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Lungless and happy about it

It is rather amazing that a terrestrial animal as big as this Ringtail salamander (Bolitoglossa robusta) from Costa Rica can spend its entire life without taking a single breath and rely entirely on gas exchange through its skin.

It is rather amazing that a terrestrial animal as big as this Ringtail salamander (Bolitoglossa robusta) from Costa Rica can spend its entire life without taking a single breath and instead relies entirely on gas exchange through its skin.

Of all the organs in my body, the one that I would be most reluctant to part with (perhaps with the exception of my eyes) are the lungs. It seems that we need them more than anything else. True, we need all the other bits, but lungs seem particularly useful. Without them the brain stops working in a matter of minutes, the vascular system loses its main reason to exist, and the biochemical processes in pretty much every cell come to a grinding halt. Like the hideous inflatable Santa in front of my neighbor’s house, the complex edifice of the human body would immediately collapse if the air supply were to be shut off. It seems that if you are a land-dwelling vertebrate you better have lungs, or you are not going to last very long. And yet, defying common sense, there is a group of terrestrial animals that got rid of their lungs altogether, and in doing so have become widely successful, outcompeting their lunged relatives in both the number of species and their collective biomass. They are the lungless salamanders of the family Plethodontidae.

The Redback salamander (Plethodon cinereus), a small, unassuming animal common in the eastern United States, is a marvel of evolution, with physiology that makes our own appear laughably inefficient.

The Redback salamander (Plethodon cinereus), a small, unassuming animal, common in the eastern United States, is a marvel of evolution, with physiology that makes our own appears laughably inefficient.

I thought of them last month, when freakishly warm weather in Boston forced me to clean up the accumulation of dog poop from the front lawn, which in any other year the snow would have mercifully covered up until spring. The unseasonal warmth also woke up a multitude of creatures that should have been fast asleep, including a couple of Redback salamanders (Plethodon cinereus), which I found under a wooden plank in the garden. Despite the ice crystals glistening in the half-frozen soil, they were surprisingly agile. “Agile” is of course a relative term, especially when talking about an animal whose metabolism is entirely dependent on oxygen passively permeating the skin. Nearly 100% of the oxygen intake and excretion of the carbon dioxide takes place on the surface of the skin of these salamanders, with the throat (buccopahryngeal cavity) accounting for an additional, small proportion of the gas exchange (perhaps for this reason lungless salamanders still retain well-developed nostrils.) Clearly, animals that are incapable of taking active breaths, and thus accelerating or decelerating gas exchange at will, cannot be marathon runners, or runners of any kind. And somehow, by employing various degrees of toxicity and the ability to subsist on low-nutrition diet of springtails and mites, lungless salamanders have managed to become the dominant family of amphibians of the Western hemisphere. Nearly 400 species have already been described and new ones are being discovered every year in both the cool, temperate forests of North America, and in the rainforest canopy of the Neotropics. In some places their numbers are staggering. A recent analysis of the population of the Southern Redneck salamander (P. serratus) of the Ozark Highlands in Missouri put their numbers at 1.88 billion (!) individuals, with the biomass equivalent to that of most whitetail deer in that region – that’s 1,400,000 kg (3,086,471 lb) of amphibian flesh.

Among many adaptations to the arboreal lifestyle are the lungless salamanders' pad-like feet. Despite of the overall similarity, this foot shape has evolved independently in different species of the genus Bolitoglossa.

Among many adaptations to the arboreal lifestyle are the lungless salamanders’ pad-like feet. Despite the overall similarity, this foot shape has evolved independently in different species of the genus Bolitoglossa.

