Red-eyed Tree Frog, or Red-eyed Leaf Frog. This female was photographed a long time ago at the OTS Finca La Selva Biological Station near Puerto Viejo de Sarapiqui in Costa Rica. As strikingly brilliant as it’s red eyes may be, vocally this is a most unimpressive frog–as it’s dry weak “cluck” sound confirms, you can’t have everything.

Frogs and toads hop, swim, crawl and climb across all continents except Antarctica. Their variety and diversity increases as you move from the colder regions towards the equator. It is the warm humid tropical forest realms that have the greatest number of species. Here, in this moist and near constant temperature, species have evolved and specialized over thousands of years. Frogs fill a variety of niches, nooks and crannies, from typical pond and streams, the forest leaf litter, to the canopy.

Costa Rica lies squarely in the tropics, at a crossroads connecting North and South America. This “rich coast” country, is bordered to the east by the warm Caribbean, and the Atlantic Ocean, and to the west by the Pacific Ocean. In between these coasts, lie lowland jungles, mountain forest draped in mosses, alpine tundra, and dry forest–and all adorned with anurans (frogs and toads that is).

Costa Rica hosts 133 species of frogs and toads placed into 8 families. Frogs and toads together form the Order Anura. This is where the term anurans comes from, just another way of saying those amphibians without tails, the “frogs and toads”. The Costa Rican Anurans are a very diverse lot, including dazzlingly gaudy poison dart frogs, and nearly invisibly camouflaged eleutherodactylid litter frogs. Their numbers include the pinky-nail sized froglets, to the fist-sized Smoky Jungle Frog, and behemoth (larger than fist-sized) Marine Toad,. There are short legged ground dwellers, strong-legged pond hoppers, and suction-cupped equipped long-limbed leaf-climbers, all finding food, trying not to be food, and seeing that enough of their frog eggs make it to adult frogs, to survive in a dynamic world.

Peeping, croaking, barking, whistling, rattling, and trilling are a few of the descriptions of frogs calling. Why do frogs call? The quick answer is to attract a mate, and to defend a territory (at least that’s why birds do). Many frogs call infrequently or not at all outside of the breeding season. In an evergreen rainforest environment, breeding occurs when sufficient rain has filled temporary breeding ponds and pools. Such temporary breeding areas will at times explode into a cacophony of several species of frogs all calling and competing for mates. This in turn attract still more frogs to the chorus, as well as frog predators.

The fact that so many frogs are nocturnal–that they operate under the cover of darkness, and that their predominant colorings are greens, browns, tans, and banded or blotched with darker tones, just yells or rather whispers “cryptic, camouflage and stealth”. Yet when it is the breeding season–they grab a megaphone, and turn it up to max and yell, “Hey, Hey, Over Here”, and yell they do with all of of their might, over and over again. OK, Megaphone–no, but an amplifying device called a vocal sac yes.. We’ve all seen the images of the frog with the inflated vocal sac under the chin. The male frogs inflate this sac, and then pushes air through vocal slits in the throat, causing vibrations. These vibrations then resonate in this pressurized air-filled sac or membrane. The point is, that frogs that often act more like army men on a mission than show-off poison-dart frogs, are now making a lot of noise, and in doing so they are putting themselves at great risk. They do this for the survival of their genes, and their species. Apparently, there’s no frog future without pond side peril in the form of pursuing predators in the present. So they squeak, chur, chip chirp and growl for all they are worth. And to a sound recordist, their calls and utterances, place them amongst the most worthy.


The Costa Rican toads include two fairly obvious groups; the true toads in the genus Bufo, and the harlequin frogs in the genus Atelopus.

Few examples of a crisis and conservation concerns are as poingent, or dire as that of the toads in Costa Rica.

