We tested tiger snake scales to measure wetland pollution in Perth. The news is worse than expected

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Damian Lettoof, Curtin University; Kai Rankenburg, Curtin University; Monique Gagnon, Curtin University, and Noreen Evans, Curtin University

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.

The wetland in Yanchep National Park, Perth, was supposed to be our ‘clean’ comparison site. Its levels of metal contamination was unprecedented.
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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.

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Does Australia really have the deadliest snakes? We debunk 6 common myths

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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.

Our research confirmed snake scales are a good indicator of environmental contamination.
Damian Lettoof, Author provided

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.

Sediment in Herdsman Lake had four times higher heavy metal levels than what government guidelines allow.
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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.

Snakes generally appear resistant to the toxic effects of heavy metals.
Kristian Bell/Shutterstock

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.

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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.

Damian Lettoof, PhD Candidate, Curtin University; Kai Rankenburg, Researcher, Curtin University; Monique Gagnon, Researcher, Curtin University, and Noreen Evans, Professor, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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‘Good luck fella, stay safe’: a snake catcher explains why our fear of brown snakes is misplaced

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Gavin JD Smith, Australian National University

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.

The author catching a brown snake. He wants to garner public respect for the creatures.
Author provided

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.

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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.

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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.

The study will examine how snakes move through the urban landscape.
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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.

Gavin JD Smith, Associate Professor in Sociology, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Six Australian Snake Myths

The link below is to an article that addresses 6 myths concerning Australian snakes.

For more visit:
https://www.lifehacker.com.au/2020/09/6-deadly-australian-snake-myths-debunked-by-an-expert/

Does Australia really have the deadliest snakes? We debunk 6 common myths

A red-bellied black snake
Damian Michael, Author provided

Damian R. Michael, Charles Sturt University; Dale Nimmo, Charles Sturt University, and Skye Wassens, Charles Sturt University

As we settle into spring and temperatures rise, snakes are emerging from their winter hideouts to bask in the sun. But don’t be alarmed if you spot one, it’s hard to imagine a more misunderstood group of animals than snakes.

Our interactions with snakes are conversation starters, with yarns told and retold. But knowing what’s fact and fiction gets harder with each retelling.

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I’ve always wondered: who would win in a fight between the Black Mamba and the Inland Taipan?

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As is so often the case with wildlife, the myths pale in comparison to what science has shown us about these incredible creatures. So let’s debunk six misconceptions we, as wildlife ecologists, often hear.

With snakes on the move this season, people and pets are more likely to spot them.
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1. Black snakes and blue tongue lizards keep brown snakes away

This is a common old wives’ tale in southern Australia. The myth goes that if you see a red-bellied black snake or a blue-tongue lizard on your property, you’re unlikely to see the highly venomous brown snake, because black snakes keep brown snakes at bay.

This myth probably originates from observations of black snakes eating brown snakes (which they do).

But it’s not one-way traffic. There are many reported examples of brown snakes killing black snakes, too. Overall, no scientific evidence suggests one suppresses the other.

There is also no evidence blue-tongue lizards prey upon or scare brown snakes. In fact, many snakes feed on lizards, including brown snakes which, despite a preference for mammal prey as adults, won’t hesitate to have a blue tongue for lunch.

2. Snakes are poisonous

While the term poisonous and venomous are often used interchangeably, they mean quite different things. If you eat or ingest a toxic plant or animal, it’s said to be poisonous, whereas if an animal stings or bites you and you get sick, it’s venomous.

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Why are some snakes so venomous?

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Venom is a specialised type of poison that has evolved for a specific purpose. For venom to work, it needs a wound to enter the body and into the bloodstream. Snakes, therefore, are generally venomous, not poisonous.

But there are exceptions. For example, the American garter snake preys on the rough-skinned newt which contains a powerful toxin.

The toxins from the rough-skinned newt can stay in a garter snake’s liver for up to a month.
Steve Jurvetson/Wikimedia, CC BY

The newt’s toxin accumulates in the snake’s liver, and effectively makes this non-venomous snake species poisonous if another animal or human eats it. Remarkably, these snakes can also assess whether a given newt is too toxic for them to handle, and so will avoid it.