Although all members of the family Plethodontidae are entirely lungless, their ancestors were not. What prompted the loss is still a mystery, and two competing theories, neither particularly compelling, try to explain it. According to the older of the two, lungless salamanders originated from a lineage that inhabited cold, fast flowing and well-oxygenated streams of the Cretaceous Appalachia (lungless salamanders still dominate the amphibian fauna of that region). The loss of lungs made them less buoyant and thus more capable of maintaining their position at the bottom of the stream while hunting for prey. But some researchers pointed out the lack of geological evidence for cold, upland environments in the Mesozoic Appalachia. Instead, they argue, lungless salamanders come from oxygen-poor tropical waters, where highly humid terrestrial environment proved to be a better alternative. Once on land, dense vegetation exerted adaptive pressure to evolve small, narrow heads, which in turn prevented the animals from filling their lungs effectively, and leading to the reliance on respiration through the skin. If this sounds sketchy to you, you are not alone. Most herpetologists today lean towards the first explanation, with the added argument that the loss of lungs happened early on in the larval development of the aquatic ancestors of the plethodontids. But the truth is, nobody really knows.

The ability to use a prehensile tail, a rarity in the animal kingdom, is one of the most amazing characteristics of the large, arboreal Ringtail salamander (Bolitoglossa robusta) from Costa Rica.

The ability to use a prehensile tail, a rarity in the animal kingdom, is one of the most amazing characteristics of the large, arboreal Ringtail salamander (Bolitoglossa robusta) from Costa Rica.

What is not in question is the fact that lungless salamanders rule the forests of North, Central, and parts of South America. Larger species tend to be ground-dwelling, whereas smaller ones live high in the canopy. The arboreal salamanders have evolved a number of cool adaptations to such a lifestyle. The Central American genus Bolitoglossa is famous for its lack of distinct fingers. Instead, these salamanders have pad-like feet that help them move on smooth, wet surfaces of rainforest trees. And although feet in all species of Bolitoglossa look similar, they are the result of two very different evolutionary processes. In smaller species, such as the colorful (and toxic) B. mexicana, the digit-less foot is the result of paedomorphosis – a developmental mechanism during which juvenile characters are retained in adult, reproductive animals. In other words, they have baby feet, and they rely on simple surface adhesion to cling to leaves and branches.

Larger species, such as the Costa Rican B. robusta, also have pad-like feet, but underneath the webbing sit fully developed digits and a complex musculature. The central part of the foot can be lifted, thus creating suction, a mechanism similar to that used by marine cephalopods. But wait, there is more. In addition to having suction cups for feet, this salamander has a prehensile, chameleon-like tail, which it uses to save itself from falling off trees. When I first saw one of these animals a few years ago pull this trick high in the branches in Tapanti National Park, I thought I was hallucinating. And the similarity to chameleons does not end there – just like those reptiles, lungless salamanders sport a long, projectile tongue (in one species the tongue is 80% as long as the body, and salamanders are pretty long animals!) They can eject it with an amazing speed, a mere 117 ms, to catch fast moving prey. And this ballistic tongue projection is an order of magnitude more powerful than that of any muscle in any other living vertebrate species.

All this to say that the next time you find a small, curled up salamander under a rock, look at it with a little more respect. This ancient animal can pull off tricks that would put many Marvel Comics characters to shame. Without taking a breath. Ever.

Ringtail salamander (Bolitoglossa robusta) on a tree branch in Tapanti National Park, Costa Rica.

Ringtail salamander (Bolitoglossa robusta) on a tree branch in Tapanti National Park, Costa Rica.

A really cool sequence of a lungless salamander (Hydromantes) using its projectile tongue (BBC).

Uo, the rain caller

A portrait of uo, or the Mexican burrowing toad (Rhinophrynus dorsalis) from Belize.

A portrait of uo, or the Mexican burrowing toad (Rhinophrynus dorsalis) from Belize.

We climbed deeper into the cave, approaching a site of a Mayan ritual. Here – Abel, our half Mayan guide explained – in this pitch-black underground chamber in one of Belize’s countless limestone caves, ancient Mayans performed gruesome bloodletting rituals, slicing women’s tongues and men’s genitals to entice gods to relieve dry, parched fields with life-giving rains. He pointed to razor-thin slivers of obsidian laying among shards of broken clay pots. In the light of my headlamp I could see a few piles of ash that looked as if the fire went out only a few hours ago, but in fact they had burned hundreds, perhaps over a thousand years before I was born, and the complete lack of air movement, or any other disturbance, preserved them perfectly.

