by Scott Leslie
AMBUSHED: AMPHIBIANS
According to the International Union for the Conservation of Nature (IUCN), fully one-third of the approximately 5,000 species of frogs worldwide is threatened with extinction. Nearly 200 species have in fact been wiped from the face of the earth in the past few decades, most recently the Kihansi spray toad of Tanzania. It was declared extinct in the wild in November 2009.
No single factor is to blame for the perilous situation frogs are in. Habitat loss and degradation, climate change, UV radiation, chemical pollutants, and disease all play a part, individually or in combination. The great bulk of threatened frog species are found in the tropics.
ARCHEY’S FROG
What does a group of four small frogs, the tuatara lizard, and the southern beech tree have in common? They are all New Zealand originals and were evolving there 80 million years ago when the islands were still part of the southern supercontinent of Gondwana. But even the lizard and the tree are newcomers compared with the family to which the frogs belong, Leiopelmatidae.
Members of the Leiopelmatidae family are rightfully called archeobatrachia in scientific parlance, or “ancient frogs.” Although the family contains but four species, all exclusive to New Zealand, it possesses an impressive provenance, diverging in an evolutionary sense from the rest of the frog world over 200 million years ago. What’s more, they have changed very little in all that time and are virtually indistinguishable from fossilized frogs found in Australia (also part of Gondwana in early times) that have been dated to 150 million years ago. Such an early split from the main trunk of the frog family tree has given the Leiopelma frogs the distinction of being living fossils and, as such, they share some unique features.
The most obvious distinguishing trait of the Leiopelma species—or New Zealand frogs, as they are known—are their round pupils, rather than the typical slitted ones of more familiar amphibians, giving them an odd—some might say endearing—doe-eyed appearance. As well, look closely at a typical frog and you can’t help but notice its conspicuous round ear drums. Well, New Zealand frogs don’t have them and apparently don’t need them, since they lack an inflatable throat sac and can’t croak or sing like other kinds of frogs. All they can manage is a thin squeaking sound, but since it looks like they don’t use it for communication, they don’t need ears. Equally odd is that they have an extra vertebrae compared with other frogs, and although they have no tails, they possess vestigial “tail-wagging muscles” (in typically snappy scientific patter, they’re called caudalipuboischiotibialis muscles). One of the New Zealand frogs’ most unusual qualities is that the young skip the tadpole stage and emerge from the egg sac as almost fully formed frogs. Archey’s frog, the most endangered and tiniest member of the Leiopelmatidae family, has all of the above, plus an unusual number of chromosomes.
Named for a New Zealand zoologist, Archey’s frogs live in high-elevation forests and moist subalpine scrub habitats on New Zealand’s North Island. Small, even by frog standards, they reach less than three centimetres in length. This diminutive stature, combined with nocturnal habits, a very effective greenish-yellow with dark mottling camouflage, and a silent disposition (remember, they can’t croak), makes them very difficult to locate. At night, Archey’s frogs move from the ground up into bushes and low trees, where they feed on small insects, worms, and other tiny invertebrates. Daylight hours are reserved for hiding out and resting on the ground under logs and rocks. Unlike most frogs, Archey’s don’t require a body of water to breed in and are apparently perfectly happy mating under logs and stones, as long as it’s damp. Once hatched, the male will carry the young around on his back for several weeks and care for them until their transformation into the adult form is nearly complete. Once they’ve left the security of his back, it will take three to four years for the young to reach full adulthood—a very long time by frog standards.
Despite its 200-million-year role as a real survivor, Archey’s frog is facing extinction. But going down the road of no return is nothing new for species of the ancient Leiopelmatidae family. Fossil records show that there were three additional family members (for a total of seven) as recently as 1,000 or 2,000 years ago. They may have been wiped out by the introduced Polynesian rat. Meanwhile, over the past decade, Archey’s frog has seen its own population plummet by over 80 percent, a possible victim of the deadly chytrid fungus. The species, which already had a small range confined to just two tiny areas on New Zealand’s North Island, has been decimated. Rats, which prey on frogs, are also likely to blame. Listed as critically endangered on the IUCN Red List, nobody knows exactly how many survive in the wild, but in one important study population, the frog’s numbers declined from 433 to just 53 over a six-year period. The frog is extremely scarce and continues to decline; it is one of the planet’s most endangered.
