"The amphibian chorus in the rain forest on El Yunque

is the most extraordinary I have heard.

As one stands at the Forester's Cabin, at about 1300 ft. altitude,

a roar of sound comes from the wooded ravine adjoining,

and from the slopes above, making a veritable Babel of frog notes."

    Karl Patterson Schmidt (1890-1957), herpetologist, describing the nocturnal sounds of the Puerto Rican rain forest in his

    Amphibians and Land Reptiles of Porto Rico, with a List of Those Reported from the Virgin Islands;

    Scientific Survey of Porto Rico and the Virgin Islands, New York Academy of Sciences.

Puerto Rican white-eyed frog, Eleutherodactylus portoricensis, male. El Yunque National Forest, north-eastern Puerto Rico.

    Traditionally, amphibians and non-avian reptiles have been lumped together by those who study and classify them. Maybe this convention began with the notion that all things that crawl or walk with their bellies close to the substrate had to be related. If you want to treat the issue from a strictly taxonomic standpoint there is little wrong with studying amphibians and reptiles together, if you so choose. As long, that is, as you bear in mind that amphibians and reptiles are not close relatives at all.

    At any rate, not even Carolus Linnaeus, the Swedish father of modern biological taxonomy and inventor of the binomial nomenclature in use today, was immune to emotional bias. He once "thanked God for not making too many of those foul-smelling, repulsive creatures."

    I most certainly differ from his unfair description of these lovely and fascinating organisms.

    Regardless of the feelings involved, it remains that placing amphibians and reptiles together because of the similarity of their appearances or lifestyles makes as much sense as doing the same with birds and bats, or sharks and fish. From a phylogenetic standpoint, it makes no sense at all.

The Denizens of the Shadows

CLASS AMPHIBIA

    Amphibians were the first chordates to invade terrestrial habitats in a permanent fashion, at least as adults. Back in the Devonian period, their ancestors (probably evolved from air-breathing, lobe-finned fishes) ventured unto land and established themselves there. Their success, as is still the case with modern species, was only partial since all amphibians must lay their eggs in water or, at the very least, in very humid microhabitats. (A few modern species species are ovoviviparous, their eggs hatching inside the mothers' bodies, which then give birth to the babies).

    The reason for this has to do with the structure of their eggs. Amphibians, like fish, are anamniotes. That is to say, their eggs lack a specialized membrane, the "amnion", which is effectively a sack of liquid protected from its outer space by yet another membrane, the shell. It is in the amnion in which the embryo develops, in the case of the more advanced amniotes. An amphibian egg that is not in water or in a sufficiently moist environment will quickly dehydrate and die. (For a description of the amniote egg, see the section "Chordates, Tetrapods, and Amniotes").

    All modern amphibians are included in the subclass Lissamphibia. The group seems to be monophyletic, that is, they evolved from an ancestor common to all. The three extant orders of amphibians are Anura (frogs and toads, although these two terms lack any real phylogenetic value), Caudata (salamanders and newts, though these again are terms that do not reflect a true separation), and Gymnophiona (caecilians, legless and almost blind amphibians, some of which possess calcite scales inside their skins).

    Among living chordates, amphibians are the only group that does not include any marine species. This ecological and biogeographic peculiarity is derived from two factors: their physiological inability, even as adults, to cope with high concentrations of salts in their blood, and the structure of their skin. All members of the class have highly permeable skins which, like their eggs, are particularly prone to loose water to their environment. Additionally, and unlike marine vertebrates like fish, whales, and sea birds, no amphibian has evolved specialized glands to excrete excess salts from the water they drink. So, if you would place a salamander in seawater, not only it would not be able drink it without poisoning itself with salt, but its skin would not prevent the internal fluids of the animal from escaping its body through osmosis. Since water moves from its higher concentration (inside the animal's body) in the direction of less concentration (the highly saline seawater) the amphibian would quickly dehydrate to death. In fact, the closest things to a marine amphibian are but a few species of toads, which adults and tadpoles can survive in slightly brackish water in mangrove swamps and littoral marshes.

A Puerto Rican whistling frog, Eleutherodactylus cochrane, adopts its water-saving posture in a dry night. It tucks its legs under itself to reduce the amount of area exposed to the air.

Toa Baja, north-eastern Puerto Rico.

A female Puerto Rican red-eyed frog, Eleutherodactylus antillensis, flattens itself against a moist rock to conserve water.

Guana Island, British Virgin Islands.

A juvenile Jamaica laughing frog, Osteopilus brunneus, flattens itself against the substrate in order to minimize water loss.

Barbecue Bottom road, north-central Jamaica.

A Cuban tree frog, Osteopilus septentrionalis, rests on a leaf during the day. Aside from its water-retention position, its turns

almost white to reflect as much sunlight as possible, thus avoiding excessive heat. From a population introduced in Puerto Rico.

    Most amphibians are rather small organisms. The smallest known is the Monte Iberia dwarf frog, Eleutherodactylus iberia, from Cuba. The largest is the Chinese giant salamander, Andrias davidianus, with a maximum length of 1.8 meters.

    There are to date about 6000 known extant species of amphibians. A number of them are in serious decline and some may well be already extinct. One cause seems to be an infection, of almost planetary distribution, of a fungal disease called chytridiomycosis. The pathogen seems to be endemic to Africa, and might have spread to many other areas of the World due to the exportation of African clawed frogs of the genus Xenopus. These frogs, when released knowingly or accidentally into the wild spread the fungus to native amphibian populations. Other factors include the severe habitat degradation of many parts of the World.

