The days are now consistently sunny, hot and dry. Changes are happening in the observable flora and fauna. Butterfly numbers are increasing in terms of both the number of species and the number of individuals. But the numbers are still very much lower than would be expected for this time of year. It could well be that the extended and intense rains of November resulted in the death of many larvae and pupae. It may take time for those numbers to recover, especially considering the continuing decline seen over the recent two decades.
This time of year is usually noteworthy for the trees and other rain forest plants coming into flower. There is some visual evidence of several trees coming into bloom but once again not in the number or variety associated with the onset of the dry season.
One other creature notable by its absence at the moment are the cicadas. January is regarded as the start of a three month period when, during the day at least, your eyes are subject to a continual sonic bombardment of an indescribable intensity. The larval stage of the cicada is spent below the ground where they feed on sap from plant roots. It is not beyond the bounds of possibility that many of the larvae were drowned thereby reducing the number of emerging adults which are generally to found in millions this time of year. For many people that aural attack will not be missed but the ramifications on the ecosystem may have long lasting effects.
One feature of the transition from the wet into the dry season that is very evident as you walk through the forest at this time of year is the production of new leaf. The feature that makes the new leaf so obvious is the color – red. Cabo Matapalo is on the South West tip of the Osa Peninsula, Costa Rica. The location is only 8⁰ North of the Equator. Any sunlight hitting the earth’s surface at this latitude is therefore intense sunlight and significantly high in ultra violet radiation. Ultra violet radiation damages developing tissue. The plants produce a red pigment called anthocyanin which is deposited over the developing chloroplasts and protects them from irradiation.
Red is the Color of New Leaf in the Rain Forest
As the chloroplasts mature the plant reabsorbs the anthocyanin and now lays it down as a layer on the bottom of the leaf surface. Light hitting the forest floor is only 1% of that hitting the canopy so light is of a premium. Light hitting the leaf will pass through and be bounced off the underlying red layer and reflected back up through the leaf surface so that any light required by the plant to carry out photosynthesis it missed on the way down it will pick up on the way back through.
Many of the young leaves hang droopily facing down. Those that have no anthocyanin and not having developed much chlorophyll, look pale and ghostly in the in the gloom beneath the canopy. At this point they are flaccid and not until water is absorbed by the cells do they become turgid and assume their horizontal light gathering aspect.
One of the butterflies that exhibits very profound seasonal fluctuations is the White Banded Fatima, (Anartia fatima). It is one of the commonest Costa Rica butterflies. It is hard to miss with the white bands on the wings contrasting starkly with the dark brown ground color as it flies in open sunny areas such as gardens and disturbed ground. It can be seen visiting a wide variety of nectar plants.
White-banded Fatima, (Anartia fatima)
White-banded Fatimas can be found throughout the year in greater or lesser numbers. This week the numbers started to increase very rapidly. In some locations there were dozens of them, all looking fresh and new. But once they reach a peak in numbers and the short-lived reproductive frenzy is over then it will not take long for them to start to take on a tattier appearance and finally within a couple of weeks they will have more or less all gone again. But later in the year the cycle will repeat.
As the dry season progresses then the creatures that live on the forest floor take shelter in the moister damp conditions beneath the leaves that litter the ground during the heat of the day. As you walk on the trails and your feet disturb those leaves that disturbance will flush the smaller creatures from their hiding places. You will see displaced skinks, beetles and frogs seeking safe refuge from your footfall and the sunlight.
Rough-skinned Dirt Frog, (Craugastor rugosus)
There are several small frogs that inhabit the forest floor. These are the rain frogs mostly in the genus: Craugastoridae. On the forest trails there are two species in particular that you may come across, the Rough-skinned Dirt Frog, (Craugastor rugosus), and Stejneger’s Dirt Frog, (Craugastor stejnegerianus). The Rough-skinned Dirt Frog, as the name suggests, has a skin covered in many protuberances. Stejneger’s Dirt Frog on the other hand has a smoother skin and a generally darker area behind the eye.
Stejneger’s Dirt Frog, (Craugastor stejnegerianus)
Both these species have life histories that have allowed them to decrease their dependency on water and become more terrestrial in habit, certainly in respect to reproduction. Whereas most amphibians must return to the water to breed, the rain frogs pair up and lay their eggs amongst the leaf litter on the forest floor. The microclimate beneath the leaves is damper than that above which suits both the frogs and their eggs, it stops them from drying up. Aquatic egg-laying frogs face the problem of having many predators in the water that will feed on the eggs and the tadpoles. Rain frogs do not face the same intense predation pressure and can therefore produce fewer but larger eggs. The larger size of the egg allows full development of the tadpole within a protective gelatinous coating. A larger amount of yolk is provided which supplies enough sustenance for the frog to complete development and emerge four or five weeks later as a tiny copy of the adult.
Stejneger’s Dirt Frog – One too many flashes and It’s Away.
Jumping in Color
Moments after photographing Stejnegers’ Dirt Frog I noticed a tiny black speck of a leaf which moved in a very distinctive and familiar fashion. The almost indiscernible black dot was a jumping spider. It had turned to look at me which is how it gave away its presence. I had to turn the camera lens on it and take same photographs to truly appreciate the amazing little creature I had in front of me.
Jumping spiders belong to the most diverse spider family: Salticidae of which there are more than 5,000 named species around the world. In Costa Rica there is not a wealth of reference material you can consult in an effort to make an identification. Sometimes family level is about as far as you can go.
