VISITORS to the banks of the Orwell were today warned about an unexpected danger from global warming - a family of Australian crocodiles has taken up residence in the river.

VISITORS to the banks of the Orwell were today warned about an unexpected danger from global warming - a family of Australian crocodiles has taken up residence in the river.

The creatures are a breed that is native in the rivers and coastal estuaries of Southern Australia, around the coast from Sydney to Perth.

The Australian Cayman (crocodylus aprifolus) is closely related to the better-known salt water crocodile which is found in the northern coastal areas of the country and was featured in the Crocodile Dundee films.

However the cayman is smaller and is considered more manageable by animal trainers. It is thought the examples in the Orwell are escapees from a commercial filmed for French fashion house Lacoste, in the Levington area in the early 1980s.

Four young Australian caymans were used in the filming and The Evening Star has established that they escaped from their cage shortly after filming was finished. They were all males - but there are fears that one or more of these could have changed sex in the cold water and started breeding.

Crocodiles can change sex when they achieve maturity if there is an imbalance between male and females in a colony.

Retired London-based animal handler Alistair Gator said: “The caymans were all very young, about two and a half feet long and frankly when they escaped there was little point in having a major search for them.

“At that size they are quite harmless and we knew that the water was too cool for them to grow. We thought they would live for a few months on fish and then die when it got cold in the winter.”

Now, however, it is clear that the cold did not kill them off - and that after being held in “suspended animation” for many years they have now started to grow.

There have been sightings of them in the river and it is clear they have grown quite large - to about six feet long.

Australian caymans rarely attack adult humans in their native country because they are too small - although they have been known to attack children.

RSPB volunteers in the area have found several dead swans in the area around the Strand at Wherstead, and on the foreshore of the Orwell Country Park.

Reptile expert Dr Furst de Forth from London Zoo has been called in to advise staff from Ipswich council's Greenways project - and told the Star that action is needed now.

He said: “The caymans have not been any danger and there was not point in warning people unnecessarily - but now there are concerns that they have reached maturity and could pose a danger in some circumstances.

“We would like to set up a programme and remove them from the river, but it might already be too late. They may already have a substantial colony in the Orwell.”

The problem had been caused by the rise in the water temperature of the Orwell over the last 20 years.

“Year on year temperatures have gone up by about a quarter of a degree every year since the caymans got into the water.

“Now every year there are about six months of the year with the water temperature above 20C - and that is the tipping point which allows the animals to grow . . . and breed.”

Dr de Forth said the important thing now was to identify the caymans' breeding sites.

He said: “They lay eggs in sand nests near the water's edge which they then cover. We know there must be at least one nest site out there and we would appeal to anyone who finds a site - or empty eggshells - to contact the authorities so action can be taken.”

A special website to record any sightings will be available at www.eveningstar.co.uk from tomorrow.

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Have you got any pictures or video of the caymans? Send them to eveningstarnews@eveningstar.co.uk.