Virtually every step that can be taken to save the species from extinction is being taken. Their habitat is protected, and predatory mammals such as rats are being eradicated. Biologists are trying to learn how chytrid fungus affects the frog and are looking for a cure for the disease. And, as a pre-emptive measure, they’ve begun a captive breeding program. With a little luck, such conservation measures may help Archey’s frog continue on its 200-million-year journey. In neighbouring Australia, another extremely rare frog struggles to continue its own unique evolutionary journey.
ARMOURED MISTFROG
Happy stories don’t crop up very often in the sobering realm of endangered species. The news reports about threatened animals and plants are almost always dire and typically elicit a “here we go again” response. We’ve pretty much come to expect bad news. That’s why the story of a little frog that lives in the rushing torrents of an Australian rainforest stream is so unusual.
First discovered in 1976, the armoured mistfrog is named for the male’s spiny skin and its penchant for hanging out on spray-soaked boulders beside waterfalls, a specialized habitat known as the splash zone. At night, the little brown and grey mottled frogs, just over three and a half centimetres long, gather along the creek to enjoy the spray—and presumably sing a song that nobody’s yet heard. During the day, they take refuge in deep cracks in the rocks around the cascade. Little is known about the frog’s ecology, since it has been observed only a few times. However, based on the habits of a separate but very similar species known as the waterfall frog, it’s thought the armoured mistfrog lays eggs under stream-bottom rocks and its offspring spend the tadpole stage living in the torrent.
Armoured mistfrogs are one of a group of amphibians (“amphibian” comes from the Greek amphi, meaning “two,” and bios, “life”—in reference to their dual aquatic and terrestrial lives) known as torrent frogs. In Australia, they are found in northeastern Queensland—if you imagine that country’s shape as resembling the head of a Scottie dog facing west, the area we’re talking about is along the eastern edge of its northern pointy ear. Torrent frogs are adapted to breeding in and living beside tumbling creeks draining the highland rainforests of the region, known as the wet tropics. Several torrent frog species have suffered dramatic population crashes since the 1980s and 1990s, possibly due to chytrid fungus, the deadly pathogen that has ravaged frog populations around the world. The armoured mistfrog was found in an area of less than 130 square kilometres at high elevations in Cape Tribulation and Daintree National Parks. Note the past tense of the preceding statement. That’s because after December 1991 the armoured mistfrog was never again seen in its known range. Experts thought it was extinct.
Fast-forward 17 years to July 2008. A doctoral student was searching for another species of torrent frog in an area more than 100 kilometres south of Daintree National Park. He happened to stumble upon what appeared to be several armoured mistfrogs in a stream. Rediscovering a long-lost species isn’t an everyday occurrence, so tissue samples were sent to the Australian National University in Canberra to verify their identity. DNA analysis confirmed they were armoured mistfrogs.
Further investigations
have revealed a tiny population of only 30 to 40 of the frogs at the site, where it lives side by side with the closely related waterfall mistfrog. Both species are infected with the same chytrid fungus that was thought to be the culprit for the armoured mistfrog’s disappearance from its original range to the north. Oddly enough, despite the fungal infection, all of the frogs appear to be quite healthy and flourishing within their habitat. In a bid to understand the disease, scientists are trying to determine why the fungus has apparently had no effect on them. It’s hoped that any new knowledge gained might contribute to the conservation of other amphibians afflicted by the deadly fungus.
As small as this newly discovered population is, it raises some hope that other populations of the species can be found. It has also encouraged a glimmer of optimism that some of Australia’s other “extinct” frog species might be waiting to be rediscovered.
