Archive for the ‘Common Tent-making Bats’ Tag

A New Age Begins   3 comments


Week Ending 11th December 2015

Weekly Weather

Average High Temp 101ºF (38.3ºC)               Average Low Temp 75ºF (24.3ºC)

Average Rainfall 1 ins (25.4mm)                    Total Rainfall 7 ins (177.8mm)

Wet and Dry

The dry season at Bosque del Cabo Rain Forest Lodge always experiences a stuttered beginning.  The lodge is located on the south west tip of the Osa Peninsula, Costa Rica overlooking the Pacific Ocean to the south and the Golfo Dulce to the east.  The region is covered by some of the last remaining tropical forest on the Pacific Coast of Central America.  Due to the pronounced seasonality of the area having a profoundly dry five months followed by a wet seven months the forests here are more correctly classified as tropical seasonal forests as opposed to tropical rain forests which are not subject to the annual dry period.

The heaviest rains of the year fall between September and November.  By December the daily deluge abates and we gradually see more of the sun.  It is easy to be lulled into a false sense of “the summer is here” as commonly a few dry, bright days with blue skies will be followed by another week of torrential downpours.  But eventually the faltering weather passes through the transitional phase and settles into a more predictable pattern.  Given a few weeks of steady, dry heat and the plant life will begin to flower.  The number of butterfly species and individuals that had dropped in the wet season begins to build once more so the days are now filled with beautiful, brightly colored wings adorned in poster reds, yellows and orange dancing around the flower heads.

There is never a shortage of mammal or bird sightings.  Currently there are many migratory warblers and tanagers chattering noisily in mixed flocks as they move from tree to tree in search of insects or fruit to eat depending on their specific diet.  The resident bird populations do not mind those long distance travelers returning to spend the winter in the warmer climes of the tropics and join quite readily with their travelling cousins in large flocks.  Monkeys abound in the trees, constantly on the move looking for food whether it is flowers, young leaves, fruit or insects.  Under the trees the large ground living rodents, Agoutis, feed on the fallen fruit and large heavily coated seeds.  Solitary male White-nosed Coatis are on the lookout for anything they can get their paws on; grubs, crabs, bird’s eggs and chicks as well as fruit or discarded food in the bins of the restaurant.  The gregarious females with young patrol in large foraging packs looking for the same food as the males but not with the same bold abandon.

The peace of the hot still sultry afternoon atmosphere is occasionally permeated by the call of a mammal or bird.  The ever active Spider Monkeys let out a series of high-pitched shrieks which sporadically turn into a hysterical frantic screaming match.  From deep in the forest the doleful Howler Monkeys bark and roar their disapproval of some irritation.  The White-faced monkeys oblivious to the presence of human observers chitter and chatter amongst themselves.  Coming from the surrounding vegetation are the chirps and cheaps of the warblers and tanagers.  But for the most part the soporific pulsating heat and the throbbing silence serve to create a languid attitude for visitors to the tropics.

Feed Me

All of a sudden the siesta is interrupted by a harsh ear-piercing screech.  Several birds of prey inhabit the area and neither the hawks nor the falcons have been blessed with a melodious call.  Commonly seen sitting at the top of the palms or on the ground are the Yellow-headed Caracaras, (Milvago chimachima).  Despite their raptorial appearance these elegant members of the falcon family are generally carrion feeders.  They can also be seen riding the backs of cattle feeding on bovine ticks.  Due to their association with cattle they are commonly seen in open pastureland.  Until 1973 they had not been recorded in Costa Rica but following widespread deforestation their distribution and geographical range spread north from Panama into Costa Rica and they can now be seen in Nicaragua.

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That nasty nasal screech was an adult Yellow-headed Caracara calling from on the ground but there was another call, similar yet more urgent.  Not too far from the adult was a newly fledged youngster that was making its first foray from the nest.  It had not yet mastered the art of flight and was demanding food from the parent bird that was watching warily over its offspring’s pitifully laborious progress hopping and jumping across the ground.  The brown speckled shabby looking youngster bore little resemblance to its sleek yellow-faced dark-browed parent standing guard over its precarious and vulnerable position.

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From Sublime to Ridiculous

Another bird seen either high or low is the Turkey Vulture, (Cathartes aura).  As you look up into the deep blue tropical sky it is likely that you will see flocks of birds soaring on the thermals.  Silhouetted against the azure background the shapes and shades circling above you will help discern the different species present.  Long thin wings bent back from the center like a Batman motive combined with a forked tail easily characterize the Magnificent Frigatebird.  A huge bird with broad, wide wings fingered at the end and divided into a monochrome white leading edge and black trailing edge leave no mistake that this is a King Vulture.  Similar in shape but uniformly dark except for grey fingered tips is the Black Vulture.  Soaring with them with the same wing form but with longer tail and complete grey trailing edge is the Turkey Vulture.

On the ground there is no mistaking the Turkey Vulture for its head bare of feathers is bright red.  Like the Yellow-headed Caracara the Turkey Vulture feeds on carrion but unlike its falcon cousin which locates food visually, the vulture has a highly developed olfactory sense and can locate the chemical signature of decomposition following the plume of molecules of death to their source hidden beneath the forest canopy.  They can often be seen beneath the palm trees feeding on the fallen palm fruit.

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Vultures are not everyone’s favorite bird but they play a vital ecological role in disposing of rotting carcasses and rubbish that won’t make to a landfill site.

Fruit and Nuts

Sitting beneath the palm trees in the company of vultures one will more often than not see Agoutis, (Dasyprocta punctata).  These large ground living rodents are related to Capybaras, Coypus, Pacas and more familiarly Guinea Pigs.  Along with the vultures they are waiting for the palm nuts to fall.  Agoutis are essentially seed eaters and have the ability to sit back on their haunches while holding the seed in their front paws which they can manipulate and turn allowing them to easily gnaw through very tough seed coats such as nuts.

At the moment there are a lot of fruits on the grapefruit tree which when ripe fall.  Eagerly awaiting this softer option dropping from above there are some Agouti individuals that pick up the sizable citrus prize in their mouths and carry it off to be eagerly consumed.  They do not eat the peel but rather the soft juicy segments inside.

