Archive for the ‘Small-headed Frog’ Tag

A New Season of Discovery   10 comments

Philip Davison. nature diaries. Osa Peninsula. 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. Amphibians. Osa Peninsula. Costa Rica.

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. Frogs

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. Wet Season.

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. Pond life.

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. Philip Davison

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. Costa Rica

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. Torrential Rain.

Parachuting Red-eyed Green Tree Frog (Agalychnis spurrelli)

Tink Frog. Frog chorus.

Tink Frog, (Diasporus diastema)

Gladiator Frog. Mud puddle nest

Gladiator Frog, (Hypsiboas rosenbergi).

Bolivian Frog. Foam nest.

Bolivian Frog, (Leptodactylus bolivianus)

Masked Tree Frog.

Masked Smilisca, (Smilisca phaeota)

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

The Trees Have Eyes   2 comments

Felipe del Bosque Blog August 5th 2013

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Don’t Be Fooled

This week has been something of a mixed bag as far as the weather goes.  We are well into the wet season now and as might be expected it has been raining a lot.  The earlier part of the week was quite pleasant with clear skies, bright sunny days and star filled cloudless skies at night.  It seemed as if we had entered that period known locally as the veranillo or little summer.  At this time of year there is a two week period where the rain stops and it dries up.  It is nice time to visit the Pacific coast of Costa Rica as there are not so many visitors as in the main holiday periods, the weather is conducive to exploration and all the vegetation is lush and green.  If this was the veranillo then it was short-lived because the rain came back.  The latter part of the week has experienced the normal weather pattern for this time of year with days overcast and the rain starting early evening then continuing through the night into the early morning.   Those are perfect conditions for wildlife watching and photography, not too hot to go out and no bright contrasting shadows.

Further into the week the rain became more persistent.  Sometimes it rained all day but with no more than a gentle drizzle followed by more heavy precipitation overnight.  Each day is different.  Some days the sun shines, some it doesn’t but whatever the weather, this is a rainforest, everything is adapted to living in constantly rainy conditions and so at least some wildlife of one sort or another should be guaranteed.

The latter part of the week dispelled the notion that we might still be in the veranillo.  There have been some violent thunderstorms producing spectacular light shows in the sky accompanied with a moderate amount of rain.  The good news is that the creeks are running with a substantial flow rate now after a period of being very dry.

Caught In The Act

It has been another eventful week as far as animal sightings go.  On several separate occasions a Puma, (Puma concolor), and Ocelot, (Leopardus pardalis), have been recorded by the trail cameras that have been set up on the Titi Trail.  This is a trail running through secondary growth.  When the ground is wet, which it tends to be for 7 months of the year, you can see quite readily the tracks of any passing animals.  Most tracks are distinctive enough to allow identification of the creature leaving them.

One day tracks from huge male Puma were found on the approach to the suspension bridge.  The cat then appears to have walked over the bridge as the tracks were readily visible in the mud straight off the lodge side of the bridge and were heading in the direction of the restaurant.  The Spider Monkeys, (Ateles geoffroyi), were most certainly aware of the predators presence as they gave off their loud and distinctive alarm call for a long time.  The tracks then left the main trail and headed off through the forest to the lookout point over the Gulf.  Finally they turned and headed down the Creek Trail to the platform of the zip-line and disappeared into the forest.  We know that the female Puma is around so this may have been a transient male searching for a mate.

Puma Print

Bosque has recently started a project whereby the animals can be seen and photographed without anyone needing to be present.  We have set up 2 trail cameras near both the entrance and exit to the Titi Trail.  The cameras have been placed looking down the trail so that if anything is either walking towards or away from the camera we should get a good 30 seconds of footage.  The cameras are motion sensitive and detect infra red.  They use passive infra red LEDs to illuminate the subject without producing any visible light or flash.

Over the past month the cameras have produced some very good photos and video of what is around and also when it is around and what it is doing.  The surprising discovery is just how often the Collared Peccaries, (Tayassu tajacu), are walking the trails.  There seem to be large herds that come back and forth.  It would appear at first that they don’t have a large territory but it may well be there are several distinct herds and unless they are somehow marked in a fashion that would allow their identity to be easy verified then we shall just have to enjoy the sight of them walking by.

One of the cameras has a resident Agouti, (Dasyprocta punctata), that seems to come out and mark the trail every hour so we can expect to get to see an endless number of videos featuring that particular individual.  But he could be living a charmed existence.  We have viewed several videos featuring Ocelots, both day and night, and we know there is a female Puma in the area, she just hasn’t been captured on our cameras yet.  She has, however, featured in a cameo role on a trail camera put up not too far from our own by a young boy from England who was staying at the lodge last weekend.