Unidentified Jumping Spider, (Salticidae).
The most distinctive feature of the jumping spiders is the large anterior forward facing eyes. These give the spider the ability to see things at close range. They can be seen orientating themselves to watch you. That is what this one was doing with me. Unlike their web-building relatives, the jumping spiders hunt their prey down. Once they identify a potential meal they will pursue it and at the last moment pounce on it, deliver the venomous bite and consume it.
Their visual abilities allow them to use coloration as a cue in mating. The males may have brightly colored legs and pedipalps to court the females. This species had bright blue legs and yellow pedipalps. When a male sees a female he performs a series a ritual dance moves which include lifting his legs in a certain sequence as well as moving in a series of set maneuvers in front of her. All the while the female is watching, scrutinizing the performance. One blunder and she will leave having no further interest. Each species of jumping spider has a very specific dance routine thereby negating the change of courting the wrong type of girl.
Unidentified Jumping Spider. Look at Those Eyes.
One of the most distinctive flowers of the forest understory is that of the Aristolochia vines otherwise known as the Dutchman’s Pipe Vine. As with most flowers the sole purpose is the achieve reproduction through pollination. Many plants have evolved ingenious means by which to use the flowers as a means to this end. The Dutchman’s Pipe is one of them.
The flowers are named after their resemble to the carved tobacco smoking pipes used in Holland. But to a carrion fly they look somewhat different. Carrion flies are attracted to the fetid odor of rotting flesh. The flowers of this species of Dutchman’s Pipe, (Aristolochia gaudotii). give off a scent which mimics the stench of a putrefying body. The pale yellow base color reticulated with maroon blotches visually emphasize the illusion.
Dutchman’s Pipe, (Aristolochia gaudotii)
The flies land but find themselves incapable of maintaining a footing on the slippery oily inner surface of the flower and slip down into the interior. They are unable to make an immediate escape as their exit is blocked by a barrage of downward pointing stiff hairs. They are trapped. During the period of vegetative incarceration, the fly struggles violently in order to gain its freedom. This results in the body becoming covered in pollen. The following day the stiff hairs wither and the fly finds its exit clear only to fly off and respond to the same trickery. This time it transfers the pollen thereby pollinating the flower after which it will be released from its temporary floral prison with a fresh coating of pollen.
Dutchman’s Pipe. Looking Down Through the Prison Bars.
Philip Davison is a Biologist, Writer and Photographer Based in Costa Rica
Observation Lists for Week Ending Monday 16th January.
Mexican Mouse Opossum
Greater White-lined Bat
Central American Spider Monkey
Golden-mantled Howler Monkey
Alfaro’s Pygmy Squirrel
Golfo Dulce Anole
Asian House Gecko
Central America Smooth Gecko
Central American Whiptail
Fitzinger’s Rain Frog
Rough-skinned Dirt Frog
Stejneger’s Rain Frog
Red-eyed Green Tree Frog
Savage’s Thin-fingered Frog
It has now been over a month since the unusually heavy rains ceased falling. During the intervening period of time there has been barely a drop of water and the rain that has fallen conveniently fell overnight. How quickly the ground has dried though. The places on the trails where some of the run off was flowing has now stopped completely. Most the trails have hardened and become firm under foot once again. The temperatures too have started to creep up and up with midday temperatures hitting the 100⁰ F, (40⁰ C), mark. At night the sky is clear and bright. With no cloud cover the temperatures go back down again hitting a pre-dawn low of around 71⁰ F, (22⁰ C).
This is the season when we start to see the trees producing flowers. Several trees have already started blooming as have some of the orchids. In the gardens the flowers attract insects, more notably the butterflies. As you walk down the forest trails, gaps in the canopy allow light to penetrate to the forest floor and these open sunny glades seem to be favored by both dragonflies and damselflies. Birds are actively seeking out nesting sites. So, there is no shortage of subjects to photograph as you leisurely wind your way around the grounds.
Night of the Pale Parasols
Sometimes a structure will appear as if overnight that will then catch the observant eye. They don’t have to be large structures but there will be something about them that make them stand out. At the side of the road on a bank where the drive had been cut through a hill and only about 4 feet from the ground I noticed a pale umbrella topped cone suspended from an exposed tree root. Beneath the fibrous parasol the cone was a squat in dimensions but covered with long pale yellow bodies. Closer examination revealed that each body had a thorax, wings, legs and a head. I was looking at wasps, more particularly the aptly named Parasol Wasps, (Apoica pallens).
Parasol Wasp Nest, (Apoica pallens)
The genus Apoica contains but six species. Strangely for wasps the parasol wasps are nocturnal. The nest consists of a swarm of workers with several queens and males. They are active at night engaged in hunting and nest building. Should you be near one of the nests after sunset and using a flashlight they will readily be attracted to its beam. During the day the wasps line up, pressed close together and cover the nest but will have no hesitation taking to the air to vigorously defend it should you venture too close.
A Hole Full of Horror
Once the sun has set then the nocturnal creatures that have been hidden away in nooks and crannies by day start to emerge. Over the past week or two, about half an hour after sundown a juvenile tarantula has been crawling from its web-lined lair hidden in a crack in tree trunk. Tentatively at first its front legs ease into the open. Once it is sure the area is safe it slowly creeps into the open and sits head down not too far from its safe refuge and waits for a meal to come by. Tarantulas do not build webs, they are ambush predators. They sit and wait for prey to come to them rather than actively hunt food. A slight tap of the foot on the tree root and this hairy arachnid behemoth quickly returns to the dark recesses of its den.
