Michael Bradley, James Cook UniversityThe wet season in tropical Australia begins with tension. Physical tension, caused by the friction of earth and clouds. Mental tension, caused by the heat, and the expectation of rain and relief. It is also an ecological tension, where every plant and animal is poised — genetically, physiologically — to grow, reap, sow and copulate within a few short months.
We call it the build-up. The tension builds, and then it breaks. It was at the point of breaking when Val Plumwood, a young philosopher from the temperate south, was taken by a crocodile.
She was an environmental activist, exploring Kakadu to experience the wilderness she’d had a hand in protecting. She was paddling upstream in a small, red, low-sided canoe when it began to rain. There are many attacks on visitors to the tropics, especially those in small watercraft, but we know more about this one than any other.
When Val began fighting for the protection of wild places in the 1970s, the saltwater crocodile was rare almost to the point of extinction. By the mid ‘80s they were protected, plentiful, and in remote places, lacked memory of the hunters’ gun. When Val climbed into her vessel that morning in 1985, she did so in good faith. They were not a known threat to someone travelling by canoe in a back channel lagoon.
But crocodiles are a threat. Young salties eat fish and crabs. As they grow, they move on to larger prey — dogs, pigs, people, horses and buffalo. Our species fits comfortably in their diet, slipping into the line-up between pigs and horses.
Crocodiles may be opportunistic hunters, but their encounters with prey aren’t chance. They think about it. They watch, and they learn. Wash your pots and pans on the riverbank every evening, and you are inviting an attack. For people along the coastline of the tropical arc between Eastern India and Australia, they colour the water’s edge with a lurking malice and the threat of a violent death.
We share our world with other dangerous animals. Sharks, for instance, kill every year. Poisonous snakes too. However, there is a difference. Snakes strike when threatened, usually by an unintentional kick in the ribs. Sharks do bite when unprovoked, but rarely, and they almost never consume us. We share our beaches with them, but you can spend your life in the water and never get bitten. The saltwater crocodile is a different beast, and it boils down to intent. As crocodile researcher Professor Grahame Webb has put it:
There is no way of avoiding nor sugarcoating the predatory nature of saltwater crocodiles. If you dive off the Adelaide River bridge, 60 km east of Darwin’s city centre, and start swimming, there is a 100% chance of being taken by a saltwater crocodile. It is not the same as swimming with sharks.
Fear and fascination
Like Val Plumwood, I too had come up north from the temperate south, and was not used to sharing my world with something that wanted to eat me.
There is a mountain range in north Queensland, cut off from the mainland by the sea. The space between is filled with a tangle of mangrove trees and snaking waterways. Heading down one of these channels in the early morning, my small boat cut around a bend, and on the far bank I saw a crocodile basking in the sun.
I eased back on the throttle and let my boat drag through the water. This was my chance to see one up close, as long as I didn’t scare it off. I was a young scientist, new to the tropics, and hadn’t yet seen a croc up close. I’d glimpsed them sliding off the banks as I motored past, or as eyes above the waterline, following my boat with interest.
I drifted closer, engine idling.
It was big. I turned the engine off to let momentum and the current take me closer. I didn’t want to disturb the creature. Apart from the occasional snapping of pistol shrimp in their burrows, the air was still and quiet. The forest around us was a deep green, reflected in the greasy green of the water. The mud bank was almost black with silt; waist-deep, from recent experience. I could see the heft of the animal as I approached.
Its muscular tail rested in an arc, and the great mass of its body bulged, unsupported on dry land. It didn’t flinch as I drew closer, it held its jaws open in a permanent, basking yawn.
Now I was close enough to see very clearly its long pointed teeth ringing the muscular bed of the lower jaw. I could see sinew and texture in the enormous muscle that connects upper and lower jaw, allowing it to slam the two shut with the bite force of Tyrannosaurus rex. I could see it too well. Current and momentum had conspired to bring me right to the bank where the animal lay. I was no longer worried about disturbing the creature. I was within striking distance. I was an outsider, intruding, and I was afraid.
The fear and fascination never quite reconciled. I had seen the crocodile as an indicator, both in the ecological sense, as my training had described, but also in a personal sense.
Ecologists like indicator species, because they tell us about a complex world in a very simple way. They stand in for a whole range of factors.
A caddis-fly larva can tell you about the purity of the alpine pond you found it in, how recently it was frozen and the stability of the seasons. A stingray can tell you about the flooding patterns of a sandbank and the abundance of invertebrates therein. They do this just by showing up. Crocodiles, to me, indicated nutrient rich tropical waters providing a glut of large bodied prey. Warm winters and big barramundi.
They indicated the sanctuary of the wild. Here was a place beyond the realm of humankind, remote, beautiful, and my place of work. They punctuated the landscape, and their presence transformed the place. In the temperate south, a bank in an inlet might be a good place to pull up for lunch, or cast a line. Here, it’s a place you don’t want to linger.