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Whereas during the day vultures and Agoutis can be seen frequenting the palm trees at night it is possible to see another creature that utilizes the palms.  If you look a little more closely at what might seem like old and dropping palm fronds you will see that they will have had another force at work.  Something has nicked through the veins of the frond to be point where it folds over.  Take a look inside and there you will most likely find the culprit responsible for this chiropteran topiary – the Tent-making Bats, (Uroderma bilobatum).

The Tent-making Bats use the tents as either day roosts or night roosts.  If they are using them as a day roost there can be as many as forty bats hanging under the frond.  They regularly change the location of each roost they are using as predators would quickly figure out where to get an easy meal.  One of the commonest predators of the tent making bats are the Squirrel Monkeys.  During the day they identify which roosts are being used by the bats climb to the fronds above and then drop onto the roost.  The startled bats come fluttering from underneath where they are picked off by the monkeys.

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Currently they are being used as night roosts.  Once the sun has set the bats leave the day roosts and fly to the selected night roosts where they wait until it is very dark before they go foraging for food.  The Tent-making Bats are fruit-eating bats and use night roosts which are never more than 80 – 100 meters away from the nearest fruiting trees which in this area are figs.  The carry the figs in their mouths back to the night roosts whereupon landing they then hold the fruit between their wings, peel off the skin with the teeth and eat the pulp.  Just before the sun rises they leave the night roosts and return to the day roosts where they will pass the day sleeping.

Philip Davison is a biologist, writer and photographer based in Costa Rica.

I’ll Be Back in The Evening   3 comments

La Tarde, Osa Peninsula, September 2013

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A Path Well Travelled

It had been exactly one year since I last visited La Tarde with my friend and fellow biologist Mike Boston.  Last year’s visit had resulted in a day trip to La Tarde included in the list of excursions offered by Bosque del Cabo Rainforest Lodge.  A certain percentage of the visitors to Bosque have an interest in the reptiles and amphibians of the area.  Bosque has a rich herpetofauna which can be experienced without too much searching.  But one thing that becomes apparent is that once you start to search further afield you will find that there seems to be pockets of isolated populations of certain species in different locations.  It might well be that you get a species of frog which occurs in large numbers in one locality and then there may be a gap of several miles or more before you encounter another population of the same species.  The reason for my first trip to La Tarde, apart from the excellent reviews I was hearing, was that the area contained a diversity of amphibian and reptile species not found at Bosque.  On my visit a year ago I was not disappointed.  But there were one or two things that I had taken photos of where the resulting images had not been great.

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So last week the weather had been perfect each day with clear blue skies and warming sun.  Each night experienced a little rain just to keep things damp and the creeks flowing.  The lodge was quiet so it seemed like an opportunity was being offered that shouldn’t be ignored.  I phoned Mike and he too seemed keen to go, despite the fact that he already spends a lot of time there.  With camera equipment packed and rubber boots at the ready off we went in the hope of capturing the images that eluded me one year earlier.

Nature Boys

It has been said before but it bears repeating that Mike and I have been friends for a long time, 37 years in fact.  We met within the first few days of starting university and found we had the same interests and passions in life, the foremost of which was natural sciences in general and herpetology in particular.  Mike had been raised in the tropics and always dreamt of returning.  I had never been but the concept of going and living in a tropical rainforest with its inherent high biodiversiy is one that continually played on my mind.  It should therefore come as no surprise that nearly 40 years after our first meeting and for the past 13 years we have lived only a few miles apart on one of the most biodiverse regions on the planet, the Osa Peninsula, Costa Rica.

Mike has been taking guided tours into the National Park for the past 15 years.  He has a reputation as one the most respected and knowledgeable guides on the peninsula.  He should be, he has spent the majority of his life studying tropical ecosystems.  He has many more feathers in his cap though.  A certain proportion of his work is tropical field studies with High School students as well as undergraduates from North America and Europe.  He has worked as a consultant in the production of many television documentaries for companies all around the world.

Change of Plan

Several years ago, rather than take people on day trips into the National Park where time and wildlife viewing were limited he changed his itinerary and started to visit La Tarde instead.  Mike has always been keen on helping to develop local small sustainable business ventures.  He feels it is important to help the people of the area to make a living from tourism without overly exploiting the area.  La Tarde was started as an ecotourism project by Eduardo Castro, a man who had formerly farmed the area but lost most of his livestock to the larger predators that live here.  Rather than fight the situation, hunting and killing the large cats, he decided to go with the natural course of events and bring in people to see just how wonderful the rich diversity of his land was.  Being such a short distance from the main town on the peninsula, Puerto Jimenez, and with stunning views as you rise up into the hills above Corcovado National Park it became the natural destination of choice for Mike and subsequently for many of the other guides in the area.

A Venomous Beginning

We arrived for a late breakfast and as we sat chatting, readying ourselves for a walk through the forest, the sky turned from bright blue to dark grey and then black.  We though it prudent of hang on for a while to see what would transpire.  In front of the restaurant area, there is a valley.  It seemed like all of that darkness sank down into the valley.  We could hear the torrential rain pummeling the vegetation below our dry vantage point.  It descended deeper and further down the valley then within 15 minutes it had rained itself out, all that was left were a few wisps of cloud that floated in the air, dissipated and disappeared.  We were good to go.

Bothriechis schlegelii

We were going to start easy.  Last year in the vegetation by the side of the restaurant there resided a small bright yellow Oropel, (Bothriechis schlegelii), the Eyelash Viper.  This snake comes in an unbelievable variety of color forms.  Today in a bush close to the ground were two more individuals but both sporting totally different base colors and patterns.  In this phase the Eyelash Viper is known as the Bocaraca.  They were both small.  The smaller of the two had a rich reddy brown base with darker brown blotches.  The other was an overall greeny blue with orange patches and rings edged in black.  They sat motionless as I set up the camera and took the shots.  Female Eyelash Vipers give birth to live young and the offspring can exhibit any one of the color variations and patterns.

