Tag Archives: Amphibians

NATURE: Screaming frogs

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Several fascinating screaming frog videos have recently come to my attention. Apparently, some species of frog will emit a high-pitched scream as a defensive mechanism when harassed or handled (this is also known as a release call). According to David Badger and John Netherton in “Frogs”:

The distress call is a scream, wail, or other loud cry emitted by a frog or toad (usually with its mouth wide open) when seized by a predator such as a snake, bird, or mammal. The apparent purpose of the cry is to startle or disorient the predator and thereby effect the release of the victim. In some species, this cry sounds unnervingly like “a cat in distress,” Duellman and Trueb report; in bullfrogs, the high-pitched scream is reminiscent of a human voice.

The smoky jungle frog (Leptodactylus pentadactylus) demonstrating its release call or “scream”:

Via BBC NEWS

Videos illustrating other frog species “screaming”
Via Living the Scientific Life (Scientist, Interrupted)


Via BuzzFeed

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CRITICALLY ENDANGERED SPECIES: Unique axolotl salamanders face extinction

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axolotlThe axolotl (Ambystoma mexicanum), a type of salamander, is a critically endangered amphibian endemic to central Mexico. This species is a “paedomorphic species, living permanently in water, and does not undergo complete metamorphosis,” so the gills are retained into its adult life. The axolotl is declining due to competition, disease transmission, and predation from introduced species, in addition to overfishing, pollution, and urbanization. Captive populations do exist, since “the species is used in physiological and biomedical research, as well as in the pet trade, but the re-introduction of captive-bred axolotls is not recommended until threats can be mitigated, and disease and genetic risks to the wild populations assessed.” From the Dallas Morning News, TX:

The axolotl, also known as the “water monster” and the “Mexican walking fish,” is a key part of Aztec legend and diet. Against all odds, it survived amid Mexico City’s urban sprawl in the polluted canals of Lake Xochimilco.

But scientists are racing to save the foot-long salamander from extinction, a victim of the draining of its lake habitat and deteriorating water quality. And nonnative fish introduced into the canals are eating its lunch and its babies.

Researchers say the axolotl could disappear in five years.

“If the axolotl disappears, it would not only be a great loss to biodiversity but to Mexican culture, and would reflect the degeneration of a once-great lake system,” biologist Luis Zambrano said.

The number of axolotls (pronounced ACK-suh-LAH-tuhl) is not known. But the population has dropped from roughly 1,500 per square mile in 1998 to a mere 25 per square mile, according to a survey using casting nets.

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NEW SPECIES of thread snake discovered on the Caribbean Island of Barbados, may be world’s smallest

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A new species of threadsnake (Leptotyphlops carlae), which probably grows less than 4 inches long (about ten centimeters) and is as thin as spaghetti was discovered on the island of Barbados by S. Blair Hedges, a Professor of Biology from the Penn State Institutes of Energy and the Environment. Hedges has “discovered or co-discovered 72 species of amphibians and reptiles, including the smallest tetrapod (a frog) and smallest amniote vertebrate (a lizard).” He also helped describe what may be the world’s smallest lizard (below).

This new species of thread snake may not be the world’s smallest species, since other similar threadsnake species may be smaller. These little snakes are poorly known, so it is probably too early to determine which species is the smallest. Furthermore, few specimens exist of these fascinating little snakes in museums. Snakes from the genus Leptotyphlops are also known as blind snakes, and they burrow to feed on insect larvae. IMAGES by Blair Hedges/Pennsylvania State University. From Science News:

Hedges studied five adult Barbados threadsnakes, including a female that’s going to be the reference specimen for the new species. Hedges and Hass found her in a remnant of forest on the eastern side of Barbados in June 2006.

She carried a single egg in her oviduct. Animals at the miniature end of their species tend to reproduce one offspring at a time, often a baby relatively large in comparison to the mother, Hedges says.

He says the Barbados snake also fits another pattern: Islands are often homes for very large or very small species. Some lineages on continents never make it out to islands, so island dwellers have opportunities to fill niches they wouldn’t on the mainland. Hence, when searching for an unusual form of an animal, such as minis or giants, islands make good places to start looking.

Over his career, Hedges has codescribed other extreme herps: A frog smaller than a dime and the smallest known lizard. Each came from an island.

More thread snake images by Nate Kley, an evolutionary biologist and herpetologist:

On the Net: Snakes hold thread of evolution evidence
On the Net: Gobbling Food Helps Threadsnakes Avoid Danger; In A Snake-Eat-Ant World, It’s Survival Of The Fastest
On the Net: Weird jaws let tiny snake gulp fast

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AMPHIBIANS: First lungless frog discovered

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IMAGE by David Bickford, National University of Singapore

A previously known frog (but only known from a few specimens) has been recently discovered to lack lungs. Barbourula kalimantanensis breathes through its skin and lives in a “clear, cold-water stream on the island of Borneo in Indonesia” which probably allows for this adaptation. Because the species was known from so few specimens the researchers were left with the dilemma of to dissect or not to dissect. They chose dissection and made a remarkable discovery. From John Roach for the National Geographic News:

“Nobody knew about the lunglessness before we accidentally discovered it doing routine dissections,” study lead author David Bickford, a biologist at the National University of Singapore, said in an email.

His colleague Djoko Iskandar at the Bandung Institute of Technology in Indonesia first described the frog in 1978 from one specimen. About 15 years later, fishermen found another individual.

“Each specimen was deemed so valuable that scientists did not want to sacrifice the animals for dissection,” Bickford said.

But the biologist immediately partially dissected several frogs when he found the species on a recent expedition to Borneo.

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ENDANGERED SPECIES: Rare New Zealand Maud Island frogs bred on mainland

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Some good news from the frog world for a change: Maud Island frogs or Leiopelma pakeka were discovered breeding on the mainland of New Zealand. The primitive frogs were introduced into the Karori Wildlife Sanctuary where froglets were discovered clinging to adult males. Maud Island frogs are an ancient species belonging to the small family Leiopelmatidae. 2008 has been declared the year of the frog to raise awareness for the amphibians, which are being devastated by the chytrid fungus, loss of habitat and climate change. From the International Herald Tribune, France:

Maud Island frogs, one of four native New Zealand frogs, had evolved little over the last 70 million years, Lukis said, resulting in distinctive features and behaviors.

They do not croak, live in water or have webbed feet, she said.

Also unlike other frogs, these hatch from the egg as fully formed frogs without going through the tadpole stage.

Eggs are laid under rocks or logs and the male sits over the eggs until they hatch as well formed, tailed froglets.

In 2006, 60 Maud Island frogs were released in the frog enclosure at the wildlife sanctuary — a security-fenced area of some 250 hectares (617 acres) set up to enable threatened native birds and other species to re-establish their numbers safe from introduced predators like rats, mice, stoats, ferrets and wild cats.

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