Many animals avoid contact with people. In protected areas of the African savanna, mammals flee more intensely upon hearing human conversations than when they hear lions or sounds associated with hunting. This fear of humans affects how species use and move in their habitat.
Throughout our lives, we interact with hundreds of wildlife species without stopping to think about it. These interactions can be direct, such as encountering wild animals while hiking in the mountains or driving through rural areas — or more deliberate, as when we engage with wildlife for food, sport, or trade. As hunters, fishers, and collectors, we kill more than 15,000 species of vertebrates — one-third of known diversity — a range of prey 300 times greater than that of any other predator our size (1).
Now, let’s look at it from the other side. Anyone who has survived an attack or a fatal accident, they understand that the experience is remembered for a lifetime. Likewise, animals store information about threatening or harmful encounters with humans (2). For them, adjusting their behaviour in response to human presence has implications for their survival and reproduction (3, 4), which are passed down from generation to generation (5). This ability to adapt, for example, determines which individuals, populations and species coexist with us in urbanised environments (6).
Response to dangerous sounds
Liana Zanette and her team measured the flight responses of wild mammals in the Greater Kruger National Park (South Africa) when exposed to sounds that signal danger (7) [video-summary]. To do this, Zanette recorded videos of more than 4,000 visits to 21 waterholes by 18 mammal species. During each visit, a speaker attached to a tree randomly played one of five playback sounds: hunting dogs barking, gunshots, lion growls, human conversations in a calm tone and, as a control, the songs of harmless birds.
Deep-sea sharks include some of the longest-lived vertebrates known. The record holder is the Greenland shark, with a recently estimated maximum age of nearly 400 years. Their slow life cycle makes them vulnerable to fisheries.
In the Arctic, there are whales that have survived since the time of Napoleon’s Empire; in the Atlantic, there are molluscs that were contemporary with Christopher Columbus’ voyages; and in Antarctica, there are sponges born before the Holocene when humans were still an insignificant species of hunter-gatherers (see video on lifespan variation in wildlife).
Long-lived species grow slowly and reproduce at later ages (1, 2). As a result, these animals require a long time to form abundant populations and to recover from fishing-related mortality.
Among cartilaginous fish (chimaeras, rays, sharks, and skates), the risk of extinction due to overfishing is twice as high for deep-sea species compared to coastal species, because the former have longer and slower life cycles (3).
In boreal forests, many hares adopt white winter coats before the snow arrives. In a snowless landscape, these white hares lack camouflage against predators. However, their early moult from brown into white fur can increase their survival and offers an advantage as the snow season becomes progressively shorter with climate change.
Throughout the year, we wear different clothing to protect ourselves from the cold or heat and for aesthetic reasons depending on the occasion. Likewise, many animals change the colour, thickness and structure of their fur and feathers in tune with the seasons.
Snowshoe hare (Lepus americanus) in a snowy (Kluane Lake/Yukon, Canada) and snowless habitat (Seely Lake/Montana, USA). This mammal moults its coat as colder temperatures, shorter days, and snowfall arrive. In the genetic populations of the temperate forests of the Rocky Mountains and the boreal forests spanning the North American continent, hares that moult from brown to white are abundant (20). However, in coastal areas, and in the third genetic population in the North Pacific, snowfall is brief and less intense, resulting in fewer white individuals. This is due to hybridisation with the black-tailed jackrabbit (Lepus californicus) over 3,000 years ago (17). The hare’s coat has an outer layer, where the longer fur gives each individual its colour, and an inner layer of short fur (19). In winter, the outer layer becomes thicker and denser, while the inner layer maintains a consistent thickness but increases in density. By biomass, the snowshoe hare is the primary herbivore in the North American boreal forest and distinguishes the trophic relationships between continents (21). In Europe, much of the boreal understory remains under snow, providing food for rodents with four-year abundance cycles controlled by small generalist predators (mustelids). In North America, the boreal understory grows above the snow and provides food for hares. In this region, snowshoe hare populations follow 10-year abundance cycles regulated by specialist predators (those that feed almost exclusively on hares), primarily the Canada lynx (Lynx canadensis) (6). Photos courtesy of Alice Kenney and Charles Krebs (Yukon) [see their ecological monitoring program here] and Marketa Zimova (Montana).
However, as the climate changes, springs arrive earlier, winters are delayed, and the frequency and intensity of precipitation have become highly variable. All of this makes it harder for species to adjust their wardrobe to temperature changes (1).