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Eyelash Vipers are arboreal and can be found everywhere from low down to higher up in the vegetation.  They tend to be nocturnal in habits which is probably why these ones were not inclined to move.  The cryptic coloration camouflages them perfectly against the background trunks and branches of trees so they hunt by ambush.  Any unsuspecting small lizard, frog, rodent, bat or bird stimulates the snake to strike.  As they live in trees they have to hold on to the prey so that the quick acting venom doesn’t result in it falling dead to the ground as a lost meal.  It is not always easy to find Eyelash Vipers so to have two in the first few minutes of the day out was something of a luxury, especially in color variations I had not seen before.


Why Eyelash Vipers?  Above each eye are two distinctive raised scales.  It is not known why they have these adornments but one theory suggests it helps keep vegetation scraping against the eye as the snake makes its way through its leafy environment.

The Poison Path

With that momentary distraction over Mike and I headed off down the trail.  In the section of path before you enter the forest you transect a Granuliferous Poison Arrow Frog, (Dendrobates granuliferus), communal territory.  Mike drew my attention to their sporadic calls, a high pitched cricket-like buzz, and it wasn’t long before he had located one.  This particular individual was rather nervous and kept disappearing under the dead leaves covering the fallen log upon which it was sitting.  The height was perfect for a photograph but every time I moved the camera it would disappear again.  When it finally did emerge into the open it was sitting with its body in half bright sun and half dark shade, the contrasting conditions of which made it hard to get a well exposed shot.  I took one but then it turned its back so I took another and then it jumped off the log and was gone.

Dendrobates granuliferus

The Poison Arrow Frogs are named after the toxic skin secretions that they possess and were widely thought to be used by the native peoples of Central and South America to coat darts and arrows which would then be fired into prey mammals such as monkeys.  You might expect that the toxins used by Poison Arrow Frogs would be fairly uniform in chemical composition and physiological effects.  Nothing could be further from the truth.  The toxins are as varied and complex as the number of species producing them.  So far over 100 different types of toxin have been identified from Poison Arrow Frogs.  Most are lipophilic alkaloids but some are neurotransmitter blockers.  Within a population of the same species the toxin can be weaker or stronger. Toxins acting as a neurotransmitter blocker affects the nerves to the diaphragm.  The diaphragm stops working, the prey asphyxiates and drops dead to the ground.  Truth to tell though, none of the Costa Rican Poison Arrow Frogs are that poisonous.  They are generically named after a Colombian Poison Arrow Frog, Phyllobates terribilis, which is a bright lemon yellow in color.  The native peoples of Colombia will not handle this species as the toxin can be absorbed through the skin.  Instead they pick the frogs up in a leaf which is held over a naked flame, stressing the unfortunate amphibian and causing it to release the toxin from the skin.

Granular Poison Arrow Frog

Interestingly the frogs diet is the key to its toxic abilities.  In the wild the frogs eat amongst other things, small ants.  If kept in captivity and denied a diet of ants the frogs no longer have toxic skin secretions.  There is much scientific study being carried out at the moment to discover why this is.  It is not entirely certain whether the frogs directly sequester the toxins from the dietary prey or whether they metabolize the toxins from the digestion of certain species.

As opposed to many amphibians which are nocturnal, the Poison Arrow Frogs are diurnal.  A frog hopping around on the forest floor during the day is a pretty easy target.  That is why they have evolved those toxic skin secretions.  But there is no point having a toxic skin secretion if the predators don’t know about it, hence the bright spectrum of glowing colors exhibited by different species. Anything glowing on the forest floor is not inviting itself as a meal, it is warning potential predators to stay away.  The bright warning coloration is known as aposomatic coloration.  Each individual species is highly variable in its coloration.  The Granuliferus Poison Arrow Frogs at La Tarde are this beautiful dichromatic red and blue.

This frog also has another fascinating aspect to its natural history.  During reproduction the male and female sit on the forest floor facing in opposite directions.  The female spawns, the male then fertilizes the egg mass.  Once the tadpoles develop the female frog carries them on her back up into the tree tops where she deposits them in the water-filled centres of bromeliads.  The female then returns with a regularity to lay an unfertilized egg in each of the aqueous incubators which serves a food supplement for the developing tadpoles.

Bats Intent

With the photos captured it was time to leave the trail and head off down into the forested valley.  Carrying a loaded camera bag and tripod I gingerly followed Mike down the steeply descending muddy path.  It wasn’t long before his eagle eyes had spotted a couple bats roosting beneath a broad bent over leaf.  These were Common Tent-making Bats, (Uroderma bilobatum), of the family: Phyllostomidae or Tailless Fruit Bats and they were culpable for the state of the leaf.  The bats create the tents by ripping through the midrib of the leaf causing it to bend over.  Having done as much the result is to have created a refuge from both the elements and predators.  Any movement along the length of the leaf stalk is amplified towards the tip alerting the bats to the presence of a predator and off they fly.  As the family name suggests they are largely fruit eaters.  Quite often they will have two sets of roosts, day and night.  During the day it is not unusual to find up to 40 bats in a roost.  Early evening as the sun starts to set the bats leave the night roosts and head off to the night roosts.  Here they wait until it is dark and then they fly out in search of whatever small fruit is in season, generally figs.  The night roosts tend to be located no more than 100 meters from the fruiting trees.  Both fruit and nectar feeding bats generally have a reduced sense of echolocation but a heightened sense of sight and scent at night.  The bats don’t feed in the trees where the find the fruit, they carry it back to the night roosts in their mouths and then hold it between the wings while eating.  Just before the sun comes up they leave the night roosts and return to where they are going to be roosting during the day.

Tent-making Bats

The Tent-making Bats have two white lines down through the face.  If during the course of the day a predator on the ground should glance up, the white lines serve to break up the outline of a clump of bats and giving the effect of dappled light being passed through the leaf.  I tried not to disturb this pair of individuals and even though they knew I was there they obliged by remaining stationary while I took their picture.