A floating log becomes an object of suspicion, and the value of a swimming hole, no matter how inviting, is measured in downstream barriers. We tend to hold crocs up as a symbols, and dangle the fact of their existence in front of southerners and tourists to prove our rugged credentials. But I had not reckoned with the animal itself.
As I fumbled for the ignition, the crocodile turned its full attention to me and slid down the bank. In one easy motion it slipped under the surface, and swam toward our boat.
I kicked the engine into gear. As the roar of my 15-horse motor sped us to safety, I wondered how on earth we live alongside these creatures. I also wondered how many of those 15 horses that croc could eat in its lifetime.
Living on the water’s edge
Crocodiles are not symbols — I was about to learn — they are living beasts capable of real material damage. I could venture into their world, but spent most of my time high above the waterline. For other people in that Indo-Pacific arc, contending with these animals is daily life. Work brought me to the islands of Papua New Guinea, where crocodiles are a threat to both people and property. While it might sound far flung, New Guinea is closer to my home in North Queensland than any Australian capital. It’s part of the same great landmass of Sahul, and shares a recognisable fauna and flora.
In the places I worked, people built their villages at the water’s edge, on volcanic black-sand beaches. That strip of coast contains all of everyday life; houses, fishing nets, canoes, livestock, children, dogs and cooking fires. So, when the largest reptile in the world crawls from the ocean of a nighttime, and carries away a squealing pig, it seems a reasonable price to pay. Especially considering the other potential prey sleeping in their beds.
I came across one of these sacrificial pigs, postmortem. I was investigating the small estuaries along the coast with a local man named Alfonse. We turned into a small creek, hidden from view by the angle of its entrance and a tall forest of mangrove trees. Estuaries in the tropics have a certain smell caused by things that want to rot, but don’t have the air to do so. Sealed under the mud, they turn black and change their chemistry. Mixed in with this is the salt, and the fresh-sap of the mangrove leaves. Some people hate it, but I relish it.
This creek had an altogether different odour. It was the smell of rotting flesh, but not the dry waft of roadkill by the side of the road. This was wet-rot. The pig had been stashed in a dead tree on the bank, and its skin was beginning to trail in the current. Crocodiles don’t like a fresh kill; they like to let it soften. That pig would have fed a village and perhaps been the central meal of a wedding or a funeral. Now it was bloating in the muddy water.
On a different trip, Alfonse told me the story of a fatal attack in his village. Alfonse is a serious man with a young family, a gentle sense of humour and a legitimate hatred of Malaysian logging companies. We were working in a system called the Langalanga, a great palm swamp, almost cut off from the sea. In the slanted afternoon light, the marine palms reflect crazily on the black water, and their fruit-rot nectar clots the air.
Some of Alfonse’s family were camped on the edge of the swamp, and had set out in a canoe to collect mussels — a happy scene repeated on occasion throughout the seasons.
A few years back, another family was doing the same, when the father was taken by a crocodile. As he was being dragged under by the legs, his wife held on to his arms, and in that brief battle there was enough time for him to say “take care of the kids”. By the time I left, a man from our team was taken by a crocodile somewhere in that same labyrinth of palms.
We are food
Crocodiles are murderous creatures. Not indifferent to our suffering, but actively in pursuit of it. They crave us, like we might crave a pizza, and they act on those impulses.
Val Plumwood learned this too, from the vantage point of her red canoe, as her path converged suspiciously with a floating log. The log was a crocodile, and from that point on, she was prey. The animal charged her craft several times. She tried to escape by climbing an overhanging tree. It burst from the water between her legs and clamped down on her torso. In that moment, in the force of realisation that accompanied the puncture wounds to her abdomen, she saw very clearly that she was food.
She was thrown into a death roll — crocodiles thrash with such force that all the air and struggle is sucked out of their prey, which they then hold underwater until drowned. Val, somehow, survived this experience. It was then repeated.
Incredibly, she surfaced and climbed to safety in the overhanging tree. She was plucked from the tree again, by her left leg, and the horror was repeated for the final time.
But, inexplicably, the crocodile’s jaws relaxed. Val wrestled free and scrambled up the mud bank. Her lower half was shredded, and she could see the raw meat of her leg muscle hanging from the bone. She staggered back through the bush until she began losing consciousness.
She gave out at the edge of the swamp, as the wet season floodwater rose around her. Here she accepted her end as food for the crocodiles waiting in the rising lagoon.
We know so much about this attack because Val survived it. But also because she was a philosopher. She didn’t just survive it, she thought about it, she examined its consequences, and she wrote about it.
One of the key Australian thinkers of our time, she challenged the way we look at the natural world. It took her the rest of her life to fully reckon with the experience of being prey. The result is a revelation of a book, pulled together posthumously, (Plumwood died of a stroke in 2008), called The Eye of the Crocodile. Val’s experience has become a centre point for me, around which all my encounters with crocodiles now pivot. The anchoring wisdom in a confusing set of facts and impulses.