    By far, most amphibians are nocturnal, a habit which helps them conserve moisture in their bodies. And one group among them - the frogs - might have been the first vertebrates to have used aerial sound to communicate among themselves. They were the first owners of true voice.

The Hailers of the Darkness

ORDER ANURA: FROGS

    Of the extant amphibian orders only Anura is to be found in the West Indies. Members of the other two orders apparently could never cross the ocean barrier between the American continents and the Antilles. (However, it should be noted that a species of aquatic troglodyte salamander may have been been sighted in Cuba, but no specimens have been collected and described, as yet).

    Having evolved long ago from a salamander-like ancestor, frogs are the most successful order of their class. There are about 5250 species of frogs described to date. As adults, all frogs can be distinguished by their short bodies, posterior legs longer than the anterior ones and usually adapted for jumping, and the lack of a tail (hence the name from the Greek: "an-oura", "without a tail"). While most species are terrestrial, a good number of them are aquatic (some completely so), and many have taken to the trees. They may also have the distinction of being the first tetrapods to have produced true vocal sounds on planet Earth. Even today, their calls fill the nights of many regions of the World.

Amphibians were probably the first vertebrates to use aerial sound as a means of communication.

A male Puerto Rican white-eyed frog, Eleutherodactylus portoricensis, advertises itself in the night. El Yunque National Forest, north-eastern Puerto Rico.

    Of the order Salientia, six families are naturally found in the Caribbean islands: Bufonidae (typical toads, Peltophryne), Dendrobatidae (poison dart frogs and their kin, Colosthetus), Eleutherodactylidae (rainfrogs, Eleutherodactylus), Hylidae (treefrogs, Hyla, Hypsiboas, and Osteopilus), Leptodactylidae (ditch frogs, Leptodactylus), and Strabomantidae (related and similar to rainfrogs).

    Most genera have multiple species on many islands, especially Eleutherodactylus, which is found throughout the Caribbean. Indeed, frogs are the vertebrate group with the highest index of endemism at the species level (more than 99 percent) in the Antilles. With very few exceptions, all species are endemic to a single island or island bank, and even to a single geographic region (usually a mountain range or cavern system) within an island.

    While frogs are not good at crossing ocean barriers due to their permeable skins sensitive to saltwater, some have used anthropogenic means to disperse far and wide. In recent years, several species of Caribbean Eleutherodactylus and Osteopilus have reached the continental United States and Panama, and even as far as Hawaii, probably hitchhiking as adults or eggs in agricultural products.

Family Aromobatidae: Skunk Frogs and Their Kin

    Aromobatids were recently separated from their dendrobatid relatives (the often deadly "poison dart" frogs) but, unlike those others, do not sequester toxins from their prey in order to develop dangerous alkaloids on their skins. They are represented in the Antilles by a single species of a genus with an otherwise continental Neotropical distribution. Allobates chalcopis is endemic to the montane rain forests of Martinique, in the Lesser Antilles. The genus is widely spread in South America, and the fact that it is not found in the intervening islands between there and Martinique represents a biogeographical oddity. Perhaps the genus is (or was) found in those islands, and either has not been discovered in them as yet, or such populations became extinct.

    Most species of Allobates are small and terrestrial, living on the leaf litter of humid amd rain forests.

Family Bufonidae: Typical Toads

    This family is almost Cosmopolitan, naturally living in all continents except for the Antarctic and Australasian biogeographic regions. Although all bufonids are toothless, that does not prevent the from being voracious animals capable of ingesting any living prey that fit through their mouths.

    Bufonids are represented in this region by the genus Peltophryne, found in the Greater Antillean insular banks save for Jamaica's. All 12 Caribbean species are endemic to these islands and comprise a monophyletic assemblage. Eight are Cuban, three are Hispaniolan, and one is Puerto Rican. These frogs are not closely related to any other bufonids in the Americas. Some species, like P. gundlachi and P. taladai of the Cuban insular bank, and P. lemur of the Puerto Rican bank, are bizarre in shape, with prominent cephalic bony crests or protruding snouts.

    Interestingly, Peltophryne seems to be allied not to Neotropical toads (which would make sense from a strictly biogeographical standpoint) but to bufonids in Africa.

Southern crested toad, nominate race, Peltophryne guentheri guentheri, male. Matadero de Honduras, southern Dominican Republic, Hispaniola.

This Hispaniolan endemic is one of the several peculiar toads native to Cuba, Hispaniola, and Puerto Rico.

These are the only Caribbean islands with native bufonids.

(Photograph courtesy of Mr. Miguel Angel Landestoy).

Southern crested toad, nominate race, female. Near Cabral, south-western Dominican Republic, Hispaniola.

Puerto Rican toads, Peltophryne lemur, three calling males and two pairs in amplexus.  Guanica State Forest, south-western Puerto Rico.

This species is seldom seen, as it comes from aestivation only during and after torrential rains that form temporary ponds in which it breeds.

The species is precariously endangered due mostly to habitat disturbance within its limited range. It was formerly found in the Virgin Islands, as well.

Its call resembles a hen's clucks, and a distant chorus of them truly sounds like a chicken roost.

Its flattened, protruding, and upturned snout and its cranial crests help it excavate burrows in which it spends most of its time.

(First photograph courtesy of Mr. Mel Jose Rivera).

Odd couple: a Puerto Rican toad perches on top of an introduced giant toad (Bufo marinus), as both sing to attract mates.

Guanica State Forest, south-western Puerto Rico.

After metamorphosing, Puerto Rican toadlets swarm by the hundreds around the lagoons where they first hatch.
They spend a few days eating and accumulating fat reserves, before hiding - perhaps for months - until the next heavy downpour.
Guanica State Forest, south-western Puerto Rico.

