Connecticut Audbon Society

Connecticut Audubon Society studies deadly amphibian disease in Connecticut


Northern Leopard Frog

Many Connecticut amphibians, like this Northern Leopard Frog, are already at risk and are now facing a deadly disease.

In the last 20 years amphibian populations worldwide have taken a nose dive. Loss and degradation of habitat has taken a huge toll and the use of harmful chemicals in the environment is particularly detrimental to amphibians. Their thin, permeable skin provides little protection from pollution and because most species spend part of their life on land and part in the water, amphibians are sensitive to contaminated water and air.

Recently, already fragile amphibian populations have been decimated by the    outbreak of a pathogen, the fungus Batrachochytrium dendrobatidis (often abbreviated as Bd or called “chytrid fungus”) which causes a deadly disease in frogs and some salamanders. This disease, chytridiomycosis, has run unchecked throughout our planet over the last 25 years, wiping out or greatly reducing amphibian populations everywhere. Cloud forest regions and other highland habitats in the tropics are particularly hit hard by this water-borne fungus, due to the pathogen’s preference for relatively cool and moist habitats. The devastating loss of biodiversity caused by this disease led to the proclamation of the international Year of the Frog in 2009, to draw attention to the plight of amphibians worldwide. More bad news regarding new outbreaks is reported almost weekly still (see this sobering article that was released recently in Scientific American, for example).

Are Connecticut amphibians infected? 


Summer campers help our research by catching lots of frogs and salamanders at the Larsen sanctuary in Fairfield

Connecticut Audubon Society’s Conservation Biologist, Twan Leenders, has been studying this disease and the effects it has on amphibian populations in the tropics for more than 15 years, and he works on trying to save some of the world’s most endangered frogs. Even though Bd has been detected almost anywhere on the planet by now, one of the few places from which we still have no data is -surprisingly – right here in New England! In addition, recent molecular studies have hinted at the fact that the fungus and the disease it causes may have actually originated here a long time ago and spread across the globe in recent years. Obviously, it is important to investigate the potential occurrence of this dangerous pathogen here in CT and the implications it may have for our local fauna. A Ph.D. student from Yale University, Kathryn Richards-Hrdlicka, is currently investigating the question of whether Bd indeed is native to New England and Twan has teamed up with her, with the Wildlife Division of the Department of Environmental Protection (DEP) and with biologists from White Memorial Foundation in Litchfield to see if the fungus is present in our state and if so, what that means for our amphibian populations.


Conservation Biologist Twan Leenders gives a Bullfrog a 'tummy rub' with a toothpick to collect samples for lab analysis while young frog catchers wait patiently to release the frog back into its pond.

It is impossible to assess whether a frog or salamander is infected with the fungus simply by looking at it. Only once it develops the disease chytridiomycosis does it become symptomatic, but amphibians tend to die so quickly once they develop the disease that sick animals are rarely found. In order to check whether our local frogs are infected, skin swabs are taken by gently scraping a toothpick over the skin of the animal and subsequently analyzing the few skin cells that stick to the toothpick in the lab to see whether DNA of the Bd fungus is present. This is a highly complex and sensitive analytical technique that depends on a much less sophisticated technique for its success: that of jumping in a swamp and catching lots of frogs and salamanders to obtain a large enough sample size.

 Young Citizen Scientists help study frog disease

After many years of fieldwork doing this type of research Twan has become a pretty good frog catcher, but his skills were put to shame recently by a group of young summer camp participants and their counselors at the Larsen Sanctuary near our Center in Fairfield. Within the span of about an hour and a half of frantic splashing, diving and netting we captured over 50 amphibians representing 8 species. All frogs, salamanders and tadpoles were swabbed to collect a sample for analysis and released right where they were caught. The swabbing procedure is entirely non-invasive and no animals are hurt in the process.


Preliminary results


Red Eft

Surprisingly, newts and efts were often found to carry the disease-causing fungus

After competing our first field season, almost 900 samples were collected and analyzed. Preliminary results show that the Bd fungus is indeed present in Connecticut and that almost a third of our frogs and salamanders may be carriers. Luckily no signs of the disease were detected so far and our amphibian populations appear to be healthy still. More information will become available as the data analysis continues and we expand our research into the 2011 field season.

Do you want to get involved? You can find out more about Connecticut Audubon Society’s Citizen Science efforts here.

All group photos © Bernard Daraz; Leopard Frog  and Red Eft photos © Twan Leenders





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