3. Australia has the deadliest snakes in the world

Approximately 20% of the world’s 3,800-plus snake species are venomous. Based on the median lethal dose — the standard measurement for how deadly a toxin is — the Australian inland taipan is ranked number one in the world. Several other Australian snakes feature in the top 10. But does that make them the deadliest?

It depends on how you define “deadly”. Death by snake bite in Australia is very uncommon, with just two per year, on average, compared to 81,000-138,000 deaths from snakes annually worldwide.

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Yes, Australian snakes will definitely kill you – if you’re a mouse

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If we define “deadly snakes” as those responsible for killing many people, then the list would be topped by snakes such as the Indian cobra, common krait, Russell’s viper and the saw-scaled viper, which occur in densely populated parts of India and Asia.

A lack of access to antivenoms and health care contribute substantially to deaths from snake bites.

Indian cobra’s are one of the deadliest snakes in the world.
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4. Snakes have poor eyesight

Compared to other reptiles, such as monitor lizards, most snakes have poor eyesight, especially species that are active at night or burrow in soil.

However, snakes that are active by day and feed on fast-moving prey have relatively good vision.

One study in 1999 showed people are less likely to encounter eastern brown snakes when wearing clothing that contrasted with the colour of the sky, such as dark clothing on a bright day. This suggests they can see you well before you see them.

Some snakes such as the American coachwhip can even improve their eyesight when presented with a threat by constricting blood vessels in the transparent scale covering the eye.

An olive sea snake can actually detect light through their tail.
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And then there’s the olive sea snake, whose “phototactic tails” can sense light, allowing them to retract their tails under shelter to avoid predation.

5. Young snakes are more dangerous than adults

This myth is based on the idea juvenile snakes can’t control the amount of venom they inject. No evidence suggests this is true.

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However, research shows the venom of young and old snakes can differ. A 2017 study showed the venom of young brown snakes is different to adults, probably to facilitate the capture of different types of prey: young brown snakes feed on reptiles, whereas adult brown snakes predominantly feed on mammals.

But it’s not just age — venom toxicity can vary among individuals of the same population, or among populations of the same species.

Bandy Bandy (Vermicella annulata). Defensive behaviours are often misinterpreted as aggression.
Damian Michael, Author provided

6. Snake are aggressive

Perhaps the most pervasive myth about snakes is they’re aggressive, probably because defensive behaviours are often misinterpreted.

But snakes don’t attack unprovoked. Stories of snakes chasing people are more likely cases where a snake was attempting to reach a retreat site behind the observer.

When threatened, many snakes give a postural warning such as neck flaring, raising their head off the ground, and opening their mouths, providing clear signals they feel threatened.

It’s fair to say this approach to dissuade an approaching person, or other animal, works pretty well.

Rhesus macaques display more fearful behaviour when confronted with snakes in a striking pose compared to a coiled or elongated posture. And showing Japanese macaques images of snakes in a striking posture sets of a flurry of brain activity that isn’t evoked when they’re shown images of snakes in nonthreatening postures.

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The same is true for humans. Children and adults detect images of snakes in a striking posture more rapidly than a resting posture. And a study from earlier this year found human infants (aged seven to 10 months) have an innate ability to detect snakes.

Snakes are amazing, but shouldn’t be feared. If you encounter one on a sunny day, don’t make sudden movements, just back away slowly. Never pick them up (or attempt to kill them), as this is often when people are bitten.

Damian R. Michael, Senior research fellow, Charles Sturt University; Dale Nimmo, Associate Professor in Ecology, Charles Sturt University, and Skye Wassens, Associate Professor in Ecology, Charles Sturt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Scientists capture rare footage of mother skink fighting a deadly brown snake to protect her babies

Author provided

Gregory Watson, University of the Sunshine Coast and Jolanta Watson, University of the Sunshine Coast

Unlike many mammals and birds, most reptiles show little sign of being caring parents. But our new research shows one lizard species may be more doting parents than we thought – the adults risking their own safety to protect their babies.

We used cameras in the Snowy Mountains of New South Wales to study the Cunningham’s skink. We were surprised to record evidence of the lizards actively defending their newborn offspring against formidable predators. Our findings are outlined in a paper released today.

Most startlingly, we recorded a mother skink aggressively attacking a large, deadly brown snake while her babies watched on. We also witnessed 12 incidents of skinks chasing magpies away from their young.