Planted To The Spot

The descent became steeper and the mud became stickier.  The forest on either side of the path was quite dense and in some places there were thick stands of heliconias growing.  The animal biomass of a tropical rainforest may only be 0.02% which is another way of saying that just about all of the forest is vegetative tissue.  But strangely enough the plants are quite often overlooked.  A frequently heard comment is “I went for a walk in the woods today but I did not see anything”.  The plant life is far more diverse than the animal life.  The Neotropical forests are home to approximately 90,000 species of flowering plants.  The whole of the North American continent, the United States and Canada combined have less than 700 species of tree.  Costa Rica, the size of West Virginia has 2,600 species of tree.  The Osa Peninsula, this tiny piece of land on the South West coast of Costa Rica has 800 species of tree, more than the whole of continental North America.

I do have a tendency to fall into the blinkered situation of only trying to photograph the wildlife and not the wild vegetation.  One of the reasons is that plant identification is not always easy.  As there were two species of flowering heliconias here I thought it might be an idea to add them to my limited collection of plant images.

Heliconias are that archetypal tropical garden plant.  Although members of the family Heliconiaceae are pantropical in distribution, the majority of species belong in the New World.  Costa Rica boasts 43 species of Heliconia, 18 of which are found on the Osa Peninsula.  The leaves are both long and broad, they bear a resemblance to banana leaves. The flowers are the distinguishing feature.  For the most part they come in shades of red, orange or yellow.  These colors attract in hummingbirds, so the heliconias are hummingbird pollinated.  Many species of heliconias have different shaped flowers  and these correlate to the different types of hummingbird that feed from them.  The reason the hummingbirds come to the heliconia is to obtain a feed of nectar.  Hummingbirds require up to eight times their own bodyweight in nectar every day just to keep themselves flying.

Heliconius imbricata

The shape of the heliconia flower dictates the species of hummingbirds that can visit them.  Different species of hummingbirds have different shaped bills and when visiting a variety of heliconia species get pollen dusted on different parts of the bill.  Theoretically one species of hummingbird could therefore pollinate several species of heliconia.  Heliconias with long flowers will be visited by hummingbirds that have correspondingly longer bills such as the hermits.  The hermits are trapliners and during the course of the morning will visit several different patches of heliconia.  Heliconias with shorter flowers will attract hummingbirds with shorter bills.  These hummingbirds tend to be very aggressive and stay in one small area defending a patch of heliconias from all comers.

Each morning a new bract opens to reveal a fresh batch of flowers which will only last one day.  Nectar not only attracts hummingbirds but also bees. The bees have a tendency to bite through the base of the flower and rob the plant of its nectar supply without carrying out its part of the relationship in terms of pollination.  To avoid this situation, the heliconias produce their nectar first thing in the morning.  That is when the hummingbirds but not the bees are active.  Also the bract fills with water, drowning the base of the flower so keeping the bees out.  If the bees do persist, they have to spend a lot of time and energy munching their way through the tough fibrous bract to get to the food supply inside.

Heliconius irrasa

Both of the species of heliconia I was looking at here had totally different shaped flowers.  The short compact flowers are Heliconia imbricata.  This species secretes a lot of liquid into the bracts rather than have them fill with rainwater.  This liquid is acidic by nature and can support its own little ecosystem of creatures living within it.  The other heliconia with the much longer, fewer and seperated flowers is Heliconia irrasa.

Death To Trees

A little  way further down the path will have any visitor to La Tarde stop in his tracks and gaze in wonder at the sight in front of him.  Encompassing the trail while towering above it is one of the largest Matapalos on the peninsula.  It stands like a giant Triffid, so living, so organic, with its giant roots descending from a location seemingly hidden in the sky.

The Matapola is otherwise known as the Strangler Fig and along with their awesome aspect they have a fascinating life history.  The Matapalo is a fig tree of the family: Moraceae.  Like any other fig it produces a copious amount of fruit.  If anything, a monkey or a bird, should consume one of those fruits and defecate at the top of a tree, that is where the Matapalo seed will germinate.  So unlike most trees which germinate in the ground and grow up, the Matapalo germinates at the top and grows down.

Ficus zarazalensis

The first thing it does upon germination is send long thin roots which grow descend like wooden plumlines to the ground.  Within a short space of time they anchor and start to take up water and nutrients.  Once this situation has been established from the point of germination at the top of the tree, the Matapalo sends out more tendrils but this time up and above the host tree.  These produce leaf which subsequently shadow the host tree and inhibit its ability to photosynthesize.   This is where this particular species of Matapalo finishes its takeover.  Those roots that came to the ground divide and subdivide spreading the alien-like trees weight over a wider surface area.  This particular species is Ficus zarazalensis.  It is an endemic found nowhere else except the Osa Peninsular.

Other species of Matapalo send the roots down the host tree’s trunk.  Here they anastomose and fuse eventually forming a huge shell around the host tree.  The host tree can no longer grow and at the top can no longer photosynthesize.  It dies and decomposes which then provides a huge amount of nutrients for the rapidly growing Matapalo  which will eventually stand a massive but hollow tree in its own right. The name Matapalo comes from two Spanish words, matar – to kill and palo which is colloquial Spanish for a tree, so roughly translated Matapalo means “Tree Killer”.  They will take over and kill any other tree except for other Matapalos.  Matapalo seeds will not germinate on Matapalo bark, the exact inhibiting factor has not as yet been identified.

Raining Frogs

We continued our trek down the trail, our goal being the creek and whatever treasure it may hold.  On the path sitting atop a small pinnacle of soil Mike noticed a tiny rain frog.  This small individual was totally unconcerned by my presence as I lowered the camera  equipment down to his level, sitting patiently while I took a few shots.  At first sight I couldn’t make out which species it was, the markings bore no resemblance to any of the species of rain frog I had seen in the area.  However with closer scrutiny I could see it was a Rough-skinned Dirt Frog, (Craugastor rugosus).

Craugastor rugosus

The Rain Frogs are totally terrestrial, they don’t need to return to water to reproduce in the manner of so many other amphibians.  The male and female pair up in the leaf litter on the forest floor which is where the female will lay her eggs.  There are only about 20-30 large, (in comparison with the adult), yolk-filled eggs.  The whole process of development takes place within the egg, there is no free swimming tadpole stage.  After 7 or 8 weeks a tiny frog, an exact replica of the adult, emerges from the egg.

