seachild_elf (seachild_elf) wrote,

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Darwin Day

Today is the 200th birthday of a man who quite changed the way we look at the world, back in his time and even today. That man was Charles Darwin. You will find him featuring on a lot of blogs today. I wanted to write something to commemorate this day too, so I decided to pick something close to my heart. Ladies and Gentlemen, I present Darwin’s Frog!

Darwin’s Frog (Rhinoderma darwinii) is –naturally- named after the man who discovered it, Charles Darwin. He came across the amphibian during the equally famous Voyage of the Beagle.

This diurnal frog hails from southern Chile and Argentina where it can be found in forest streams, swamps and leaf litter on the forest floor. It’s a relatively small frog, about 2,5 to 3,5 cm. At least, small compared to the European frogs I’m used to. Males and females look alike, but females tend to be slightly larger.

It can either be green, as in the picture, or brown.  You can easily spot the camouflage trick the frog is relying on for its protection: a leaf-shaped frog will be harder to spot among many other leaf-shaped… leaves.  If a predator does see through the disguise, the frog will play dead, by throwing itself onto its back. The belly of the frog is white and black, possibly also as a deterrent to predation. A further distinct, visual aspect of Darwin’s Frog are the unwebbed front feet. Some of the toes on the hind feet usually are webbed.

The Darwin’s Frog has an interested take on raising its young: the tadpoles are carried around in the vocal sac of the male. Therefore the female lays only a small number of eggs, less than thirty, unlike many other anurans. The eggs are deposited in the leaf-litter and mommy then heads off never to be seen again.  Dad gets to become a single parent and is left with all the babysitting.

As soon as the male can spot movement in the eggs, he takes them into his mouth and places them in his vocal sac. As the tadpoles continue to develop while squatting in the vocal sac, dad’s throat visually grows thicker. Just think about what it would be like, having thirty squirming babies deposited on your vocal chords. The course of parenthood never did run smooth... After about fifty days the tadpoles reach metamorphosis, and dad throws them out of the house, into the wide world where they happily go about their business of bothering insects and other small invertebrates for dinner.

Darwin’s Frog is listed on the IUNC Red List of Threatened Species as ‘vulnerable’. Its total population is estimated to have declined more than 30%.  Some of the separate populations, both inside preserved areas and outside, have disappeared completely between surveys, where in other areas a visible density decline is also noted. The main cause of the decline of Darwin’s Frog is thought to be habitat loss and degradation caused by human activity. Climate change and diseases are thought to play a role as well in the species’ decline.

However, the fungal infection chytridiomycosis, that is blamed for the extinction and decline of many amphibian species around the world, has not been reported yet in Chile. Thank god for small miracles, I guess. But let’s not cry victory too soon. The Darwin’s Frog close cousin, and the only other member of the Rhinoderma-genus and Rhinodermatidae-family, the Chile’s Darwin’s frog (Rhinoderma rufum) is considered extinct by most since it hasn’t actually been seen for… well longer than I have been alive. Until its extinction can be confirmed, the Red List  gives it still as ‘critically endangered’. 



The IUNC Red List of Threatened Species,

Vocal Sac-Brooding Frogs: Rhinodermatidae - Darwin's Frog (rhinoderma Darwinii): Species Account,

300 Frogs, Chris Marrison, Grange Books, 2007
Tags: darwin day, darwin's frog
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