Puerto Rican toad, juvenile male. Guanica State Forest, southwestern Puerto Rico.
  This juvenile male already shows the protruding snout and bony crests that allows it to dig into the ground to protect itself from droughts.

Puerto Rican toad, Peltoprhyne lemur. Arecibo, northern Puerto Rico.

The northern populations of the species might in fact represent a different taxon from those of the south.
(Photograph courtesy of Mr. Mel Jose Rivera).

Cuban spotted toad, Peltophryne taladai, male. Monte Iberia, Baracoa, south-eastern Cuba.

(Photograph courtesy of Dr. David Ortiz Martinez).

Eastern giant toad, Peltophryne peltacephala, male and a female. Guantanamo Naval Base, Guantanamo, south-eastern Cuba.

(Photographs courtesy of Mr. Joseph Burgess).

Eastern giant toad, Peltophryne peltacephala, male. El Yayal, Holguin Province, north-eastern Cuba.

(Photograph courtesy of Dr. Richard C. West).

    A few bufonids (and other organisms) in the Caribbean spend much of their time in hiding, coming into the open once or twice a year, or even only once every few years. The aforementioned Peltophryne lemur is one of such species. This and ecologically similar species make an appearance only after torrential rains associated with widespread tropical systems or cold fronts. During such times, they emerge by the hundreds or thousands and make their way to temporary ponds where they spend just a few days. Then they will call, quickly mate, eat voraciously, only to disappear again for a long period. The weather phenomena that trigger these reproductive episodes can be very unpredictable and, indeed, the toads seem to respond directly not so much to humidity but to sharp declines in atmospheric pressure, like those preceding tropical storms which pour many centimeters of rain in a few hours. This kind of very specific stimulus-response relationship on the part of the amphibians lessens the risk of their coming out to mate after a violent but otherwise very short-lived downpour that will not provide enough water for decent-sized ponds.

    The behavior seems to be related to the prevailing climate thousands of years ago, when the Antilles were much drier than they are today, as happened during the last ice age. Then, the toads had to adapt to very harsh conditions where water was a precious commodity, and a mistake in judging the right moment for mating would spell a waste of energy and almost certain death. Apparently, the eight to ten thousand years that have elapsed since the last glacial era have not been enough for the genetically-controlled behavior of the toads to "relax and enjoy" the present, much milder conditions.

Family Eleutherodactylidae: Rain Frogs

    This family of about 200 species is distinguished by several characteristics, one of which is the "T" shape of the last phalanxes of their digits. This usually have an adhesive pad that helps in climbing, although many terrestrial species have such greatly reduced. This American (mostly Neotropical) taxon is composed of several genera which relationships among themselves are uncertain. One of them, Eleutherodactylus, is the largest in the Caribbean region.

    Eleutherodactylus is the most widespread genus of frogs in the Caribbean, found in almost every insular bank large or small. They are divided into two main assemblages. An eastern Caribbean group is mainly arboreal and almost all species possess an external throat sack that amplifies the sounds of their calls. These are most often some variation of a whistle. Many species in this group, especially in Puerto Rico and the Lesser Antilles, are arboreal in habits. However, they are now widespread in the Caribbean, including western land masses like Cuba, but not the Cayman Islands, the Bahamas, and Jamaica. A western Caribbean group is found in the Bahamas, Cuba, Jamaica, Hispaniola, the Cayman Islands, and reaches east to the Virgin Islands (strangely, skipping Puerto Rico proper). Most species are terrestrial lack a vocal sack, and their calls consist mainly of chirps and low, raspy sounds.

    Some species in both groups depart from the norm, and have invaded habitats not usual for their clade, or behave more typical members of their group.

    None of these frogs has a tadpole stage, but instead all species of the genus lay their eggs on land. For this they choose humid microhabitats, like spaces under rocks and rotting vegetation, the axillae of bromeliad's leaves, and even lay them exposed on the leaves of rain forest plants as long as the atmospheric humidity is high enough. Most species exhibit parental care for the eggs, a rather unusual behavior among amphibians. However, it is the male which usually stays close to the eggs in order to protect them from predators - snails, birds, snakes, and even adults of their own species. Sometimes the caretaker of the eggs sits on them to transfer humidity directly from its body to the clutch. After hatching, the neonates are almost miniature replicas of the adults, albeit with tiny, vestigial tails that are quickly absorbed within a few hours. The babies remain in the nest for a few days, during which the adult will fiercely defend them against intruders.

    Antillean species range in size from the smallest amphibian in the World, the Cuban Eleutherodactylus iberia (which is challenged for that title by a South American frog) to rather large frogs like Eleutherodactylus zeus, also from Cuba, Eleutherodactlus inoptatus of Hispaniola, and Eleutherodactylus karlschmidti of Puerto Rico. Unfortunately, a number of these peculiar species seem to be declining, and some might already be extinct.

    In general terms, rainfrogs are medium to small - even tiny - in size, though a few species can be quite large. The majority of species are less than 10 centimeters in length, and some are the smallest amphibians alive today. Their common name makes allusion to the fact that many species call before and during rain, be it day or night. Like their diurnal ecological counterparts, the anoline lizards, they exploit a wide variety of structural niches, from the ground to the crowns of emergent trees in rain forests. Some species have adapted to inhabit holes in tree trunks, bromeliads, the leaf litter of forests, caverns and crevices, while others carry a semi-fossorial existence, burrowing under debris. Others have adapted secondarily to a semi-aquatic life in cold mountain streams of both the Greater and Lesser Antilles.

