’s rays.  You can still see them; they are all lined up, appearing as little silhouettes as the rising sun shines down through the plant leaves.

Parachuting Red-eyed Green Tree Frog, (Agalychnis spurrelli)

More or less the same species of birds and butterflies have been seen in the grounds.  There has however been another migrant turn up, one more warbler, the Yellow Warbler, (Dendroica petechia).  As the name suggests, it has a yellow head and breast, with a dirtier yellow color to the back and wings.  The distinguishing feature is the male’s breast which is streaked with a series of orange dashes.

Some Mammals: Familiar or Not

Monkeys are a common sighting around the grounds of Bosque but there are two or three other mammals that visitors will see and quite often get mixed up even though they not related and do not remotely resemble one another.

The White-nosed Coati, (Nasua narica), is related to the raccoon familiar to most people in North America.  They have a deep rich brown fur and a little bit of white coloration around the muzzle which gives them their name.  The tail is sometimes ringed with dark and pale alternating bands and is generally held straight up in the air while the head is down foraging.   Just like their northern cousins, coatis are omnivorous and they will eat anything they can their paws on; grubs and crabs dug out of the ground, eggs and chicks from nesting birds as well as fruit.  They are accomplished climbers and today I watched one up a Coconut Palm, working away in an effort to dislodge the prized meal from its point of attachment.

The males are solitary and if you ever hear of one being referred to as a coati mundi, that is a single solitary male.  The females are gregarious and will be found in large groups accompanied by the young ones.

The other mammal commonly seen around the grounds is a large rodent, the Agouti, (Dasyprocta punctata). They are big caviomorph rodents, the closest relative of which people will be familiar with are the Guinea Pigs.  Agoutis are seed eaters.  Today there were several sitting under a large fruiting palm tree in front of the cabins, feeding on the fallen palm nuts.  Agoutis have the ability to sit on their haunches and you will quite often see them with large, tough shelled nuts, turning them in their front paws to gnaw through and get to the nutritious seed inside.  A common question I get is “What is that large rabbit-like creature with tiny ears and no tail”?  Easy, it is an Agouti.

A Lucky Escape

Tonight, after dinner, as I was talking to some guests in the restaurant, there was a splat behind me.  Normally anything going splat would be a treefrog jumping, freefalling and hitting the ground.  They don’t seem to suffer from the experience.  But on this occasion it was not a treefrog but rather surprisingly a young Grey Four-eyed Opossum that had lost its footing in the roof beams and fallen.  To be honest, it looked as if the impact had killed it.  I picked it up to remove it and could feel its heart was still beating, so I took it out into the entrance, kept it warm and within 5 minutes it had made a full recovery.  Not only that but in terms of thanks, it ran up my arm and sat on my shoulder so that I could return and show the diners that the day had a happy ending.

Caterpillars: Don’t Be Too Rash

One of the more surprising things about the area is that given the number of species of butterfly I have recorded, and bear in mind that number will be dwarfed by the number of moth species there are in the area, I very rarely see caterpillars.  When I do, I try to get a photo to add to the records.  A sentiment that I have now repeated on several occasions, is to bemoan the lack of adequate reference material to help identify certain organisms.  Caterpillars fall into one of two categories; very distinctive or not.  Even those you think may pose no problem in identifying turn out to be not as distinct as you first thought.  Over the past couple of weeks I have happened upon two caterpillars that have proved slightly easier to put a name to than normal.

 

 

This is the caterpillar of one of the Hawk moths, a Sphinx Moth, (Xylophanes chiron).  I found it on the underside of a leaf in the tropical garden.  The adult I found near my cabin.  The adult moth is to be found resting during the day on mossy covered tree trunks.  The body of the moth is covered in dense green “fur”.  The wings too, are a mossy green and both these features blend the moth in perfectly with its background.  The camouflage is aided by the wings having a broken band patterned as an exact copy of tree bark.