At the heart of her insight is the knowledge that we are food — “juicy, nourishing, bodies” for the rest of the animal kingdom. We forget that. Or perhaps, we never really come to know it. Val knew, but when she found herself as prey, she rejected the idea. I’ll let her speak for herself here:
My disbelief was not just existential but ethical — this wasn’t happening,
couldn’t be happening. The world was not like that! The creature was breaking the rules, totally mistaken, utterly wrong to think I could be reduced to food. As a human being, I was so much more than food. Were all the other facets of my being to be sacrificed to this utterly undiscriminating use, was my complex organisation to be destroyed so I could be reassembled as part of this other being?
With indignation as well as disbelief, I rejected this event. It was an illusion! It was not only unjust but unreal! It couldn’t be happening. After much later reflection, I came to see that there was another way to look at it. There was illusion alright, but it was the other way around. It was the world of ‘normal experience’ that was the illusion, and the newly disclosed brute world in which I was prey was, in fact, the unsuspected reality, or at least a crucial part of it… both I and the culture that shaped my consciousness were wrong, profoundly wrong —about many things, but especially about human embodiment, animality and the meaning of human life.
In the end, we are just another animal, scratching around on the surface of the earth. Like a few other terrestrial vertebrates, we sometimes forage in shallow seas and there, form part of the coastal food chain. In the Indo-Pacific arc, at this moment in ecological history, that food chain finishes with the saltwater crocodile.
They are simply the inheritors of their evolutionary mantle, held long before we ever dipped our toes in the water. In our brief history on this earth, we have rarely been at the top of our own food chains.
We are food, and not just for crocodiles. We live our lives trying to avoid eye contact with the fact, but it is always there in our peripheral vision. We are victim to a constant gnawing of insects, bacteria, fungus, and when we die — no matter how hard we try to bury and embalm — we finally succumb. Diseases like Ebola haunt our collective imagination, but their worst symptoms are simply the failing of our own immune system to hold back the flood of decay that will find us all when we stop breathing.
‘Life as a circulation’
Ecologists no longer talk about food chains as if there is a top and a bottom. Food loops, cycles of productivity and nutrients, hold the great ecosystems of this earth in place, as vast organised structures of recycling viscera. Our denial of our place in them is what Val came to see as “dualism” — the belief in a hierarchy of nature with ourselves at the top; different, unique, separate. Outsiders on our own planet. Because of this, crocodiles seem like monsters of a senseless world, a world to be feared.
We think of ourselves as somehow separate from the rest of nature’s bloom and rot. This man vs wild illusion butts up against reality in ways that now threaten our existence.
The experience of being outside of nature allows us to deny the urgency of the many crises now facing our planet. We see the signs, but it is easy to distance the collapse of the natural world from the continuity of our own lives, and hold an unreasonable faith that the human world will go on indefinitely. But this is denial. Nature, as we know, can crush us in its jaws. To face the reality that confronts us as a species, we must feel like insiders — part of our own planet. But what would that look like?
In Arnhem Land, where Val was attacked, people have lived alongside crocodiles for thousands of years. They see themselves differently — not as outsiders, but as part of the landscape. Indigenous philosophies, such as those of the Yolngu, see human or animal life as existing for others, not just itself. The crocodile is not hideous for eating humans. They are animals to be understood and respected, through the kind of insider knowledge gained over thousands of years. They take life, but are also capable of acting in good faith.
Their maternal tenderness is equally important. They punctuate the landscape as powerful beings, reminding us to tread carefully, because the world is not arranged for our pleasure alone. This resonated with Val who understood “life as a circulation, as a gift from a community of ancestors”. Death, whether by crocodile or otherwise, is recycling, a “flowing into an ecological and ancestral community of origins”.
In the time it took me to write this, a man named Andrew Heard was taken from his dingy in that tangle of creeks in North Queensland where I still work. The police found his vessel upside down and some of his remains in the mangroves. They caught a four-metre crocodile, cut it open, and found the rest of him inside.
Then they killed another one. We could just keep going, get rid of them all. Fifty years ago, we almost did. At a time like this, with everyone reeling in shock, and grappling with some measure of personal fear, I understand the impulse.
I’m going out there again tomorrow, as usual. Older now, my fear and fascination have turned into something else. Despite their intentions for us, I like having them around. To me, they are indicators — but they indicate more than warm winters and big barramundi. They indicate a living world, giving and taking, and a society that’s starting to find its place in it.
As I motor down the creek, they punctuate the landscape, reminding me that we’ve decided, together, there are lives that matter beside our own. That despite the pain we may face in the future, we’re beginning to find our way. They indicate hope.
This essay received an Honourable Mention in the 2021 Nature Writing Prize.
Jane Melville, Museums Victoria and Reid Tingley, Monash UniversityMost of the incredible diversity of life on Earth is yet to be discovered and documented. In some groups of organisms – terrestrial arthropods such as spiders and scorpions, marine invertebrates such as sponges and molluscs, and others – scientists have described fewer than 20% of species.
