And Then There Were None… The Future Of Frogs?
“Frogs, so common in these humid forests, are crucial links in the ecology. If they disappear, all kinds of food chains will be broken and the effect could be little short of catastrophic to wildlife in general. And sadly, for now at least, it seems like the golden frog has waved its last in the wild.”
My plans for a lazy morning disappeared when I heard Sir David Attenborough’s disquieting words in his BBC documentary series ‘Life in Cold Blood’. I sat on the edge of my bed watching the entire series including the concluding sequel about the remote forests of Panama where a scientist announces that they were the last crew to film golden frogs in the wild! Local scientists are then shown collecting the last remaining frogs from the area before they fall victim to a fatal fungal disease – Chytridiomycosis. Believed to cause mass and rapid extinctions among amphibians, Chytridiomycosis is caused by the fungus Batrachochytrium dendrobatidis (Bd).
I couldn’t help but think of the many nights I had spent in the forests of the Western Ghats. I remember the time I was walking along with a bunch of classmates from my Masters course in Wildlife Biology and Conservation, one rainy night in the Periyar Tiger reserve, looking for frogs. In just one small patch of five by five metres of rainforest we saw at least 12 species of frogs (perhaps one was even taxonomically unknown!). On the way back to the camp, while passing over an elephant trench, one of us noticed a brown, oily snake-like creature, which on closer observation turned out to be a caecilian! When we walked through the entire trench, which was about two metres deep, we came across 11 individuals of the same species! They were all out in the rain, probably to mate or feed! Intrigued we tried photographing one and realised they were shy of light. So we left them to continue their rendezvous with one another, satisfied and blissful at such an amazing night…
The cacophony of frog calls accompanied by the sounds of gushing crystal streams is a given for all those who have spent time in the wild. What if these wonderful musicians vanish one day? What if we lose this amphibian orchestra forever? Could the amphibian population in the Western Ghats share a similar fate as that of the golden frog?
As many as 133 species of amphibians have been described from the Western Ghats and with approximately 12 new species discovered recently, this is a one-of-its-kind biodiversity hotspot. As many as 112 species are endemic to the region and there is still an on-going debate on the phylogeny of many of the remaining species. But while scientists are debating the taxonomy of amphibians, there is a deadly fungus looming in the background that has infected almost 93 species in six continents across the globe. The Western Ghats is highly vulnerable and steps need to be taken to prevent and control the spread of the fungus, should it reach our shores.
My literature survey suggested that Australia had been the worst affected so far with almost 22 per cent of its frog species infected. Frog populations in Panama, Ecuador, Venezuela, Central and North America, New Zealand and Spain have also recorded rapid declines attributed to the fungus. The first and only report from Asia was an outbreak in Japan in a collection of a private owner, although no reports from the wild populations in Asia are known yet.
Chytridiomycosis affects mostly frogs although other amphibians including salamanders, caecilians and toads are equally at risk. In the wild, the afflicted frogs show thickened rough skin prone to peeling and small skin tags are seen on the toes. But there are other changes that are not visible to the naked eye. Victims of the fungus display inactive behaviour and some are known to excrete small quantities of reddish faeces which ultimately lead to death. In some cases, large quantities of mucous and skin lesions are seen. Microscopic examinations of individuals show skin lesions on the ventral abdomen, drink patch and digits. Various developing stages of the fungus are seen in the epithelium tissue on the outer skin. Since amphibians drink and breathe through their skin, and as this fungus affects the outer layer of skin, it prevents them from performing physiological functions such as osmoregulation (water balance) and biological defence mechanisms such as employing toxins and alkaloids present in the skin.
How it spreads?
A number of modes of transport have been speculated for the fungus. It may be spread through waterbodies such as streams into rivulets and then rivers by the amphibians themselves or by other vectors such as migratory fish and water birds. In countries such as Australia, the introduced cane toad acts as a vector for the transport of the fungus. Since it can survive in soil as well, the extraction of soil and its consequent dumping in other areas may also aid the spread of the fungus. The fungi’s viability without any host is a matter of concern since this implies that it can be transported very easily by vectors over long distances. Studies have even shown the zoospores can attach to bird feathers making migratory water birds prolific vectors for the same.
Climate chytrid paradox
Scientists have tested the effect of climate change and temperature shifts in many areas on the spread of the chytrid fungus. Recent declines in Harlequin frogs in Ecuador and those of the Atelopus genus in Costa Rica and Panama have been linked to changes in the climate that create an optimum environment for Bd to spread. Scientists have also suggested a 1,000 m. break-point for the virus which they believe cannot survive extreme weather conditions. This is precisely why we need to focus on the Western Ghats where moderate temperatures that are highly conducive to triggering an epidemic prevail. The disease is the bullet, climate change the trigger.
Time to clean the slime
The most imperative step for us is to be prepared and initiate preventive measures immediately. A systematic and planned screening of frogs throughout the Western Ghats is a high priority. Teams of well-trained researchers should start using non-lethal methodology for collecting superficial samples from the skin of amphibians. These samples should then be sent for a PCR (Polymerase chain reaction) assay, a molecular technique used to detect the presence of Bd. The general procedures involve taking a swab from the lower abdomen and ventral portions of the frog’s body including the hind limbs and preserving the sample in ethanol. These are then sent to a laboratory for the assay. The advantage of this non-lethal method is the ease of collecting and the sensitivity to even the slightest presence of the fungus.
Conservation agencies in India, especially those working in the Western Ghats, need to be aware of the potential lethality of the fungus for amphibians and must cooperate to prevent an outbreak of Bd. Any dead or dying frog found in the wild needs to be examined for the disease but precautions should also be taken to swab appropriately or else there are chances of finding false negatives. The most imminent threat arises from animals being brought from outside the country which includes exotic birds since they can be likely vectors of Bd.
It is imperative to train forest staff, conservation agencies, volunteers and concerned people such as backpackers and trekkers to detect signs of the fungus in amphibians in and around wilderness areas. Sign boards should be put up and researchers should talk to ensure that such information is effectively disseminated using the media so that more enthusiasts are roped in to help. It will also be important for the government to set up shelters, terrariums and laboratories where live amphibians can be stocked so as to enable reintroduction if populations drop in case of an outbreak. Such a measure, though a last resort, may be the only option in the event of an uncontrolled outbreak in the wild.
Time to Act
Given the impact of the chytrid fungus exacerbated by climate change in decimating populations worldwide, it is crucial for scientists and conservationists to act swiftly. Amphibians have been linked to canaries in coal mines. In bygone days canaries were carried in cages deep into mines and if they died, miners quickly evacuated the mine to avoid toxic gases. Amphibians are performing the same service for us humans, but we should be able to recognise and heed the warnings.
One way or the other, frogs and other amphibians are vital to our ecosystems, performing countless services including keeping insect populations in check. They have also been a part of our mythology and culture for eons and India cannot allow these beguiling creatures to vanish.
By Girish Arjun Punjabi