We originally set out to record how species such as skinks will cope with climate change. But this evolved into a study of the fascinating and surprising social bonds between lizard offspring and their parents.

Sun-loving skinks live together in social groups.
Authors provided

What is the Cunningham’s skink?

The Cunningham’s skink (Egernia cunninghami) is a large, sun-loving, spiny lizard native to southeast Australia. It’s named after Alan Cunningham, an explorer who collected the first specimen in the Blue Mountains.

The skinks are active during the day. They feed on invertebrates such as insects, snails and slugs, as well as vegetation.

The Cunningham’s skink lives in social groups – a behaviour very rare among lizards and reptiles. In these groups, mothers give birth to live young (rather than eggs) then live alongside their kids, sometimes for several years.

The species has strength in numbers – living in a group makes it easier to spot threats, which helps the group survive.

Thew offspring of Cunningham’s skinks can stay with the parents for several years.

The mother of all discoveries

Using video and thermal imaging, we observed the skinks on 32 days over three years.

Among reptiles, evidence of parental protection in their natural environment has been rare and typically anecdotal. We witnessed four birthing sessions, and then monitored skink encounters in the presence of their offspring.

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Videoing nature can be tricky. Often, the action takes place away from where you’ve directed your camera. So when we saw a snake, it was a scramble to get a free video camera and start recording.

We witnessed two separate encounters with an eastern brown snake. The first involved the snake sneaking up on six-day-old skinks basking in the sun (see footage below). We recorded the mother running towards the predator and biting it for several seconds. The snake writhes around before the mother releases her grip and returns unharmed to her young.

The following year, we encountered two adult skinks attacking another eastern brown snake in bushes. Juvenile skinks were nearby. The skinks bit tight to the snake’s body, and the snake dragged them for more than 15 metres before the skinks released their grip.

Snakes were not the only predator vanquished by the protective skink parents – Cunningham’s skinks regularly chased magpies away from their young. We observed 12 encounters between skinks and magpies. In each case, an adult skink aggressively chased and/or attacked the magpie after the bird came close to the group.

Thermal camera image showing the mother skink attacking the snake while her babies watch on.

What does this all mean?

Some animals rarely interact with others of the same species, even their offspring. In fact, available data suggests infanticide – where mature animals kill young offspring of the same species – can occur among some skink species.

We saw no such behaviour among the Cunningham’s skink, or aggression towards each other.

While the aggression of the adult skinks towards predators took place in the presence of young, the adults may have been exhibiting self-defence or territorial behaviour. Regardless, the attacks on predators in the presence of newborns does reflect parental care, either directly or indirectly. Our future field excursions will hopefully shed more light on this.

Understanding the factors that bring parents and offspring together, and keep them together, is important in our broader understanding of social evolution – that is, how social interactions of species arise, change and are maintained.

It will also help us understand how animals cooperating with and caring for each other can benefit both the individual, and the whole.

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Gregory Watson, Senior Lecturer, Science, University of the Sunshine Coast and Jolanta Watson, Lecturer in Science, University of the Sunshine Coast

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How we tracked the eating habits of snakes in Africa with the help of a Facebook group

A boomslang eating a bullfrog.
Provided by author/ G Cusins

Bryan Maritz, University of the Western Cape and Robin Maritz, University of the Western Cape

Snakes are a diverse lineage of reptiles that are found on every continent except Antarctica. Despite differences in appearance, habitat preference, defence tactics and underlying biology, one thing is common to all 3,800 species of snakes — every last one is a predator.

Pasha 75: Facebook helped us to learn what snakes eat. Why this is important.
The Conversation Africa, CC BY-NC-ND7.04 MB (download)

As predators, snakes are likely to fulfil important roles in ecosystems. Knowing what snakes eat can help scientists better understand ecological connections among snakes and other species. This will lead to a better understanding of how ecosystems function and how ecological communities might be affected by changes in habitat or climate.

Some snake species have also evolved potent venoms which aid in subduing prey. Mounting evidence suggests venom composition is adaptive and linked to what snakes eat. Although snake venoms have evolved primarily for feeding, venomous snakes also bite defensively.

Incidents of snake bites on people prompted the World Health Organisation to declare snakebite a neglected tropical disease in 2017. Given the link between venom biochemistry and feeding, a detailed understanding of a species’ diet can inform research dedicated to mitigating the effects of snakebite.

