Native Frogs and a Suffocating Fungus

Who hasn’t collected tadpoles as a child, and watched them transform into the handsome prince – well, they might if you were prepared to kiss the adult frog! The frog prince has its origins in a Brothers Grimm fairy tale, but there is a grim future ahead for frogs with a suffocating disease that is spreading across the globe.

With the exception of Antarctica, amphibians inhabit every continent in the world and are closely associated with both water and land. In fact, the word amphibian derives from ancient Greek, meaning “both kinds of life”.  The distinguishing feature of amphibians that permits this dual life – skin that is permeable to water and air – comes at a cost: amphibians are at a greater risk of disease and fungal skin conditions, some of which can be deadly.  

The highest profile of these diseases, Chytridiomycosis, is the infection of amphibian skin cells caused by the chytrid fungi Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). First discovered in Queensland in 1993, this infection affects the skin and disrupts how amphibians breathe and move water and minerals through their skin. The disease is now widespread throughout Asia, Africa, the Americas, Europe, and New Zealand, with the true impact on frog populations unknown.  

As for many of our indigenous species, New Zealand is home to one of the most ancient lineages of frog, and all three native frog species in New Zealand are classified as At Risk or Threatened. The primary agents contributing to their threat status are mammalian predation and disease. The three species belong to the ancient genus Leiopelma and include two terrestrial and morphologically similar taxa: Archey’s frog (L. archeyi) and Maud Island frog (L. pakeka), and one semi-aquatic species, Hochstetter’s frog (L. hochstetteri). New Zealand frogs have long been isolated from the rest of the world, yet even they have not escaped the clutches of chytrid fungus. 

It doesn’t help that the disease is difficult to detect without specific tests, but Chytrid fungus has been detected in Archey’s frog populations and is thought to have contributed to a population crash on the Coromandel Peninsula between 1996-2001. Interestingly, individual Archey’s frogs have demonstrated the ability to eliminate Bd and be treated for chytridiomycosis. The percentage of the population able to eliminate Bd is unknown, as is the effect the disease could have on other Leiopelma species. For this reason, it is important that researchers follow guidelines to eliminate human mediated spread of this and potentially other infectious diseases.  

Any survey or research work on frogs requires a permit from the Department of Conservation, and the permit requires that all necessary protocols to prevent the spread of the disease are adhered to. Experienced ecologists at Boffa Miskell have worked with Archey’s and Hochstetter’s frogs for 15 + years, with over 600 new Archey’s frogs records alone resulting from survey work. These surveys include working through the night across large numbers of sites in warm, wet and humid conditions – when Archey’s frogs are most active. We know the risks that our ecologists pose as disease vectors and so we take all necessary precautions to eliminate human mediated routes of disease transmission. To protect the frogs, researchers undertaking frog surveys wear powder-free nitrile gloves to ensure nothing on human hands gets transferred to a frog. Once captured, individual frogs are placed into a Ziplock bag for immediate measurement, rapid external condition assessment and identifying photographs. This technique minimises handling time and prevents equipment touching the frogs. Gloves and Ziplock bags are disposed of after each individual and Trigene is used to clean boots and tools between sites.  

New Zealanders have recently demonstrated our ability to effectively respond to virus outbreaks and eliminate community transmission. We can take what we have learnt from the COVID-19 pandemic, such as strict hygiene protocols and isolation of outbreaks, and apply it to other viruses or diseases, such as chytridiomycosis. Boffa Miskell ecologists are very careful in our handling of native frogs, but if chytrid fungus is to be eliminated from communities, we all need to work together to achieve this. The best method for this is to leave the handling of native frogs to the experts with the permits, to not release exotic wildlife into New Zealand’s delicate ecosystems, and to support research that could change the tide on this suffocating fungus. 

At the end of the day no species enjoys being kept in ‘Level 4’ isolation or being swabbed – and, for the purposes of social distancing, no more kissing frogs!!  

For further information please contact Katherine Muchna