    Indeed, and in a manner similar to that of anoles, the diverse species of rainfrogs can be segregated into different ecomorphs. (See the section on Antillean anolines for an explanation of the concept of "ecomorph"). Unlike anoles, however, the genus has radiated much more unequally in each of the Antilles.

The photographs above show a series of Puerto Rican rainfrogs which live sympatrically in the eastern rain forests of the island. From left to right, they are:

Eleutherodactylus unicolor, E. whitmanae, E. brittoni, E. richmondi, E. locustus, E. antillensis, E. portoricensis, E. coqui, E. cochranae, E. gryllus, and E. hedriki.

Although similar in general appearance, they actually exhibit diverse morphological traits and behaviors, adapted to different microhabitats.

In fact, these species represent a continuum in vertical distribution, from the exclusively terrestrial E. unicolor, passing through

inhabitants of increasingly taller grasses and shrubbery, to the exclusively arboreal E. hedriki, which occupies the forest's canopy.

Notice the increase in the size of the toe pads, from left (terrestrial species) to right (arboreal species).

This spatial segregation allows for a multitude of species to coexist without excessive competition.

    Species that are highly specialized tend also to be the most easily recognizable at first glance, since their morphologies or colors are concurrently modified to fit their microhabitats and lifestyles. On the other hand, the most ecologically versatile species usually have a very generalized appearance and people not familiar with them find it very difficult to tell them apart from similar species.

    It is known that at least some rainfrogs, unlike most frogs, fertilize their eggs internally. In fact one species, the Puerto Rican golden frog, Eleutherodactylus jasperi, has the distinction of being the first frog ever discovered to be ovoviviparous. The babies hatch from their eggs while still inside the female, which then "gives birth" to them.

Male common Puerto Rican frogs, Eleutherodactylus coqui, guard the clutch of eggs laid by the female.

First photograph: El Verde Biological Station, north-eastern Puerto Rico.
Second photograph: El Yunque National Forest, north-eastern Puerto Rico.

The Puerto Rican wetland frog, Eleutherodactylus juanariveroi, lays small clutches of eggs on the leaves of plants in a swamp.
In the first photograph, the male hides from the camera in the axilla of a leaf. Notice two neonates in front of him (they are out of focus).
In spite of the occasional proximity of the adult male there is no parental care of the eggs and neonates in this species, a departure from the usual behavior in Caribbean eleutherodactylids.

Toa Baja, North-eastern Puerto Rico.

Eggs of a rainfrong, Eleutherodactylus sp. laid under a layer on moss on a tree trunk.
El Yunque National Forest, north-eastern Puerto Rico.

Eggs and embryos of Eleutherodactylus coqui laid inside a bromeliad.

El Yunque National Forest, north-eastern Puerto Rico.

The same batch of eggs shown above, a few days later. Tiny froglets are now beginning to hatch from the eggs.

A vestigial tail can be noticed pressed against the flank of this individual. It will disappear in a few hours.

A male Puerto Rican treehole frog, Eleutherodactylus hedriki, peeks from its lair in (where else) a hole in a tree.

A few moments later, after it retreated, disturbed by the light of the flash, a neonate emerged from the hole.

Some eggs can be barely visible behind it, and they belong to two different clutches, one of which had already hatched.

As with many Caribbean rainfrogs, it is the male that offers parental care to the babies.

El Verde Biological Station, north-eastern Puerto Rico.

    Rainfrogs' calls vary widely. They can be low grunts, loud barks, raspy screeches, metallic hammerings, telegraphic clicks, piercing whistles, insect-like chirps, bird-like warbles, drawn-out croaks, as well as eerie and beautifully melodious trills. A number of species lack a vocal sack, yet are capable of emitting calls, all the same. These are often raspy or grunt-like.

    Calls travel better through air and are more easily perceived when they are uttered from above ground-level. This phenomenon is clearly noticed in species that call from shrubs, trees, or rocky outcrops, like Eleutherodactylus cochranae, E. hedriki, and E. martinicensis. Terrestrial species like E. unicolor, E. richmondi, and E. lentus utter much simpler, often monosyllabic calls which do not carry far.

    The summertime nocturnal chorus of 13 species of rainfrogs in the El Yunque National Forest, Puerto Rico, together with that of insects, can be almost deafening. The cacophony of all the different amphibian calls is sometimes loud enough for you to have to yell to make yourself heard from only a short distance away. This could easily be the naturally noisiest region of the Caribbean, at night. Species that emit similar calls may vocalize at different times during the night, thus avoiding interspecific competition.

    The main centers of evolutionary radiation for Caribbean rainfrogs are the Greater Antilles. Each of the four insular banks have a multitude of taxa, and Hispaniolan and Cuban banks, in particular, are inhabited by tens of species each. The single richest region in terms of species is the mid-level slopes of the Massif the la Hotte mountain range, in Haiti, where as many as 19 species are found living sympatrically. Indeed, it is in the montane regions of the Caribbean where most species are found. The eleutherodactylid faunas of the Lesser Antilles and the Bahamas are simpler in structure, yet the first boast their own local endemics.

    Some species of rainfrogs are very versatile in an ecological sense, occupying a wide variety of habitats as long as humidity stays at a tolerable minimum. The Puerto Rican common and red-eyed frogs, the Hispaniolan giant and tuck-weep frogs, and the Lesser Antillean frog fall into this category of species. They can be found practically everywhere in their respective islands as long as the habitat is humid enough, and they even make wide use of man-made and disturbed habitats.