Even our knowledge of more familiar creatures such as fish and reptiles is far from complete. In our new research, we studied 1,034 known species of Australian lizards and snakes and found we know so little about 164 of them that not even the experts know whether they are fully described or not. Of the remaining 870, almost a third probably need some work to be described properly.
Documenting and naming what species are out there – the work of taxonomists – is crucial for conservation, but it can be difficult for researchers to decide where to focus their efforts. Alongside our lizard research, we have developed a new “return on investment” approach to identify priority species for our efforts.
We identified several hotspots across Australia where research is likely to be rewarded. More broadly, our approach can help target taxonomic research for conservation worldwide.
Why we need to look at species more closely
As more and more species are threatened by land clearing, climate change and other human activities, our research highlights that we are losing even more biodiversity than we know.
Conservation often relies on species-level assessments such as those conducted by the International Union for Conservation of Nature (IUCN) Red List, which lists threatened species. Although new species are being discovered all the time, a key problem is that already named “species” may harbour multiple undocumented and unnamed species. This hidden diversity remains invisible to conservation assessment.
One such example are the Grassland Earless Dragons (Tympanocryptis spp.) found in the temperate native grasslands of south-eastern Australia. These small secretive lizards were grouped within a single species (Tympanocryptis pinguicolla) and listed as Endangered on the IUCN Red List.
But recent taxonomic research split this single species into four, each occurring in an isolated region of grasslands. One of these new species may represent the first extinction of a reptile on mainland Australia and the other three have a high probability of being threatened.
Scientists call documenting and describing species “taxonomy”. Our research shows the importance of prioritising taxonomy in the effort to conserve and protect species.
Taxonomists at work
Many government agencies do take some account of groups smaller than species in their conservation efforts, such as distinct populations. But these are often ambiguously defined and lack formal recognition, so they are not widely used. That’s where taxonomists come in, to identify species and describe them fully.
Our new research was a collaboration of 30 taxonomists and systematists, who teamed up to find a good way of working out which species should be a priority for taxonomic research for conservation outcomes. This new approach compares the amount of work needed with the likelihood of finding previously unknown species that are at risk of extinction.
The research team, who are experts on the taxonomy and systematics of Australia’s reptiles, implemented this new approach on Australian lizards and snakes. This group of reptiles is ideal as a test case because Australia is a global hotspot of lizard diversity – and we also have a strong community of taxonomic experts.
Australia’s lizards and snakes
Of the 1,034 Australian lizard and snake species, we were able to assess whether 870 of them may contain undescribed species. This means we know so little about the remaining 164 species that even the experts could not make an informed opinion on whether they contain hidden diversity. There is so much still to learn!
Of the 870 species experts could assess, they determined 282 probably or definitely needed more taxonomic research. Mapping the distributions of these species indicated hotspot regions for this taxonomic research, including the Kimberley, the Tanami Desert region, western Victoria and offshore islands (such as Tasmania, Lord Howe and Norfolk Islands). Some areas in the Kimberley region had more than 60 species that need further taxonomic research.
We found 17.6% of the 282 species that need more taxonomic research contained undescribed species that would probably be of conservation concern, and 24 had a high probability of being threatened with extinction. Taxonomists know that there are undescribed species because there is some data available already but the description of these species – the process of defining and naming – has not been done.
These high-priority species belong to a range of families including geckos, skinks and dragons found across Australia.
The high number of undescribed species, especially those with significant likelihood of being endangered, was a shock to even the experts. The IUCN currently estimates only 6.3% of Australian lizards and snakes require taxonomic revision, but this is obviously a significant underestimate.
A race against extinction
Beyond lizards, there is a huge backlog of species awaiting description.
Recent projects have used genetic analyses to discover unknown species, including a $180 million global BIOSCAN effort aiming to identify millions of new species. However, genetics is only a first step in the formal recognition of species.
The taxonomic process of documenting, describing and naming species requires multiple further steps. These steps include a comprehensive diagnostic assessment using a combination of evidence, such as genetics and morphology, to uniquely distinguish each species from another. This process requires a high level of familiarity and scholarship of the group in question.
Among the Australian lizards and snakes alone, there is a backlog of 59 undescribed species for which only the final elements of taxonomic research are awaiting completion.
To work through these taxonomic backlogs – let alone species that are so far entirely unknown – resources need to be invested in taxonomy, including research funding and increased provision of viable career paths.
Without taxonomic research, the conservation assessment of these undocumented species will not proceed. There are untold numbers of species needing taxonomic research that are already under threat of extinction. If we don’t hurry, they may go extinct before we even know they exist.
Citizen science is ripe with benefits. Programs can involve hundreds, sometimes thousands, of volunteers who collect reliable, long-term and geographically widespread data. These people donate their time for a cause (or just for fun).
For biodiversity conservation, these kinds of data are invaluable to enable important large-scale projects, from assessing wildlife recovery after bushfires to shedding light on how warming oceans threaten fish.
But we’ve found the benefits of citizen science extend well beyond data collection.