Juvenile Tarantula. Unidentified Species.
Tarantulas have a reputation they don’t deserve. It is unlikely that anyone has died from an American tarantula bite. The thought of being bitten by a large, hairy spider is what most likely unnerves most people. Whereas a tarantula bite is relatively harmless for humans, the neurotoxic venom that is injected will subdue and kill insects reasonably quickly. The female tarantulas are larger in body size and live longer than the males. A female tarantula can live anything up to 25 years. On one occasion last week I saw this juvenile catch and eat a long-horned beetle that had ventured too close. Tarantulas mash the prey with the chelicerae and suck out the juices.
Tarantula. Unidentified Species.
It is never a good idea to get too close to a tarantula in case it becomes threatened. The bite might not pose a problem for a human but the tarantulas have another means of defense. Using the legs they flick barbed urticating hairs from the body which can become lodged in a potential predators eyes or upper respiratory tract causing severe distress.
Tarantula. Unidentified Species.
The tarantulas belong to the spider suborder: Mygalomorphae. They are a rather older evolutionary group of spiders and can be characterized by the chelicerae, (fangs), facing directly down. Most of the world’s 903 species of tarantula live in the tropics and form the family: Theraphosidae. The name tarantula is something of a misnomer as they were named after the European tarantulas which belong to the family: Lycosidae or Wolf Spiders, the bites of which supposedly, (again without any basis in fact), would cause people to go into wild convulsions.
Tarantula. Unidentified Species.
Unravelling the Thread of Death.
There has been one other nocturnal hunter that I have seen over recent weeks that I don’t normally find with a great deal of regularity, the Brown Blunt-headed Tree Snake, (Imantodes cenchoa). These long, slender serpents become active as the sun sets. The body is very thin with the neck drawn out into a super narrow section. Supported at the end is a short head bearing large bulbous eyes. The body is triangular in section with a light tan base color interrupted along its length by large dark brown saddle markings.
The presence of this snake spells instant doom for small sleeping lizards that may have taken refuge in a “safe” zone at the tip of a leaf. Normally the amplified movements of a predator along the length of a leaf would immediately alert the lizard to imminent danger allowing it to jump to safety and flee into the undergrowth.
Brown Blunt-headed Tree Snake, (Imantodes cenchoa)
Not so with the Brown Blunt-headed master of stealth. Its light weight and slender form permit movement without disturbance. The eyes and tongue search for signs of a meal. The triangular body section give rigidity enabling the prowling snake to reach out into the darkness and snatch the sleeping victim from its secure perch.
The adults can reach several feet in length. Over the past week I have found and an adult and a juvenile. The photo is of the juvenile which I found on several separate occasions at different locations around the pond.
Philip Davison is a Biologist, Writer and Photographer Based in Costa Rica
Sunny Days are Back Again
The weather has most certainly turned a corner. After the record-breaking deluge that occurred continually over the course of the last five weeks we now have the opposite situation, no rain. Not a single drop of rain has fallen over the past week. The skies have been clear and bright blue. The sun has been shining brightly. The temperatures are on the rise. The night skies have been clear and filled with stars. Just within the space of seven days, the formerly soft muddy trails have started to harden up. There are, of course areas where the ground is stiff soft and in places water continues to run off but these are now few and far between. One trail had a new lake form as the water was unable to run off. Walking along a familiar path I was finding myself waist deep in water. I imagined that this new water feature may persist for months before the ground was exposed once more. I was wrong. Walking the trail a few days ago, all the water had gone. The path was very muddy but no longer submerged.
Zapatero Trail at Bosque del Cabo Rain Forest Lodge.
It was fortunate that the heavy rain stopped as the flowering season for many of the trees commences in December. Should the trees bloom and then become bombarded with persistent downpours, the flowers can be knocked from the trees before they have been pollinated. The result of this is a lack of fruit later in the dry season as the plants have not set seed. There are many animals whose lives depend on the bounteous supply of mixed fruits that comprise their diet that should the flowering and fruiting seasons fail then they simply starve to death. This happened in 2005 when substantial numbers of Spider Monkeys and Toucans were, quite literally, just dropping out of the trees. Necropsies carried out by veterinarians showed that they were suffering from very low body fat. They were starving to death. Everything looks good at the moment for a bumper harvest as I have seen many trees starting to produce blooms.
The Sun is Shining Over the Golfo Dulce Once More.
Caught in the Eye of a Cat
The frogs are still out in numbers but those numbers will start to dwindle as we head into the dry season. There are creatures that feed on frogs and they too have been out and about at night, the snakes. One of the commoner snakes around the pond after sunset is the Cat-eyed Snake, (Leptodeira septentrionalis). It feeds on frogs at all stages of their life history. More particularly it searches out clumps of Red-eyed Green Tree Frog eggs which it finds suspended beneath the leaves overhanging the water. The gelatinous masses are stuck in position and when the tadpoles reach about 7 or 8 days in age, the jelly liquidizes allowing the tadpoles to drop into the water where they complete the initial stage of their life history before emerging as froglets. Frogs eggs make a perfect meal for the snake, they don’t run away or fight back and are packed with protein. At the height of the amphibian breeding season, May, June and July, there are so many egg masses that the snakes start to look well fed and bloated. Now, because there is little amphibian reproduction taking place, the snakes also fish for the tadpoles from beneath the water surface, take froglets as the emerge from the water and if they get the opportunity they will eat the adults too.
