WA melon-headed whale stranding investigation findings 'inconclusive'
Marine researchers have been unable to determine why 10 whales stranded themselves on Western Australia's far north earlier this year.
The melon-headed whales were found by residents at Crab Creek, east of Broome and about 2,000 kilometres north of Perth, in January.
Melon-headed whales are small, toothed whales belonging to the oceanic dolphin family.
The Department of Biodiversity, Conservation and Attractions (DBCA) collected scientific information from the dead mammals to investigate the incident.
But it has since confirmed the cause of the stranding would remain unknown.
Marine scientist Holly Raudino said the species had only stranded twice previously in WA, so the incident was unusual and concerning.
She said research team members had done everything they could with the samples available.
"We hadn't anticipated how quickly the head and the soft tissues would decompose," she said.
"By the time we received the head, it appears that decomposition had already set in.
"We're always trying to improve on our efforts as much as we can and as funding permits."
Findings initially suggested the stranding was caused by intense noise, due to severe damage to the mammals' ears.
But because of significant decomposition, results regarding the ears were comprised and deemed inconclusive.
"Elsewhere in the world when this species is stranded, it's been suspected to be in relation to exposure to an intense noise source," Ms Raudino said.
The species is primarily found in deep water worldwide.
The whales travel in pods ranging from 100 to more than 1,000 members.
While the ultimate cause of the stranding is undetermined, Ms Raudino said the team's findings would help inform broader global understanding and research into strandings generally.
Envrions Kimberley executive director Martin Pritchard said the stranding had shocked residents.
He said it was disappointing the cause would not be fully understood.
"We have a world-class marine environment here and there's a responsibility on the government to make sure we know what's going on and to manage it properly," he said.
"We're a wealthy country; surely we've got the resources to monitor our marine life so we can understand what's been going on in our oceans."
Mr Pritchard said at the time of the incident there were reports of "very large noises" in the area cause by "pile drivers".
"We were concerned that could have had a direct impact on the whales," he said.
"Now we'll never know."
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ABC News
16 hours ago
- ABC News
Radiation at Montebello Islands still 4,500 times higher than WA coast after nuclear blasts
Cam McGurk's stories of one of Australia's most heavily irradiated areas come drenched in warm Pilbara sunshine. "I actually spent my honeymoon at the Montebello Islands," Mr McGurk, a longtime member of the Ashburton Anglers fishing club, said. "It was the middle of COVID, so all the travel restrictions were in place … that was the one island holiday where I could take my beautiful wife. The fondness locals like Mr McGurk feel for the islands, about 1,300 kilometres north of Perth, could soon be given fresh pause. According to a landmark study published today, the archipelago's atomic contamination runs astonishingly deep. The Montebello Islands were the site of three British atmospheric nuclear weapons tests between 1952 and 1956. Two of the around 174 spits of sandy earth are still subject to hour-long visitation limits. Since 2019, a team of researchers from Edith Cowan University has sought to measure precisely how much plutonium remains in the islands' marine sediment. Their findings have now revealed levels reaching up to 4,500 times higher than the rest of the WA coast. Scientists spent eight days on the Montebello Islands, diving to gather surface sediment from the ocean floor. Samples were sent to the Australian Radiation Protection and Nuclear Safety Agency, the chief regulator for historic nuclear testing sites. "We're able to essentially create a map with the over 66 locations that we took samples of sediment from," lead researcher and PhD candidate Madison Williams-Hoffman said. Ms Williams-Hoffman said two "mechanisms" were spreading radiation through the islands over the past 70 years. "The first one is the plume trajectories … like the mushroom clouds that you conjure in your mind when you think of nuclear detonations," she said. "Those travelled with the wind direction at the time of the detonations." Second, decades of tides and severe weather dispersed residual plutonium in unexpected ways. "There are two cyclones a year that directly impact that part of WA, and so sediment is being tossed up and around, and things [are] moving," Ms Williams-Hoffman said. She said concentrations in the islands' north were "comparable" to other places touched by nuclear testing, including French Polynesia and the Marshall Islands. Any degree