Rough-skinned Dirt Frog

Water World

We were almost at the bottom of the path now.  A few more steps and we were in the stream.  The last time I visited La Tarde I photographed some Water Anoles, (Norops aquaticus), that we don’t find at Bosque.  Unfortunately I was photographing under a waterfall in very dark, wet conditions that the photos didn’t turn out too well.  I wanted to correct that situation.

Walking along the creek we came to an overhang where Mike knew there was a good probability of finding the sought after lizards.  Sure enough within moments of arriving at an overhang he pointed one out sitting on a small outcrop, its form all but indistinct from the dark, damp rock wall.  I was faced with the same problem as last time, low light and water falling from above.  But with a little perseverance and an umbrella held overhead aided by the fact that the subject was quite happy not moving I managed to get the shots.

Norops aquaticus

There are seven species of anoles on the Osa Peninsula, five of which can be found at Bosque but as already mentioned not Norops aquaticus.  Given the amount of water and perfect habitat conditions that is surprising but just as with localized populations of the poison arrow frogs that is probably the same situation with the anoles.  Norops aquaticus, apart from its obvious partiality for wet habitats, is easily distinguished from other anoles by the broad brown transverse bands across its body and a  pale band running along  the length of its body on either side.

The anoles were not the only creatures inhabiting this dark dank area.  On the dripping wall, facing head down was a large spider.  This was one a water spiders of the genus: Trechalea.  The body of a water spider is covered in water resistant hairs which not only keep them dry but also allow them to walk over the surface of the water. As might be expected the water spiders don’t make a web, they have a very specific way of hunting depending on species.

Trechalea sp

Some cling to the rock surfaces as this one was doing and catch prey passing by.  The spiders body is covered in various types of hair or setae which can be sensitive to odor, movement or touch.  Other species sit at the edge of the water anchored by the hind legs while the other legs are placed on the surface of the water.  Any prey item in the water causes vibrations which are recognized by the spider.  If it approaches too close the spider pounces and envenomates it.

A little further down the creek nestled into a drier nook, were a roost of bats.  Our activity initially spooked them and they flew off  but it did not take long before they returned and settled back into position.  They were in an even less convenient position to photograph than the anole or the spider.  They were hanging from the rock wall beneath the overhang, looking up into the falling water.  They still had not settled and nervously moving from one spot to another not so far away but far enough to have to reposition the camera.  Eventually I did manage to get a few shots.

Carollia sp

It is sometimes very difficult to identify bats to species level unless you have them in your hand.  Unless the bat has some very distinctive morphological features then quite often you need to be looking at the depth of greying down through the fur, counting warts on the lips and counting cusps on the teeth amongst other things.  As far as we could tell these were more Short-tailed Fruit Bats of Family: Phyllostomidae related to the tent-making bats we has seen earlier.  These were of a different Subfamily: Carollinae.  This is where the identification ends, as even if you have the bat in hand the four species that inhabit Costa Rica are notoriously difficult to tell apart.  All we can say is that they belong to the Genus: Carollia.  Just like the Tent-making Bats, these are for the most part fruit eaters.  But when fruit is out of season they are not adverse to feeding on insects too.

Short-tailed Fruit Bat

The time was getting on and we were getting hungry so it was time to return.  I had obtained that for which I had primarily returned but I can’t imagine it will be my last trip to La Tarde.  There are a host of other plants and creatures that I am sure are waiting to be discovered.

Driving back down the road there was one more stop we had to make.  There is another heliconia Mike has seen on the way up, another endemic plant to the area.  The flower was past its best but nonetheless it deserved a photo.  This species in Heliconia danielsiana. It prefers wet but open situations which is why it was growing at the side of the road and not in the forest.  It can be recognized by its rusty colored, hairy pendent inflorescence.

Heliconia danielsiana

If you visiting the area and have a desire to visit La Tarde, then you experience will be enhanced many fold by going with Mike Boston.  Take a look at his website and then contact him directly.




(00 506)  2735 5670


Galling Tales From Under a Tent   Leave a comment

Felipe del Bosque Blog February 20th 2012

Baked Earth

The weather conditions, as would be expected at this time of year, continue to be hot and dry.  There have been some nights with cloud and one brief sprinkling of rain but it would be a surprise if we ended up with any measurable precipitation.  The days are clear and sunny with the temperatures constantly in the upper 90’s.

The trails through the forests are now rock hard and starting to crack up as they lose moisture at deeper levels.

Return to Camp

The Puma sightings continue all around the grounds of Bosque.  Last week a group of four friends videoed the resident half-tailed female as she walked nonchalantly past their house.  Several days later another couple found a male Puma lying asleep on the Titi Trail.  It proved too much of a perfect subject and they obtained a really nice picture.  One of our staff was busy washing her hands early one morning when she saw a male Puma walk in front of her.  She followed it shoeless and hands covered in soap along a forest trail before it left the path and headed into the forest.  Two more guests were out on an early morning walk before leaving the lodge when they saw a Puma heading down on the trail towards the suspension bridge.

Over recent weeks, the Tent-making Bats, (Uroderma bilobatum), have been finding their way back under the leaves of some of the palms near the restaurant.  The bats used the leaves every night for the first eight years of my residence here but for the next four years used the same roosts less and less, eventually stopping altogether, only making occasional returns.

Tent-making Bats

One night while out on a Sunset Tour, we had a Kinkajou, (Poto flavus), walk across the path in front of us, go to the edge of the pond and start to drink.  It is very rare to see a Kinkajou on the ground but the exceedingly dry conditions must have forced this one from the trees to get a drink.  Kinkajous are nocturnal arboreal feeders on flowers but they may also take nectar, insects and lizards.  They have a very low muscle mass and so sometimes may seem emaciated.  As this one leant forward to drink, the specialized limbs which can rotate 180° could clearly be seen with rear toes facing backwards to hold the pond edge.