    An example of a generalist species is the common Puerto Rican frog, Eleutherodactylus coqui. This most abundant amphibian on that island is present in all but the driest areas, and might be the best studied member of its entire genus. Its vernacular name in the island, "coquí" (pronounced "ko-KEEH"), is an onomatopoeia of its disyllabic call. After nightfall, millions of individuals ascend up the tree trunks to the canopy of mesic and hydric forests to hunt for insects and to sing and mate. At dawn, instead of climbing down the same route, they throw themselves almost en masse from the canopy and into the void, extending their legs widely to slow their descent by a sort of parachuting, and landing with a wet, slapping noise on the leaves of the forest's undergrowth. The phenomenon, which lasts for a few minutes every morning, gives another nuance to the term "rainfrogs."

From the damp corners of gardens at sea level to the cool summits of the central highlands, the voice of the coqui is the voice of Puerto Rico.

A male common Puerto Rican frog, Eleutherodactylus coqui, emits its call from a shrub.

Ciales, central Puerto Rico.

A female common Puerto Rican frog perches high on a branch. The adhesive pads of its toes are clearly visible.

El Yunque National Forest, north-eastern Puerto Rico.

    The call of E. coqui, in particular, shows an interesting variation that so far seems to depend on altitude. The calls of populations found at or close to sea level are short in duration and high in pitch. On the other hand, populations that are found on the high mountains emit calls which are louder, longer in duration and lower in pitch. The animals of higher altitudes are also quite larger than their counterparts of the lowlands. It is not known, at the present time, if any of these differences are due to genetic differences between the two sets of populations or if, instead, they are mere morphological variations attributable solely to differences in humidity and temperature between the lowlands and the montane regions. Indeed, members of some populations in the western mountains are small and have calls similar to those of the lowlands.

    As it happens with some other members of this genus, female common coquis are capable of uttering calls. However, these are totally different from those of males. They are very low-pitched, slow, irregular, and grating. In fact, they are seldom heard, even if they may be emitted at any time of night or day. They seem to only serve as aggressive warnings against other individuals of either sex that attempt to invade their lairs.

    The common coqui must be one of the frogs with the widest range of color variations. From almost black to fiery orange, passing through many shades of gray, mauve, brown, and yellow, and with any combination of dorsomedian and dorsolateral stripes, spots, blotches, bands, and marmorations, several individuals placed together would look like members of different species.

Common Puerto Rican frogs, Eleutherodactylus coqui, females, showing a few of the numerous color variations within the species.

First four individuals: El Yunque National Forest, north-eastern Puerto Rico.

Next three: Carite State Forest, east-central Puerto Rico.

Last one: Guilarte State Forest, west-central Puerto Rico.

    In recent years, E. coqui has become infamous in some regions, like the Hawaiian islands, where it probably arrived in plant pots and bromeliads. I has spread widely there (the Hawaiian archipelago has no native amphibian fauna) and hordes of them reportedly annoy the local people when they sing loudly by windows and in gardens, at night.

    E. coqui comprises a superspecies with its two sisters, E. portoricensis in the Puerto Rican mainland, and E. schwartzi in the northern Virgin Islands.

    The Puerto Rican white-eyed frog, Eleutherodactylus portoricensis is sympatric E. coqui throughout its range in the mesic, mainly montane forests of Puerto Rico. The two species can be very difficult to tell apart by sight, since they share many of their color hues and patterns (although E. portoricensis is not as polychromatic). Called "white-eyed" for their chalky or silvery white upper irises, E. portoricensis may in fact lack that trait, sometimes. Taking into consideration their morphology, only by comparing the ridges on the upper snout ("canthi rostrali") can one tell them apart for certain. Such are more sharply defined and angular in E. portoricensis. Their calls, although similar, can however be immediately distinguished if one pays close attention to them. The call of the white-eyed frog is softer and less far-carrying, with the second note being of less duration than the first and without a rising inflexion (all these traits in opposition to those of the call of E. coqui).

    The third "coqui" is allopatric in relation to the other two. Eleutherodactylus schwartzi only inhabits the mesic forests of some of the larger northern Virgin Islands. Its call is very similar to that of the lowland form of E. coqui. On a geological time scale, this might be a very young species, evolved only after the fragmentation of the Puerto Rican insular bank at the end of the last planetary glacial period, between 8000 and 10000 years ago.

Puerto Rican red-eyed frog, Eleutherodactylus antillensis.
First photograph: male, Carolina, north-eastern Puerto Rico.
Second photograph: Rio Grande, north-eastern Puerto Rico.

This most abundant amphibian in Puerto Rico after the common coqui also has a basic two-part call, but much faster and hollower in quality,

a series of quick "ko-KEH", sometimes interjected by an aggressive warning to other males, "ko-KI-KI-KI-KI-KI...".

In the near presence of a female, the male will lower its voice, as if to entice its shy partner to come closer.

This species is also found in the northern Virgin Islands and has been introduced into Panama, Central America.

Tuck-weep frogs, Eleutherodactylus abbotti, male and female. Los Arrollos, south-western Dominican Republic, Hispaniola.

Its irregular call is often heard, even during the day, in many humid areas. It consists of a short series of "tucks" followed by a series of whispery "weees".

(Photographs courtesy or Mr. Marcos Rodriguez).

 

Southern pastel frog, Eleutherodactylus leoncei, male and two females.

First two photographs: Bahoruco Mountains, south-western Dominican Republic, Hispaniola.

Third photograph: Los Arrollos, south-western Dominican Republic, Hispaniola.

(Photographs courtesy of Mr. Marcos Rodriguez).

 

La Hotte frog, Eleutherodactylus bakeri. Pic Macaya National Park, south-western Haiti, Hispaniola.

(Photograph courtesy of Mr. Eladio M. Fernandez).

