Go to North Queensland to look at some rainforest bats.


GENEVIEVE HUSSEY: To many people, bats like these are simply a nuisance.

DR DAVID WESTACOTT, CSIRO TROPICAL FOREST RESEARCH CENTRE: They're noisy, they're smelly, this sort of thing, and they're also an agricultural pest in these areas.

There's lots of tropical fruits grown up here -- flying foxes just love tropical fruits.

GENEVIEVE HUSSEY: But the species of bat, called the spectacled flying fox, has another side to its nature that most of us aren't aware of.

Scientists are discovering just how vital they are to the survival of our World Heritage-listed wet tropics rainforests.

CSIRO researcher Andrew Dennis says he's found the spectacled flying fox is unique in its ability to spread the rainforest seeds long distances.

ANDREW DENNIS: The seeds that these animals swallow, which are only very small seeds, can stay in the gut for up to 19 hours.

This means it gives them the opportunity to move some seeds very large distance -- scores of kilometres, perhaps over 100 kilometre.

GENEVIEVE HUSSEY: But the spectacled flying fox has developed a taste for a new introduced plant -- wild tobacco.

The flying fox loves its berries but they come at a high price.

ANDREW DENNIS: They're very short plants, they grow out in pastures, and this means that the flying foxes are coming down much lower to forage than they normally would and it's bringing them in contact with paralysis ticks.

SAMANTHA FOX, JAMES COOK UNIVERSITY: Within two to three days the bats first are unable to fly, then they lose the ability to hang, so they tend to fall to the ground, and then it paralyses all their organs as well, so they can't breathe.

GENEVIEVE HUSSEY: Each year, the bat hospital on the Atherton Tableland, just west of Cairns in north Queensland, cares for hundred of flying foxes stricken with tick paralysis.

Despite their best efforts, they can only save half of the tick-infested bats.

JENNY MACLEAN, TOLGA BAT HOSPITAL: In a bad year of tick paralysis, we reckon 5 per cent to 10 per cent of the local colony is getting tick paralysis, so the bats are always having their babies at the tick paralysis time of the year, and a lot of the bats that we find in the colony are mums with bubs.

GENEVIEVE HUSSEY: It will take months of hard work before these orphaned babies can fend for themselves.

JENNY MACLEAN: The spectacled flying fox -- the one that's being affected by the tick paralysis -- is now listed as a vulnerable species because the numbers have gone down.