Red-eyed Green Tree Frog, (Agalychnis callidryas)
Red-eyed Green Tree Frog Eggs
Cat-eyed Snake, (Leptodeira septentrionalis)
Cat-eyed Snake. Close up.
The Fatal Velvet Kiss
Whereas the Cat-eyed Snakes feed on the smaller frogs, there is a much larger snake which feeds on the larger frogs. One of the largest frogs in Costa Rica is the Savage’s Thin-fingered Frog, (Leptodactylus savagei). A huge amphibian might make a satisfying for meal for any number of creatures. To lower the risk of being predated upon Savage’s Thin-fingered Frog has several defenses. It has a toxic skin secretion that can cause intense irritation of mucus membranes. Should this prove ineffective it has a secondary defensive measure. When it is caught, it issues a loud cry not dissimilar to a crying baby. More importantly the call resembles the distress call of young caiman. If there any adult female caiman in the area they charge in to defend their young, which means hopefully as far as the frog is concerned, it can then make its escape as its attacker is attacked.
Savage’s Thin-fingered Frog, (Leptodactylus savagei)
But there are predators from which there is generally no escape. It is not uncommon to see by the pond at night some substantially large sized Terciopelos, (Bothrops asper). They are large pit-vipers in the same subfamily as rattlesnakes. Like rattlesnakes they have a venomous bite that spells certain death for any prey victim it strikes. An adult female can reach up to 6 feet, (2 meters), in length. A snake that size demands a big meal and the Savage’s Thin-fingered Frog fits the bill.
Once the sun sets out come the Terciopelos. They place themselves around the pond where an encounter with a frog is likely. They are ambush predators; the cryptic coloration of muted browns and greys camouflage them perfectly against the background. They remain motionless, camouflage works best if it is still. Frogs, being mostly nocturnal, have large light gathering eyes. They rely on movement to find food which is usually anything smaller than themselves, particularly arthropods, but sometimes smaller frogs too. But the only movement they will detect from a hungry coiled Terciopelo will be one that is over in a flash.
Terciopelo, (Bothrops asper)
The pit-viper is not so visually acute especially at night although its eyes will detect close movement. Once the feeding response has been stimulated then the tongue comes into play, slowly flicking out then in again, each time tasting the air. The tongue can detect parts per million of scent particles in the air and because it is forked it can pick up the gradient of a scent plume. You and I may not know what a frog smells like but the snake does. Then there are the pits that give it the sinister name pit viper. These lie one on either side of the head between the eye and the nostril. They are lined with cells that detect minute differences in background infra-red radiation. They work best at responding to the presence of warm blooded prey such as rodents but their efficiency could also differentiate the small difference in body heat of even a cold-blooded creature such as a frog against the background temperature.
The unsuspecting frog passes by. The snake has already drawn its head and neck into tightly sprung S-shaped. The strike happened so fast that it would probably have been unaware, there would have been no time to react, no chance of escape. As the snake’s head shoots forward and the jaws open, two long hinged fangs that lie flat against the upper part of the mouth now swing down. They are simply two hypodermic syringes attached to glands that contain virulent life-ending cytotoxic venom. The fangs puncture the skin like two needles, the force of the bite pushes them deep into internal tissues and organs. The snake quickly recoils to avoid any retaliatory action by the victim in its final moments, not that a frog could inflict any damage but the bite of a rodent might. The quantity of venom injected will spell doom and instant death for the unfortunate amphibian. It probably would not feel anything from this lethal injection, the effects of which would most certainly be instantaneous.
The frog takes one or two steps forward then collapses dead in its tracks. The snake is in no hurry. The meal is ready whenever it would care to dine. Lying patiently in the shadows the Terciopelo begins to smell the air with its tongue once more. Once it is feels secure in the demise of its victim it slips forward, the tongue constantly flicking in and out over the cadaver. It is searching for the head. Snakes have no way of rendering a meal into small pieces and must swallow the prey whole. Savage’s Thin-fingered Frog is a giant among amphibians, its body larger than the snakes head. To deal with this inconvenience the snakes lower jaw disengages at the midpoint as do the upper and lower jaws where they hinge together at the side of the head. Now the snakes gape can accommodate the huge frog body. The snakes skin is highly elastic allowing it to stretch as it moves forward over the meal and with continuous backward moving S-shaped waves the feast is delivered finally to the stomach. The snake moves away back into the shadow of the undergrowth where it will lie motionless for some time until it has digested the hearty dinner.
Terciopelo eating a Savage’s Thin-fingered Frog
There are times when even the top predators can become prey. Where there are snakes then there might be snakes that eat snakes. Sure enough on occasion by the pond where the Terciopelos lie in wait there is a hunter that actively seeks them out. A hunter that is immune to the deadly venom. A hunter that can overpower with impunity its adversary. That hunter is the Mussurana, (Clelia Clelia)..
