This spider-eating, nest-sharing bat was once safe from fire, until the Black Summer burned its rainforests

The golden-pointed bat, Phoniscus papuensis. Credit: George Madani, Author Provided

Golden-tipped bats are peculiar creatures. At night, they prey in the understory for orb-weaving spiders, which they gently pluck from their sticky webs. During the day, they sleep in excavated cellars at the bottom of nests made by two rainforest birds.

Unfortunately, although their rainforest nests usually protect them from fire, our new research found that this is no longer guaranteed. Rainforests grow in areas not normally burned by fires. But prior to the Black Summer of 2019/2020, many of these areas had dried out, setting the stage for fires of unprecedented size and intensity. As a result, large tracts of rainforest along the coasts of southeastern Australia were badly burned.

Our study confirms experts’ predictions that golden-tipped rainforest-dependent bats would be severely affected. We found that the fires caused a large reduction of suitable habitat.

Why is this rainforest bat so special?

Like birds, Australia’s many bat species come in many different shapes and sizes. Some fly fast in the open, while others fly slowly with great dexterity among the cluttered vegetation. The delicate gold-tipped bat is a “junk specialist”, hunting in the understory and plucking its favorite orb weaver spiders from their webs without getting caught. Its wings are optimized for slow, cautious flight.

Amazingly, golden-tipped bats sleep in chambers they excavate beneath the elaborate hanging nests of two birds, the yellow-throated bushes and brown gerygone. These birds nest in moist vegetation, which infiltrates the drier eucalyptus forests along the eastern coast of Australia along a network of trench lines.

This spider-eating, nest-sharing bat was once safe from fire - until the Black Summer burned its rainforests

A group of golden-tipped bats resting in a space they’ve dug under a hanging nest of the yellow-throated bushes. Credit: Fiona Backhouse, Author Provided

The birds have the top bunk, and the little bats—all six ounces—make room in the basement. The woolly, golden fur of the sleeping bats matches their mossy, bird-built houses.

These rainforest shelters give these bats access to wet and dry forests, allowing them to forage more widely at night.

Why are fires so bad news in rainforests?

Animals in fire-prone eucalyptus forests have developed mechanisms to cope with wildfires. But rainforest plants and animals didn’t have to learn these tricks. In rainforests, fire is a rare and devastating event.

Fire events classified as extreme are uncommon (by definition) and we rarely have the opportunity to measure their effects on forest animals. Climate change has been linked to increasingly dangerous fire weather events and more frequent mega fires at extreme levels in southeastern Australia.

To find out what this means, our study measured the impact of the 2019/20 megafires on this bat.

This spider-eating, nest-sharing bat was once safe from fire - until the Black Summer burned its rainforests

We placed these harp traps to capture gold-tipped bats in unburnt (left) and burnt (right) locations. Author provided

What have we done?

A year after the fires, we set harp traps in rainforests ranging from heavily burned to completely unburned. Our aim was to understand whether golden-tipped bats were present at each site and to use this data to model the effects of the fire on the habitat of this species.

The result? In locations where a very severe fire had raged, we saw that the modeled occupancy dropped sharply from 90% to 20%. Even a year later, the heavily burned rainforest was no longer used by this species.

Burnt places also had few scrubs and gerygones, and almost none of their nests. On the plus side, we captured 66 golden-tipped bats in unburnt rainforest, showing that this elusive and poorly studied species persists in reasonable numbers.

We attached small radio transmitters to our captive bats to watch them move and rest in fire-infested habitats. Tracking bats over steep gullies of dense undergrowth was hard work, as they moved to new roosts almost daily.

The bats chose to roost in unburnt spots, which was not surprising since their favorite bird’s nests were easily consumed by fire. Avoiding burnt areas could indicate that movement in fire-affected landscapes will be restricted.

This spider-eating, nest-sharing bat was once safe from fire - until the Black Summer burned its rainforests

Gold-tipped bats showed a strong preference for roosting sites in unburnt locations. In this figure, bat habitats (blue triangles) and fall locations (yellow dots) are shown against the mapped fire impacts in one study area.

Our study also tested whether a modest mop head could serve as a stopover for these bats until the scrubwrens and gerygones could return and build new nests.

Why joke? Because these bats were previously found in an old mop head.

We haven’t registered them as yet while using the mops, but we will continue to monitor them over the coming breeding season.

What happens when extreme fires become commonplace?

In many dry eucalypt forests, corridors of rainforest that follow gullies and creeks provide essential food and shelter for wildlife such as the golden-tipped bat, significantly increasing local biodiversity.

Climate change threatens rainforest-dependent wildlife in southeastern Australia through soil drying, increasing drought and increasing severe weather. Together, these make it possible for unburnt rainforest to go up in flames.






These unusual golden-tipped bats sleep beneath the hanging nests of two rainforest birds. Video by Lachlan Hall and George Madani.

Animals that depend on rainforests are not adapted to handle fire. Increasing frequency of extreme fire events as the world warms will cause major disturbances in the forests of South East Australia.


Rainforest birds are declining in the wake of summer black fires


Provided by The Conversation

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Quote: This spider-eating, nest-sharing bat was once safe from fire, until the Black Summer burned its rainforests (2022, Aug. 31) Retrieved Aug. 31, 2022 from https://phys.org/news/2022-08-spider-eatnest-safe -black-summer parts.html

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