Endangered rainforest frogs persisting at Brooklyn

Brooklyn Wildlife Sanctuary, in far North Queensland, supports a greater diversity of wildlife than any other single AWC property – including 20 per cent of Australia’s frog species.

Several of these frog species are restricted to Brooklyn’s mountainous east. Many are endemic to, or find refuge within, the sanctuary’s 4,000-hectare section of the World Heritage Listed Wet Tropics Bioregion.

This important high elevation habitat has been the focus of Brooklyn’s most recent frog survey – targeting threatened stream-dwelling species – which has produced some encouraging results.

Large numbers of endangered frogs

Brooklyn’s threatened stream-dwelling frog survey, so far conducted between heavy rainfall periods brought on by ex-tropical cyclone Imogen, aims to monitor the abundance and altitude gradient of threatened endemic wet tropics frogs.

Encouragingly, during the recent upland element of the survey, large numbers of the endangered Common Mist Frog (Litoria rheocola) and Waterfall Frog (Litoria nannotis) were found.

© Pat Webster/AWC

© Pat Webster/AWC

© Pat Webster/AWC

© Pat Webster/AWC

The team also discovered records of the vulnerable Serrated-armed Tree Frog (Litoria serrata).

© Pat Webster/AWC

These species were impacted heavily following the arrival of chytrid fungus in the late 1980’s, which severely affected species with small distributions and elevational ranges – like many found on Brooklyn. 

The continued presence of these frogs on Brooklyn is therefore a beacon of hope; highlighting not only the immense biodiversity significance of the sanctuary, but also the importance of effective conservation management and science-led habitat protection. 

© Pat Webster/AWC

“Many leeches”

Like all AWC properties, scientific research forms the basis of our conservation management at Brooklyn. The science team regularly measure a suite of ecological health indicators across a diverse variety of habitats and elevations.

Inevitably, some surveys will be easier than others. This was not one of them.

© Emily Rush/AWC

This survey was no simple undertaking for AWC ecologists, Andy Howe and Emily Rush, who were joined by AWC volunteer, Pat Webster.

The night commenced with an hour and a half of tough hiking to reach the start of the first transect (survey area). The leech-riddled terrain was so difficult to work in that seven hours later, only three transects had been completed. As Emily explains,

“It was hectic terrain and we had a run in with many leeches (one giant one on my head!) as well as a stinging tree, which Andy was unlucky enough to encounter first. We finished the survey at 1:30am, exhausted after a difficult trek upstream.”

© Emily Rush/AWC

More to come

The level of species and ecosystem diversity on Brooklyn reflects a broad range of topography and a steep rainfall gradient across the property.

Cloud-capped mountains dominate Brooklyn’s east, rising to over 1,000m and receiving an average rainfall of over 4,000mm. Some of Australia’s richest rainforests are found here.

Wet sclerophyll forest in the west eventually opens into the wide grassy floodplain of the Mitchell River; where, at 300m altitude, the average annual rainfall is just 900mm.

© Emily Rush/AWC

As such, more than one survey is required to measure Brooklyn’s varied frog populations.

Having completed the upland element of the threatened stream-dwelling frog survey, the lowland transect is now on the horizon – but timing is everything.

The team need to act before the heaviest wet season rains arrive, rendering the creeks inaccessible; but they cannot start too soon, as not enough rain means not enough frogs.