In a new research paper, we show how our environmental citizen science program TurtleSAT
is not only an important source of knowledge and skill development, but also influences participants’ attitudes and behaviours towards the environment.
Saving the turtles
TurtleSAT has so far engaged more than 1,600 volunteers who collect observations of freshwater turtles. Almost 10,000 sightings have been registered since it launched in 2014. The data will ultimately help turtle conservation and management across the country.
Turtles live in most freshwater habitats across mainland Australia, from wetlands to rivers, and are a vital component of the ecosystem. For example, in previous research, we revealed turtle scavenging can remove fish carcasses from the water five times faster than natural decomposition, dramatically improving water quality.
But turtle numbers have been in steep decline since the 1970s, mainly due to fox predation, road collisions, diseases and poor water quality.
The benefits of the TurtleSAT app to scientists have been clear from the start. Most recorded turtle sightings (alive and dead) have involved turtles crossing roads and nests that are either intact or have been destroyed by foxes.
Creating environmental stewards
However, the benefits to participants were less clear. So, we surveyed them to gauge any changes in behaviour or attitudes since they got involved.
Of the 148 participants who responded, most (70%) said they’ve learned more about turtles and feel like they’re helping them by participating. After one of our school workshops, for example, a parent told us she didn’t know turtles could live outside the ocean until her daughter began participating in TurtleSAT.
After learning about the turtle population decline, 39% of respondents started restoring habitats, 35% protected nests and 30% implemented pest management mechanisms, such as fox control and predator exclusion fences.
Importantly, 70% of respondents said participating in the program made them more worried about turtles than they were before.
These findings show how a mostly self-directed project can provide benefits to citizen scientists, while also providing a platform for them to contribute to the conservation of animals they love.
Local issues motivate action
Citizen science programs link the fields of science and the humanities to create an educated and informed public that knows how to solve problems and, most importantly, care enough to do so.
One reason many people aren’t motivated to address climate change and other global issues is the effects are relatively distant from their day-to-day living.
Most people aren’t forced to confront the specifics of climate change (such as extreme weather disasters) in their everyday lives, and so can treat it as an abstract concept. Simply put, this doesn’t motivate people to act.
Citizen science programs, however, can show how climate change does actually affect participants. They become equipped with the information and tools to make significant positive changes to their local area and, most importantly, see direct outcomes.
For example, when citizen scientists spot migratory birds in their neighbourhood, it can help researchers develop long-term databases to evaluate whether changes in migration timing can be attributed to average spring temperature changes.
Likewise, we’re monitoring the timing of turtle nesting with TurtleSAT, as many turtles in eastern Australia are cued to nest in late spring. Similar research found Loggerhead sea turtles were nesting earlier due to warmer ocean temperatures.
This knowledge wouldn’t have been possible without long-term citizen science data.
Local action, global significance
Making a difference at a local level can even address global issues, such as extinction risks. Citizen science may now re-define the phrase “think global, act local” to “think local, act local, network global”.
The I Spy a Wollemi Pine survey, for example, encourages people from all around the world to log sightings of Wollemi pine. These trees are cultivated in many countries, but fewer than 1,000 remain in the wild.
The simple act of paying attention to nearby trees means scientists can learn what environments the Wollemi pine can tolerate, and better protect it from extinction.
Joining in is easy
Technology advances have largely driven the explosion of citizen science projects over the last decade. Most people have a computer, camera and GPS in their pockets when they carry their smartphone, so taking part in a citizen science project has never been easier.
If you’re interested in joining a project, you can jump on board one that’s already established, or even develop your own for a common environmental issue in your local area.
You can search for citizen science programs through the Australian Citizen Science Project Finder. To help you get started, check out:
WomSAT: if you have a passion for wombats and are concerned about road mortality and disease (such as mange)
Sea Slug Census: snorkelers and divers can upload photos and discuss the identities of some of these weird and wonderful creatures
Australia’s wetlands are home to a huge range of stunning flora and fauna, with large snakes often at the top of the food chain.
Many wetlands are located near urban areas. This makes them particularly susceptible to contamination as stormwater, urban drainage and groundwater can wash metals — such as arsenic, cadmium, lead and mercury — into the delicate ecosystem.
We know many metals can travel up the food chain when they’re present in the environment. So to assess contamination levels, we caught highly venomous tiger snakes across wetlands in Perth, and repurposed laser technology to measure the metals they accumulated.
In our new paper, we show metal contamination in wild wetland tiger snakes is chronic, and highest in human-disturbed wetlands. This suggests all other plants and animals in these wetlands are likely contaminated as well.
34 times more arsenic in wild wetland snakes than captive snakes
Urban growth and landscape modification often introduces metals into the surrounding environment, such as mining, landfill and waste dumps, vehicles and roadworks, and agriculture.
When they reach wetlands, sediments collect and store these metals for hundreds of years. And if a wetland’s natural water levels are lowered, from agricultural draining for example, sediments can become exposed and erode. This releases the metals they’ve been storing into the ecosystem.