Of the 14 species of toads listed for this small republic, 4 or more of them are already thought to be extint, or nearly so. The most famous of these lost amphibians is the Golden Toad (Bufo periglenes). While this once spectacular explosive breeder would show up at breeding pools with the rains annually in the Cordillera de Tilaran in the Monteverde Cloud Forest Preserve, they have not been seen since 1987. A Google image search still yields close to 5000 results for “Golden Toad”. The species lived recently enough to be relatively well photographed, but it is now extant, only in memory, and as specimens and jpegs.

Marine Toad (Bufo marinus)–above. One of the 14 species of toads found in Costa Rica. This one is in the family subfamily Bufoninae, a Bufo or “true toad”. Note the classic warty skin, and the swollen bumps behind the eyes. Bufos produce toxins to make themselves unpalatable to things that would eat them.
Bufo sp. another of the “true toads”
(Atelopus zeteki) is an example of a harlequin frog. These harlequin “frogs” and the toads in the genus Bufo are members of the toad family Bufonidae. The species above, the Panama Golden Frog is found in neighboring Panama. The Costa Rican Atelopus species included several abundant or very common examples. Most of of these species suffered dramatic population declines in the late 1980s and early 1990s, and are now locally extinct.

Glass Frogs

Small frogs mostly 2 to 3 centimeters in length, usually green, with their eyes pointed forward. These frogs are usually found near streams, holding on to leaves. They lay their eggs on the leaves that overhang the water and the adult frogs will protect the egg masses. When the tadpoles are ready to hatch they fall to the stream coinciding with rains, perhaps to conceal their entrance into the water.

Glass frogs have transparent skin on their bellies through which you can see their digestive track, and their hearts may be seen beating. This transparency gives them the name “glass frogs”. So much to say about so little a critter. Glass frogs have green bones, yet another amazing adaptation, in acheiving enough concealment to survive against the many specialized predators with which they share the forests of Central and South America.

We share a world with amazing creatures, great and small. Many of such, are easily overlooked, and at time even invisible to the determined observer. There will soon come a time when such small marvels are even more difficult to observe, as with age hearing wanes and falters. The high frequencies disappear first, and it is in these registers, that the glass frogs call, with short, sharp chips. How I would know that glass frogs were about was by listening.. and now, or soon, I’ll be left just hoping that they are still there, hanging from the leaves, adhering to the surfaces as they dangle over streams, guarding their clear, jewel-like eggs.

To me their translucent green and often speckled skin on the topside only further cements the name and notion of glass frog.



(Cochranella albomaculata) Yellow-flecked Glassfrog photographed near the Los Patos Field Station, Corcovado National Park, Puntarenas Province, Costa Rica (Note the green bones)

Links: Centrolenidae (Glass frogs) 

The mp3 sound file which is supposed to play when this page loads, includes a sea of nocturnal insects, and the sharp, short, high-pitched metalic sounds of the species pictured above. They were calling from rainforest along a creek at night.

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Poison-dart Frogs
This group of frogs owe their name to the fact that several species of South American Dendrobatids have been used by Amerindians to coat the tips of their blow darts and or arrows, with the toxic secretions from these frog’s skin. Have a blow dart, or an arrow? Do you need to make it more lethal, or give it more stopping power? One answer was to find a special brightly colored frog, and to either rub the arrow tips on its back, or to cook, or sweat the poison out of it, and capture the toxic liquids that dripped off. Some frogs are so toxic, that you should not even handle them with uncovered hands. This is not so much the case with the 8 Dendrobatid that occur in Costa Rica. However the uses and treatments of such amazing creatures underscores their evolutionary path.

These are frogs that are active during the day, they are for the most part, brilliantly colored or at least adorned with bold stripes. This to would-be frog-eaters is should be an obvious message “eat me, and you will be sick, or worst than sick”

Polar opposite to camouflage, this is aposematic coloration, or warning coloration, as is the yellow and black of bees, and the bright banding on a coral snake. The toxic secretions of these frogs is dependent upon diet. Captive raised poison-dart frogs which are not fed ants,do not develop the toxins necessary to back up the threat,which has led to their niche, that of a slow diurnal insectivorous amphibean.–one that can look pretty, and sing proudly in the light of day, or at least where some of it might penetrate the canopy.