Hawk Moth, (Xylophanes chiron), caterpillar

Hawk Moth, (Xylophanes chiron)

 

The second caterpillar is so very distinctive there should be no problem identifying it.  But there would be a big problem if you got too close.  The caterpillar belongs to yet another moth, a very insignificant small brown moth, the Saddleback Moth, (Acharia stimulea), belonging to the family Limacodidae.  The adult is the equivalent of what birders refer to as a “little brown job”.  Take a look at the caterpillar again though; its body has many protuberances bearing a covering of sharp spiny hairs.  If you touch the caterpillar, even ever so slightly, these urticating hairs deliver a chemical that will immediately result in a painful ulcerated rash that will last for several days.  So with the caterpillars, don’t be too rash to touch.

Saddleback Moth,(Arachia stimulea), caterpillar

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

 

Eyelash Viper Feature

Local weather conditions may differ drastically from year to year and during 2009 the Osa Peninsula experienced a particularly rainless dry season.  Normally, from December through to April, there is at least some rain, not much; it is after all the dry season, but last year, barely a drop.  This was then followed by a very dry wet season.  When the rains should have arrived in May, they did not, and this condition carried on unabated throughout June and July.  For visitors to the Osa Peninsula, the conditions could not have been more perfect, lots of hot, sunny days, perfect vacation weather.  But that interruption in the natural rain cycle was having a profound effect on the fauna and flora of the area.

Rain forest trees are very dependent on their water source and if this becomes limited in supply, they begin to suffer environmental stress.  The first obvious sign is that they will shed leaves.  Should the stress continue, they begin to shed branches.  Finally, if we end up, as we did in 2009, with a drought in a rain forest, the trees divert a lot of energy into reproduction to ensure the passing on of their genetic material lest they themselves die.

That is exactly what we saw in 2009.  Visitors were treated to a canopy high display of flowering, rarely equaled, with a veritable kaleidoscope of color; yellows, reds, purples and pinks painted like a pastel infusion among the normal mix of greens at the treetops.  Some of the trees did not just flower once; they produced blooms two or three times throughout last season.  The exuberant flowering display led in turn to a profusion of fruiting, the trees were quite literally hanging with fruit.

This series of events led in turn to a very good reproductive year for those animals whose diet depends to a greater or lesser extent on nectar or fruit, such as Spider and Howler Monkeys, Toucans, Hummingbirds and Manakins.  This year visitors have been treated to the sight of huge flocks of toucans and a great many of the female Spider and Howler Monkeys carrying young ones.

But what a difference a year makes.  In a complete reversal of last year, 2010, so far, has been a wetter than normal year.  Rather than the tired looking yellows and browns evident in last year’s vegetation, this year has remained luxuriously verdant and that bodes well for another group of animals; the amphibians.  Despite a myriad of problems causing global declines in amphibian populations, here on the Osa Peninsula, the frogs are still holding their own.

Mating pair of Red-eyed Green Tree Frogs, (Agalychnis callidryas)

There are certain species that one can almost rely upon to be present right throughout the year; Marine Toads and the picture postcard child of Costa Rica, the Red-eyed Green Treefrog.  With the onset of the rains though, all those species that have been noticeable by their absence for the previous five months emerge once again, sometimes in numbers so large that it begs the question, “Where has such a biomass of amphibian life been hiding for almost half the year?”

When they do emerge, it is with only one thing in mind; reproduction.  Around the breeding pools, the cacophony of the calling males renders it all but impossible to make yourself audible.  The initial heavy rains of the season immediately encourage a response from Costa Rica’s largest treefrog, the Milky Frog.  Within hours on the evening of the first downpour a full breeding choral congregation of males, in numbers upwards of fifty will have accumulated in the pond.  The deafening din of their ardor can be heard from great distances.  After several nights of this repeat performance, they once again decline in numbers until it is only a very occasional chance sighting that you will experience during the remaining rainy months.