There have been a number of other animals passing by in greater or lesser numbers: White-nosed Coatis, (Nassua narica), White-lipped Peccary, (Tayassu pecari), Tamanduas, (Tamandua mexicana), Nine-banded Armadillos, (Dasypus novemcinctus), Red-tailed Squirrels, (Sciurus granatensis), Tayras, (Eira barbara), Pacas, (Agouti paca), Common Opossum, (Didelphis marsupialis), Striped Hog-nosed Skunk, (Conepatus semistriatus),  Great  Curassow, (Crax rubra), Great Tinamou, (Tinamus major).  But let’s not forget that this is just the activity on the ground in the vicinity of the cameras, there is also a whole load of other activity going on up and above this level in the trees.

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Quadruple Vision

It doesn’t take long once the sun has set to go out and find a great many creatures that have been hiding during the day.  My nightly excursions to the pond this week have been rewarded with sightings of Northern Raccoons, (Procyon lotor), Common Opossums and Nine-banded Armadillos.  While looking at these nocturnal mammals your flashlight may catch the diamond sparkles being reflected from the grass, from the plants, from the tree trunks, everywhere in fact.  Follow the sparkles in and you will be amazed to find it is your light being reflected back at you from the eyes of spiders.  Not only might that revelation be somewhat astounding but also the size of the spiders themselves which may be tiny.  Depending upon the angle at which you catch it, the eyeshine may be silver, blue, green or orange but with the spiders always a sparkle.

Have a care though because not all of the spiders are tiny.  Once the sun sets below the horizon, emerging from safe daytime refuges come the Wandering Spiders, (Cupiennius spp) to set up their positions on the leaf tops or stems.  The Wandering Spiders don’t build webs, they are ambush predators.  They sit and wait.  The legs are covered  in hairs of differing types each of which performs a specific function.  There are tactile hairs which are stiff and are sensitive to touch.  A similar hair, the trichobothrium is super sensitive to the slightest touch as well as eddies in air currents.  There are chemosensory hairs that detect changes is the molecular environment around them.  There are slit-like structures called sensillae near the joints of the legs.  These detect vibration and mechanical movement of the substrate.


Even though the spider has eight eyes they are not necessarily used for hunting but all that other highly receptive sensory apparatus ensures the spider knows whether there is predator or prey close by.  If it is the latter then it is generally goodbye.  I have seen the Wandering Spiders jump and take moths from the air, I have seen then jump on any small passing invertebrate and I have even seen then eating the Red-eyed Green Tree Frogs, (Agalychnis callidryas), at the pond.

Wandering Spiders are not dangerous, they will not kill you but they will give a nasty little ulcerated bite.  And they can jump so don’t get too close.  But if you leave them alone they won’t bother you.

Small Head and bulging Red Eyes.

The rains always bring out the frogs.  June, July and August is the best time to see frogs at Bosque as it is the main breeding season for many of the species to be found on the grounds.  Year by year there is a flux not only in the species to be found but also in the numbers of those species.  The Red-eyed Green Tree Frogs are present all year, every year but in much greater numbers in the wet season when their distinctive “chuck chuck” calls can be heard everywhere around the pond.  Their egg masses can be seen throughout the year too hanging as they do from the underside of leaves overhanging the water where the diligent female has placed them.

Over the past week there have been male Red-eyed Green Tree Frogs calling from every level of vegetation immediately next to or in the close vicinity of the pond.  The males set up their territories once the sun has set and then call to attract a mate.  The female which is much bigger than the male selects a partner for the evening depending on the quality of his call, the deeper the better.  The frogs pair up and visit the pond about 3 times over the course of the evening.  Each time the female absorbs a lot of water through her skin, fills her bladder and then they amplected couple make their way to a leaf overhanging the water.  The female lays a group of about fifty eggs which the male sitting on her back fertilizes as she expels them.


The eggs hang over the water for about a week until the tadpoles have developed enough to wriggle free and drop into the water where they have to complete the aquatic stage before metamorphose into froglets which leave the water and disappear into the vegetation before emerging some time later as adults.

The Small-headed Frog, (Dendropsophus microcephala), on the other hand may or may not be present each year.  Sometimes there are just one or two calling over the course of a season, last year there were none.  This year on the other hand they have arrived in huge numbers.  I was never sure in the years gone by whether they were being outcompeted by the more commonly seen and heard Banana Frog, (Dendropsophus ebraccatus), which are always here in reasonably large numbers.  This year though they haven’t appeared in such profusion as in years past.  I think it is time to start the frog counts again.


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 

Try Again

Several months ago there was a White-necked Jacobin Hummingbird, (Florisuga mellivora), that had nested right by the path on the Zapatero Trail.  The nest contained 2 eggs but one day both the eggs had disappeared and despite the fact the nest was intact the female was nowhere to be seen.  Then, a couple of weeks ago on a different part of the Zapatero Trail, there appeared another nest looking exactly the same and of the same species.  Although the two nest sites seemed somewhat removed, when looking at the map, the trail curves round at 180º so the second nest in actual fact lay very close to but just uphill of the first.  My guess would be that it is the same female.  She might have chosen a different location but not too far away based on the failure of the prior brood.