The Mussurana is a snake with a solidly muscled body. It has a beautiful deep gloss grey color which radiates a fabulous deep blue iridescence. The underside is a soft eggshell cream. It is a powerful constrictor. The teeth at the back of the jaws are strong and allow it to hold onto its writhing victim while it throws around it those ever-tightening coils. This is a non-contest, the Terciopelo has little or no chance. Finally, it succumbs and expires. The hunter has become the hunted and the frogs have one less problem in their territory.
Mussurana, (Clelia clelia)
Philip Davison is a Biologist, Writer and Photographer Based In Costa Rica
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 1st 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.
The clement weather conditions are continuing to prevail. The rain we are receiving is most certainly intense but by no means prolonged. If there is one day of rain it is being followed by two days of sun. This time of year there are very few visitors. September and October are not big holiday periods. For anyone who does want to visit Costa Rica at this time of year you can certainly avoid the crowds but you also run the risk of being confined to your cabin unless you want to suffer a constant soaking. For those of us who do live here then the quiet time and unseasonably dry and sunny conditions give us time to go and explore a little more or in my case catch up with the writing.
I’m Lichen That
One night when I was out doing my nightly frog counts I came across one of the Anolis lizards that I see more often up in the canopy, a Lichen Anole, (Anolis pentaprion). This individual was sleeping but when I turned the lights on to video the creature in its state of slumber the instant change from night to apparent day woke it. Not only did the lizard stir but the increase in light levels drew in some of the insects including one of the few species of night-flying wasps, Apoica pallida. It landed near the lizard’s head so presenting itself as an easy meal the advantage of which it was not going to refuse despite having only just being disturbed from its sleep. With a quick snap of the jaws the wasp was caught, chewed up and down the body and then swallowed. The Anolis then soporifically walked up the small branch on which it was clinging, climbed atop a leaf into a darker location than it was now finding itself, closed its eyes and went back to sleep.
Anolis lizards are a very diverse genus with many closely related genera belonging to the family: Polychrotidae. There are well over 200 species of Anolis and each species quite often is divided into a number of subspecies. Anolis lizards are similar to geckos in that they have an anatomically specialized structure to the toes, (lamellae), that allow then to climb with ease including smooth vertical walls and even panes of glass. Anolis lizards are generally small and unless you notice some movement as they jump through the vegetation then they can easily be overlooked. In terms of ecology smaller species inhabit the lower levels of the forest and conversely larger species the higher levels.
Although the family is species rich, it is not always easy to identify the individuals to species level. One factor that does help is the males have a loose flap of skin under the chin called a dewlap. Thankfully each species has a different color dewlap, particularly pronounced in this area. The loose skin is attached to a rod of cartilage fixed at the jaw over which the lizard has muscular control. The lowering of the cartilage extends the skin revealing the brightly colored flag which is in stark contrast to the more usual body color and it is used to intimidate and scare rival males from the territory or used to court females. Certainly if you see that bright flash of color appear as if from nowhere then there will be a second individual you may not be so aware of but it will be somewhere close by in the vicinity. The dewlap of the Lichen Anole is a deep purple edged with magenta and is not as large as in some other species. Most females do not possess a dewlap and because there is a strong sexual dimorphism can prove a little more difficult to identify. Here on the Osa Peninsula there are only seven species of Anole and they are all fairly distinct in appearance both male and females.
There are two particular species that seem to have reacted to this year’s slightly abnormal weather conditions. One is a butterfly and the other is a frog. They have both been recorded in numbers in excess of those normally found.
The Luna Satyr, (Pierella luna), is a largish brown butterfly that is normally found throughout the year but for the most part as solitary individuals or in small groups. It is found flying very close to the forest floor in the dark, dank, shady conditions beneath the forest canopy. You will quite often only notice it when it momentarily passes by your feet, wings beating slowly, as it moves from one side of the path to the other. It will disappear under the vegetation and when it settles the muted grays and browns of its now still wings blend it immediately into the background. It prefers the denser aspect of secondary forest as opposed to the more open situation beneath primary forest. This may have something to do with the distribution of its larval host plant, species in the family: Heliconiaceae, many of which can be found in secondary forest habitat.
This year when walking along trails through secondary forest Luna Satyr could be found in huge numbers much larger than experienced before. I am not sure what triggered the population explosion but the adults have not been hard to find, sometimes in groups numbering ten or more. The slightest disturbance caused by your footfall will have them momentarily take to the air before quickly alighting once more on the ground.
A Big Bunch
The Banana Frog, (Dendropsophus ebreccatus), is one of those small tree frogs that you can more or less guarantee you will see if you go to the pond at night. They are ever present throughout the year. At the height of the amphibian breeding season which starts when the rains arrive in April, gets into full swing in May and draws to a close by the end of August, the Banana Frog males can be both seen and heard in reasonably large numbers every night. Those numbers reduce outside of the breeding season to the point where during the dry season it might only be one forlorn male out calling but there will always be one.
The males emerge as the sun slowly sinks beneath the western horizon. They set up their territories on the Water Lettuce or Water Hyacinth and call vigorously with a protracted “Eeeack”. The larger egg bearing females emerge a little later, select a male on the quality of his call, makes her way over to the male of choice, they pair up and later she lays a sheet of small jelly coated eggs on the surface of a leaf which the male fertilizes. The eggs develop here for 7 or 8 days, the tadpoles wriggle free and slip below the surface of the water from where they will emerge about 8 weeks later as small froglets.