The blood rituals seemed to work, and rains came back every year. Why the Mayans thought that the gods would get a kick out of people injuring themselves is a mystery (I guess gods all over the world have similar tastes.) But, as it turns out, the Mayan self-mutilation might have been for nothing because another creature was already working on their behalf, calling to Chaac, the Mayan god of rain.

Resembling a small balloon, uo is surprisingly agile as it runs and hops on the forest floor.

Resembling a small balloon, uo is surprisingly agile as it runs and hops on the forest floor.

Uo, as the rain-calling animal is known among the Mayans, an onomatopoeic name based on its strange courtship song, is a frog. But it is difficult to tell by just looking at it as it is a frog like no other. When I saw it for the first time it took me a second to make sense of the fist-sized black and red balloon with short, stubby legs. It seemed that an animal like this could not possibly be able to walk, but in fact these frogs are remarkably agile and can even jump. But what it is really good at is digging.

The mouth of uo is very small and surrounded by cushion-like pads.

The mouth of uo is very small and surrounded by cushion-like pads.

Uo, or the Mexican burrowing toad (Rhinophrynus dorsalis), as it is known among herpetologists, is the only member of a relatively basal (“primitive”) family of amphibians, the Rhinophrynidae. Its closest living relatives are equally strange, strictly aquatic clawed frogs of South America and Africa (Pipidae). Rhinophrynus are found in low laying forests from the southernmost tip of Texas to Costa Rica. Among frogs they are unique in having their tongue attached to the back of the mouth the way we, mammals, do – in all other frogs the tongue is attached at the tip, and is flipped forward and upside-down when hunting.

Rarely seen on the surface of the ground, uo is a strictly fossorial frog, emerging only at the onset of torrential rains of the wet season.

Rarely seen on the surface of the ground, uo is a strictly fossorial frog, emerging only at the onset of torrential rains of the wet season.

Looking at the face of this animal it is difficult to see any resemblance to a typical frog. Uo’s mouth is tiny and surrounded by strange cushion-like pads. Electron microphotography revealed that every single cell around the mouth of the frog is armed with a keratinous spike, which likely protects the mouth when the frog pushes forward through the soil. Like most fossorial frogs, uo buries itself backward, using its short but powerful hind legs as shovels. It also inflates its body rhythmically as it goes deeper into the soil to widen and stabilize the sides of the burrow. But once fully dug in, the frog can move forward, pushing its snout towards termite and ant colonies, the source of its food. Apparently nobody has ever seen uo feeding, as it all happens underground, but it seems that it hunts by sliding the tongue along special grooves in its toothless mouth and swallows the prey – stinging ants and biting termites – alive and whole. To minimize the effect of the aggressive insects, the esophageal lining has leaflike projections that vastly accelerate food digestion.

Perhaps not the most graceful of frogs, uo’s morphology is perfectly adapted to fossorial lifestyle and hunting for social insects.

Perhaps not the most graceful of frogs, uo’s morphology is perfectly adapted to fossorial lifestyle and hunting for social insects.

When I was in Belize last week, teaching photography at BugShot, it was clear that the rain god Chaac had already heard the call of uo, and was very generously spilling his rain-filled gourds onto the earth. After a few days my black backpack turned moldy white, and my laptop flickered and died. Mosquitos seemed to target mostly the corners of my eyes and deposited several botfly larvae onto my skin, but seeing the amazing uo made it all worthwhile.

A male uo.

A male uo.

Sapo

A pair of Giant leaf frogs (Phyllomedusa bicolor) from Suriname, which I mistook for a four-eyed chimera.

A pair of Giant leaf frogs (Phyllomedusa bicolor) from Suriname, which I mistook for a four-eyed chimera.

