Jon Bielby - Conservationist

What sort of amphibian extinction are you studying?
I’m studying extinction processes and declines in amphibians particularly declines related to the chytrid fungus. The chytrid fungus has a profound effect on metamorphosis (when a tadpole becomes a frog). Metamorphosis takes a lot of energy and is very stressful to tadpoles so the fungus takes advantage of this weakness and infection in metamorphs is usually fatal.

As part of my studies I am going to Sardinia on 6th August for 10 days to capture live amphibians and study them. After that I will be going to the Pyrenees to look for dead amphibians that have been infected by the chytrid fungus. Normally when an animal dies its body is consumed quickly but because of the aggressive nature of the disease infected ponds are often littered with hundreds and thousands of dead metamorphs so that makes study much easier.

How many amphibian species have gone extinct recently?
It’s really hard to determine exactly how many species have gone extinct because amphibians can be quite shy and reclusive. Just because we haven’t seen them doesn’t mean they’re gone forever. Some amphibian species that we think have gone extinct are the gastric-brooding frog of Australia and the golden toad of Costa Rica. The gastric-brooding frogs were found in Queensland and eastern Australia and we think they went extinct in the mind-1980s, the golden toad was found in a small region of high-altitude, cloud-covered tropical forest in Costa Rica and that frog was last seen in 1989.

There are many reasons why an amphibian species goes extinct but it’s probably due to diseases that accelerate the decline.

What sort of problems are cane toads in Australia causing and what is being done to stop them?
Cane toads are a very serious problem in Australia because they are an introduced species. This means that they have not evolved in Australia alongside its other wildlife, so they are wreaking havoc on the native species there. Cane toads were introduced in 1935 in attempt to control the cane beetle which was feeding on sugar canes. However, the toads weren’t interested in eating the beetles when there was lots of yummy Australian wildlife to feast on. 3000 toads were initially released in Queensland and at last count there were over 200 million on the east coast.

Cane toads are very hard to get rid of because they are almost invincible as a species! They can produce thousands of eggs when they reproduce and they can eat almost anything. They are also very poisonous, so that means that any natural predators like reptiles or birds that eat a cane toad end up being poisoned to death as well.
Cane toads also out compete native amphibians for food resources, spread diseases and they can ravel large distances so have infested a large amount of Australia’s east coast.

To deal with the cane toad problems Australian officials use an ultraviolet light to lure and capture cane toads and the University of Queensland is researching a way to switch the genes of female toads so that they become males and the population dies out.

What are the biggest and smallest amphibians?
The smallest is probably a species from Cuba that is about 4mm big. The largest is the Japanese salamander which can grow up to a metre! There are limits on how big an amphibian can grow because of something called surface area to volume ratio. The bigger an animal the more volume it has. Amphibians don’t breathe like birds or mammals, oxygen diffuses directly through their skin. So larger amphibians have a larger body volume but less skin surface area so they are limited by how much oxygen can diffuse through their skin and into their tissues. Too large and they suffocate!

What is the most deadly amphibian?
Probably the Phyllobates terribilis (The golden poison frog). 1 milligram of its poison can kill hundreds of people.

Where do frogs get their poison from?
Frogs get their poison from the food they eat. They eat a lot of mites and ants and these insects have poison in their stingers. The frogs consume the poison and assimilate into their own bodies and the poison becomes more powerful and is secreted onto the skin to protect the frogs from being eaten by animals like birds and lizards. The colourful markings on the poison arrow frogs serve as warnings to any animal that is thinking about making a meal out of the frog, the colours say ‘don’t eat me, I’m dangerous!’

What are the most unusual amphibians that you’ve seen?
The gastric-brooding frog is pretty unusual, although it’s probably extinct now. This frog swallows its eggs and broods them in its stomach, and while it does this it stops producing stomach acid and digestive juices (so it doesn’t digest its own eggs). When the young hatch they pop right out of the frog’s mouth!

Darwin’s frog does something similar: the male of the species swallows the eggs and broods them in a pouch in his vocal chords.

What are the most unusual ways that amphibians have been used by people?
Well there are lots of good examples but perhaps the most unusual example I know if is the use of the Xenopus frog. This frog is used as a pregnancy test! In order to test for pregnancy a woman’s urine is put into the water with the frog and if the urine has hormones associated with pregnancy then the Xenopus frog produces eggs!

Poison arrow frogs are used by South American jungle tribes to poison the tips of their arrows. They rub the arrow tips over the frogs’ skin and the arrow instantly becomes deadly poisonous. South American natives also make use of the toxic secretions on the skin of tree frogs, but in a different way. Before battle the warriors lick the frogs and the secretions cause them to enter an altered state of mind and heightens their senses for the battle ahead.