Every day as I walked the Zapatero Trail the female White-necked Jacobin would sit tight until I approached to passing.  She would then take off and wait for me to go further down the trail before returning to the nest.  As the chick grew progressively larger the female would spend less time on the nest.  The chick now filled the nest and one day as I got closer I could see the nest was empty so I hope on this occasion the chick had managed to take to the air and fly off.


There is a low success rate for breeding birds.  The forest is full of predators and parasites.  Certainly around the lodge if there is a nest containing either eggs or chicks it doesn’t take long for an individual of the species Tropical Bird-eating Snake, (Pseustes poecilonotus), to pay visit.  These snakes can reach well over 6 feet in length so can eat birds of most sizes here.  Quite often the birds have to raise 2 or 3 clutches a year to have 1 successful set of fledglings.

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 0.67 ins.  Total Weekly Rainfall 4.70 ins

Average Daily Rainfall 16.8 mm.  Total Weekly Rainfall 117.9 mm

Highest Daily Temp 84°F.  Lowest Daily Temp 74°F.

Highest Daily Temp 28.8°C.  Lowest Daily Temp 23.3°C.

Species List for the Week


  • Mantled Howler Monkey
  • Spider Monkey
  • White-faced Capuchin Monkey
  • Nine-banded Armadillo
  • Common Opossum
  • Common Tent-making Bat
  • Western Red Bat
  • Northern Raccoon
  • White-nosed Coati
  • Agouti
  • Red-tailed Squirrel
  • Collared Peccary


  • Mealy Amazon
  • Orange-chinned Parakeet
  • Red-lored Amazon
  • Scarlet Macaw
  • Great Curassow
  • Laughing Falcon
  • Pale-billed Woodpecker
  • Black-hooded Antshrike
  • Chestnut-backed Antbird
  • Short-billed Pigeon
  • Red-capped Manakin
  • Chestnut-mandibled Toucan
  • Golden-crowned Spadebill
  • Great Tinamou
  • Little Tinamou
  • Black-throated Trogon
  • Black Vulture
  • Turkey Vulture


  • Barred Ameiva
  • Cat-eyed Snake
  • Central American Smooth Gecko
  • Central American Whiptail
  • Common Anolis
  • Common Basilisk
  • Clawless Gecko
  • Four-lined Ameiva
  • Golfo Dulce Anolis
  • Green Iguana
  • Litter Skink
  • Mediterranean House Gecko


  • Banana Frog
  • Black and Green Poison Arrow Frog
  • Fitzinger’s Rain Frog
  • Golfo Dulce Poison Arrow Frog
  • Marine Toad
  • Milky Frog
  • Parachuting Red-eyed Green Tree Frog
  • Red-eyed Green Tree Frog
  • Rough-skinned Dirt Frog
  • Savage’s Thin-fingered Frog
  • Small-headed Frog
  • Tink Frog


  • Anartia Fatima
  • Anartia jatrophae
  • Colobura dirce
  • Dryas iulia
  • Heliconius erato
  • Heliconius ismenius
  • Heliconius sapho
  • Hermeuptychia hermes
  • Mesosemia zonalis
  • Morpho cypris
  • Morpho menelaus
  • Philaethria dido
  • Phoebis sennae
  • Pierella luna


  • Alamandra  cathartica Flowering
  • Alpinia purpurata Flowering
  • Apeiba tibourbou Fruiting
  • Arachis pintoi Flowering
  • Arundina graminifolia Flowering
  • Attalea rostrata Fruiting
  • Bauhinia variegata Flowering
  • Cascabella thevetia Flowering and Fruiting
  • Citrus spp  Fruiting
  • Clusia vallerii Fruiting
  • Cocos nucifera Flowering and Fruiting
  • Crestentia alata flowering and Fruiting
  • Costus speciosus Flowering
  • Dypsis lutescens Flowering and Fruiting
  • Etlingera elatior Flowering
  • Ficus insipida Fruiting
  • Heliconia chartacea Flowering
  • Heliconia latispatha Flowering
  • Heliconia pogonantha Flowering
  • Heliconia psittacorum Flowering
  • Heliconia rostrata Flowering
  • Hibiscus rosa-sinensis Flowering
  • Hymenaea coubaril Fruiting
  • Hymenocallis littoralis Flowering
  • Ixora coccinea Flowering
  • Lantana camara Flowering and Flowering
  • Lagerstroemia speciosa Fruiting
  • Morinda citrifolia Fruiting
  • Musa acuminate Flowering and Fruiting
  • Nephelium lappaceum Fruiting
  • Pachira quinata Flowering
  • Piper auritum Flowering and Fruiting
  • Piper nigrum Fruiting
  • Piper umbellatum Flowering and Fruiting
  • Pleiostachya pruinosa Flowering
  • Plumeria rubra Flowering
  • Stachytarpheta frantzii Flowering
  • Zammia sp Flowering



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