KEY POINTS:
Dr Phil Bishop is happy. Some frogs have croaked, as in died. Why does that bring a smile to his face? Because he is confident he can isolate the cause of death, in this case a fungus he has been researching for the past five years.
In August,
a Dunedin enthusiast bought several green and golden bell frogs, an introduced species, from a supplier in the North Island where the amphibians live, only to discover they have been dying at regular intervals. The good news is, some are still alive.
"This morning we managed to determine the dead frogs were quite heavily infected with chytrid fungus. Of the live frogs, two or three are looking dodgy, so it's quite likely they've got chytrid as well, which is really exciting for us because nobody has been able to isolate a New Zealand strain," Dr Bishop says.
It's a timely breakthrough. Tomorrow marks the start of New Zealand Frog Week, a celebration of our seven species. Of those, four native varieties (Archey's frog, Hamilton's frog, the Maud Island frog and Hochstetter's frog) are included on the Zoological Society of London's evolutionarily distinct and globally endangered list.
In fact, the most endangered amphibian in the world is the Archey's frog, which only occurs in New Zealand.
Dr Bishop says there are now between 10,000 and 20,000. Although such numbers are unlikely to raise alarm bells among laypeople, the rate of decline in the past five years has been dramatic.
"We haven't pinpointed what the decline is caused by. We think it's probably a disease, but we need to try to do something about it."
A senior teaching fellow at the University of Otago's department of zoology whose expertise includes frog biology, the global decline of frog populations and animal communication, Dr Bishop's interest in frogs and toads began at the age of 4 when he was living in Britain. Later he completed a PhD on the social organisation of anuran (frog and toad ) choruses and spent 15 years in Africa before moving to New Zealand with his South African wife to further his interest in frog communication, particularly earless frogs.
During his fieldwork in South Africa, he discovered and named a new species of frog, Arthroleptella ngongoniensis, and in 1995 initiated the Southern African Frog Atlas Project, which took nearly 10 years to complete.
Dr Bishop started NZ Frog Week in 2002 in an attempt to raise awareness of the dangers facing amphibians as well as develop a wider appreciation of the animals.
This year is also International Year of the Frog, though that "doesn't mean all our problems are going to be solved in a year's time", he says. "It's just the start of trying to fix a global issue."
Dr Bishop says scientists first noticed a decline in global frog populations in 1989. Subsequent research often tended to focus on documenting that decline. However, he describes such observation as "morally irresponsible", adding it's more important to focus on survival solutions, hence his research into developing an antibiotic for the chytrid fungus.
"Our frogs are getting a lot of environmental insults from us and it puts a lot of stress on them and they become open to things like disease. It's like the last straw that breaks the camel's back."
Habitat loss is another concern. Since humans arrived in New Zealand, three species of native frogs have been lost, Dr Bishop believes. Climate change, too, is an issue.
"It might seem nice and wet, and if you look at the monthly rainfall you might not see any difference, but on a daily variation you might see we are getting a large dump of rain rather than a small amount every day. The humidity in the frogs' habitat could be quite different from what it used to be."
The susceptibility of frogs to environmental change has scientists likening them to canaries in a coalmine. A frog's skin is used to control water levels and is also a secondary respiratory system. In short, it can breathe and drink through its skin.
"It's a very sensitive structure. If there is anything nasty in the air, soil or water, then the frogs are going to pick it up. If the frogs start disappearing from the environment, you know there is something subtly wrong."
Frogs are also a great source of scientific benefit. Dendrobates auratus, the green and black poison dart frog, is a source of toxin for Central and South American hunters. At one point, medical studies were being conducted into a compound called epibatidine, found in the dart frog and believed to be about 200 times more potent than morphine in blocking pain in animals.
And according to a Times of India report last year, tree frogs, lizards and bush crickets inspired a team of Indian researchers to create a super glue. After studying the creatures' sticky toe pads, scientists at the Indian Institute of Technology made an adhesive tape by running air or oil-filled micro-channels through a soft, elastic material, making it stickier than conventional glues. During initial research, scientists found the pad on the bottom of a tree frog's toe was coated with a mucus film. This layer of fluid led scientists to think that the pads cling to a surface by wet adhesion.
To lose a species of frog is to lose potential health benefits, Dr Bishop says. He points to an Australian gastric breeding frog, which ate its eggs, switched everything off in its stomach then hatched the eggs internally. When the eggs turned into froglets and were ready to metamorphosise, the mother then vomited up the youngsters.
"Now, that frog has become extinct recently, so we have lost any understanding of how it could turn off its gastric juices in order not to dissolve the eggs.
"The treatment for gastric cancer or stomach ulcers ... we've lost that connection. It could have had fantastic health benefits."
Closer to home, little brown tree frogs infected with the chytrid fungus have been discovered at Purakaunui, on the Otago Peninsula.
"We know the chytrid fungus is here in Dunedin. And that is a worry because if people have frogs in their garden and want to keep them, then they have to be very careful. It's much better if people don't move frogs or plants from pond to pond."
The fungus lives in the skin of amphibians and feeds off keratin, the same compound found in fingernails and hair. The fungus disrupts the balance of the skin; the frog can't regulate its salt levels; it dies pretty rapidly.
Earlier this month Dr Bishop was named Auckland Zoo's inaugural Conservationist of the Year, an award he describes as "very good for me, but very good for the frogs as well". The $1000 prize will go towards a frog conservation project.
"I've had a lot of people ring me up and congratulate me. They think it's appropriate that someone who has acted in frog conservation has been given the award in the year of the frog."
Not everyone shares Dr Bishop's love of frogs. In the 18th century, famed Scandinavian biologist Carl Linnaeus described them as, "foul and loathsome creatures ... abhorrent because of their cold body ... filthy skin ... harsh voice, squalid habitation, and terrible venom". More recently, in Dunedin, there have been complaints about some frogs' acoustic ability.
"We've had several cases in the last two weeks of people ringing us, complaining that they need to get rid of the frogs in their garden. We've even had Dunedin noise control responding to complaints about frogs, trying to get rid of them. But you don't see anybody ringing up noise control to shoot the neighbours' blackbirds."
Obviously, the culprits do not belong to one of the four native species, none of which makes a noise.
Frog noises need not come from the amphibians either. Dr Bishop is a master of many amphibian utterances.
"If you call, frogs can't help themselves. If they are there, they will call back.
"I often get people taking photos of me when I'm impersonating frogs. It's usually when I'm trying to check a field. Those photos often end up on embarrassing websites."
Something special
New Zealand's four native frogs - Archey's frog, Hamilton's frog, Maud Island frog and Hochstetter's frog - do not call or croak because they have no vocal sac.
Among their other distinctive features, the endemic amphibians have no external eardrums, no tadpole stage and have cartilaginous ribs, indicative of a primitive amphibian that would have crawled.
They also have vestigial tail-wagging muscles similar to the salamander family.
The primitive native frogs swim using alternate legs - like a dog paddle - instead of a frog kick.
Among the world's most ancient frogs, their ancestors reached New Zealand by continental drift from the supercontinent of Gondwana millions of years ago.
- OTAGO DAILY TIMES