It may seem counterintuitive, but many small, cryptic animals, those that blend perfectly into their environment, are much easier to find at night than during the day. Katydids, walking sticks, snakes – these animals usually spend their days absolutely still, but at night they feed and court, making their presence known through their movement. Others, including moths and spiders, can be spotted at nigh by their eyeshine, reflected in the light of a headlamp. Over the years I have learned how to recognize some of the animals by the color and size of the glow of their eyes. For example, small green eyeshine in the grass – lycosid spiders, large green in the savanna – antelopes (or cats), small orange in a tree – moths, large orange in the water – crocodiles etc. It goes without saying that the eyeshine always occurs in twos (even eight-eyed spiders display eyeshine only in their two largest eyes), or as single eyeshine, when the animal is not facing the viewer.

I was therefore quite confused when during a night walk in the rainforest of Suriname a few years ago I spotted four, large and brightly glowing orange eyes in a tree in a distance. They were moving in unison, clearly attached to one body, and by their diameter and spacing I figured that the animal had to be at least the size of a large rat. I had to find out what it was.

A female and a male of P. bicolor from southern Suriname.

A female and a male of P. bicolor from southern Suriname.

Of course, once I got closer and was able to put the spotlight on the entire animal, the truth turned out to be somewhat less exciting than a four-eyed chimera, but interesting nonetheless. The strange creature was a pair of Giant leaf frogs (Phyllomedusa bicolor) in amplexus – the male firmly gripping a much larger female – moving slowly towards a branch overhanging a stream, where the female clearly intended to lay her eggs. As their name implies, these frogs are huge. I am not absolutely sure, but I believe that they might be the largest tree frogs in the world, easily reaching the length of 5 inches or so. Like other members of the genus Phyllomedusa they spend their life in the trees, and lay egg clutches on leaves overhanging forest streams or other small bodies of water.

A clutch of freshly laid eggs of P. bicolor.

A clutch of freshly laid eggs of P. bicolor.

And indeed, in the morning I found a fresh clutch of eggs glued to leaves over the stream. The two animals were still hanging nearby, the female noticeably thinner than the night before. I took some photos of the pair, all along wondering if I should try to lick them. In the end the smaller, more responsible part of my brain prevailed, but to this day I am curious what would have happened.

The skin of Phyllomedusa bicolor (“Sapo”) is full of potent peptides, such as phyllocaerulin, phyllomedusin, and dermorphins, all of which have incredibly powerful effect on humans. On smaller animals, such as rodents, the effect is simple – it kills them. But to something the size of a man the same compounds are not lethal. Rather, after an initial, very unpleasant reaction that includes violent vomiting and passing out, you apparently wake up refreshed, much stronger, resistant to hunger and thirst, and with heightened senses and the ability to cope with stress. The Matsés Indians of Peru and Brazil have known that for a long time, and they routinely use the extract of the Sapo skin before hunting expeditions. Unfortunately, the delivery method of the extract does not sound very pleasant, to either the man or the beast – they first burn their own skin, then peel it off (!), and only then rub in the extract, which has been obtained by, essentially, torturing the poor frog for three days. (The entire process is described in excruciating detail in a paper by Erspamer et al. 1993. Toxicon 31: 1099-1111.)

Three species of Leaf frogs (Phyllomedusa) found in Suriname (from the left clockwise): P. vaillantii, P. tomopterna, and P. bicolor. These frogs are also known as monkey frogs, on the account of their grasping hands and the ability to run up vertical lianas.

Three species of Leaf frogs (Phyllomedusa) found in Suriname (from the left clockwise): P. vaillantii, P. tomopterna, and P. bicolor. These frogs are also known as monkey frogs, on the account of their grasping hands and the ability run up vertical lianas.

But helping people get high is not the only reason why Phyllomedusa frogs have evolved this amazing pharmacopeia. I did a quick search on MEDLINE and found 167 research papers on various compounds present in their skin, including both those that serve as predator repellents (e.g., alkaloids, quinones), and a vast array of antimicrobial, antifungal, antiviral, and even cancer-suppressing peptides. These may lead to the development of new treatments for assorted ailments afflicting the humankind, and hopefully means that sooner or later I will be able to experience the positive effects of the “sapo” without having to peel off my singed skin.

Tiger monkey frog (Phyllomedusa tomopterna) from Suriname.