This is what we suspect happened in Yanchep National Park’s wetland, which was supposed to be our “clean” comparison site to more urban wetlands. But in a 2020 study looking at sediment contamination, we found this wetland had higher levels of selenium, mercury, chromium and cadmium compared to urban wetlands we tested.
And at Herdsman Lake, our most urban wetland five minutes from the Perth city centre, we found concentrations of arsenic, lead, copper and zinc in sediment up to four times higher than government guidelines.
In our new study on tiger snake scales, we compared the metal concentrations in wild wetland tiger snakes to the concentrations that naturally occurs in captive-bred tiger snakes, and to the sediment in the previous study.
We found arsenic was 20-34 times higher in wild snakes from Herdsman Lake and Yanchep National Park’s wetland. And snakes from Herdsman Lake had, on average, eight times the amount of uranium in their scales compared to their captive-bred counterparts.
Tiger snakes usually prey on frogs, so our results suggest frogs at these lakes are equally as contaminated.
We know for many organisms, exposure to a high concentration of metals is fatally toxic. And when contamination is chronic, it can be “neurotoxic”. This can, for example, change an organism’s behaviour so they eat less, or don’t want to breed. It can also interfere with their normal cellular function, compromising immune systems, DNA repair or reproductive processes, to name a few.
Snakes in general appear relatively resistant to the toxic effects of metal contamination, but we’re currently investigating what these levels of contamination are doing to tiger snakes’ health and well-being.
Our method keeps snakes alive
Snakes can be a great indicator of environmental contamination because they generally live for a long time (over 10 years) and don’t travel too far from home. So by measuring metals in older snakes, we can assess the contamination history of the area they were collected from.
Typically, scientists use liver tissue to measure biological contamination since it acts like a filter and retains a substantial amount of the contaminants an animal is exposed to.
But a big problem with testing the liver is the animal usually has to be sacrificed. This is often not possible when studying threatened species, monitoring populations or working with top predators.
In more recent years, studies have taken to measuring metals in external “keratin” tissues instead, which include bird feathers, mammal hair and nails, and reptile scales. As it grows, keratin can accumulate metals from inside the body, and scientists can measure this without needing to kill the animal.
Our research used “laser ablation” analysis, which involves firing a focused laser beam at a solid sample to create a small crater or trench. Material is excavated from the crater and sent to a mass spectrometer (analytical machine) where all the elements are measured.
This technology was originally designed for geologists to analyse rocks, but we’re among the first researchers applying it to snake scales.
Laser ablation atomises the keratin of snake scales, and allowed us to accurately measure 19 contaminants from each tiger snake caught over three years around different wetlands.
We need to minimise pollution
Our research has confirmed snake scales are a good indicator of environmental contamination, but this is only the first step.
Further research could allow us to better use laser ablation as a cost-effective technology to measure a larger suite of metals in different parts of the ecosystem, such as in different animals at varying levels in the food chain.
This could map how metals move throughout the ecosystem and help determine whether the health of snakes (and other top predators) is actually at risk by these metal levels, or if they just passively record the metal concentrations in their environment.
It’s difficult to prevent contaminants from washing into urban wetlands, but there are a number of things that can help minimise pollution.
This includes industries developing strict spill management requirements, and local and state governments deploying storm-water filters to catch urban waste. Likewise, thick vegetation buffer zones around the wetlands can filter incoming water.
Sun, sea … snakes: all three are synonymous with the Australian summer, but only the first two are broadly welcomed. And of all Australia’s snake species, brown snakes are among the most feared.
To some degree, this is understandable. Brown snakes are alert, nervy and lightning-fast over short distances. When threatened, they put on a spectacular (and intimidating) defensive display, lifting the front half of their body vertically, ready to strike.
They are also fairly common, and well adapted to suburban life – especially the eastern brown species. And of course, certain species have a highly toxic venom designed to immobilise the mammals they prey on.
Besides my work as a sociologist, I’m also a professional snake catcher and handle scores of venomous snakes during the warmer months. I don’t expect people to love snakes, but I believe greater knowledge about them will help with their being respected more as keystone ecological creatures.
Not just wicked serpents
Around two Australians die each year from snake bites, and the brown snake family causes the most human – and likely pet – fatalities. But compare that figure with the annual road toll (1,188 deaths in 2019) or the 77 people killed by horses and cows in Australia between 2008 and 2017. You can see why many herpetologists – or snake experts – feel our fear of snakes is somewhat misplaced.
Where does this fear come from, then? It partly arises from the representation of snakes throughout human history as menacing. The fact snakes are cold-blooded, with an unblinking stare, means humans have often depicted them as callous and cold-hearted. Examples include the serpent who corrupts Eve in the Book of Genesis, and monstrous mythological characters such as Medusa.
Partly because of these and other depictions, snakes are often considered something to be feared. When they slither into our manicured back yards, they are seen as a “problem” that has transgressed our sanitised domestic lives. And this fear is often transferred down the generations.
