Roe a ‘bat-astrophe’

RESIDENTS and picnickers around Bibra Lake could be plagued by midges and mosquitoes as a consequence of the Perth Freight Link, says a self-taught bat expert.

East Fremantle’s Joe Tonga has been working on a self-funded campaign to increase the number of microbats around Bibra Lake but says much of the 60-strong colony roosts in the path of Main Roads’ bulldozers. With most of the large trees they rely on already gone, he says his handful of bat boxes is all that stands in the way of a bat-tastrophe.

“Without them, the mozzies will be breeding, so I hope [the bats] know where some of my boxes are nearby,” he told the Herald.

Mr Tonga says each microbat can gorge on 1000 mosquitoes or midges every night.

Main Roads’ environmental report acknowledges bats will suffer but says none of the five species present are endangered. It doesn’t discuss the consequences for bug numbers if bats die.

Mr Tonga says microbats are in serious decline across Perth because of widespread habitat destruction, but he’s optimistic his one-man campaign to restore numbers will succeed: his bat box building workshops are popular and he’s put extra effort into educating the next generation.

He praises Cockburn council: it’s trying to control midges at Yangebup Lake using microbats and recently asked Mr Tonga to install 10 more boxes. He says it’s probably too early for the project to start showing results, as the population probably needs to triple to have any impact on the huge swarms that can leave window sills coated up to 10cm deep.

A disappointing impediment is a lack of interest from the scientific community.

“If there’s no mining money involved, there’s no research,” he sighs. As a result, there are no definitive bat numbers and he has to rely on his own observations to get a handle on their situation.

Tiny, nocturnal and weighed down by a sinister reputation, bats go under the radar despite their key role in ecosystems.

Mr Tonga says they are, like frogs, a critical “indicator” of environmental health.

There are nine species in Perth, and though they have a small wing span, they’re capable flyers that use echo-location to navigate.

They live mainly in wet sclerophyll forests of karri, jarrah and tuart eucalypts, but clearing has seen more of them trying to find room in urban areas. Mr Tonga says that’s a tough call, given the competition they face from tougher rivals.

Associate professor Trish Fleming from Murdoch University says there are some simple tricks for helping bats survive in the city.

“We tend to remove dead branches from trees, while they are actually very important for animals that need hollows,” she told the Herald.

“As long as they are not dangerous, old and large trees are very important habitat for bats.

“Some bats also use hollow logs on the ground — so removing ‘firewood’ means you are removing habitat for animals.

“Many people are putting up bat roost boxes as potential sites for them, but hollows would still be their preference.”


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