In this context, body colour is a critical factor for birds and mammals that undergo an annual moult (2). In 21 species from the cold latitudes of the Northern Hemisphere, some individuals are brown in summer, but turn white in winter, while others remain brown year round (3). This phenomenon includes weasels, rodents, ptarmigans, foxes, rabbits and hares.
Imagine growing up beside the eastern Mediterranean Sea 14,000 years ago. You’re an accomplished sailor of the small watercraft you and your fellow villagers make, and you live off both the sea and the land.
But times have been difficult — there just isn’t the same amount of game or fish around as when you were a child. Maybe it’s time to look elsewhere for food.
Now imagine going farther than ever before in your little boat, accompanied maybe by a few others, when suddenly you spot something on the horizon. Is that an island?
The western coast of Cyprus. CJA Bradshaw / Flinders University
When you beach your boat to have a look around, you can’t believe what you’re seeing — tiny boar-sized hippos and horse-sized elephants that look like babies to your eyes. There are so many of them, and you’re hungry after the long journey.
The diminutive beasts don’t seem to show any fear. You easily kill a few and preserve the meat as best you can for the long journey back.
When you get home, you are excited to let everyone in the village know what you’ve found. Soon enough, you organise a major expedition back to the island.
Of course, we’ll never know if this kind of scenario took place, but it’s a plausible story of how and when the first humans managed to get to Cyprus. It also illustrates how they might have quickly brought about the demise of the tiny hippopotamusPhanourios minor, as well as the dwarf elephantPalaeoloxodon cypriotes.
In light of new genetic research on the identity of ‘wild dogs’ and dingoes across Australia, the undersigned wish to express concern with current South Australia Government policy regarding the management and conservation of dingoes. Advanced DNA research on dingoes has demonstrated that dingo-dog hybridisation is much less common than thought, that most DNA tested dingoes had little domestic dog ancestry and that previous DNA testing incorrectly identified many dingoes as hybrids (Cairns et al. 2023). We have serious concerns about the threat current South Australian public policy poses to the survival of the ‘Big Desert’ dingo population found in Ngarkat Conservation Park and surrounding areas.
We urge the South Australian Government to:
Revoke the requirement that all landholders follow minimum baiting standards, including organic producers or those not experiencing stock predation. Specifically
Dingoes in Ngarkat Conservation park (Region 4) should not be destroyed or subjected to ground baiting and trapping every 3 months. The Ngarkat dingo population is a unique and isolated lineage of dingo that is threatened by inbreeding and low genetic diversity. Dingoes are a native species and all native species should be protected inside national parks and conservation areas.
Landholders should not be required to carry out ground baiting on land if there is no livestock predation occurring. Furthermore, landholders should be supported to adopt non-lethal tools and strategies to mitigate the risk of livestock predation including the use of livestock guardian animals, which are generally incompatible with ground and aerial 1080 baiting.
Revoke permission for aerial baiting of dingoes (incorrectly called “wild dogs”) in all Natural Resource Management regions – including within national parks. Native animals should be protected in national parks and conservation areas.
Cease the use of inappropriate and misleading language to label dingoes as “wild dogs”. Continued use of the term “wild dogs” is not culturally respectful to First Nations peoples and is not evidence-based.
Proactively engage with First Nations peoples regarding the management of culturally significant species like dingoes. For example, the Wotjobaluk nation should be included in consultation regarding the management of dingoes in Ngarkat Conservation Park.
Changes in South Australia public policy are justified based on genetic research by Cairns et al. (2023) that overturns previous misconceptions about the genetic status of dingoes. It demonstrates:
Most “wild dogs” DNA tested in arid and remote parts of Australia were dingoes with no evidence of dog ancestry. There is strong evidence that dingo-dog hybridisation is uncommon, with firstcross dingo-dog hybrids and feral dogs rarely being observed in the wild. In Ngarkat Conservation park none of DNA tested animals had evidence of domestic dog ancestry, all were ‘pure’ dingoes.
Previous DNA testing methods misidentified pure dingoes as being mixed. All previous genetic surveys of wild dingo populations used a limited 23-marker DNA test. This is the method currently used by NSW Department of Primary Industries, which DNA tests samples from NSW Local Land Services, National Parks and Wildlife Service, and other state government agencies. Comparisons of DNA testing methods find that the 23-marker DNA test frequently misidentified animals as dingo-dog hybrids. Existing knowledge of dingo ancestry across South Australia, particularly from Ngarkat Conservation park is incorrect; policy needs to be based on updated genetic surveys.