Now is the time of the frog though and during the next seven months we are treated to a nightly chorus of serenading males of different species, some of them more melodious than others; the jackhammer mating call of the Marine Toad, the chuck of the Red-eyed Green Treefrogs, the sound of little metal bells tinkling from the Tink Frogs, clipped chirps of Banana Frogs and what you would swear sounded like two blocks of wood being knocked together that announce a Gladiator Frog male is looking for a mate.

Banana Frog, (Dendropsophus ebreccatus)

Yet there is one more amphibian phenomenon that only a lucky few experience; the explosive breeding display of Parachuting Red-eyed Green Tree frogs.  This is the second species of Red-eyed Green Tree frog to be found on the Osa Peninsula.  They are rarely, if ever seen, living as they do at the tops of the trees, but several times during the rainy season following several days of concerted torrential rain out they come, and they come in their hundreds.  They receive the parachuting part of their name from having large hands and feet that are extensively webbed.

Parachuting Red-eyed Green Tree Frogs, (Agalychnis spurelli). Mating pair

Taking the monsoon-like conditions as their cue, they launch themselves from above, opening the hands and feet, spreading the webbed fingers and toes, allowing them to effectively ‘glide’ to the lower levels.  The males and females pair up and then not long before dawn they start to lay eggs, everywhere, covering the surfaces of the leaves overhanging the ponds.  The eggs develop for seven to ten days, liquidize, slip off the leaves and plop into the water which is where the normal tadpole stage will then take place.  The explosive breeding frenzy has to end before sunrise; the frogs need to take shelter from the drying effect of the sun’s harmful rays on their delicate skin.

If you are out early enough you will be awestruck by the sight of hundreds of pale green frogs trying to climb up into shadowy parts on the underside of leaves.  Sometimes the weight of such huge numbers will snap the vegetation in which they are attempting to seek refuge.  It really does have to be seen to be believed.

Eyelash Viper, (Bothriechis schlegelii). Gold phase – Oropel

In all my years living on the Osa Peninsula I have seen the elusive Eyelash Viper, (Bothriechis schlegelii), on only four occasions.  It is not necessarily because they are rare but more to do with the fact they are very cryptically colored, the point of which being, to avoid being seen by both predator and prey.  Although they come in several color forms, the ones I have seen at Cabo Matapalo have all been the green mottled morph. The camouflage coloration blends the contours of the body perfectly against the moss covered branches of the plants where they sit as ambush predators awaiting the approach of a small lizard, frog, bird or rodent on which they feed.

The most distinguishing feature of this small pit viper are the two spine-like scales protruding over the eye giving it the name Eyelash Viper.  There is no definitive answer as to why it has these scales, possibly to push vegetation out of the way which may scratch the snake’s unlidded eyes.  One other eponymous feature  to the pit vipers is the small hole on the front of the face between the nostril and the eye.  These house acute sensory apparatus that detect very small changes in background infrared radiation allowing the snake to detect the presence and location of it prey.

Eyelash Viper, (Bothriechis schlegelii). Motteld phase- Bocaraca

The Eyelash Viper is a small snake, especially given the size some other vipers can grow to.  It is a nocturnal predator and will take a variety of prey ranging from frogs, lizards, birds and mammals. Unlike terrestrial vipers which envenomate their prey, release it, then seek it out after it has died, the arboreal vipers have a strongly prehensile tail and tend to hold on to their prey after biting.

Eyelash Vipers are distributed from Mexico down through Central America into Venezuela.  They prefer shrubby vegetation found in secondary growth.  In Costa Rica the yellow morph is know as the oropel, (golden skin), while the mottled morph is known as the bocaraca.

Due to its size, cryptic coloration and preference for resting during the day in the lower areas of vegetation it is responsible for biting those people who work in those areas.  Although deaths from the bite of an Eyelash Viper are rarely fatal, there can be some long term issues with impairment of movement particularly if bitten on the hands.  Viper venom varies between species and can be quite complex in chemical make-up.  Generally they contain a cocktail of fast acting proteolytic enzymes that cause a multitude of effects including tissue necrosis and death.

http://www.veridionadventures.co.uk