Whereas this time of year when all the other frog species have either disappeared from the breeding pond or are present in only small numbers, the Banana Frog has seen a surge in numbers. There are presently in the region of 20 calling males every evening. It could well be that they are taking advantage of the lack of competition from other species, although there are not too many other species that do use the Water lettuce, (Pistia stratiote), and Water Hyacinth, (Eichhornia crassipes). The tadpoles of other frogs do have to compete for space and food once they have entered the water, some of which may be larger and/or more voracious than D. ebreccatus tadpoles. It may simply be the fact that there is still a lot of rain which is perfect for the eggs but that is the norm every year. Whatever the reason if you could down to the pond at the minute after sunset you will be greeted by a vociferous chorus of amorous Banana Frogs.
Seeing You Walk for the First Time
Last week I happened across an insect that has proved to be somewhat difficult to identify. What initially caught my eye were the colors, most strikingly the bright yellow. The head was small but the body was long and soft. The wings too were brightly colored but in green. My first thoughts were that it was some kind of Phasmid or Walking Stick, more precisely a winged walking stick. It did not seem to be disturbed when I moved it from the bare white stucco wall where its colors were making it rather conspicuous to some nearby vegetation where it was less obvious. Not moving is part of a Phasmids game plan though. I took some photos and headed off to my reference library.
Winged Walking Stick
As with most insects that I see for the first time after 16 years of living here I just know the identification is going to be difficult. Insects are so prohibitively numerous in number of species, especially tropical insects. The reference material available is limited and by no means exhaustive. So after some searching I was not really any further forward than still being confident it was a winged phasmid. Time to scour that great resource the internet. Scrutinizing photo after photo all I could conclude that it was a winged phasmid but there was nothing I could see that looked remotely like this individual. So if there are any phasmid experts that may be reading this and could enlighten me as to a genus or species I would love to hear from you.
Winged Walking Stick
Philip Davison is a biologist, writer and photographer based in Costa Rica.
Dry and Sunny. Cold and Wet
We are well into the wet season now. Both July and August had particularly high levels of precipitation with July receiving a total of 37 inches of rain, (918 mm), and August 33 inches, (842 mm). Mostly the rain fell in the evening and so did not disrupt the day too much. The first ten days in September had been very sunny and dry but that has now changed and increasingly the rains are becoming heavier and more prolonged which is the norm for this time of year. Several days ago over 9 inches of rain dropped from the sky in a 24-hour period.
But when the sun does shine it changes everything. The dark and dank atmosphere lifts and the butterflies take the air again. The grounds are teeming with groups of female White-nosed Coatis, (Nasua narica) with the young interspersed among the adults. They all move slowly in the same direction with heads down and striped tails stuck vertically up. They are omnivores and so when it comes to food anything is game. Follow the group through an area and you will see small pits where their keen noses have found a tasty grub or crab and the sharp claws have extracted it. Any fallen fruit will halt progress and keep the group occupied in a feeding frenzy for a while.
Tropical Checkered Skipper
Crossing through or sitting to the side of the groups of coatis you will see large rodents which look like oversized Guinea Pigs. These are Agoutis, (Dasyprocta punctata). These relatively large rodents are seed eaters and will normally be seen beneath the palm trees feeding on the fallen palm nuts.
The picture would not be complete without the background sight and sound of the birds. Up in the trees, if not always visible but easily heard, are the Black-mandibled Toucans, (Ramphastos ambiguous) and the visually stunning Scarlet Macaws, (Ara macao). Hopping around on the ground are the ever present Black Vultures, (Coragyps atratus) which like the coatis take advantage of whatever food presents itself.
Last week I was out on doing my weekly butterfly counts. I always carry the camera with me as occasionally something will turn up out of the blue. Because my focus is on the Lepidoptera and I don’t want to lug around too much weight I normally only have the 105 mm macro lens and a flash gun with me. If something larger or farther away appears then I am a bit stuck. This is what happened on this day. I had just finished photographing a small butterfly close to the ground. As I stood up I noticed a Blue-crowned Motmot, (Momotus momatus), about 30 feet away but close to the ground. I had no real hope of getting a good image but thought I would try for something anyway. The end result was not brilliant but more than I had expected.
There are only 9 species of motmot and they are largely confined to Central America. They are very handsome birds and the Blue-crowned Motmot is possibly the most striking of them all. The long tail feathers end in two distinctive ‘tennis racquet” shapes below a bare area of the shaft. While perched on a branch the tail flicks to a fro like a feathered pendulum. The name motmot comes from the call which is a soft but distinct moot moot. Motmots are distantly related to kingfishers and share the same habit of bank nesting. Around the grounds of Bosque del Cabo, if the path cuts through an area leaving steep earthen sides they will quite often have many entrances leading down into tunnels. Some of them may be land crabs, some of them maybe entrances to a Leaf-cutter Ant nest and some of them maybe Blue-crowned Motmot nest holes. If they do have chicks, then listening at the entrance you will hear the cheeping of the young inside.
Later on that same morning as had almost finished my walk I perceived a shape on the ground in front of me that, although bearing the color of dead dry leaves was most certainly not. The creature was a Helmeted Iguana, (Corytophanes cristatus). These lizards, if seen at all, are usually found head up holding onto the side of small tree trunks and branches. When approached they move almost imperceptibly to keep themselves at 180⁰ on the opposite side of the trunk to the observer. This one however was on the ground so it had nowhere to go.