Unfortunately, the details of many African snake diets remain a mystery. Historically, information on snake diets has come from dissecting preserved museum specimens or fortuitous observations of snake feeding that are published as brief notes in journals or newsletters.

More recently, methods for studying snake feeding habits have embraced technology. These include fixed videography studies of ambush predators like puff adders and timber rattlesnakes, as well as DNA analysis of faecal material from smooth snakes. But these approaches cannot be used for many snake species, and they require a significant amount of time, effort, and resources.

Snake diets can be difficult to study, so, in 2015 we realised that photographs and videos of snakes feeding were being shared regularly on Facebook. We set out to gather these observations using a dedicated Facebook group – Predation Records – Reptiles and Frogs (Sub-Saharan Africa) – and to record the shared observations systematically. Our findings showcase how the network of active users on Facebook can help us to collect ecological data quickly and cheaply.

Our study

After several years of community participation in our study, we turned more than 1,900 observations of reptiles or amphibians eating or being eaten into scientific data. Our database includes 83 families of predators and 129 families of prey.

For snakes, we gathered more than 1,100 feeding records. We soon saw that social media had helped gather these feeding records faster than ever before. The data collected from Facebook represent 27% of scientifically documented snake feeding records in southern Africa. More than 70% of all feeding records had not been recorded previously in the scientific literature.

A boomslang eating woodpecker chick.
Provided by author/ L Van Wyk

To find out how data from social media compared to data collected using other platforms, we used iNaturalist (a popular citizen science platform) and Google Images to find observations of feeding snakes. Facebook outperformed both platforms in terms of the overall number of observations collected.

Finally, we noticed that observations collected from the different platforms produced different prey profiles, suggesting that certain prey may be over – or underrepresented in studies depending on the source of the observation.

Nearly all methods used for studying snake diets have biases. This may be why there are striking difference between what social media and the existing scientific literature revealed.

Facebook also let us identify prey more precisely. Most of the prey was photographed while being eaten or after regurgitation. On the other hand, prey collected from the stomachs of museum specimens are often partially digested, making the identification process difficult.

Our findings highlight the remarkable power of citizen science to reveal undocumented details about the natural world. In the case of snake diets, specifically, it is the harnessing of thousands of social media users that facilitated the data collection.

This is mainly because snakes feed secretively and relatively infrequently in the wild. But social media and the widespread use of smartphones with cameras means that even difficult to observe events can now be recorded in large numbers and across different geographic areas.

The continued detection of new feeding interactions shows how there is much to be learned about these remarkable animals. As more observations are made, the full picture of a species’ diet will be revealed. By using a community of observers, more data and information can be gathered for little to no cost.

Going forward

While our study was restricted to southern Africa, expanding data collection efforts like this into the rest of Africa is necessary. Given that Africa experiences some of the world’s heaviest snakebite burden, details on the biology of its snakes will prove useful. If ever there was an opportunity to gather novel, important ecological information about snakes in Africa, this is it.

Globally, there are hundreds of groups on Facebook – some of which have close to 200,000 members – dedicated to sharing original photographs and observations of snakes. More generally, Facebook groups exist for most classes of animals and plants, and these communities have unprecedented observational power for researchers asking appropriate questions of the natural world.

Bryan Maritz, Senior Lecturer, Biodiversity and Conservation Biology, University of the Western Cape and Robin Maritz, Research fellow, Biodiversity and Conservation Biology, University of the Western Cape

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Snake Bites

Deep breath: this sea snake gathers oxygen through its forehead

Hydrophis cyanocinctus has a mysterious hole in the top of its skull.
Alessandro Palci, Author provided

Alessandro Palci, Flinders University and Kate Sanders, University of Adelaide

Only fish have gills, right? Wrong. Meet Hydrophis cyanocinctus, a snake that can breathe through the top of its own head.

The 3m species, which is native to Australian and Asian coastal waters, can draw in oxygen with the help of a unique set of blood vessels below the skin in its snout and forehead.

The network of blood vessels works very similarly to a fish’s gills, and represents a newly discovered addition to the extraordinary range of adaptations that sea snakes use to thrive below the waves.

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There are dozens of sea snake species in the Indian and Pacific oceans, but none in the Atlantic or Caribbean. Why?