 

Hispaniolan cordillera frog, Eleutherodactylus patriciae. Valle Nuevo, Central Dominican Republic, Hispaniola.

Its call is a short, rising trill. (Courtesy of Mr. Marcos Rodriguez).

First two photographs: male. (Courtesy of Mr. Miguel Angel Landestoy).

Third photograph: female (Courtesy of Mr. Marcos Rodriguez).

 

Bahoruco hammer frog, Eleutherodactylus armstrongi. Bahoruco Mountains, southwestern Dominican Republic, Hispaniola.

(Photograph courtesy of Mr. Marcos Rodriguez).

 

Yellow split-toed frog, Eleutherdactylus flavescens.

First photograph: Samana, north-eastern Dominican Republic, Hispaniola. (Courtesy of Mr. Marcos Rodriguez).

Second photograph:  Los Haitises National Park, northern Dominican Republic, Hispaniola. (Courtesy of Dr. Richard E. Glor).

Puerto Rican melodious frog, Eleutherodactylus whitmanae, males. El Yunque National Forest, north-eastern Puerto Rico.

This tiny and visually unimpressive species has one of the most beautiful amphibian voices on Earth, consisting in a series of metallic whistles.

The call begins with one or two almost inaudible notes, then rises sharply before gradually descending in pitch and strength.

A chorus of them somewhat resembles wind chimes, as the utterance of one male elicits all those nearby to respond,

often creating a wave of calls that travels through the montane rain forest from one direction to another.

Many tourists mistake the calls for those of birds.

 

Hispaniolan montane frogs Eleutherodactylus montanus, males. Valle Nuevo, central Dominican Republic, Hispaniola.

First photograph: courtesy of Mr. Miguel Angel Landestoy.

Second photograph courtesy of Mr. Eladio M. Fernandez.

As the name implies, this is another species with a attractive  call.

 

Eleutherodactylus sp. Pic Macaya National Park, south-western Haiti, Hispaniola.

(Photograph courtesy of Mr. Eladio M. Fernandez).

 

Puerto Rican whistling frog, Eleutherodactylus cochranae, male. San Juan, north-eastern Puerto Rico.

Like the red-eyed frog, it is found in the northern Virgin Islands, as well. Its voice is a short, piercing whistle, sometimes followed by one or two "ticks".

It is a highly arboreal species usually found in bromeliads or within the axils of leaves.

 

Martinican frog, Eleutherodactylus martinicensis, male and female. Eggleston, south-central Dominica, Lesser Antilles.

Although the name seems to imply that it is endemic to Martinique, the species is actually found in several other Lesser Antillean islands.

Its call is a single, rising whistle, sometimes followed by a short series of clicks.

The call might be confused with that produced by E. johnstonei (below).

 

Lesser Antillean frogs, Eleutherodactylus johnstonei, three males and a female.

First photograph: Mount Hartman Bay, south-western Grenada, Lesser Antilles.

Other three photographs: Grand Etang National Park, central Grenada, Lesser Antilles.

Its call is a sharp double whistle, the second syllable being higher-pitched.

Occasionally, it utters a softer alarm call, suddenly shifting the pitch of the same.

This is a sort of "weed" species, in that it has invaded many islands outside its natural range with the unwitting help of man,

sometimes displacing native amphibians. Its true home island is believed to be Saint Lucia, Lesser Antilles.

 

Dominican frog, Eleutherodactylus amplinympha.

Syndicate Nature Trail, Syndicate, north-western Dominica, Lesser Antilles.

This is the only member of its genus endemic to that island, and largest in the Lesser Antilles.

It is a montane species  found at and over 600 meters of altitude, in highland rain and cloud forests.

 

    Some species of Eleutherodactylus have very narrow habitat requirements. For example, the Puerto Rican cave frog is a denizen of caverns, caves, and crevices. As can be expected, species that are very specialized in their habitat requirements are most vulnerable to human disturbance.

    Several habitat specialists are shown below.

    Some rainfrogs are extremely dependent on a specific habitat for their survival. The tiny Puerto Rican elfin frog only inhabits holes and crevices in the maze of mossy root tangles that covers the ground of the cool cloud forests of the Luquillo Mountains. It simply cannot live anywhere else, since its very peculiar microhabitat is scarce to non-existent in the rest of the island. Other species, like E. richmondi, are much more versatile in their ecological requirements but are nonetheless seriously threatened by habitat degradation. A number of populations have been extirpated in recent years, and the remaining are endangered.

Puerto Rican elfin frog, Eleutherodactylus unicolor, male. El Yunque National Forest, north-eastern Puerto Rico.

It lives only in the cloud forests of the Luquillo Mountain Range, and is the only exclusively terrestrial rainfrog in the insular bank.

An individual of this species could sit on an eye of the E. inoptatus shown lower down on this page, and with room to spare.

Although quite common in its restricted range, and even as it is very vocal, its microhabitat of

moss- and liverwort-covered root tangles on the forest's floor makes it next to impossible to observe.

Its peculiar and unmusical call, quite loud for the size of the animal, is a short trill composed of six or seven notes.

A chorus of them sounds like a group of insects.

Puerto Rican bronze frog, Eleutherodactylus richmondi. El Yunque National Forest, north-eastern Puerto Rico.

First three photographs: males. Last photograph: female.

Its voice is a "teck", uttered from the ground or a low bush. Occasionally, it utters a very short trill composed of two to four notes.

This last call is similar to that of its close relative, E. unicolor, (above).

The call is hardly noticeable above the din caused by other species, unless one is quite close to the animal.

Montane cricket frogs, Eleutherodactylus haitianus. Central Mountain Rage, Dominican Republic, Hispaniola.
Its voice is a sustained ticking.