of similarity was remarkable because the Marshall Islands suffered a cumulative nuclear impact 700 times greater than the Montebello Islands. "It makes us question what's different between the two sites," Ms Williams-Hoffman said. The legacy of British nuclear testing in Australia is fraught with displacement and disease. Following three major tests conducted on the Montebello Islands, two more nuclear devices were detonated at Emu Fields and another seven at Maralinga in South Australia. Ray Kaye, former president of the Australian Ex-Services Atomic Survivors Association, said it was crucial the impacts of radiation were recorded. The 85-year-old, who later contracted leukaemia, was awarded a medal by the British government for his involvement in the SA nuclear tests. Mr Kaye reminisced on a 2016 trip with his fellow veterans to the Montebello Islands, marking the 60th anniversary of the blasts. WA Parks and Wildlife marine program coordinator Tim Hunt said managing radiation on the Montebello Islands was an "interesting" part of the job. "When I came into this role almost nine years ago, I never thought I'd have to get my physics hat on and learn about radiation," Mr Hunt said. He noted that exposure to marine sediment was far less concerning to authorities. "I'm not an expert, but people aren't going down and putting their head in the sand at 10 or 16 metres," he said. "Our current understanding is that the measures we have in place are sufficient to mitigate that risk." Visitors to Trimouille and Alpha Islands, where the three tests took place, are advised to restrict their time to no more than one hour per day, and not to disturb the soil or handle any relics. Ms Williams-Hoffman said the results were an important step in understanding the repercussions of radionuclides in Australia. Next, researchers will evaluate the effects of such high radiation on the environment. "It's kind of like walking before you can run," she said. "Now that we have these numbers or values in hand, then we can later do those assessments in terms of … how much radiation a person, or perhaps most important with sediment considering it's under water … the animals, the fish, and the plants are exposed to." For Cam McGurk, his appreciation for the "boating and fishermen's playground" reels back to 1998, when a special permit was needed to travel there. He mused that the legend of atomic testing had likely shielded the islands from over-tourism, but supported further monitoring.
ABC News
3 days ago
- ABC News
The polyphagous shot-hole borer kills trees. Why is it so lethal, how is it treated, and can it spread across Australia?
The Western Australian government yesterday announced that it would stop trying to eradicate an invasive pest that's killing trees in and around Perth and start managing it instead. The pest, the polyphagous shot-hole borer (Euwallacea fornicatus), is a tiny beetle native to South-East Asia that has been silently spreading in the Perth metropolitan area for at least four years. The only approved treatment for the sesame-seed-sized pest is to chop down plants it has infested and chip them into tiny pieces. It's something that local councils have been forced to do to hundreds of trees, including dozens of huge, old Moreton Bay figs, to try to stop the beetle's spread. Last year, a $41 million plan was approved to wipe the pest from Australia's shores, but the WA state government this week said eradication was now no longer feasible. So why is this particular pest so problematic, and if it can't be eradicated, are there other treatments on the horizon? The beetle drills tunnels into tree trunks and branches, leaving distinctive "shot holes" in the bark. But despite being adept at chewing through wood, the polyphagous shot-hole borer doesn't eat it. Wood is mostly made of cellulose which, while plentiful, is incredibly hard to digest. "No animal has evolved the capacity to do this on its own — they always do it with a microbial friend," Theo Evans, an entomologist at the University of Western Australia, said. "With termites, for example, they have a range of bacteria and protozoa. In the case of these wood-boring beetles, they use a fungus," Dr Evans said. The fungus eats the wood, and the beetle eats the fungus. And it's the fungus — not the beetle, nor its tunnels — that ends up killing the tree. Once inside a branch or trunk, the growing fungus needs water, so it sends out filaments to tap into the tree's circulatory system. These fungal filaments can block those vessels, and essentially starve the tree of water and nutrients. The pest was first detected in WA in East Fremantle in August 2021 when a resident noticed two box elder maples in her garden looked unwell, and had shot holes in their bark. It was soon confirmed that the infestation was the polyphagous shot-hole borer, a pest that had been wreaking havoc in places like California, Israel and South Africa for more than a decade. But while this