Tiger monkey frog (Phyllomedusa tomopterna) from Suriname.

My crumbling beliefs

A posion arrow frog (Dendrobates pumilio) next to a timber fly (Pantophthalmus sp.) on a palm leaf at La Selva Biological Station, Costa Rica.

A poison arrow frog (Oophaga pumilio) next to a timber fly (Pantophthalmus sp.) on a palm leaf at La Selva Biological Station, Costa Rica.

I always assumed that there existed at least a few immutable truths about the natural world, dogmas that had no exceptions, no matter how hard you looked for them. One of them, I thought, was the rule that flies, which cartoons and children books made me believe were the favorite food of frogs, should be significantly smaller than the frogs. And I pretty much accepted this gospel, until one day I found in the rainforest of Costa Rica, sitting on a palm leaf, a frog and a fly. This singular sighting shattered my entire belief system, or at least the part that pertained to frogs and flies. Because you see, the fly was a timber fly, a member of the family Pantophthalmidae, which are the largest flies in the world, some reaching the wingspan of 100 mm. Next to one of these monsters an adult poison arrow frog looks almost like a dog next to a horse.

A female Pantophthalmus bellardii from Paloverde, Costa Rica; notice the partially retracted, telescopic ovipositor.

A female Pantophthalmus bellardii from Paloverde, Costa Rica; notice the partially retracted, telescopic ovipositor.

Timber flies are a small family, consisting of only 2 genera and 22 species, all found in the lowland rainforests of Central and South America. In addition to their unholy size they differ from other flies in that their larvae are wood burrowers, something that traditionally has been the domain of longhorns and other beetles. There are other flies that feed on wood (some Syrphidae and Asilidae), but those are incapable of drilling their own tunnels in the wood and can only use those already created by beetles or other insects.

Little is known about the behavior of adult timber flies. Nobody is really sure if they feed at this stage, and if so, on what. They have never been seen mating, although oviposition has been observed. Females have a long, telescopic ovipositor, which they use to deposit eggs in the cracks of dead and live wood, depending on the species. These insects are not common – in all my years in the tropics I have only seen them four times, but each time my faith in the unshakable laws of nature suffered a bit more. What’s next, a land arthropod as big as a cat?

A portrait of Pantophthalmus cf. pictus from Guanacaste, Costa Rica.

A portrait of Pantophthalmus cf. pictus from Guanacaste, Costa Rica.

A female Pantophthalmus bellardii.

A female Pantophthalmus bellardii.

The miracle of parallel evolution

Herpetologists, can you tell which is which? Left: Centrolenella spinosa from Costa Rica, right: Hyperolius cf. pusillus from Mozambique.

Herpetologists, can you tell which is which? Left: Centrolenella spinosa from Costa Rica, right: Hyperolius cf. pusillus from Mozambique.

I have been going through photos taken during a recent trip to Mozambique, and every now and then I am struck by the similarity of some of the African organisms to their counterparts on other continents. One of the best such examples is that of Neotropical glass frogs (Centrolenidae) and some African reed frogs (Hyperoliidae). Their resemblance to each other is uncanny – the two animals display a virtually identical, nearly translucent body, and only the shape of their toe pads reveals which is which. And yet these two lineages of frogs are separated by at least 150 million years of evolution, with many forms that look nothing like them in between, but ended up evolving the same, homologous morphology.*) These two groups differ quite significantly in their biology, however. The South and Central American glass frogs are forest animals, spending most of their life in the trees, often high in the rainforest canopy. They lay their eggs on the underside of leaves that hang over fast flowing streams. Males of these frogs often guard multiple egg clutches, until hatching tadpoles are washed off by rain into the stream below. The African “glass frogs”, members of the Hyperolius nasutus species complex and a few others, have a very different lifestyle, and are found in open, grassy areas of the southern part of the continent. They lay eggs underwater in big clumps attached to submerged plant stems, and exhibit no parental care.