(Photographs courtesy of Mr. Miguel Angel Landestoy).
(Audio courtesy of Mr. Marcos J. Rodriguez).

Mozart's frog, Eleutherodactylus amadeus, male. Pic Macaya National Park, south-western Haiti, Hispaniola.

(Photograph courtesy of Mr. Eladio M. Fernandez).

Virgin Islands yellow frogs, Eleutherodactylus lentus, male and female. Barrenspot, central Saint Croix, United States Virgin Islands.

This is one of only two amphibians which are endemic to the Virgin Islands.

It emits a soft call which is seldom heard. I managed to record its voice, though my fumbling thumb did not do a great job at it.
 

Red-rumped leaflitter frog, (northern race, Eleutherodactylus weinlandi chersonesodes). Los Haitises National Park, northern Dominican Republic, Hispaniola.

(Photograph courtesy of Mr. Eladio M. Fernandez).

Monan frog, Eleutherodactylus monensis, males. Mona Island.

(Photographs courtesy of Mr. Joseph Burgess).

Hispaniolan yellow-mottled frog, (nominate race, Eleutherodactylus pictissimus pictissimus). Bahoruco National Park, south-western Dominican Republic, Hispaniola.

La Selle red-legged frog, Eleutherodactylus furcyensis. Los Arrollos, south-western Dominican Republic, Hispaniola.

(Photograph courtesy of Mr. Marcos Rodriguez).

Macaya dusky frog, Eleutherodactylus ventrilineatus, male. Pic Macaya National Park, south-western Haiti, Hispaniola.

(Photograph courtesy of Mr. Eladio M. Fernandez).

Cuban flat-headed frog (nominate race, Eleutherodactylus planirostris planirostris), male. From a population introduced into Jamaica. Near Negril, western Jamaica.

Short-nosed green frog, Eleutherodactylus brevirostris, male. Pic Macaya National Park, south-western Haiti, Hispaniola.

(Photograph courtesy of Mr. Eladio M. Fernandez)..

Cuban groin-spot frog, (eastern race, Eleutherodactylus atkinsi orientalis). El Yunque de Baracoa, eastern Cuba.

(Photograph courtesy of Dr. David Ortiz Martinez.).

    A few large species in Hispaniola are mainly terrestrial. Inhabitants of the forest's lowest level, they call from the ground or from low bushes. One species, P. inoptatus is huge by the regular standards of Caribbean rain frogs.

Hispaniolan giant frog, Eleutherodactylus inoptatus, male. Bahoruco Mountain Range, south-western Dominican Republic, Hispaniola.

One of the the largest of its genus in the Antillean region, this handful of a frog is mainly terrestrial, but will occasionally call from trees and bushes.

It's low-pitched and grating croaks are a common sound throughout many mesic forests in its island.

Green spiny frog, Eleutherodactylus nortoni, female. Massif de la Hotte, south-western Haiti, Hispaniola.
(Photograph courtesy of Mr. Eladio M. Fernadez).

    Most Jamaican species of Eleutherodactylus are terrestrial. None have a well defined gular sack and, indeed, their calls tend to be raspy or "dry" by comparison to those of the Lesser Antillean and Puerto Rican insular banks.

    Several Jamaican species are shown below.

Jamaican forest frog, Eleutherodactylus gossei. Port Antonio, north-eastern Jamaica.

The call of this species is a series of soft whistles that accelerate before coming to an abrupt end.

The tiny Jamaican masked frog, Eleutherodactylus luteolus, male and female. Barbecue Bottom, north-central Jamaica.
The call of this species is a weak, low chirp.

Western yellow bellied frogs, Eleutherodactylus pantoni, male and female. Windsor, north-central Jamaica.

The call of the species is usually a hollow, two-note noise.

Eastern yellow-bellied frog, Eleutherodactylus pentasyringos, male. Port Antonio, north-eastern Jamaica.

Its call is longer than that of its sister species, E. pantoni.

Family Hylidae: Treefrogs

    True treefrogs (Hylidae) are naturally present in the Bahamas and the Greater Antilles save for Puerto Rico. All species except one belong to the endemic West Indian genus Osteopilus. The trait common to all of these species is that, in adults, the inner skin layers of the top of the head become ossified and fused to the skull. Some, like the Cuban and Bahamian O. septentrionalis and the Hispaniolan O. vastus, can be very large frogs. Some species have been introduced into areas outside their native ranges. The Cuban treefrog has been introduced into Puerto Rico, the Virgin Islands, and continental Florida, in the United States.

    The other genus present in the Antilles is Hypsiboas, widespread especially in the Neotropics, but with only one species here: the Hispaniolan green streamfrog, Hypsiboas heilprini.

    All West Indian hylids seem to be of South American origin, in spite of the fact the Mesoamerica is closer and is, thus, a more obvious source for these frogs in the region.

Hispaniolan green streamfrogs, Hypsiboas heilprini, males.

It's call is quite different from those of other Caribbean hylids.

First photograph: Yamasa, east-central Dominican Republic, Hispaniola. (Courtesy of Mr. Miguel Angel Landestoy).

Second photograph: Bahoruco Mountains, south-western Dominican Republic, Hispaniola. (Courtesy of Mr. Eladio M. Fernandez).

(Audio file courtesy of Mr. Jurgen Hoppe).

A recently metamorphosed tadpole of Hypsiboas heilprini, with its tail still visible.

Near Matadero de Honduras, southern Dominican Republic, Hispaniola.

(Photograph courtesy of Mr. Pedro Genaro Rodriguez).

    Several Caribbean hylid frogs produce skin secretions that act as an excellent deterrent toward predators. Such substances can produce a maddening itch on human hands (I should know).