I slowly lowered myself to my knees then leaned forward till I was lying on my belly close to the iguana. As I lowered myself the lizard also lowered its head and turned away from me presenting just the large flat expanse of the top of the skull. I got several body shots and then re-positioned myself for the portrait. Always moving slowly, I managed a couple of profiles before it took fright, raised up on its hind legs and ran off into the undergrowth.
A Short Jump
When the sun does shine, one group of animals you can count on seeing are the grasshoppers. Particularly on hot, bright days just strolling along paths in more open garden-like areas your movement will likely as not disturb grasshoppers which are laborious flyers. Their wings don’t carry them too far before they land in the vegetation again. To get close, once more stealth is of the essence. They can be seen setting the hind legs in readiness for takeoff again. If you do spook one, it doesn’t take much to watch where it flies to and lands.
Although I like grasshoppers I have to admit I do not find them the easiest of creatures to identify. The reference material available tends to be for American or European species which doesn’t help a lot in Costa Rica. Nonetheless when viewed close up their almost armor-like exoskeleton make them good macro subjects.
The Funeral Dragon
Although not as obviously abundant as butterflies are the dragonflies. They can be found around most damp or wet areas from ponds and streams to water filled ruts on the trails. Each individual has a variety of preferred perches where they settle momentarily before taking to the air to catch prey or chase off neighboring males. Their activity is endless particularly if it is a hot sunny day. To capture an image all you have to do is concentrate on one perch then sit and wait, the individual to whom it belongs will return.
This species is Erythodiplax funerea, I am assuming so called because of the black coloration on the lower two thirds of the wing. It is one of the species that I do not find near water, these ones were in the middle of the tropical garden. I also commonly find them very low in the vegetation along the forest paths. Their behavior is the same though constantly taking off flying to a new vantage point then returning a few seconds later.
So all in all despite the rains, those sunny days still provide for ample opportunity to get out, enjoy the sights and sounds and maybe take some photographs too.
Philip is a biologist, writer and photographer based in Costa Rica.
Ray of Light
This July was probably the wettest that I have experienced in 16 years of living on the Osa Peninsula. Here at Cabo Matapalo the total rainfall for the month was 38 inches. But a lot of the rain came in heavy torrential downpours. We did see a great deal of sun between the downpours. Also much of the rain fell overnight. One morning following a night long deluge the sun rose but while still low in the sky it cast rays of light through the tree trunks. The shafts of light were emphasized by the rapid rising misty droplets creating a heated steam.
The early morning sun breaks through.
Close Encounters of the Bird-eating Kind.
Snakes are notoriously hard to find in a tropical rain forest. There are snakes on the ground and snakes in the trees, there are snakes out at night and there are snakes out during the day but locating snakes can be a thankless task at best and fruitless preoccupation at worst. Sometimes snake hunters come to the lodge armed to the teeth with knee length leather boots, grab sticks and snake hooks wanting to engage in 24 hours snake hunting trips. I have to lower their expectations by telling them that they can turn over every log and rock in the forest and they won’t find snakes. Conversely people come and walk with trepidation on the forest trails in a state of dread in case they happen upon a snake. Invariably these will be the people who will find them.
Last week while out on the butterfly transect I was walking through a section of forest, handheld recorder in one hand, camera in the other when I noticed a fairly large snake on the forest floor just to the side of the trail. I stepped off the path to a position in front of the snake which had frozen and was watching me as I sunk slowly to my knees while lifting the camera to my eye.
As well as being hard to find snakes are difficult to photograph due to the linear dimensions of the body. Unless they are coiled then only the head will be in focus while the rest of the body is either out of shot or too long for the depth of field to accommodate. As I leaned forward to get my belly on the ground the snake lifted its head and the performance began.
The snake I was looking at was a Tropical Bird-eating Snake, (Pseustes poecilinotus). It is also known as the Hissing or Puffing Snake as it has a tendency to turn its head sideways while flattening its neck laterally to give the impression of being larger than it actually is. It whatever it is that is upsetting the snake, in this case me, it will strike out. I managed to stay out of range as I did not want to risk a bite to the face. This species is non-venomous but a snake bite in the vicinity of the eyes may not be such a pleasant experience. However I did manage to get several shots before rising to my feet and continuing on my way while letting the snake go about its business once more.
Tropical Bird-eating Snake, (Pseustes poecilinotus)
Tropical Bird-eating Snakes are one of the larger serpents to be found in this area. Fully grown they can reach up to 6 feet in length. The ground color of the body is a pale blue/grey fused with orangey-brown patches. The lips and lower sides are a brighter orange and quite often with a yellow belly and dark top to the head. As the name suggests their principal prey item are birds, more particularly chicks and eggs taken from nests. Rodents make up some of the diet and I have seen them eat bats too.
Tropical Bird-eating Snake in Threat Pose
Remember if you visit the area it is highly unlikely that you will see a snake and the ones that you may stumble across will probably be non-venomous. The snakes want as little interaction with you as you will of them and they will make themselves very scarce in short time so it is not something that should detract from the enjoyment of walking the trails.
Pecked Out Eyes
One of the comments that I come across is the eye spots on an Owl Butterfly when the wings are open resemble the eyes of an owl, (or any other large potential predator), and scare off whatever is trying to catch the butterfly. As I have said previously in this blog it sounds like a good anti predator strategy but fails when put into practice as when the butterfly opens it wings, the spots which are on the ventral surface are then underneath and can’t be seen.