In my snake-catching work, I have extricated snakes from backyards and homes, a shopping centre, parks and school classrooms. I’ve even removed snakes from a woman’s boot, under a soccer team’s kit bag and inside a weapons bunker! About 85% of the snakes I work with on callouts are eastern browns.
Many callers wanting a snake removed experience intense emotions, from shock and hostility to awe and reverence. Most want the snake taken as far away from their property as possible.
After catching a snake, I release it into a suitable non-residential environment. I always wonder what happens to it next. The threats snakes face are numerous. They can be harmed or killed by humans, pets, feral animals or predators. They are also threatened by habitat loss, climate events and contaminated prey items.
I release each with the departing words: “Good luck fella, stay safe, stay out of trouble.”
Tracking snake movements
Eastern brown snakes are timid and reluctant to strike unless provoked. They are generally solitary animals except during breeding periods. They perform a crucial ecological role by eating vermin such as mice and rats, controlling the numbers of other native species and providing a food source for various animals.
Information on how brown snakes move through and use urban space is limited. We urgently need more understanding of their daily habits, especially as urban development encroaches on their natural habitat, increasing the chances of conflict with humans or pets. More insight is also needed on whether it’s damaging to relocate hundreds of snakes each year.
A study in Canberra funded by the Ginninderry Conservation Trust aims to answer these issues. A team of researchers, including myself, will track the movements of 12 eastern brown snakes in the urban environment. We will do this using telemetry – tracking technologies fitted to the snakes. Some devices will be implanted into the snake under the skin, and others attached externally above the tail.
We will examine:
movements of adult male and female eastern browns
how far they travel
the times of day and temperatures when they are active
where they go dormant in the cooler months
the refuges they use to navigate the hostile environment they live in.
Our team will also explore the effects of catching a snake and releasing it into new habitat within a designated range (5km in the ACT, and 20km in NSW). We will examine how the snake responds to the stress of being captured and moved, the risks it might confront in an unfamiliar landscape, and whether it survives. We will also explore the implications for other snakes in the release habitat and the genetic consequences of interbreeding between geographically distinct populations.
Knowledge breeds greater tolerance
We anticipate the study’s findings will help educate the public about how snakes operate in suburbia. It will also inform translocation policies and conservation efforts.
We also hope to show how eastern browns are vital – not superfluous or undesirable – parts of thriving ecosystems. The better we understand snakes, the less we might fear them. This may also mean we are less disposed to relocating or harming them.
How do we save whales and other marine animals from plastic in the ocean? Our new review shows reducing plastic pollution can prevent the deaths of beloved marine species. Over 700 marine species, including half of the world’s cetaceans (such as whales and dolphins), all of its sea turtles and a third of its seabirds, are known to ingest plastic.
When animals eat plastic, it can block their digestive system, causing a long, slow death from starvation. Sharp pieces of plastic can also pierce the gut wall, causing infection and sometimes death. As little as one piece of ingested plastic can kill an animal.
About eight million tonnes of plastic enters the ocean each year, so solving the problem may seem overwhelming. How do we reduce harm to whales and other marine animals from that much plastic?
Like a hospital overwhelmed with patients, we triage. By identifying the items that are deadly to the most vulnerable species, we can apply solutions that target these most deadly items.
Some plastics are deadlier than others
In 2016, experts identified four main items they considered to be most deadly to wildlife: fishing debris, plastic bags, balloons and plastic utensils.
We tested these expert predictions by assessing data from 76 published research papers incorporating 1,328 marine animals (132 cetaceans, 20 seals and sea lions, 515 sea turtles and 658 seabirds) from 80 species.
We examined which items caused the greatest number of deaths in each group, and also the “lethality” of each item (how many deaths per interaction). We found the experts got it right for three of four items.
Flexible plastics, such as plastic sheets, bags and packaging, can cause gut blockage and were responsible for the greatest number of deaths over all animal groups. These film plastics caused the most deaths in cetaceans and sea turtles. Fishing debris, such as nets, lines and tackle, caused fatalities in larger animals, particularly seals and sea lions.
Turtles and whales that eat debris can have difficulty swimming, which may increase the risk of being struck by ships or boats. In contrast, seals and sea lions don’t eat much plastic, but can die from eating fishing debris.
Balloons, ropes and rubber, meanwhile, were deadly for smaller fauna. And hard plastics caused the most deaths among seabirds. Rubber, fishing debris, metal and latex (including balloons) were the most lethal for birds, with the highest chance of causing death per recorded ingestion.
What’s the solution?
The most cost-efficient way to reduce marine megafauna deaths from plastic ingestion is to target the most lethal items and prioritise their reduction in the environment.
Targeting big plastic items is also smart, as they can break down into smaller pieces. Small debris fragments such as microplastics and fibres are a lower management priority, as they cause significantly fewer deaths to megafauna and are more difficult to manage.