IRANIAN GORGAN MOUNTAIN SALAMANDER
Although the plight of the world’s frogs has received much attention recently, the same can’t be said of their amphibian cousins, the salamanders. Many of them are also threatened with extinction, particularly in Mexico and Central America, but you’d have to go to a cave in Iran to find what is likely the rarest one of all.
The world is so focused on Iran’s politics that the country’s rich and varied natural heritage is often overlooked. Its diversity of wildlife is impressive: over 8,000 species of plants, 1,900 of them found nowhere else; 500 species of birds, 160 species of mammals (including the endangered Asiatic cheetah, also discussed in this book), 219 species of reptiles, and 23 species of amphibians, not to mention nearly 200 freshwater, inland fish species.
Iran is included in two of the world’s 34 biodiversity hotspots, the Caucasus and the Irano-Anatolian. Dr. Norman Myers, who created and developed the concept of the biodiversity hotspot, defines one thusly: “To qualify as a hotspot, a region must meet two strict criteria: it must contain at least 1,500 species of vascular plants (> 0.5 percent of the world’s total) as endemics, and it has to have lost at least 70 percent of its original habitat.” That it is part of two such hotspots shows just how important Iran and its natural treasures are to the biosphere as a whole and just how threatened those natural treasures are. That said, imagine a scene from the Iranian landscape and chances are sun-drenched desert or arid mountains come to mind. What doesn’t come to mind is a cool limpid pool in a dark grotto. But that is precisely where one of the world’s most endangered amphibians lives. Shir-Abad Cave, located in the eastern Elburz Mountains near the Caspian Sea, in northwestern Iran, is the only place on earth inhabited by the Gorgan Mountain salamander. Less than 20 centimetres long (most of it tail), with a body shape reminiscent of a lizard, this four-legged, four-fingered and -toed aquatic creature with smooth yellowish skin was unknown to science until 1979. That’s when a single animal was collected and described. Thirty years hence and the small amphibian remains extremely rare: only about 100 adults are known to exist.
The Gorgan Mountain salamander’s entire universe is limited to one small spring-fed, underground pool 100 metres long by 10 metres at its widest. Here, secreted away beneath the earth, generations immemorial of the small animal have been born and have died while on its evolutionary path, its existence unknown to the rest of the world until three decades ago. Perhaps its stay-at-home way of life isn’t surprising for a water-loving species that is surrounded by dry mountain forest: it would desiccate and die if it tried to disperse. And although its larvae have occasionally been seen outside in the stream that drains the cave, mature salamanders have only ever been found in the cave pool itself.
The Gorgan Mountain salamander may have always been rare, a disjunct, far-flung species of the primitive 110-million-year-old Asiatic salamander family. Although the cave and surrounding forests are protected as a Natural National Place of Iran, the species faces several immediate challenges. Its extremely limited range and one-of-a-kind habitat, and a tiny, closed population, are like ticking time bombs of extinction. A single mishap, such as someone (the place is often visited by people) spilling insect repellent into the water, could wipe out an entire ancient species. And there is currently no real recovery plan for the Gorgan Mountain salamander. At this point, its survival is merely a matter of chance.
TROUBLED WATERS: FISH
The largest group of vertebrates of all, there are about 20,000 species of fish living in the planet’s salt and fresh waters (by contrast, birds, in second place, have half that number). According to the IUCN, one-fifth of them are threatened with extinction, including most of the sharks, which are surpassed only by the dwindling sturgeon family for the dubious distinction as the most endangered group of large animals on earth.
RIVER SHARKS
Of all the planet’s creatures, none excite fear and awe like the sharks, yet we kill an incredible 270,000 of them every day. Many species might cease to exist within a mere 20 years. That’s nearly half a billion years of evolution snuffed out in the blink of an eye.
The latest research shows that the collapse of the shark population is drastically upsetting aquatic food webs in complex ways not yet fully understood. For example, their decline is responsible for the death of coral on some coral reefs; and the removal of sharks from Chesapeake Bay has already resulted in the crash of the scallop fishery there. The main culprit for this state of affairs? A largely unregulated, unrestrained, unsustainable, and withal brutal global fishery. A major component of this is the finning industry, which chops off sharks’ fins and tails to fill the demand for shark fin soup in Asia or to obtain cartilage for use in unproven natural health products.