New Nests

The bird nesting season is well under way.  For several weeks now three pairs of Great Kiskadees have made nests around the restaurant garden area.  One of them is very obvious in the fork of a large Guanacaste tree.  In the forest there are several Scarlet Macaw, (Ara macaw), and Chestnut-mandibled Toucan, (Ramphastos swainsoni), nests.  The toucans and macaws are both cavity nesters that utilize holes in trees well above ground level but you can see them coming and going, disappearing inside the tree before emerging sometime later.  There is also a nest of a Purple-crowned Fairy Hummingbird, (Heliothryx barotti), sitting precariously on top of a leaf belonging to one of the broader leafed plants not too far from the restaurant.  At the moment it contains one jelly bean sized white egg.

There was a new first for me this week with the spotting of a Hook-billed Kite, (Chondrohierax uncinatus), during the course of a morning Primary Forest Tour on the Zapatero Trail.  I saw the bird fly through the trees and land on a branch some distance away.  These kites are normally found in forests near water feeding on lizards and snails.  We don’t have a high abundance of snails at Bosque but we certainly have many lizards.

One Year On

One of the Green Iguanas, (Iguana iguana), hatched last year has taken to sleeping nightly in some of the bushes by the pond.  It still sports the bright green coloration of a juvenile but is now twice the hatchling length.  We see the newly hatched iguanas around May and June but don’t often see the adults which tend to frequent the higher levels of trees.  The adults can reach 5 or 6 feet in length, are darker in color and the diet changes from insectivorous to more herbivorous with age.

Green Iguana

I have seen a few young Central American Smooth Geckoes, (Thecadactylus rapicauda), on the walls of several Bosque buildings.  Last week I also found the egg of a Mediterranean House Gecko, (Hemidactylus frenatus), in a tiny cavity low down in a Star Fruit Tree.

One night a young Boa Constrictor, (Boa constrictor), turned up, crossing the floor of the bar as the guests were eating in the restaurant.  Down by the pond the Cat-eyed Snakes, (Leptodeira septentrionalis), are still out but only two or three a night rather than the large numbers we find during the wet season when their main food source, frogs and frog eggs are available in abundance.

Boa constrictor

Cat-eyed Snake

This week on the Zapatero Trail we found a large Tropical Bird-eating Snake, (Pseustes poecilinotus), lying across the path.  As we approached it gave a display that nicely illustrates its other names; the Hissing or Puffing Snake.  It spreads its neck laterally giving itself a larger profile while at the same time expelling air through its glottis making a deep and intimidating hissing sound.  It is, in fact, a totally harmless but is inclined to bite and repeatedly so.

Tropical Bird-eating Snake

Wet Behind The Ears

Something stimulated the Smokey Jungle Frogs, (Leptodactylus savegei), into breeding action this week.  Two males could be heard calling in different locations.  The following evening, two females had joined the company of one of the males at the pond.

Smokey Jungle Frog

For several weeks a single male Banana Frog, (Dendropsophus ebreccatus), would emerge from the shade when the sun set and sit on top of the Water Hyacinth calling forlornly for a mate.  None came and one night the male disappeared.  The hungry Cat-eyed Snakes probably found him while patrolling the pond for froglets emerging from the water and he most likely ended up in one of their stomachs.

Banana Frog

Soft and Blurry

At the moment as you wander through primary forest, secondary forest, the gardens and the driveway, you will be surrounded by swirling masses of brightly colored wings as we reach the zenith of annual butterfly activity.

The most obvious of the butterflies are the Heliconiids or longwings.  They tend to be decked in bright gaudy colors and so are the most noticeable.  Many species can be found around the Lantana bush, a little way beyond the pond.  On the forest floor you will see some of the Satyrs or browns.  The commonest is Pierella luna, a medium sized and subtly marked butterfly that always remains close to the forest floor.  As soon as it settles, the color of the wings blend in with the background dead leaf litter and it disappears from view.  At the moment there is another brown butterfly to be seen on the Zapatero Trail, Antirrhea philoctetes.  It is not actually one of the Satyrs although it is similarly colored; it is one of the Morphinae which are well known for the spectacularly impressive Blue Morphos.

Pierella luna

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

 Galling Problem

One of the unusual things people sometimes see on the underside of leaves is small pointed fleshy projections.  These are galls and they are the result of a tiny wasp laying eggs in the plant tissue.  The wasp belongs to the Hymenopteran family Cynipidae.  There are many species of gall wasp and each one causes a different looking gall to be formed.  Even within one species of wasp, depending upon where the egg was laid, different parts of the plant can produce a different gall.  Even within the life history of the gall wasp, different generations at different times of the year can produce different looking galls.

Plant Gall

Gall wasps are so small that they are barely visible to the naked eye, you really need a hand lens to see them and in fact you are far more likely to see the galls and not the wasps.  The mechanism involved with the production of a gall is not fully understood.  The wasp lays an egg in the plant tissue; it is then possible that the wasp larva uses its saliva to cause a reaction in the undifferentiated plant cells resulting in a mass of tissue being deposited around the larva in the form of a cyst.

Plant Gall

The larva develops within the cyst to eventually emerge as a new adult.  The gall may not only house the gall wasp but a host of other small insects too including parasitic wasps of a different family and larvae of parasitic flies.

A Dose of Shingles

The forest is home to a myriad species of vines and their woody forms, lianas.  Vines and lianas have a different early life history to most plants.  When a seed germinates the young plant generally grows towards the light.  If a vine or liana was to grow towards the light, they would end up in a temporary sunfleck on the forest floor, have nowhere to go and so wither and die.  Vine and lianas initially grow towards darkness, a situation known as skototropism and it normally results in the vine growing towards the base of a tree.  When it makes contact there is a hormonal change that takes place and the vine now starts growing up towards the light.  So it has to find the platform before it can climb it.

Shingle Leaves

Many vines as they make their way up from the forest floor into the canopy they change their leaf form.  While growing along the forest floor, the stem may be leafless or have very small leaves.  At it starts to climb the tree the leaves remain small and overlap like a series of shingles.  This helps keep a constant humid microclimate close to the leaves.  The small overlapping leaves are probably all that a developing plant can support.