Flexible film-like plastics, including plastic bags and packaging, rank among the ten most common items in marine debris surveys globally. Plastic bag bans and fees for bags have already been shown to reduce bags littered into the environment. Improving local disposal and engineering solutions to enable recycling and improve the life span of plastics may also help reduce littering.
Lost fishing gear is particularly lethal. Fisheries have high gear loss rates: 5.7% of all nets and 29% of all lines are lost annually in commercial fisheries. The introduction of minimum standards of loss-resistant or higher quality gear can reduce loss.
Other steps can help, too, including
incentivising gear repairs and port disposal of damaged nets
penalising or prohibiting high-risk fishing activities where snags or gear loss are likely
and enforcing penalties associated with dumping.
Outreach and education to recreational fishers to highlight the harmful effects of fishing gear could also have benefit.
Balloons, latex and rubber are rare in the marine environment, but are disproportionately lethal, particularly to sea turtles and seabirds. Preventing intentional balloon releases and accidental release during events and celebrations would require legislation and a shift in public will.
The combination of policy change with behaviour change campaigns are known to be the most effective at reducing coastal litter across Australia.
Reducing film-like plastics, fishing debris and latex/balloons entering the environment would likely have the best outcome in directly reducing mortality of marine megafauna.
Lauren Roman, Postdoctoral Researcher, Oceans and Atmosphere, CSIRO; Britta Denise Hardesty, Principal Research Scientist, Oceans and Atmosphere Flagship, CSIRO; Chris Wilcox, Senior Principal Research Scientist, CSIRO, and Qamar Schuyler, Research Scientist, Oceans and Atmospheres, CSIRO
In recent months, three humpback whales were spotted in the East Alligator River in the Northern Territory’s Kakadu National Park. Contrary to its name, the river is full of not alligators but crocodiles. And its shallow waters are no place for a whale the size of a bus.
It was the first time humpback whales had been recorded in the river, and the story made international headlines. In recent days, one whale was spotted near the mouth of the river and scientists are watching it closely.
The whales’ strange detour threw up many questions. How did they end up in the river? What would they eat? Would they get stuck on the muddy river bank?
And of course, there was one big question I was repeatedly asked: in an encounter between a crocodile and a humpback whale, which animal would win?
The humpback whales were first spotted in September this year by marine ecologist Jason Fowler and fellow scientists, during a fishing trip. Fowler told the ABC:
I noticed a big spout, a big blow on the horizon and I thought that’s a big dolphin … We were madly arguing with each other about what we were actually seeing. After four hours of raging debate we agreed we were looking at humpback whales in a river.
The whales had swum about 20 kilometres upstream. Fowler photographed the humpback whales’ dorsal fins as evidence, and reported the unusual sighting to authorities and scientists.
Thankfully, two whales returned to sea on their own, leaving just one in need of help. There was concern it might become stranded in the shallow, murky tidal waters. If this happened, it might be attacked by crocodiles – more on this in a minute.
Experts considered a variety of tactics to encourage the whale back out to sea. These included physical barriers such as nets or boats, and playing the sounds of killer whales – known predators of humpback whales.
But none of these these options was needed. After 17 days, the last whale swam back to sea on its own.
The whale that spent two weeks in the river has recently returned and been spotted swimming around the mouth of the river. It appears to have lost weight – most likely the result of migration. It is now being monitored nearby in Van Diemen Gulf.
Questions are now being raised about the health of the animal, and why it has not headed south for Antarctic feedings waters.
So why were whales in the river?
There are various theories as to why they swam into the East Alligator River. Humpback whales are extremely curious, and may have entered the river to explore the area.
Alternatively, they may have made a navigation error – also the possible reason behind September’s mass stranding of pilot whales in Tasmania.
And the big question – what about the crocs?
Long-term, a humpback whale’s chances of surviving in the East Alligator River are slim. The lower salinity level may cause them skin problems, and they may become stranded in the shallow waters – unable to move off the muddy bank. Here the animal might die from overheating, or its organs may be crushed by the weight of its body. Or, of course, the whale may be attacked by crocodiles.
In this case, my bet would be on the whale – if it was in relatively good condition and could swim well. Humpback whales are incredible powerful creatures. One flick of their large tail would often be enough to send a crocodile away.
If a croc bit a whale, their teeth would likely penetrate the whale’s skin and thick blubber. But it would take a lot more to do serious harm. Whale skin has been shown to heal after traumatic events, including the case of a humpback whale cut by a boat propeller in Sydney 20 years ago. Dubbed Bladerunner, it survived but still bears deep scars.
The whale sighting continues to fascinate experts. Scientists are hoping to take poo samples from the whale in Van Diemen Gulf, and could also collect whale snot to learn more about its health. However, the best case scenario would be to see the whale swim willingly to offshore waters.
This unusual tale will no doubt go down in Australian whale history. If nothing else, it reminds us of the vulnerability – and resilience – of these marine giants.
The author would like to thank Northern Territory Government whale expert Dr Carol Palmer for her assistance with this article.
The link below is to an article that addresses 6 myths concerning Australian snakes.