Damaged Blue Morpho, (Morpho helenor)
Many predators when aiming to catch, subdue and kill their prey will direct an attack in the area of the eyes because lying behind the eyes is the major part of the central nervous system, the brain. Destroy the prey’s brain and the battle is over. So many butterflies have a ruse that will use this attack to their advantage, they create a false eye. It is usually large and distinct and placed at the trailing edge of the hind wing. Any bird or lizard taking a peck or bite at the “eye” area will only be rewarded with a tatty piece of wing membrane while the main body of the butterfly makes its escape.
Damaged Owl Butterfly, (Caligo eurilochus)
With these two butterflies this damage can be seen quite nicely illustrated. The Blue Morpho, (Morpho helenor), has a line of eye spots down the trailing edge of the upper and lower wing. As can be seen the wing has already been pecked at and torn in that area yet the butterfly is still capable of flight. With the Owl Butterfly, (Caligo eurilochus), very obviously the attack was directed against the “eye”. More often than not, unless it is newly emerged, the Owl Butterflies will be missing this part of the wing when seen in the wild. It buys the butterfly a second change to locate a mate to partner with and reproduce.
It is thought that the term bug comes from the Old English word for a goblin. The tern bug when applied zoologically refers specifically to the order: Hemiptera. This order is divided into two sub orders depending upon the structure of the wings. The sub order: Heteroptera have the wings divided almost equally into a thick basal part and a thin distal part. The sub order: Homoptera have the wings completely thin and cellophane-like.
As you can see this Big-legged Bug, (Pachylis tenuicornis), is a heteropteran with wings being clearly divided into two textures. It belongs to the family: Coreidae, the Big-legged or Flag-legged Bugs. The hind legs are very swollen and stout. This individual flew past me in an area of grassland where it landed not too far away on the ground. The thing that caught my eye was the bright red coloration of the body beneath the wings.
Big-legged Bug, (Pachylis tenuicornis)
The Big-legged Bugs when attacked by a predator lift the wings to reveal that bright coloration which warns of an impending defensive measure, notably that it is about to spray from glands an offensively odorous fluid. The fluid discharges from a gland on the thorax and opens by way of a pore on either side. The gland has a valve which allows one or the other or both pores to discharge at once. The cuticle around the pores is sculpted so that when the fluid is sprayed some of it remains on the body providing even further protection. Thankfully I did not disturb this individual so much as to stimulate such a reaction.
How to Spin a Golden Orb
One of the commonly seen spiders in this area, due to their large size and elaborate webs, is the Golden-orb Spider, (Nephila clavipes). Its large size and striking black and yellow coloration along with the “furry” legs make it look very dangerous but it is in fact totally harmless to humans.
Female Golden-orb Spider, (Nephila clavipes)
Like just about all other spiders they are carnivores using both traps and venom to catch and immobilize the prey. The trap is the web or orb. In the case of the Golden-orb Spider it is made from a yellow silk which gives the spider its name. Outside the forest the web is made from a deeper yellow silk which attracts bees so a large percentage of its diet in more open areas is bees. Inside the forest it is made from a much paler silk.
Normally with orb weavers when something lands in the web they rush towards it and envelope it in sheets of silk to completely immobilize it before injecting the venom. The Golden-orb Spiders on the other hand bite first and then wrap in silk. If the victim caught in the web is a large or aggressive ant or wasp she won’t take it on because there is a good chance she will be stung o bitten before she can get her bite in.
Webs are fascinating structures. Although not so obvious to the human eye each spider has a web that is structurally pertinent to the species. That means there are as many different types of webs as the number of species that create them. As most people are aware the web is made from silken strands that are meticulously meshed together to produce one of nature’s most amazing death traps.
Silk is not exclusive to spiders, some other invertebrates are capable of producing silk, it is just that spiders are the unreserved masters in the production and utilization of silk and all spiders are capable of producing silk. Silk itself is a remarkable substance. It is a proteinaceous material stored as a liquid in the spinning glands. When spun by the spider it turns from a water soluble liquid to an insoluble silken thread and this change occurs due to tension orienting the molecules rather than exposure to air. The nature of the thread means it has both strength and elasticity. Spiders can produce many types of silk depending upon the use to which it will be put. In a web there may be dry silk which is stiff and used as the framework while a moist viscous silk capable of stretching 300% of its original length is used as the sticky catch net.
Golden-orb Spider, (Nephila clavipes) producing silk
The spider has 3 pairs of independently mobile spinnerets on its abdomen. Each spinneret ends in a spigot through which the silk gland exudes the silk. As the proteinaceous silken thread is produced other cells in the silk glands secrete mucopolysaccharides which give it a viscous coating. The mucous coating takes water from the atmosphere which separate into small droplets along the length of the fiber which in turn gives it the highly elastic quality to take the momentum from a large insect hitting the web as well as the glue-like adhesiveness which then holds it there.
Golden-orb Spider close up of spinnerets
I used extension tubes with a 105mm macro lens to try and capture a close up of the spinnerets of this Golden-orb Spider. The spider is fairly large which made the task a little easier. You can see the silken line being produced as well as the mucous globules along its length.
Philip Davison is a Biologist, Writer and Photographer Based in Costa Rica.