Seems to me that parallel evolution is another argument against the existence of a magical intelligent designer – if the designer is intelligent enough to invent loa loa and the HIV virus, why are so many of its designs so incredibly repetitive? (I say “its” because if this omnipotence exists, I cannot imagine that it sports a set of male, or any other, genitalia.) If I could create anything I would at least give some frogs laser eyes. Or make tiny dragons with wings. Oh, wait.

One distinguishing feature of true glass frogs is the position of their eyes, which point forward, giving them more human-like appearance.

One distinguishing feature of true glass frogs is the position of their eyes, which point forward, giving them more human-like appearance.

African reed frogs have more typical eyes, positioned on the sides of the skull.

African reed frogs, like this Hyperolius cf. pusillus from Gorongosa National Park in Mozambique, have more typical eyes, positioned on the sides of the skull.

*) Parallel evolution is different from convergent evolution in that in the former similar structures evolve independently but use homologous elements e.g., pterodactyl and bat wings, whereas in the latter similar solutions are developed by using unrelated, non-homologous elements e.g., shells of ostracod crustaceans and clams.

Mozambique Diary: The Abominable Frogman

Some of the frog species recorded by MO Roedel during the Cheringoma biodiversity survey.

Some of the frog species recorded by MO Roedel during the Cheringoma biodiversity survey.

If frogs tell their children scary stories, one of them certainly must be about the Abominable Frogman, a strange, giant creature that comes in the middle of the night to snatch unsuspecting frogs and take them away. And, like so many scary stories, this one would have a kernel of truth in it, for the Frogman does exist and his name is Mark-Oliver (MO) Roedel.

MO is the leading expert on African frog biology and systematics, based at the Museum für Naturkunde in Berlin, and we were extremely fortunate that he was able to join our biodiversity survey of the Cheringoma Plateau in Gorongosa. Every evening, as soon as the sun started to set, MO donned his headlamp and rubber boots, stuffed his pockets with plastic bags and a digital recorder, and headed out for a nightly amphibian hunt. He was a discerning stalker – after over 20 years of experience in Africa MO knows the call of almost every frog on the continent, and was able to identify scores of Gorongosa species without ever laying eyes on them, and only the rarest or unusual calls attracted his full attention. So good was he at recognizing different call patterns that he could pinpoint an unknown, possibly new to science species of a tiny reed frog from a 100 m away, in a cacophony of hundreds of other frogs rattling on at the same time. He would then slowly stalk it through the shallow pond, completely oblivious to the water pouring into his boots which were always an inch too short, and grab the poor animal with a swift flick of his wrist.

As MO’s frog collection continued to grow it was easy to be startled by the sight of what looked like tiny humans, their arms and legs outstretched and fastened with pins, marinating in a tray of formalin on the table of our laboratory tent; the macabre illusion was completed by a small toe tag attached to each specimen. But appearances aside, the small number of specimens that were collected during the survey were sacrificed for a very good reason. Positive identification of frog species is often impossible in the field as it requires detailed examination of minute skeletal characters or other features that cannot be gleaned from a live, wiggling animal. And identifying an organism is the first, most important step in an effort to protect it.

The Eye of Sauron from the Lord of the Rings movies seems to have been inspired by that of the Yellow-spotted tree frog (Leptopelis flavomaculatus).

The Eye of Sauron from the Lord of the Rings movies seems to have been inspired by that of the Yellow-spotted tree frog (Leptopelis flavomaculatus).

During a visit to the Ministry of Tourism in Maputo I learned of a terrifying possibility of reclassification (degazetting) of some of Mozambique’s national parks to allow for industrial development, mining mostly, to take place within their boundaries. Such downgrading was to be justified by the notion of those areas’ seemingly low biodiversity, the result of both the civil war and subsequent poaching and illegal logging. Without getting into the politics of such potentially disastrous decisions, I am convinced that our survey and every species we documented prove that national parks in Mozambique are bursting with life, often sheltering organisms that can be found nowhere else. Each name of an orchid, a mouse, or a frog that we can add to the list of species living in a national park adds weight to the argument that we must protect such areas at all cost. Luckily, Gorongosa is under no threat of being reclassified, but other, less developed parks may be. After hearing about our Cheringoma survey, the Head of the Department of National Parks and Reserves immediately saw its incredible value, and urged us to do it in all national parks in Mozambique.