was the first confirmed report of the beetle in the state (and Australia more broadly), it would not have been the site of the first infestation, Dr Evans said. "Those trees were dying, so the beetles must have been in those trees for a minimum of two years, and possibly three or four because it takes that long … for the fungus to spread through the tree and clog its vascular system." It's also unclear how the beetle reached WA in the first place. What seems likeliest is the pest hitched a ride on wood used as packaging or filler around large, heavy items such as farm machinery, Dr Evans said. This wood filler, called dunnage, is supposed to be treated to kill any pests inside, but sometimes that doesn't happen. The beetle can survive in cut wood for up to seven months. Being a beetle, the polyphagous shot-hole borer has wings, but "it's a terrible flyer", Dr Evans said, capable of only flying around 30 metres at a time. "When you're only 1.5 millimetres long and you spend most of your life living inside a tree, you're not going to be an acrobat." Nor does it get transported on the wind. The minute a breeze picks up, the beetle retreats into a tunnel until it dies down again. It's thought the pest spread across the Perth metropolitan area in plant prunings. For instance, affected branches lopped off by arborists to protect power lines could've been unwittingly transported kilometres away. Chipping infested wood to under 2.5 centimetres results in a shot-hole borer death rate of more than 99 per cent. But "if it's a mature tree and it's got literally tens of thousands of beetles in it, that's still hundreds of beetles that survive", Dr Evans said. The shot-hole borer attacks WA native forest trees, including the marri (Corymbia calophylla) and karri (Eucalyptus diversicolor). "These are important trees, not just for the WA bush, but there are close relatives throughout the bush across Australia," Dr Evans said. "Now we don't know how badly affected the trees are going to become, because normally when the beetles are found infesting the trees, they get cut down and chipped. "So we don't see if the tree can survive a long time with the beetle … but it could end up being quite bad." Nor do we know exactly how the shot-hole borer might affect orchard trees in Australia. There is some information from fruit trees grown in Perth backyards, but nothing from commercial operations outside of the city. One lesson learnt from growers overseas is in avocados. The fruit seems to be highly susceptible to the polyphagous shot-hole borer, but the beetle tends to attack branches rather than the trunk. "With some careful pruning, which obviously costs more money and it does lower productivity of the tree a little, people in Israel and parts of the US have found that it's not a particularly bad problem," Dr Evans said. That said, when avocado trees were introduced into Australia, we managed to avoid bringing any pest species with them. So if the polyphagous shot-hole borer gets into local avocado orchards, "it will actually be quite a big problem, because growers don't have to think about those sorts of insect pests [at the moment]", he added. And just because the pest has behaved a certain way abroad does not mean it will act the same way here. The beetle has attacked Moreton Bay fig trees in Perth, but has had less of an impact on figs overseas. "So there's obviously local variation, probably a combination of the climate, the soil type, and water availability that changes the susceptibility of the plants," Dr Evans said. It's hard to say, Dr Evans said. Unsurprisingly, the beetle seems to thrive in climates similar to its native home. So while it might not do too well in relatively chilly Tasmania, it may well get a foothold along the east coast, especially from Brisbane up. Annual long, hot summers and wet winters may make plants more susceptible to the pest too. During punishingly dry summers, water-stressed plants may simply have very little capacity to fend off the beetle and fungus combination, and simply succumb to infestation. Trials mostly in the US have tested a handful of insecticides against the shot-hole borer with very little success — mostly because they were sprayed chemicals that might've landed on the bark of the tree, but couldn't get to the beetle inside its tunnel. So researchers, including Dr Evans, are trialling a combination of insecticide (to kill the beetle) and fungicide (to kill the fungus), which can be administered inside the tree. While he can't comment on his findings yet, "the results are very promising", he said. "We'll never get rid of [the need to] chop and chip. I think there are going to be some trees that are just too far gone and chop and chip is the only option. "But for trees that are early in the infestation, I think some of these methods are going to work and they're going to save the tree." For more on the polyphagous shot-hole borer, check out the full episode of Lab Notes.