Many sharks are threatened with extinction, but none more so than the members of the genus Glyphis, a group of freshwater species so rare that we don’t even have names for some of them yet. Known as river sharks, they belong to the same family as iconic oceanic varieties such as the lemon, tiger, and reef sharks. Stocky, with a high, arching back; broad, rounded snout; and prominent fins, these grey-coloured fish are similar in appearance to more familiar sharks. What really sets them apart is where they live: in murky freshwater habitats. Sharks are synonymous with the deep blue sea, not the silt-ridden, warm fresh water of a meandering tropical river. Yet this is exactly the kind of environment in which species belonging to the Glyphis genus have adapted to.
Because they are so well hidden in the cloudy waters of southern Asia and tropical northern Australia, nobody knows for certain how many species of river sharks there are. Historically, they were largely known from a scattering of specimens and museum records from the 19th century. In the 1990s, though, the capture of specimens of the Ganges shark and the discovery of a hitherto unknown species in Borneo seemed to awaken interest and concern for this obscure group of underwater predators. Only four species have been named, three of which are listed as critically endangered on the IUCN Red List. There are, however, several more about which so little is known that they haven’t been officially named yet. Instead, they are called Glyphis sp. A, Glyphis sp. B (the provisional name given the newly discovered species from Borneo), Glyphis sp. C, and so on. River sharks are exceedingly rare animals, and though their actual numbers are unknown, only a few individuals of each species have ever been seen.
Very little is known about their biology. Good vision is not much use in water the consistency of chocolate milk, so their eyes have become small. However, they have evolved a keen sense of smell, hearing, and electroperception for hunting (the ability to read weak electrical impulses given off by surrounding objects is common to all sharks, though this capacity may be heightened in river sharks). Once prey have been located, Glyphis sharks seize them with small, serrated teeth. They are thought to bear live young.
GANGES RIVER SHARK
It’s hard to imagine a shark living in the turbid, polluted waters of eastern and northeastern India, but that’s where this two-metre-long fish makes its home. In 1996, the Ganges shark re-emerged after an absence of a century and a quarter, w
hen two of them were caught—the first since 1867. Little stands between the Ganges shark and extinction. Inhabiting the Ganges and surrounding rivers, along whose banks hundreds of millions of people live, the obscure shark has been fished for centuries. Moreover, pollution and the construction of dams have degraded its habitat.
It is thought to hunt by skimming along the bottom while looking toward the surface with its upward-facing eyes to pick out prey backlit by the sun. Because the Ganges and other northern Indian rivers are prone to flooding, the shark may also play an important ecological role by scavenging drowned livestock swept into the swollen rivers.
Strangely enough, this small shark has a reputation as a man-eater—in Bengali it is known as baagh maach, or tiger fish. Indeed, in the past it might have occasionally mistaken a human for a potential meal and taken a bite. But it’s hard to imagine it as a killer, considering its relatively small size and its tiny teeth, so the Ganges shark may have gotten a bad rap. In fact, the real culprit is probably a much larger, much more aggressive species. The bull shark, at up to four metres in length and weighing over 300 kilograms, is known to swim up rivers around the world, often travelling far into the middle of continents. It has plied the Mississippi all the way to St. Louis and beyond, and made it 4,000 kilometres inland from the Atlantic to the city of Iquitos in the Peruvian Amazon. They are also found in some of the same rivers in India as the Ganges shark. (At this point it must be noted that bull sharks are not a freshwater species. They are a marine species with a tolerance for low salinity and a predilection for inland exploration.) All of this is by way of saying that given that bull sharks kill more humans than any other fish on earth—usually attacking in very shallow water—it’s a good bet that the Ganges shark got its man-eater reputation by being confused with its nasty cousin.