31/03/2011 03:08:19 Super-tough toads have calloused feet from travelling
April 2011: The battle to halt the damaging spread of cane toads in Australia is proving tougher than originally thought.
In 2005 when Kimberley Toad Buster (KTB) volunteers first began the fight to slow down the movement of cane toads making their way from the Northern Territories towards the border with Western Australia.
'When we initially started toad busting we had been told by scientists and toad experts that toads were only travelling about 25 to 30 km per year, did not swim well in fast flowing water, had low tolerance to saline conditions, that there was a less than five to ten per cent survival breeding rate, that the lungworm parasite was 20 years behind the front and so on. The list was endless,' said Sharon McLachlan, KTB secretary.
Their resilience is frightening
'It did not take us long to realise that much of the information we had received might have applied to the Queensland toads but not to those that were hell bent on reaching Western Australia.'
Not only were these frontline toads moving an average of 80 km a year, they were larger, extraordinarily resilient to the saline conditions of some of the rivers they were crossing and that the breeding survival rate appeared to be more in the vicinity of 75 to 85 per cent.
KTB volunteer Del Collins said: 'I timed one female toad that stayed underwater for 1.2 hours. These guys are super-Rambo toads.
Said Sharon: 'Their resilience is frightening. These toads, irrespective of injuries are determined to keep travelling west and I have no doubt they will reach Perth eventually.'
'Explorer' toads march ahead to find breeding grounds
KTB volunteers also established that there was a clear pattern emerging in the behaviour and characteristics of frontline toads making their way into WA. Leading the cane toad pack are the predominantly male explorer toads accompanied by the odd, very large female.
'These toads are huge,' stated Ben Scott-Virtue, field co-ordinator. 'The females are often, on average, as large as 17.5 cm from snout to tail bone and the males around 14 to 15cm. Their back legs are between 2cm to 4cm longer than their bodies and the pads of their feet are blackened and calloused from constant travelling. They can often be up to 30 km in front of the main breeding colonising front,' he added.
Once these colonisers have found an ideal breeding area they begin to call in the closest wave of the breeding population numbers travelling behind them. Once the breeding population has been established and the very large females have dropped their eggs the explorer toads move on.
It is time for some serious re-thinking
In dry landscapes these explorers use cattle trails and moist cow dung to move between water holes. When confronted by really dry conditions, the toads simply use the deepest and dampest burrow or other ground hollow to hibernate in, often sacrificing the uppermost layer of toads to ensure that some survive.
'We have dug up to 30 toads out of a deep burrow months after the area has dried out and it is obvious they are simply waiting for the next rain,' said Lee Scott-Virtue KTB president and founder. 'All previous cane toad invasion predictions have been wrong and anyone seriously thinking that the Great Sandy Desert is going to stop these invading Rambos has got to do some serious re-thinking.'
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