ABC News
3 days ago
- ABC News
Lab Notes: The tiny beetle ravaging Perth's trees
Belinda Smith: Dramatic scenes have been unfolding in Perth's majestic parks. News Grab: Trees in Perth's iconic Kings Park ground into dust. A bare scar on the hill where Moreton Bay fig trees once stood. Belinda Smith: And just last month, a couple of kilometres away at Hyde Park, dozens of trees were chopped and chipped. News Grab: Seeing the trees on the islands go, it's so, so sad. Belinda Smith: And it's all because of a beetle about the size of a sesame seed called the Polyphagus shot-hole borer. So how has this tiny pest caused such massive problems? Hi, I'm Belinda Smith and you're listening to Lab Notes, the show that dissects the science behind new discoveries and current events. To explain how the beetle spreads and what can be done about it is Theodore Evans, an entomologist at the University of Western Australia. Now, more than 50 huge old Moreton Bay fig trees in Kings Park have been chopped down. What impact has this had on the area? Theodore Evans: It looks like a war zone, as people have used those words. And they're horrified. And people would go for walks through that part of Kings Park and now they aren't because there's no shade on a 40 degree day. It's deeply unpleasant. Belinda Smith: Yeah, I imagine, you know, in a hot and dry city like Perth, losing all that tree canopy must be pretty extreme. Theodore Evans: Perth already has the lowest tree canopy of any capital city in Australia. So it's a not good situation that is going to get even worse. Belinda Smith: The reason Perth is chopping and chipping hundreds of trees is because of a wood-boring beetle. And their favourite food, you guessed it, is... Theodore Evans: Wood. And wood is made up of cellulose, lignin and hemicellulose. And cellulose in particular is the most abundant biological molecule on the planet. And it's one of the hardest things to digest. So it's a huge resource if you can crack the secret to digest it. Belinda Smith: And the polyphagous shot hole borer has figured it out. Theodore Evans: So polyphagous comes from the Greek, which means many eating, because they eat a very wide variety of plants. And Belinda Smith: this varied vego menu is pretty rare for insects. Theodore Evans: Think about a caterpillar, for example. They only eat one species of plant or a very small number of close relatives. And we call those monophagous, meaning one eating. It's much harder to be polyphagous because you have to be able to digest plant matter from all these different plant families that aren't related. And they probably have a whole range of defensive chemicals. And you have to be able to overcome that much wider range of defensive chemicals. Belinda Smith: Why did this polyphagousness evolve in this particular beetle species? Theodore Evans: This beast evolved in South and Southeast Asia, along with a whole bunch of its relatives. And that's probably got something to do with its polyphagous nature, because those diverse rainforests, they have huge numbers of diverse plant species. It's kind of hard to specialise on one species when you've got such diversity around you. Belinda Smith: What do the beetles look like? Theodore Evans: Their head is kind of pushed underneath their thorax. If you remember, insects have three body parts, head, thorax and abdomen. And so they kind of look from above, they almost look like they have no head. And the whole body is almost like a short cylinder. And they sort of chew and they chew and they turn as they chew. Like a drill, almost. Exactly, just like a drill. Not surprising, given what they're living in. Belinda Smith: And these holes are usually the first sign of the pest's presence. But it's not the holes or even the beetles themselves that kill the tree. So Theodore Evans: part of their trick of being polyphagous is to have a symbiotic friend. In this case, it's a fungus. As I said, it's very hard to digest cellulose and those other compounds in wood. And no animal has evolved the capacity to do this on its own. They always do it with a microbial friend. So with termites, for example, they have a range of bacteria and protozoa. With the case of these wood-boring beetles, they use a fungus. They're normally not an organism that can invade the tree on their own. They usually piggyback on somebody else. Belinda Smith: So when a polyphagous shot hole borer drills into a tree, it's the piggybacking fungus that digests the wood. Theodore Evans: And then these beetles just eat the fungus. Belinda Smith: But the real problems arise when the fungus gets thirsty and starts growing into the water vessels inside the tree. Theodore Evans: And eventually they clog up those vessels and they basically starve the tree of water and nutrients. And that's how the tree ends up dying. Belinda Smith: Right. Okay. So it's actually the fungus that causes that clogged circulation, which then spills the end of the tree. Eventually. That's correct. Right. Okay. So when was the shot hole borer first discovered in WA? It Theodore Evans: was first found by the West Australian State Government Department of Primary Industries on the 6th of August in 2021. And it was found in two box elder maple trees in East Fremantle. These were trees planted by the owner of the property and they were her pride and joy. She's a very keen gardener and these trees were looking very unhealthy. The leaves were dying, turning yellow, falling off. And she looked carefully at the bark and realised that there were these shot holes. And within a short time, the experts had identified it as polyphagus shot hole borer, Eulacia fornicatus. And that has been spreading in different parts of the world over the last roughly 20 years. And so it's well known as an invasive species. Yeah, Belinda Smith: it's been found in California, Israel and South Africa before. And while the East Fremantle infestation was the first confirmed report of polyphagus shot hole borer in Western Australia