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In evolutionary terms, sea snakes are relative newcomers to aquatic life, having evolved from land-based snakes only about 16 million years ago. This is much more recent than marine mammals such as whales and dugongs, which arose around 50 million years ago.

The roughly 60 known species of sea snakes have nevertheless developed an impressive array of adaptations to marine life. These include salt glands under the tongue, nostrils that face upwards and can be sealed by valves, paddle-like tails to facilitate swimming, and the ability to absorb oxygen and eliminate carbon dioxide through their skin.

Some sea snakes have even evolved light sensors on the tips of their tails, possibly as a way to avoid having them nibbled off by predators when partially hidden in crevices.

An Arabian Gulf sea snake (Hydrophis lapemoides) in its natural environment.
Keith DP Wilson/flickr

A mysterious hole in the skull

Just when we thought we had uncovered all the strange things sea snakes do, we discovered something new. As we report today in the journal Royal Society Open Science, the annulated sea snake Hydrophis cyanocinctus effectively has a set of gills on its forehead.

The first sign of something unusual was an odd hole (in anatomical terms, a “foramen”, the Latin word for “hole”) in the roof of this species’ skull.

This hole is reminiscent of the “pineal foramen” found in several lizard species, which contains a tiny light-sensitive organ called the pineal eye. Could sea snakes also have a pineal eye?

No trace of such a foramen has ever been found in a modern snake. In fact, snakes are thought to have lost the pineal foramen at least 100 million years ago, which is the age of the oldest reasonably complete fossil snakes.

However, because some sea snakes have light-sensitive organs in their tails, we couldn’t rule out the possibility of a light-sensitive organ reappearing in its ancestral position in the skull – snakes did evolve from lizards, after all.

Not an eye, but a lung

We decided to investigate this unexpected foramen in H. cyanocinctus more closely. We obtained some live specimens from Vietnam, where sea snakes are commonly sold as food in fish markets, and generated images of the soft tissues around the foramen using a combination of traditional and computer-assisted methods.

Head of the annulated sea snake (Hydrophis cyanocinctus) and its blood vessels (highlighted after digitally removing muscles and skin). Note the large vein connecting the network of blood vessels on top of the skull to the inside of the braincase (arrow).
Alessandro Palci, Author provided

These images revealed that this snake does not have a pineal eye. What actually goes through the mysterious hole in its skull is a large blood vessel (sometimes paired). This blood vessel then travels forward and branches into a complex network of veins and sinuses immediately under the skin of the forehead and snout.

We then examined other snakes, both terrestrial and marine, using the same methods, and realised that this network of blood vessels in H. cyanocinctus is unique.

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Did snakes evolve from ancient sea serpents?

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While a network of blood vessels is expected to be present under the skin of all snakes, what is special about H. cyanocinctus is the greatly exaggerated size of the blood vessels and the fact that they converge towards a single large vein that goes into the brain.

Gills on top of the head

This strange network of blood vessels makes sense when we consider that sea snakes can breathe through their skin. This happens thanks to arteries containing much lower oxygen concentrations than the surrounding seawater, which allows oxygen to diffuse through the skin and into the blood.

However, these low oxygen levels in arterial blood can cause problems, because the brain may not get the oxygen it needs. The dense network of veins on the forehead and snout of these sea snakes helps solve this problem by picking up oxygen from seawater and redistributing it to the brain while swimming underwater.

If you think that sounds similar to what fish do with their gills, you’re absolutely right. H. cyanocinctus has managed to evolve a respiratory system that works in much the same way as gills, despite the vast evolutionary distance between these two groups of species. Truly, these snakes are indeed creatures of the sea.

Alessandro Palci, Research Associate in Evolutionary Biology, Flinders University and Kate Sanders, Senior lecturer, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Banning exotic leather in fashion hurts snakes and crocodiles in the long run

Yellow anaconda (snake) skins pegged to dry by indigenous people in Argentina.
Tomas Waller, Author provided

Daniel Natusch, Macquarie University; Grahame Webb, Charles Darwin University, and Rick Shine, University of Sydney

We are all familiar with the concept of “fake news”: stories that are factually incorrect, but succeed because their message fits well with the recipient’s prior beliefs.

We and our colleagues in conservation science warn that a form of this misinformation – so-called “feelgood conservation” – is threatening approaches for wild animal management that have been developed by decades of research.