MO was not the only one interested in catching the colorful reed frogs (Hyperolius marmoratus)

MO was not the only one interested in catching the colorful reed frogs (Hyperolius marmoratus)

Some of the frogs collected by MO may turn out to be new to science. We found a gorgeous, silver and black Kassina deep in limestone caves of Gorongosa, and this species is quite likely undescribed. Some Hyperolius may be new as well, as is an interesting, big-eyed Leptopelis. Each is a potential endemic, and thus a strong argument for Gorongosa’s protected status. All in all, MO and the rest of the herpetological team documented 33 species of frogs, more than tripling the number of species of amphibians known from the park. And thus the bad news is that the Abominable Frogman does exist and sneaks up on frogs at night. But he is actually their best friend and defender.

MO and a rather angry, and very deadly, Twig snake (Thelotornis capensis)

MO and a rather angry, and very deadly, Twig snake (Thelotornis capensis)

Mozambique Diary: The Marbled half-piglet

Although officially known as the Shovel-nosed frog (Hemisus marmoratus), I think you will agree that a direct translation of its scientific name, the Marbled half-piglet, is more appropriate.

Although officially known as the Shovel-nosed frog (Hemisus marmoratus), I think you will agree that a direct translation of its scientific name, the Marbled half-piglet, is more appropriate.

Walking around the Chitengo Camp in Gorongosa, especially after the rain when the earth is soft, I often run into two types of cute, pig-like creatures. Warthogs are the more noticeable ones, digging around for roots and grubs, completely unafraid of the busy activity of the preparations for the opening of the tourist season. But if I look carefully at the ground under my feet I often see what appears to be another kind of a tiny, fat piglet. These are Shovel-nosed frogs (Hemisus marmoratus), a species of subterranean amphibians that are remarkably adept at digging into the soil. A closer look reveals the root of their scientific name (“hemi-” means “half” in Greek and “sus” is “a pig” in Latin) – their pudgy little body ends in a sharp snout and, unlike other burrowing frogs that dig with their hind feet, these dive in head first, using the snout as a wedge and their short legs to push the body underground. They are not great jumpers and so they prefer to run if scared, and as soon as they find a suitable patch of soil they start pushing the potbellied body into the earth. If the soil is soft they completely disappear in a matter of seconds.

The preferred mode of escape of the Shovel-nosed frog is to disappear underground. Their pointy snout and powerful hind legs allow them to dig in completely in only a few seconds.

The preferred mode of escape of the Shovel-nosed frog is to disappear underground. Their pointy snout and powerful hind legs allow them to dig in completely in only a few seconds.

Often, however, the ground is too hard to dig, and the only choice is to stand their ground. Already quite portly, they gulp in air and inflate the body, turning it into a small balloon, and making it difficult to swallow by a snake or another predator.

The Shovel-nosed frogs feed mostly on termites and ants, which explains their exceptionally small mouth, but it is not clear whether they are able to feed underground or only on the surface. Their reproductive biology is quite interesting – rather than laying eggs directly in the water, the female lays them in a burrow a few weeks before the onset of rains, and waits for the wet season to come. During this time she defends the eggs and newly hatched tadpoles against ants and other predators. If the conditions allow she then digs a connecting channel to a larger pond where the tadpoles complete their development, or carries them there on her back. This strategy gives the tadpoles an edge over other species because they enter the water and begin feeding before the eggs of other frogs have a chance to hatch.

If unable to dig, a Shovel-nosed frog inflates its body, making itself difficult to swallow.

If unable to dig, the Shovel-nosed frog inflates its body, making itself difficult to swallow.

Update: Yesterday I wrote about a search for the world’s largest orb-weaving spider, which appears to occur in Gorongosa. Alas, after a long search Matjaž and Ingi were not able to find it. I will continue looking and let you know as soon as I find it.