Philodendron sp

As the vine grows up the side of a tree, the shape of the leaf now changes.  It now becomes long stalked and has a large light gathering leaf surface.  Strangely enough it is not increased light levels that cause the leaf to change shape as the change will occur in the open where light is hitting the full length of the tree but rather the developmental age of the plant stem.

If you look carefully at lower levels of the tree trunks you will see the small overlapping shingle leaves tightly hugging the trunk.  Turn your gaze up and you will see the large leaves that you are probably more familiar with.

Text and Photographs are taken from the forthcoming book:

The Natural History of Bosque del Cabo by Philip Davison

Temperature and Rainfall

Average Daily Rainfall 0.00 ins.  Total Weekly Rainfall 0.00 ins

Average Daily Rainfall 0.00 mm.  Total Weekly Rainfall 0.00 mm

Species List for the Week


  • Howler Monkey
  • Spider Monkey
  • Tent-making Bats
  • Agouti
  • Red-tailed Squirrel


  • Red-lored Amazon
  • Scarlet Macaws
  • White-crowned Parrot
  • Hook-billed Kite
  • Mangrove Black Hawk
  • Roadside Hawk
  • Lineated Woodpecker
  • Blue-crowned Motmot
  • Black-hooded Antshrike
  • Chestnut-backed Antbird
  • Common Paureque
  • Short-billed Pigeon
  • White-tipped Dove
  • Blue-crowned Manakin
  • Red-capped Manakin
  • Chestnut-mandibled Toucan
  • Summer Tanager
  • Rufus Piha
  • Bright-rumped Atilla
  • Dusky Flycatcher
  • Great Kiskadee
  • Great Tinamou
  • House Wren
  • Black-throated Trogon
  • Black Vulture
  • Turkey Vulture


  • Barred Ameiva
  • Central American Whiptail
  • Five-lined Ameiva
  • Cat-eyed Snake
  • Clawless Gecko
  • Golfo Dulce Anolis
  • Tropical Bird-eating Snake


  • Banana Frog
  • Marine Toad
  • Red-eyed Green Tree Frog
  • Smokey Jungle Frog
  • Stejneger’s Dirt Frog


  • Agraulis vanillae
  • Anartia fatima
  • Anartia jatrophae
  • Antirrhea philoctetes
  • Autochton neis
  • Dryas iulia
  • Eueides lybia
  • Eurema daira
  • Glutophrissa drusilla
  • Heliconius erato
  • Heliconius hecale
  • Heliconius ismenius
  • Heliconius sapho
  • Heraclides cresphontes
  • Hermeuptychia hermes
  • Magneuptychia libye
  • Morpho helenor
  • Morpho Menelaus
  • Opsiphanes tamarindi
  • Parides erithalion
  • Philaetria dido
  • Pierella luna
  • Phoebis argante
  • Phoebis sennae
  • Pyrisitia nise
  • Pyrrhogyra crameri
  • Pyrrhogyra otolais
  • Quadrus cerialis
  • Urbanus simplicius
  • Urbanus tanna


  • Aphelandra golfodulcensis Flowering
  • Bamboo Orchid Flowering
  • Black Alligator Tree Flowering and Fruiting
  • Calabash flowering and fruiting
  • Cannonball Tree Flowering and Fruiting
  • Clusia rosea Flowering
  • Garlic Tree Flowering
  • Milky Tree Fruiting
  • Monkey Comb Tree Flowering and Fruiting
  • Mountain Rose Flowering
  • Ox Eye Vine Fruit
  • Passion Vine Flowering and Fruiting
  • Stinky Toe Fruiting


Flocking to a Disco Fight   2 comments

Felipe del Bosque Blog Sept 19th 2011

Something Strange

Not much change in the weather this week over last.  The days remain bright and sunny for the most part but with a small amount of rain falling just about every night.  It could well be that the wet season is going to bypass us completely this year or it is going to arrive with a vengeance later than usual.

Return of the Migrants

This is the time of year when all those birds that migrated north for the northern summer started to return back to their native lands for the southern summer.  Technically Costa Rica lies north of the equator and now we should be entering the winter, but here there are only two seasons wet and dry.  The worst of the wet season has yet to occur, but the temperatures remain pretty constant all year round, so even if it is not dry and sunny, it will almost certainly not be freezing either, which would be a terminal situation for most small tropical birds.

There tends to be a natural northern bias to migrating birds, people from northern latitudes regard them as their birds flying south to escape the winter whereas most of the birds migrating are from tropical bird families that have migrated north for the summer.

Why would a tropical bird leave these conditions and fly north.  The reason would be with regard to food availability for growing chicks.  The 21st of September is the vernal equinox when the earth’s position around the sun is at that point where all points on the globe receive 12 hours of daylight and 12 hours of night.  With Costa Rica lying so close to the equator, this situation does not change much over the course of the year, the longest day and the shortest day differing by approximately 45 minutes.

When the birds fly north, they now have summers where the day length is much longer, particularly the further north you fly.  This provides extended foraging time for food, which for growing chicks involves the consumption of a lot of protein, particularly in the form of insects.  Northern summers provide this huge boost in a food source in a way that the tropics don’t.  So in essence you have more available food and longer hours in which to find it.

Now the chicks have fledged it is time to return home to the tropics.  Over the past week I have seen Yellow Warblers, Prothonotary Warblers, Black and White Warblers and Mourning Warblers all in the garden areas in front of the Bosque del Cabo restaurant.

Flyweight Fight

On one afternoon stroll around the grounds I heard the sounds of an avian altercation accompanied by the frenzied buzzing of wings somewhere in a thicket off to the side of the garden.  Upon closer scrutiny I could see a Rufus-tailed Hummingbird, (Amazilia tzacatl), attempting to encourage a larger Violet-crowned Woodnymph, (Thalurania colombica), to remove itself from the area.  The subject of this dispute was a patch of Heliconias in bloom.

Heliconia sp    Heliconia sp    Heliconia sp

Heliconias are essentially a family of plants from the American tropics.  Their flowers come in variety of shapes and sizes but whatever form the blooms take, they are all colored in multifarious shades of red, orange, or yellow, colors attractive to hummingbirds.  Due to the different species of Heliconia having different shaped flowers, as the hummingbirds visit them, it results in pollen being dusted on different parts of the bird’s anatomy.  So in theory, one species of hummingbird could potentially pollinate a variety of Heliconia species.

