That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

A recent study has challenged what we know, or thought we knew, about frog communication.  Researchers were astonished to discover that the calls of male Emei Music Frogs, (Babina daunchina) inform females of such details as the length and width of the singer’s burrow.

Construction Skills Needed

Named for the males’ banjo-like calls (they really do sound like banjos, please check video below), the Emei Music Frog is native to marshy habitats in central and southwestern China.  Females deposit their eggs in burrows constructed by the males, and the tadpoles develop there as well.  The ability to construct a safe burrow is, therefore, an important consideration when females go “mate shopping”.  You can see photos of the unique nests and egg masses of a related species, Japan’s Ryuku Brown Frog, here. Read More »

In the late 1980’s I was privileged to breed the now rarely-seen Smoky Jungle Frog, Leptodactylus pentadactylus, a large (8 inch snout-vent length) Latin American native that constructs foam nests on land.  In the wild, rain washes the tadpoles into a nearby pool, where they develop in normal frog fashion…following suit, I successfully reared a number in water.  I subsequently learned that some frog nests are placed far from the water’s edge, and that the tadpoles therein develop entirely on land.  But what did they eat…the nest’s foam, perhaps?  There were theories, but no answers.

Subterranean Frog Nests

Herpetologists working with the closely related Mountain Chicken Frog (L. fallax) at the Durrell Wildlife Conservation Trust have recently solved the riddle – and captured the bizarre event on film.  Mountain Chicken Frogs, highly endangered and limited to Dominica, St. Kits, Martinique and a few neighboring islands, lay their eggs in foam nests underground, and the tadpoles develop without ever seeing water.

The startling footage taken by the researchers, shows scores of tadpoles gorging on unfertilized eggs produced by their mother.  In sharp contrast to certain more “civilized” oophagus (egg-eating) poison frog tadpoles, the chicken frog larvae do not wait until the eggs are actually deposited, but rather swarm about the female’s cloaca, eating ravenously as the eggs emerge.  It’s quite a scene!

A Taxing Time for Mom

Subsequent research has revealed that the harried mother uses her rear legs in an attempt to re-distribute the unusual food, and perhaps to give all of her gluttonous progeny a chance to feed.  She has her work cut out for her…the 25 to 50 tadpoles that she rears require 10,000 to 25,000 unfertilized eggs to see them through to metamorphosis!

Further Reading

Frogs break all the rules when it comes to reproductive behavior, constantly surprising even the most seasoned herpetologists.  To read about tadpoles that “petition” their mother for food, please see my article Begging Behavior Among Strawberry Poison Frog Tadpoles.

Smoky Jungle Frog image referenced from wikipedia and originally posted by Ltshears
Leptodactylus fallax image referenced from wikipedia and originally posted by TimVickers

Frogs are full of surprises when it comes to reproduction – there are species that incubate eggs below the skin of their backs and in the vocal sacs, while others carry them wrapped about their rear legs or construct foam nests on land.  But in May of this year Boston University biologists working in Panama uncovered what may well be the oddest reproductive strategy of all – a frog that actively chooses to lay its eggs on either land or in water, depending upon the threats presented by each habitat.  To date this is the only example of an egg that can hatch in either environment, and these frogs are the only vertebrates known to show such reproductive flexibility.

When breeding near shaded ponds, hourglass frogs lay their eggs on tree leaves overhanging the water (the tadpoles drop into the water upon hatching), thus avoiding fish and other aquatic predators.  However, when utilizing ponds exposed to the sun, the majority of the frogs lay their eggs directly in the water, lest they dry out before hatching.

The “decision” is not governed genetically, because the same female frog will choose different egg laying sites when placed in a shaded or un-shaded pond.

Amphibians were the first group of vertebrates to evolve some independence from water.  Biologists are now studying the hourglass frog to determine if its unique egg-laying flexibility might shed light on the evolution of terrestrial amphibian eggs.

You can read more about the hourglass treefrog and its relatives at:
http://research.amnh.org/herpetology/amphibia/references.php?id=10041