Dendrobates pumilio the Strawberry poison-dart frog, or the Blue jeans poison-dart frog is a fairly common small frog of the forest floor, and lower level of the lowland Caribbean Rainforest. The sound which should load with this page, is insect-like, and while the piece provided here is just a snippet, it is not uncommon to hear several males singing from low perches, each with a song like this however lasting upwards of a minute.

Links: Dendrobatidae (Poison-dart frogs)

(Phyllobates lugubris)–above, is the striped poison dart frog of the Caribbean lowlands and foothills. The trilled call of this species is heard low near the forest floor. This individual was heard, photographed and sound recorded at OTS Finca La Selva. The voice of (P. lugubris) has a plaintive ringing quality.

(Phyllobates vittats)–left, is the striped poison-dart frog of the Pacific lowland rainforest in Costa Rica. The vocalizations of frogs are used to advertise the presence of a male. Male frogs want to both attract a mate, and protect a territory, or a space within their habitat.

The male (P. vittatus) to the left has actually been drawn to the top of this rotting log in Corcovado N.P. by playing back a recording of its own song. Male poison-dart frogs are very territorial, and aggressive towards tresspassers.

If you are standing and playing a recording in their territory, you may end up with poison-dart frog on the toes of your rubber boots.

The original photo included part of the tape recording equipment. The recorder was being played on the log–and “presto-dendro-batid”

(Dendrobates granuliferus) -right, photgraphed in Corcovado National Park, Costa Rica, lowlands near the Sirena Field Station. The Pacific rainforest counterpart to the much better known, and more often photographed (Dendrobates pumilio) of the Caribbean versant.

(Dendrobates auratus)-left, the black and green poison-dart frog, is found on the southern Pacific rainforest of Costa Rica. Personally I’ve seen and photographed very few from near the Sirena Field Station in Corcovado N.P.

Though the individual photographed to the left is from a captive individual. This does seem to be one of the more common captive bred species.

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Tales of the tailless?
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Contact and Copyright



Tree Frogs
Tree frogs, or Leaf frogs–the family Hylidae, represent a large family of more than 800 species worldwide. Costa Rica’s 43 species of tree frogs accounts for one third of the republic’s frogs.

Their tree and leaf-climbing adaptations include large adhesive toe pads, long limbs, binocular vision, and impressive jumping ability. Some species spend their entire lives in the canopy. Others visit ponds and streams to breed, while some are found predominently on the forest floor. The most famous hylid in Costa Rica is no doubt the Red-eyed tree frog (Agalychnis callidryas) –see image on home page.



Tree frogs such as the (Smilisca baudinii) pictured above have wide, suction cup-like toe pads which aid them in climbling and holding on to leaf and limb surfaces (they do pretty well on glass as well). (Smilisca baudinii) has one of my all time favorite calls, a loud rapid series of deep honks.The quality of the sound has is like the honking from a clown’s horn.

Links: Tree Frogs



Leptodactylid Frogs
Leptodactylid frogs, sometimes refered to as Neotropical frogs, and rain frogs, are the frog family with the most representative species in Costa Rica. The 46 species listed account for a third of Costa Rica’s anuran diversity.

Many of these species are very cryptically colored, blending masterfully into the forest litter layer. Quite a few of them are refered to as litter frogs. These are many a little brown job, hopping toad-like, and hiding under the fallen and decaying leaves. Others as the Smoky jungle frog to the left, complete with mosquito, are more formidable. In the rain forests of Costa Rica there is not a bigger frog (though there is a bigger toad). This frog is both a sit and wait predator, which will station itself patiently until it’s prey gets just close enough, as well as an active predator, one that will approach a chorus of vocalizing frogs, and close in to make the kill. There was always something very cool about these frogs, I would sometimes think of them as the jaguar, of the frog world. The picture above is of a frog near it’s burrow.