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FROSTY’S RAMBLINGS Global threat to our garden ponds

PETER FROST is worried about a new infection threatening our native amphibians

 A NEW and virulent infection is threatening British frogs, toads and perhaps other amphibians. 

After a journey halfway around the globe the severe perkinsea infection (SPI) has been found for the first time in European tree frog tadpoles kept in an aquarium in Surrey.

Severe perkinsea infection has caused the death of huge populations of tadpoles across the United States and researchers also found the disease in wild populations in Panama. 

The disease causes bloating in frog tadpoles, leaving them unable to dive and leading to rapid death from multiple organ failure in 95 per cent of affected populations.

Now the disease has turned up in European tree frogs bought from a pet store and kept in an aquarium in Surrey. 

The responsible owner called in amphibian specialist vets but it was impossible to trace the source. 

We do know nearly a third of all amphibian species are threatened with extinction. The two main threats are disease and habitat destruction. 

There is no cure for SPI, which was first detected in New Hampshire in 1999 and is now recognised as one of the most significant causes of mass mortalities among tadpoles in the US.

Ten of the 81 tadpoles tested in Panama had the SPI-causing protist organism. 

Protists include most algae and some fungi. Five of 10 tadpoles taken from the Surrey aquarium where the tree frogs were breeding had SPI.

Researchers did not wait to see whether the disease developed in populations in Panama, whereas in the British aquarium population, tadpoles had already developed the disease, which is why the aquarium owner contacted called in experts.

Now those experts are calling for large-scale screening of amphibian populations, particularly those being bought and sold in the exotic pet trade, to monitor disease and reduce the risk of spread. 

A new British website, tadpole-doctor.co.uk, has been set up so that people can help to identify and report amphibian disease early. 

Did you know that the international trade in frogs for meat and for zoological and private pet collections is very large? 

The frog meat trade alone is worth more than £70 million a year. 

Regular readers of my environment pages will know how much I love our native amphibians, so this new threat to frogs and toads is particularly worrying. 

All our native amphibians are already under threat — some seriously so. 

Some suffer from lack of suitable habitat, which is why garden ponds are so important to their survival. 

They are also susceptible to a number of other viruses that can reduce populations dramatically.

Let’s start with our two native toads; the common toad (Bufo bufo); and the much rarer natterjack toad (Epidalea calamita). 

Spot the natterjack from the bright yellow stripe down its back.

We have just four native frogs. The common frog (Rana temporaria) comes in many distinct colours, some quite spectacular, and this can sometimes cause confusion.

Other British frogs are: the pool frog (Pelophylax lessonae); the moor frog (Rana arvalis) and the agile frog (Rana dalmatina).

My local specialist reptile shop offers no less than 13 species of pet tree frogs from £13 to £100. 

Many of these can be and are kept outside in garden enclosures. 

We have three native newts. I think newts are my favourite native wild animal. 

I’m slightly embarrassed to admit I keep them as pets as a very young boy before I knew any better. But I still love these pond dragons today.

Newts are members of the huge salamander family. In Britain the most spectacular, and most protected by law is the great crested newt (Triturus cristatus) — truly a dragon if only six or so inches long.

More common is the smooth newt (Lissotriton vulgaris) and the very similar palmate newt (Lissotriton helveticus). 

Again, exotic pet stores sell salamanders and newts. Dozens of species are available. £15 will buy you an alpine newt. Between £50 and £100 will buy a spectacular colourful salamander.   

The release of any exotic species into the wild is a criminal offence under the Wildlife and Countryside Act 1981. 

However, over the years many exotic amphibians have been introduced to our countryside either deliberately our as escaped pets.

Perhaps the most amazing story — and introduction — is of the African clawed frog (Xenopus laevis). 

For at least two decades from about 1930, this frog provided the most reliable pregnancy test available.

Previously pregnancy tests involved injecting a woman’s urine into a variety of laboratory animals, including rats, guinea pigs or different species of frogs. 

After 10 days the animal was killed and examined for changes in its sexual organs.

The African clawed frog was similarly injected with a woman’s urine but in this case the frog would start to lay eggs to indicate pregnancy. 

The frog lived and could even be used again for future tests. Hundreds of thousands of this frog were first imported and then bred to provide the test animals. Some escaped.

We have a couple of exotic and attractive foreign salamanders that are well established in various places in Britain. 

The fire salamander (Salamandra salamandra) is brightly coloured, black with yellow, orange or red spots or stripes. 

One of Europe’s largest salamanders, it can grow to be six to nine inches (15-25cm) long. 

It is common all over Europe and now established in many locations in Britain where it can live for 50 years. 

Most British escapees were petshop-bought. Some were smuggled back from foreign holidays wrapped in a wet flannel in a waterproof toilet bag. Naughty naughty.

Midwife toads (Alytes obstetricans) are a feminist’s delight. The females lay their eggs in chains and the males wrap the strings of eggs around their back legs to keep them safe. 

These tiny toads — only as big as a fifty pence piece — have spread to parts of Bedfordshire and Northamptonshire since a local nursery imported them from France in clumps of ornamental pond plants around 1900. 

They seem to really enjoy our climate and gardens and are spreading to locations all across Britain. 

They have reached as far as Wales and Yorkshire as well as some parts of outer London. 

Today this little toad is a real nuisance. The male’s very loud mating call sounds exactly like an iPhone bleep. 

One other introduced toad has the delightful name of yellow-bellied toad (Bombina variegata). 

It isn’t common but that hasn’t stopped me adding its name to my insult vocabulary.

On a recent edition of Radio 4’s Gardener’s Question Time a woman sent in a picture of what looked like frog spawn hanging in a tree. 

One expert said it had been laid in the tree by a tree frog. The other three experts said it was common frog spawn and had probably been accidentally dropped by a bird that had lifted it from a pond. 

I’m with the three experts because tree frogs all over the globe lay their eggs in water — sometimes just a puddle — but never up a tree.

Are their tree frogs in Britain? Yes, there are. Again, mostly escapees or deliberate introductions. 

The European tree frog (Hyla arborea) can easily survive all but our harshest winters and certainly were common here a couple of thousand years ago. 

In addition the Australian green tree frog (Litoria caerulea), sold as pets, has been spotted in the wild and may bred here.

I have written about tigers, about whales, even recently about a Welsh walrus, but watching colourful playful crested newts doing their mating dance reinforced my love of England’s green and pleasant land like nothing else ever could and also reminded me of the desperate need to protect our countryside and the creatures that share it with us. 

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