Heliconia sp    Heliconia sp    Heliconia sp

Hummingbirds need to feed on approximately 8 times their own bodyweight everyday just to keep themselves flying, so once they find a productive food source they don’t give it up.  Rufus-tailed Hummingbirds, despite their diminutive size are very pugnacious little birds.  They will take on, challenge and expel any interlopers into their territory with gusto.

Heliconia sp    Heliconia sp

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

Rolling the Disc’s

Costa Rica is a very special little country in many respects, not one of the least is its bat diversity.  It may only encompass .03% of the land surface of the earth, but it hosts 12% of the planet’s bat species.

Around the grounds of Bosque, if you look closely, and in the right places, you will come across several different species of bat.  The Common Tent-making Bats, (Uroderma bilobatum), have their roosts under the large leafs of palms or bananas where they have ripped through the veins, causing the leaf to fold over.  These bats can be occasionally seen under various palm leaves close to the Bosque restaurant.  The continually change the location of the day roosts to avoid having their main predators, Tropical Bird-eating Snakes and Squirrel Monkeys being able to easily locate them.  They change their night roosts depending upon which of the trees are fruiting as they never forage too far from the nearest fruiting trees.

Common Tent-making Bats

Nectar feeding and fruit eating bats tend to attracted to musky smells rather than sweet smells.  Bananas are both bat pollinated and dispersed in the wild hence the flowers and fruit have that very musky smell.

On the Zapatero Trail and in small caves, both on the Pacific and Saino Trails, you may have the opportunity of seeing the White-lined Sac-Winged Bats, (Saccopteryx bilineata).  You will generally find a male with a harem of females in their typical repose of clinging head down to the sides of the tree or rock face but with the head distinctively held away.  You may be lucky enough to see the male fluttering up and down serenading his collection of female followers.

Spix's Disc-winged Bat

The third species of bat commonly found around the grounds of Bosque also uses plant leaves but this time the unfurled leaves of Heliconias, bananas and Calathea.  If you look down into one of these rolled up green cylinders, if the diameter and situation are suitable, you may see a small group of 2 or 3 Spix’s Disc-winged Bats, (Thyroptera tricolor).  The disc refers to the modified suckers on the wings which allow them to stick to the slippery inside of the leaf surface.  As opposed to other bats which roost head down, Spix’s Disc-winged Bats characteristically roost head up allowing them an easy flight up and away from danger should it threaten.

Spix's Disc-winged Bat

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 88°F.  Average Daily Temp Low 73°F.

Average Daily Rainfall 0.21 ins.  Total Weekly Rainfall 1.27 ins

Average Daily Temp High 30.8°C.  Average Daily Temp Low 22.8°C.

Average Daily Rainfall 5.3.  Total Weekly Rainfall 37.3 mm

Species List for the Week


  • Howler Monkey
  • Spider Monkey
  • White-faced Monkey
  • White-nosed Coati
  • Agouti
  • Red-tailed Squirrel
  • Spix’s Disc-winged Bats
  • Nine-banded Armadillo


  • Orange-chinned Parakeet
  • Red-lored Amazon
  • Scarlet Macaw
  • Great Currasow
  • Crested Caracara
  • Roadside Hawk
  • Yellow-headed Caracara
  • Golden-naped Woodpecker
  • Pale-billed Woodpecker
  • Black-hooded Antshrike
  • Chestnut-backed Antbird
  • Dot-winged Antwren
  • Short-billed Pigeon
  • White-tipped Dove
  • Long-tailed Hummingbird
  • Purple-crowned Fairy
  • Rufous-tailed Hummingbird
  • Stripe-throated Hermit
  • Violet-crowned Woodnymph
  • Chestnut-mandibled Toucan
  • Plain Xenops
  • Streak-headed Woodcreeper
  • Bright-rumped Atilla
  • Golden-crowned Spadebill
  • Great Kiskadee
  • Southern Beardless Tyrannulet
  • Tropical Kingbird
  • Masked Tityra
  • Rufous Piha
  • Bananaquit
  • Blue Dacnis
  • Cherrie’s Tanager
  • Golden-hooded Tanager
  • Gray-headed Tanager
  • Black and White Warbler
  • Mourning Warbler
  • Tennessee Warbler
  • House Wren
  • Riverside Wren
  • Great Tinamou
  • Black-throated Trogon
  • Black Vulture
  • Turkey Vulture


  • Barred Ameiva
  • Four-lined Ameiva
  • Golfo Dulce Anolis
  • Central American Smooth Gecko
  • Clawless Gecko
  • Mediterranean House Gecko
  • Brown Blunt-headed Snake
  • Cat-eyed Snake


  • Marine Toad
  • Parachuting Red-eyed Green Tree Frog
  • Red-eyed Green Tree Frog
  • Banana Frog
  • Masked Smilisca
  • Smokey Jungle Frog
  • Black and Green Poison Arrow Frog
  • Fitzinger’s Rain Frog
  • Tink Frog


  • Anartia fatima
  • Anartia jatropha
  • Glutophrissa Drusilla
  • Heliconius erato
  • Heliconius ismenius
  • Heliconius sapho
  • Heraclides cresphontes
  • Hermeuptychia hermes
  • Morpho menelaus
  • Opsiphanes tamarindi
  • Phoebis sennae


  • Bamboo Orchid Flowering
  • Black Alligator Tree Fruiting
  • Calabash flowering and fruiting
  • Cannonball Tree Flowering
  • Clusia Vine Fruiting
  • Dinner on a Plate Fruiting
  • Monkey Comb Tree Flowering
  • Candlestick Plant Flowering
  • Figs Fruiting
  • Golden Trumpet Vine Flowering
  • Hog Plum Fruiting
  • Jacaranda Flowers and Fruit
  • Ox Eye Vine Flowers
  • Protium Fruits
  • Santa Maria Flowering and Fruiting
  • Water Hyacinth Flowering
  • Yayito Fruiting
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