Friday, October 05, 2007

Frogs: whistle blowers

Common Southeast Asian toad males fighting over calling space
Frogs/toads are famously vocal and are characterized as calling 'ribbid ribbid' or 'croak' or what have you. The truth is frog calls are amazingly varied and come quite melodious. Their calls are species-specific and meant to attract mates. Males call, fight for calling spots, risking predation, in an attempt to mate with a nice large gravid female. A quick google will land you many calls of species all over the world, unfortunately there are not many Indian ones to be found.



Common Southeast Asian toads mating. The female's below and big!
I've linked two recordings of two of the frogs I've made on campus along with the pictures of the frogs. I simply didn't know that we had many frogs on campus. Our few ponds are well hidden away and not perennial and my ears are tuned to other sounds. But a few others, including Ashok, are much better at this than I am. We went looking a few nights and I've so far added three more frogs to my list which had only one before. Ashok has heard more and I'm sure they are here. This is reassuring, they are still here.


A male Alpine cricket frog and its call
Which brings me to why I called them whistle-blowers. It has nothing to do with their ability to call, I assure you. Frogs have permeable skin, shell-less eggs, and their life-cycle is spent exposed to both land and water. There is something frighteningly vulnerable about these creatures. And this vulnerability makes them good canaries in the coal-mine that is our planet. They are often the first to succumb to pollution, disease, climate-change and invasive species. Monitoring them is a good way of assessing an ecosystem's health. They are indicator species letting us know quickly that something is going wrong.

Ornate narrow mouthed toad and it's call

Frogs all over the world began indicating rather frantically somewhere around the late 1980's and early 1990's. Among the first problems that were noticed by some frog watching kids were deformed frogs. By the time we had confirmed that these deformities were more common than could be explained by normal variation, very widespread and affected many species, we were already into the late nineties. Even today well into the 2000's we don't really have a prime candidate for what causes these problems. We have three candidates instead, increased UV radiation, chemical contaminants in the water and parasites. At least two and possibly the third as well are directly related to problems that have been created by humans, are anthropogenic. We are doing things to the earth's ecosystems that it's most sensitive denizens simply cannot take.

An Alpine cricket frog plagued by fewer mosquitoes than the photographer.
So just how bad is what we are doing? A deformed frog is eventually an individual. And an individuals story is nowhere nearly as telling as the population's story that began emerging around the same time. The Golden toad, a beautiful Costa Rican amphibian, was in trouble according to herpetologist Martha Crump's observations in 1987. We saw the last Golden toad in 1989. In two short years they disappeared.

There were many many reports after that talking about amphibian declines. Large numbers of once common frogs were simply disappearing, entire populations simply wiped out. Rachel Carson's 'Silent Spring' was transposed onto silent streams. Bruce Wilcox noted that between 1996 and 1998 of the 1874 backboned animals added to the Red List of Threatened Species, 1646 (89%) were amphibians! The statistics compiled in AmphibiaWeb also sound quite grim and this is not a resolved crisis. The causes for this decline are perhaps as complex and multiple as they were for the deformities. A large part of the decline is now believed to be explained by an epidemic of fungus. A fungus that is helped along by global warming.

Has anyone heard of the boiling frog experiment? We might be conducting it on a grander scale than we think and the frogs have already died.

The call of the two frogs : Alpine cricket frog & Ornate narrow mouthed toad

Further Links:
Ashutosh on the drugs that could be discovered from frogs
Jeff with much more on frogs.

Update on frogs: A story from BBC suggesting that there might be a cure for the Chyrtrid fungus!

6 comments:

Ashutosh said...

Great post and pictures! There is also the huge numbers of potential drugs that we can harvest from these creatures:
http://ashujo.blogspot.com/2005/11/praise-warts-please-most-important.html

Jeff Davis said...

Thanks for your great article. The Red List nugget is one I hadn't come across. Thanks again. I'll link to this post from my frog blog: https://frogmatters.wordpress.com

Natasha said...

Thanks Ashutosh and Jeff, for the praise and also the links with quite useful information.

Sunil said...

very nice post Natasha. Frogs and other amphibians are indeed "sentinel" species with respect to climate change or environmental stress. Another thing most of us don't realize is the amazing number of frog species around the world. A particularly diverse area is the silent valley ecosystem around the Nilgiris. By some estimates there are well over a 100 amphibian species there, and many remain unidentified. I was surprised to read about the "discovery" of a new species there as recently as a couple of years ago (link)

Natasha said...

Silent Valley and the Western ghats in general are extremely biodiverse. Here's yet another tiny frog that was found in the WG recently.

http://www.hindu.com/seta/2007/10/04/stories/2007100450021500.htm

The older more famous and significant one was the purple frog
http://news.bbc.co.uk/2/hi/science/nature/3200214.stm

manu.an said...

hello its great to study frogs especially in western ghats hub of diverse eco system....