The issue came to a head in February when major UK-based retailer Selfridges announced it would no longer sell “exotic” skins – those of reptile species such as crocodiles, lizards and snakes – in order to protect wild populations from over-exploitation.

But this decision is not supported by evidence.

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Too simplistic

Banning the use of animal skins in the fashion industry sounds straightforward and may seem commendable – wild reptiles will be left in peace, instead of being killed for the luxury leather trade.

But decades of research show that by walking away from the commercial trade in reptile skins, Selfridges may well achieve the opposite to what it intends. Curtailing commercial trade will be a disaster for some wild populations of reptiles.

How can that be true? Surely commercial harvesting is a threat to the tropical reptiles that are collected and killed for their skins?

Actually, no. You have to look past the fate of the individual animal and consider the future of the species. Commercial harvesting gives local people – often very poor people – a direct financial incentive to conserve reptile populations and the habitats upon which they depend.

If lizards, snakes and (especially) crocodiles aren’t worth money to you, why would you want to keep them around, or to protect the forests and swamps that house them?

Women raise Burmese pythons at a small farm on Hainan Island, China.
Daniel Natusch, Author provided

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Biggest man-eaters in the billabong

The iconic case study that supports this principle involves saltwater crocodiles in tropical Australia – the biggest, meanest man-eaters in the billabong.

Overharvested to the point of near-extinction, the giant reptiles were finally protected in the Northern Territory in 1971. The populations started to recover, but by 1979-80, when attacks on people started to occur again, the public and politicians wanted the crocodiles culled again. It’s difficult to blame them for that. Who wants a hungry croc in the pond where your children would like to swim?

Saltwater crocs are the reason many beaches are not open for swimming in northern Australia.
Shutterstock

But fast-forward to now and that situation has changed completely. Saltwater crocs are back to their original abundance. Their populations bounced back. These massive reptiles are now in every river and creek – even around the city of Darwin, capital of the Northern Territory.

This spectacular conservation success story was achieved not by protecting crocs, but by making crocs a financial asset to local people.

Eggs are collected from the wild every year, landowners get paid for them, and the resulting hatchlings go to crocodile farms where they are raised, then killed to provide luxury leather items, meat and other products. Landowners have a financial interest in conserving crocodiles and their habitats because they profit from it.

Saltwater crocodile eggs collected in the Northern Territory, Australia.
Daniel Natusch, Author provided

The key to the success was buy-in by the community. There are undeniable negatives in having large crocodiles as neighbours – but if those crocs can contribute to the family budget, you may want to keep them around. In Australia, it has worked.

The trade in giant pythons in Indonesia, Australia’s northern neighbour, has been examined in the same way, and the conclusion is the same. The harvest is sustainable because it provides cash to local people, in a society where cash is difficult to come by.

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Decisions without evidence

A collector captures a yellow anaconda in Argentina.
Emilio White, Author provided

So the evidence says commercial exploitation can conserve populations, not annihilate them.

Why then do companies make decisions that could imperil wild animals? Probably because they don’t know any better.

Media campaigns by animal-rights activists aim to convince kind-hearted urbanites that the best way to conserve animals is to stop people from harming them. This might work for some animals, but it fails miserably for wild reptiles.

We argue that if we want to keep wild populations of giant snakes and crocodiles around for our grandchildren to see (hopefully, at a safe distance), we need to abandon simplistic “feelgood conservation” and look towards evidence-based scientific management.

We need to move beyond “let’s not harm that beautiful animal” and get serious about looking at the hard evidence. And when it comes to giant reptiles, the answer is clear.

The ban announced by Selfridges is a disastrous move that could imperil some of the world’s most spectacular wild animals and alienate the people living with them.

Daniel Natusch, Honorary Research Fellow, Macquarie University; Grahame Webb, Adjunct Professor, Environment & Livelihoods, Charles Darwin University, and Rick Shine, Professor in Evolutionary Biology, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Snake venom can vary in a single species — and it’s not just about adaptation to their prey

Wolfgang Wüster, Bangor University and Giulia Zancolli, Université de Lausanne

Few sights and sounds are as emblematic of the North American southwest as a defensive rattlesnake, reared up, buzzing, and ready to strike. The message is loud and clear, “Back off! If you don’t hurt me, I won’t hurt you.” Any intruders who fail to heed the warning can expect to fall victim to a venomous bite.