There are multiple dingo populations in Australia. High-density genomic data identified more than four wild dingo populations in Australia. In South Australia there are at least two dingo populations present: West and Big Desert. The West dingo population was observed in northern South Australia, but also extends south of the dingo fence. The Big Desert population extends from Ngarkat Conservation park in South Australia into the Big Desert and Wyperfield region of Victoria.
The Ngarkat Dingo population is threatened by low genetic variability. Preliminary evidence from high density genomic testing of dingoes in Ngarkat Conservation park and extending into western Victoria found evidence of limited genetic variability which is a serious conservation concern. Dingoes in Ngarkat and western Victoria had extremely low genetic variability and no evidence of gene flow with other dingo populations, demonstrating their effective isolation. This evidence suggests that the Ngarkat (and western Victorian) dingo population is threatened by inbreeding and genetic isolation. Continued culling of the Ngarkat dingo population will exacerbate the low genetic variability and threatens the persistence of this population.
Have you ever watched a nature documentary and marvelled at the intricate dance of life unfolding on screen? From the smallest insect to the largest predator, every creature plays a role in the grand performance of our planet’s biosphere. But what happens when one of these performers disappears?
In this post, we delve into our recent article Estimating co-extinction risks in terrestrial ecosystems just published in Global Change Biology, in which we discuss the cascading effects of species loss and the risks of ‘co-extinction’.
But what does ‘co-extinction’ really mean?
Imagine an ecosystem as a giant web of interconnected species. Each thread represents a relationship between two species — for example, a bird that eats a certain type of insect, or a plant that relies on a specific species of bee for pollination. Now, what happens if one of these species in the pair disappears? The thread breaks and the remaining species loses an interaction. This could potentially lead to its co-extinction, which is essentially the domino effect of multiple species losses in an ecosystem.
A famous example of this effect can be seen with the invasion of the cane toad (Rhinella marina) across mainland Australia, which have caused trophic cascades and species compositional changes in these communities.
The direct extinction of one species, caused by effects such as global warming for example, has the potential to cause other species also to become extinct indirectly.
We’ve just published a new paper showing that young red kangaroos (Osphranter rufus) protected by the dingo-proof fence take more time to grow up than their counterparts on the other side, who quickly outgrow the risk of being a dingo’s next meal.
Published in the Journal of Mammalogy, our article led by Rex Mitchell also revealed that there are more young and female kangaroos inside the dingo-proof fence, showing that the fence impacts on different aspects of the red kangaroo’s life cycle.
Red kangaroos are one of the dingo’s favourite prey species, so it’s not surprising to find fewer of the smaller females and younger animals when there are more dingoes around. However, we didn’t expect that young animals inside the fence were lighter and smaller than those outside the fence. Read the rest of this entry »
Following my annual tradition, I present the retrospective list of the ‘top’ 20 influential papers of 2022 as assessed by experts in Faculty Opinions(formerly known as F1000). These are in no particular order. See previous years’ lists here: 2021, 2020, 2019, 2018, 2017, 2016, 2015, 2014, and 2013.
Carnivores are essential components of trophic webs, and ecosystem functions crumble with their loss. Novel data show the connection between calcareous reefs and sea otters under climate change.
Trophic cascade on the Aleutian Islands (Alaska, USA) linking sea otters (Enhydra lutris) with sea urchins (Strongylocentrotus polyacanthus) and calcareous reefs (Clathromorphum nereostratum). With males weighting up to 50 kg, sea otters have been IUCN-catalogued as Endangered since 2000. The top photo shows a male in a typical, belly-up floating position. The bottom photo shows live (pinkish) and dead (whitish) tissue on the reef surface as a result of grazing of sea urchins at a depth of 10 m. Sea otters are mesopredators, typically foraging on small prey like sea urchins, but their historical decline due to overhunting unleashed the proliferation of the echinoderms. At the same time, acidification and sea-water warming have softened the skeleton of the reefs, allowing for deeper grazing by sea urchins that eliminate the growth layer of living tissue that give the reefs their pinkish hue. Large extents of dead reefs stop fixing the excess in carbonic acid, whose carbon atoms sea water sequesters from the atmosphere enriched in carbon by our burning of fossil fuels. Photos courtesy of Joe Tomoleoni taken in Moss Landing – California, USA (otter), and on the Near Islands – Aleutian Archipelago, Alaska (reef).
For most, the decisions made by people we have never met affect our daily lives. Other species experience the same phenomenon because they are linked to one another through a trophic cascade.
