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  BBC 15 Feb 06
Toxic toads 'threaten disaster'
By Rebecca Morelle BBC News science reporter

Toxic cane toads are evolving into a 'eco-nightmare' that are able to cover huge distances, a study says.

Scientists, writing in the journal Nature, found the toads are getting leggier, moving faster and further than their shorter-legged counterparts.

Cane toads were introduced for pest control in Australia 70 years ago, but have proved an ecological disaster. They are now found in an area covering over a million square kilometres, but there is no known method of control.

Incredible distances

Cane toads (Bufo marinus), which can weigh up to 2kg, are toxic and highly invasive. Since their arrival in Queensland in 1935, they have been sweeping through Australia leaving a trail of dead creatures in their wake.

To investigate their worrying spread, scientists looked at cane toads invading the Northern Territory of Australia, at a site about 60km east of Darwin. They caught the toads, measured them, and also attached a radio-transmitter, weighing about 5-6g, around their waist to track their movements.

"During an invasion process the individuals at the front are there because they have moved the furthest," explained Dr Ben Phillips, an author on the paper and an evolutionary biologist at the University of Sydney, Australia. "We showed that the toads that are the first to arrive at the front are the ones with the longest legs, and the ones last to arrive have shorter legs. "The front toads also have much longer legs than the older populations in Queensland."

'Ecological nightmare'

They discovered that the toads were moving incredibly quickly, covering distances about five times faster than when they arrived 70 years ago. "They are moving around 55km a year on average, which is a long way to hop if you are a toad," said Dr Phillips.

The researchers believe their findings indicate evolution is favouring longer-legged toads which can travel further, quicker, meaning they can encroach on new territories faster than ever before.

The scientists say the toads are causing an "ecological nightmare", killing many native creatures including snakes, monitor lizards and mammal predators, which are poisoned after eating their toxic skin.

So far, scientists have been unable to find a successful way of controlling the ever-spreading invaders, which are now on the cusp of invading Darwin. "How to control them is the $64 million question," said Dr Phillips. "A lot of time and money has been spent researching how to control toads, but it is an ongoing problem."

PlanetArk 16 Feb 06
Long Legged Cane Toads Lead Australia

LONDON - Cane toads in Australia have developed longer legs to enable them to invade more territory, scientists said on Wednesday.

The toads, which are a threat to native species, were introduced into Australia 70 years ago to control insect pests in sugar cane fields. They now spread across a range of a million square kilometres in the north and east of the country.

Their territory is likely to get larger because the toads' longer legs make them faster, according to Richard Shine and researchers at the University of Sydney. "We find that toads with longer legs can not only move faster and are the first to arrive in new areas, but also that those at the front have longer legs than toads in older populations," Shine said in a report in the journal Nature.

The researchers studied toads leading the invasion about 60 km (37 miles) east of the northern city of Darwin. They discovered that the first toads to arrive in new areas had longer hind legs than those that came later. The scientists believe the toads evolved longer legs to conquer new territory to get to better food supplies.

They added that efforts to control the pests should be launched before the toads evolve into even more dangerous adversaries.
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