But the consequences of that bite are surprisingly unpredictable. Snake venoms are complex cocktails made up of dozens of individual toxins that attack different parts of the target’s body. The composition of these cocktails is highly variable, even within single species. Biologists have come to assume that most of this variation reflects adaptation to what prey the snakes eat in the wild. But our study of the Mohave rattlesnake (Crotalus scutulatus, also known as the Mojave rattlesnake) has uncovered an intriguing exception to this rule.

What’s in those glands? It depends where you are!
W. Wüster

A 20-minute drive can take you from a population of this rattlesnake species with a highly lethal neurotoxic venom, causing paralysis and shock, to one with a haemotoxic venom, causing swelling, bruising, blistering and bleeding. The neurotoxic venom (known as venom A) can be more than ten times as lethal as the haemotoxic venom (venom B), at least to lab mice.

The Mohave rattlesnake is not alone in having different venoms like this – several other rattlesnake species display the same variation. But why do we see these differences? Snake venom evolved to subdue and kill prey. One venom may be better at killing one prey species, while another may be more toxic to different prey. Natural selection should favour different venoms in snakes eating different prey – it’s a classic example of evolution through natural selection.

This idea that snake venom varies due to adaptation to eating different prey has become widely accepted among herpetologists and toxinologists. Some have found correlations between venom and prey. Others have shown prey-specific lethality of venoms, or identified toxins fine-tuned for killing the snakes’ natural prey. The venom of some snakes even changes along with their diet as they grow.

We expected the Mohave rattlesnake to be a prime example of this phenomenon. The extreme differences in venom composition, toxicity and mode of action (whether it is neurotoxic or haemotoxic) seem an obvious target for natural selection for different prey. And yet, when we correlated differences in venom composition with regional diet, we were shocked to find there is no link.

Variable venoms

In the absence of adaptation to local diet, we expected to see a connection between gene flow (transfer of genetic material between populations) and venom composition. Populations with ample gene flow would be expected to have more similar venoms than populations that are genetically less connected. But once again, we drew a blank – there is no link between gene flow and venom. This finding, together with the geographic segregation of the two populations with different venoms, suggests that instead there is strong local selection for venom type.

Mohave rattlesnake feeding on a kangaroo rat, one of its most common prey items.
W. Wüster

The next step in our research was to test for links between venom and the physical environment. Finally, we found some associations. The haemotoxic venom is found in rattlesnakes which live in an area which experiences warmer temperatures and more consistently low rainfall compared to where the rattlesnakes with the neurotoxic venom are found. But even this finding is deeply puzzling.

It has been suggested that, as well as killing prey, venom may also help digestion. Rattlesnakes eat large prey in one piece, and then have to digest it in a race against decay. A venom that starts predigesting the prey from the inside could help, especially in cooler climates where digestion is more difficult.

But the rattlesnakes with haemotoxic venom B, which better aids digestion, are found in warmer places, while snakes from cooler upland deserts invariably produce the non-digestive, neurotoxic venom A. Yet again, none of the conventional explanations make sense.

Clearly, the selective forces behind the extreme venom variation in the Mohave rattlesnake are complex and subtle. A link to diet may yet be found, perhaps through different kinds of venom resistance in key prey species, or prey dynamics affected by local climate. In any case, our results reopen the discussion on the drivers of venom composition, and caution against the simplistic assumption that all venom variation is driven by the species composition of regional diets.

From a human perspective, variation in venom composition is the bane of anyone working on snakebite treatments, or antidote development. It can lead to unexpected symptoms, and antivenoms may not work against some populations of a species they supposedly cover. Anyone living within the range of the Mohave rattlesnake can rest easy though – the available antivenoms cover both main venom types.

Globally, however, our study underlines the unpredictability of venom variation, and shows again that there are no shortcuts to understanding it. Those developing antivenoms need to identify regional venom variants and carry out extensive testing to ensure that their products are effective against all intended venoms.

Wolfgang Wüster, Senior Lecturer in Zoology, Bangor University and Giulia Zancolli, Associate Research Scientist, Université de Lausanne

This article is republished from The Conversation under a Creative Commons license. Read the original article.