New homes being built for Kangaroo Island native bees

A male green carpenter bee. Photo Remko Leijs
A male green carpenter bee. Photo Remko Leijs

The last remaining population of green carpenter bees in South Australia is just clinging to existence after the devastating Kangaroo Island bushfires.

Now a new collaborative program being undertaken by scientists from the University of Adelaide and SA Museum, as well local volunteers and landowners is trying to ensure the native bee's future.

To help save the species, new nesting stalks are being built for these bees, through help of the Kingscote Men's Shed and funds raised via the Australian Entomological Society and the Wheen Bee Foundation .

Entomologist Dr Katja Hogendoorn from the University of Adelaide's School of Agriculture, Food and Wine is asking locals who own intact bush blocks with old dead banksia trunks to get involved.

Graeme Connell and the volunteers at the Kingscote Men's Shed are helping to build nesting stalks for green carpenter bees. Photo Remko Leijs

Graeme Connell and the volunteers at the Kingscote Men's Shed are helping to build nesting stalks for green carpenter bees. Photo Remko Leijs

"We would survey their property, and if suitable with enough size and good vegetation, place some nesting stalks, and ask them to check them on occasion for us to see whether any bees have started to use them," Dr Hogendoorn.

KI entomologist Dr Richard Glatz and other local volunteers have worked for years on studying and providing emergency habitat for the native bees after the 2007 fire.

He is the point of contact for locals to get involved and can be reached at richard@dess.net.au

Dr Glatz said in addition the carpenter bee, there were 10 Kangaroo Island insect species that made the federal priority list for funding after the fires, as well as three arachnids.

Together with arachnologist and fellow KI local, Dr Jess Marsh, they are hoping to receive funding to conduct a survey of threatened insects.

"We have started looking at various sites on KI to prioritise them for these surveys. The carpenter bee is a separate project," Dr Glatz said.

"In reality, there are many other species that may have been heavily impacted on KI. Some aren't described, some have very few records, some have had their entire known range burnt etc."

An artificial stalk nesting site in a yakka or Xanthorrea grass tree. Photo Remko Leijs

An artificial stalk nesting site in a yakka or Xanthorrea grass tree. Photo Remko Leijs

The carpenter bee story

The green carpenter bee (Xylocopa aerata) has been extinct on mainland South Australia for more than a century - and scientists worry that last summer's catastrophic bushfires have significantly increased the extinction risk of the Kangaroo Island population.

"After the 2007 fires, we bolstered the remaining population by providing nesting materials until new dead Banksia trunks, suitable for nesting, would become available," Dr Hogendoorn said.

"In long-unburnt areas adjacent to Flinders Chase National Park, carpenter bee nests were still present . From there, they colonised the many dry grass tree stalks that resulted from the fire in the park."

But the grass tree stalks only remain available for a period of 3-5 years after fire, so after that, scientists placed new artificial nesting stalks in fire-affected areas where the bees still occurred. Almost 300 female carpenter bees have successfully used the stalks to raise their offspring.

"To see our efforts - and most importantly, more than 60 years of unburnt Banksia habitat that these bees rely on - destroyed by the 2020 fire was utterly devastating," says Dr Hogendoorn.

"There were more than 150 nests containing mature brood in the stalks we had provided."

The yellow dots represent known green carpenter bee nests. In red: the area burnt in 2020. Only a subset of the remaining green and yellow patches still have the right vegetation for the green carpenter bee. Image: Nature Maps SA/Remko Leijs

The yellow dots represent known green carpenter bee nests. In red: the area burnt in 2020. Only a subset of the remaining green and yellow patches still have the right vegetation for the green carpenter bee. Image: Nature Maps SA/Remko Leijs

Scientists will survey remnant long unburnt areas on Kangaroo Island for remaining green carpenter bees.

They will also search conservation areas around Sydney, and in the Great Dividing Range in New South Wales, where much of the species' natural range was also burnt.

"Encouragingly, we have already found a few natural nests on Kangaroo Island, but the remaining suitable areas are small and isolated, and densities are likely to be low," Dr Hogendoorn said.

Dr Hogendoorn and colleagues at SA Museum are working with Kangaroo Island landholders to place new nesting stalks in areas with good floral support, to enhance reproduction and help the bees disperse into conservation areas once suitable.

"As we have learnt, success is not guaranteed... extensive and repeated bush fires, combined with asset protection and fuel reduction burns, are making longtime unburnt habitat increasingly rare," she said.

 A male green carpenter bee. Photo Remko Leijs

A male green carpenter bee. Photo Remko Leijs

Carpenter bee facts

  • The green carpenter bee is a buzz-pollinating species. Buzz pollinators are specialist bees that vibrate the pollen out of the flowers of buzz-pollinated plants.
  • Many native plants, such as guinea flowers, velvet bushes, Senna, fringe, chocolate and flax lilies, rely completely on buzz-pollinating bees for seed production. Introduced honey bees do not pollinate these plants.
  • Carpenter bees are so named because they excavate their own nests in wood, as opposed to using existing holes.
  • With a body length of about 2 centimetres, it is the largest native bee in southern Australia.

Vulnerable to fire

Green carpenter bees are vulnerable to fire and the availability of their nesting materials is intricately connected with fire.

  • The bees mainly dig their nests in two types of soft wood: dry flowering stalks of grass trees and, crucially important, large dead Banksia trunks. Unfortunately, dead wood burns easily.
  • Grass trees flower prolifically after fire, but the dry stalks are only abundant between two and five years after fire.
  • Banksia species don't survive fire, and need to grow for at least 30 years to become large enough for the bees to use. With increasingly frequent and intense fires, there's not enough time for Banksia trunks to grow big enough, before they're wiped out by the next fire.
  • If the nest burns before the offspring matures in late summer, the adult female might fly away but won't live long enough to reproduce again.
  • The bees need floral resources throughout the year to survive.

The carpenter bee is not the only species under threat from wildfire. Many Australian plants and animals are not resilient to high frequency fires, no matter their intensity or time of year.

As for Kangaroo Island, there's also concern for several small mammals , glossy black cockatoos , and a range of invertebrate species .

Further reading

Check out The Conversation article titled, ''Jewel of nature': scientists fight to save a glittering green bee after the summer fires ' by University of Adelaide scientists Dr Katja Hogendoorn, Dr Remko Leijs (also South Australian Museum) and Dr Richard Glatz. Parts of the original article have been published here.

Parts of the article were first published in the University of Adelaide Faculty of Sciences blog and republished with permission

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