and Australia more broadly. Theodore Evans: This can't be the original site of the very first infestation for a couple of reasons. But one is those trees were dying. So the beetle must have been in those trees for a minimum of two years and possibly three or four because it takes that long for the beetle to breed up, for the fungus to spread through the tree and clog its vascular system. Belinda Smith: How did they get to Western Australia? Theodore Evans: So what we think has happened is the beetle came in on green wood, so wood that hasn't been properly dried, used as dunnage. And dunnage is essentially the bracing, the filler for large heavy items. And so it's likely that something got brought into Perth. It had green wood dunnage to hold it in place and it hadn't been heat treated to dry it out and kill any organisms, which they're supposed to do. But obviously that takes time and money to do and it's often skipped. Belinda Smith: How well has the shot hole borer been contained since its discovery a few years ago? Theodore Evans: I would say the average person in Perth who follows the shot hole borer news would say not very well because every six months or so we hear a new report of an infestation that was outside the previously defined quarantine zone. The Belinda Smith: shot hole borer may be awesome at drilling into wood, Theodore Evans: but... This beetle is a terrible flyer, like all very small beetles. Oh really? Terrible flyer. When you're only one and a half millimetres long and you spend most of your life living inside a tree... And your Belinda Smith: head's tucked away underneath your thorax. Theodore Evans: Exactly. You know, you're not going to be an acrobat. And so in field experiments done in the United States, the distances that they flew were around 30 to 35 metres and they all stopped flying at high wind speeds. Belinda Smith: So if they're barely flying and they're not being blown around, how do they spread between suburbs? Theodore Evans: That's all humans. Belinda Smith: Yeah, we are shuttling the shot hole borer around, particularly when trees get pruned. The Theodore Evans: arborist takes those cut branches away and they might transport them dozens of kilometres. This beetle can survive in these cut wood for up to seven months. Belinda Smith: So shot hole borer love wood, but there are particular trees that they really enjoy. Theodore Evans: So number one on the list is Acer negundo, the box elder maple. Number two on the list are Erythrina x sykesii, which are coral trees. And Erythrinas are found in Africa through to India. So these trees get attacked very heavily and so they succumb rapidly. Belinda Smith: Others are robinia, hibiscus, plane trees and figs, like the giant morton bay figs recently chopped down in Perth. And people are worried about trees outside of the metro area too. We Theodore Evans: know that the borer does attack WA native forest trees, including a range of paperbark Melaleuca, including Corymbia eucalyptus species such as the Marri. And they also attack Callitris. So these are important trees in not just WA's bush, but there are close relatives throughout the bush across Australia. Belinda Smith: Agriculture could be affected too, because in other parts of the world, avocado trees, for instance, are highly susceptible to the pest. Theodore Evans: They also affect pears and apples. They attack and can kill macadamias and mangoes and mulberries. Belinda Smith: How concerning is the threats that the borer poses beyond WA's borders? Theodore Evans: That's a very hard question to answer. There's been some modelling to look at where it might thrive in Australia and essentially wherever there are trees, it will do well. Not so well in Tasmania, because it's a bit cold, but it should absolutely thrive on the east coast and particularly sort of north of Sydney from Brisbane up into the tropics, because that most closely matches the temperatures of its native range. How badly the plants are going to suffer is a harder question to answer. Belinda Smith: Right now, the only approved way to stop the beetle spread is cutting down trees and putting them through a wood chipper. Some insecticide sprays have been tested on the borer, but they didn't work. Theodore Evans: And the reason they didn't work is because if you're spraying an insecticide through the air and it lands on the bark of the tree, it doesn't get to the beetle. The beetle is inside the tunnels and nobody has yet tried to test some of the chemicals that can get into the wood of the tree, or they haven't done very much of it. And so there is hope in trying to look at these other approaches. Belinda Smith: And Theodore is among the researchers who have been testing these other approaches. My Theodore Evans: very first tree that I started experimenting on with my most favoured chemical, because this particular chemical is both fungicidal and insecticidal, so it kills the borer and the fusarium fungus. And we have managed to protect one tree, which is a stone throw from Hyde Park. So it's constantly being attacked by Polyphagous Shot Hole Borer. And we've managed to protect that tree now for a year. Belinda Smith: Oh, congratulations. Thank you. I feel like that is well, that is worthy of a celebration. Theodore Evans: We'll never get rid of chop and chip. I think there are going to be some trees that are just too far gone and chop and chip is the only option. But for trees that have only, that are early in the infestation, I think some of these methods are going to work and they're going to save the tree. Belinda Smith: That was Theodore Evans, an entomologist at the University of Western Australia. Thanks for listening to Lab Notes on ABC Radio National, where every week we dissect the science behind new discoveries and current events. I'm Belinda Smith. This episode was produced on the lands of the Wurundjeri and Menang Noongar people. Fiona Pepper's the producer and it was mixed by Riley Mellis. We'll catch you next week.