    All Antillean members of this family lay their eggs in water and pass through the usual amphibian tadpole stage. Depending on the species, their tadpoles inhabit habitats ranging from fast mountain streams to stagnant temporary pools in the lowlands. Some species breed almost exclusively in bromeliads.

Tadpoles of Jamaican laughing frog, Osteopilus brunneus, developing in a bromeliad's water deposit.
Barbecue Bottom, north-western Jamaica.

The individual on the left is in a water-conservation position.

(Photograph courtesy of Mr. Pedro Genaro Rodriguez).

Osteopilus dominicensis, mating pair. El Manaclar, south-central Dominican Republic, Hispaniola.

(Photograph courtesy of Mr. Miguel Angel Landestoy).

The largest West Indian hylid: the Hispaniolan giant treefrog, Osteopilus vastus, female. Bahoruco Mountains, south-western Dominican Republic, Hispaniola.

(Photograph courtesy of Mr. Eladio M. Fernandez).

Disturbed from its water-conservation position, this individual exhibits the light coloration typical of daytime.

This reflects sunlight more easily, helping the animal to keep cool and avoid loosing precious moisture.

(Photographs courtesy of Mr. Karl Questel).

Cuban treefrogs. From populations introduced into Puerto Rico and the Virgin Islands.

First photograph: Cambalache State Forest, northern Puerto Rico.

Second photograph: Mount Sage, west-central Tortola, British Virgin Islands.

Hispaniolan yellow treefrog, Osteopilus pulchrilineatus. Yamasa, east-central Dominican Republic, Hispaniola.

(First photograph courtesy of Mr. Miguel Angel Landestoy).

(Second photograph courtesy of Mr. Eladio M. Fernandez).

Jamaican laughing frog, Osteopilus brunneus. Port Antonio, north-eastern Jamaica.

Its name derives from the quality of it calls.

Green bromeliad frog, Osteopilus wilderi. Barbecue Botton, north-central Jamaica.

Even the bones of the species are green, to better camouflage the animal against its background.

Its weak calls are emitted from the same bromeliads where it lives.

Jamaican snoring frog, Osteopilus crucialis, male. Windsor, north-central Jamaica.

This large species mimics the moss and lichen covered tree trunks and rock walls from where it often calls.

Family Leptodactylidae: Ditch Frogs

    Leptodactylids are a group of American frogs largely confined to the neotropics. They are represented in the region by the "ditch frogs" or "foam-nest frogs".

    These amphibians do not lay their eggs in open water. Instead, they excavate muddy hollows near the margins of slow-moving streams, ponds, and even small temporary pools. The eggs are deposited in them, together with a mucous secretion that froths up into a foam in which the eggs are suspended and kept humid and, apparently, free of pathogens due to a sort of natural antiseptic present in the mucus. After hatching, the tadpoles may spend several days in their foam nest before a heavy rain or a flood washes them out into open water. In some species, and during the development of the tadpoles, the females may lay additional, unfertilized eggs on which the larvae feed. As with the rainfrogs and their type of parental care (discussed below), this means of reproduction allows the newborns to avoid aquatic predators for as long as possible.

    The approximately 40 species of the genus are quite varied in size and color. In the Caribbean, ditch frogs are found in Hispaniola and Puerto Rico (L. albilabris), several of the Lesser Antilles (L. fallax and L. validus), and some islands in the Western Caribbean (L. insularum). Greater Antillean and Western Caribbean species derive from Central America, while those endemic to the Lesser Antilles are of South American origin.

    Perhaps the best-studied West Indian species is L. albilabris. It exhibits a peculiar geographic distribution between two different Greater Antillean Islands. While it is widespread in the Puerto Rican bank, it is restricted in the northern Dominican Republic to the Samana Bay. The unknown reason why it has not spread throughout such a huge island with abundant habitat presents a biogeographic puzzle. (It must be said that the seriously endangered, Lesser Antillean L. fallax, is also distributed among several banks).

    It has been discovered that the males of some species, like the Puerto Rican ditch frog, L. albilabris, communicate with other individuals not only by airborne sound, but through the use of seismic vibrations, as well. Every time a male utters its call, its vocal sack hits the ground or water under it, creating a small shockwave. Sound moves through solids and liquids faster than through air. Such vibrations are perceived by the frogs through the middle ear, and by combining data from air and ground waves, each individual precisely calculates distance between itself and the nearest individuals. In that way, males keep a safe distance from each other, avoiding overly strong competition for space and, thus, for food and mates.

    The acuteness of a Leptodactylus frog's inner ear is such that it can detect the stealthiest person walking toward it at a distance of several meters. Indeed, at least Leptodactylus albilabris can be infuriatingly difficult to capture by merely following its calls. Not only are these ventriloqual, but as the frog detects the collector from a distance it falls silent.

Family Strabomantidae

    This South American and Central American family has recently being separated from the similar eleutherodactylids. Indeed, they look very much alike, morphologically.

    Only one genus is found in the West Indies. Two species of Pristimantis are found in the insular banks of of Grenada and Saint Vincent, southernmost among the Antilles and very close to South America.

Saint Vincent's frogs, Pristimantis shrevei.

First photograph: male, Vermont Nature Reserve, south-western Saint Vincent, Saint Vincent and the Grenadines, Lesser Antilles.

Last two photographs: females, Mount Soufriere, northern Saint Vincent, Saint Vincent and the Grenadines, Lesser Antilles.

The call of this species is a low series of "ticks", difficult to hear until one is close to the animal.

(Audio file courtesy of Dr. Luis O. Nieves).