A trophic cascade occurs when a predator limits the abundance or behaviour of its prey, in turn affecting the survival of a third species in lower trophic levels that have nothing directly to do with the predator in question (1).
Sea otters (Enhydra lutris) represent a text-book example of a trophic cascade. These mustelids (see video footage here and here) hunt and control the populations of sea urchins (Strongylocentrotus polyacanthus), hence favouring kelp forests — the fronds of which are eaten by the sea urchins.
Removing the predator from the equation should lead to more sea urchins and less kelp, and this chain of events is exactly what happened along the coasts of the North Pacific (2, 3). The historical distribution of sea otters once ranged from Japan to Baja California through the Aleutian Islands (see NASA’s photo from space, and documentary on the island of Unimak), a sub-Arctic, arc-shaped archipelago including > 300 islands between Alaska (USA) and the Kamchatka Peninsula (Russia), extending ~ 2000 kilometres, and having a land area of ~ 18,000 km2.
But the fur trade during the 18th and 19th centuries brought the species to the brink of extinction, down to < 2000 surviving individuals (4). Without otters, sea urchins boomed and deforested kelp ecosystems during the 20th Century (5). Now we also know that this trophic cascade has climate-related implications in other parts of the marine ecosystem.
Underwater bites
Doug Rasher and collaborators have studied the phenomenon on the Aleutian Islands (6). The seabed of this archipelago is a mix of sandy beds, kelp forests, and calcareous reefs made up of calcium and magnesium carbonates fixed by the red algae Clathromorphum nereostratum. These reefs have grown at a rate of 3 cm annually for centuries as the fine film of living tissue covering the reef takes the carbonates from the seawater (7).
Last week, researchers at the University of Melbourne announced that thylacines or Tasmanian tigers, the Australian marsupial predators extinct since the 1930s, could one day be ushered back to life.
The thylacine (Thylacinus cynocephalus), also known as the ‘Tasmanian tiger’ (it was neither Tasmanian, because it was once common in mainland Australia, nor was it related to the tiger), went extinct in Tasmania in the 1930s from persecution by farmers and habitat loss. Art by Eleanor (Nellie) Pease, University of Queensland. Centre of Excellence for Australian Biodiversity and Heritage
Advances in mapping the genome of the thylacine and its living relative the numbat have made the prospect of re-animating the species seem real. As an ecologist, I would personally relish the opportunity to see a living specimen.
The announcement led to some overhyped headlines about the imminent resurrection of the species. But the idea of “de-extinction” faces a variety of technical, ethical and ecological challenges. Critics (like myself) argue it diverts attention and resources from the urgent and achievable task of preventing still-living species from becoming extinct.
The rebirth of the bucardo
The idea of de-extinction goes back at least to the the creation of the San Diego Frozen Zoo in the early 1970s. This project aimed to freeze blood, DNA, tissue, cells, eggs and sperm from exotic and endangered species in the hope of one day recreating them.
The notion gained broad public attention with the first of the Jurassic Park films in 1993. The famous cloning of Dolly the sheep reported in 1996 created a sense that the necessary know-how wasn’t too far off.
The next technological leap came in 2008, with the cloning of a dead mouse that had been frozen at –20℃ for 16 years. If frozen individuals could be cloned, re-animation of a whole species seemed possible.
After this achievement, de-extinction began to look like a potential way to tackle the modern global extinction crisis.
The intensity of threats to biodiversity from human endeavour becomes weaker as the distance to them increases.
As you move away from the big city to enjoy the countryside, you’ll notice the obvious increase in biodiversity. Even the data strongly support this otherwise subjective perception — there is a positive correlation between the degree we destroy habitat, harvest species, and pollute the environment, and the distance from big cities.
Remote locations are therefore usually considered safe havens and potential reservoirs for biodiversity. But our new study published recently in Nature Communications shows how this obvious pattern depicts only half of the story, and that global conservation management and actions might benefit from learning more about the missing part.
Communities are not just lists of individual species. Instead, they consist of complex networks of ecological interactions linking interdependent species. The structure of such networks is a fundamental determinant of biodiversity emergence and maintenance. However, it also plays an essential role in the processes of biodiversity loss. The decline or disappearance of some species might have detrimental —often fatal — effects on their associates. For example, a parasite cannot survive without its hosts, as much as a predator will starve without prey, or a plant will not reproduce without pollinators.
Events where a species disappears following the loss of other species on which it depends are known as co-extinctions, and they are now recognised as a primary driver of the ongoing global biodiversity crisis. The potential risk stemming from ecological dependencies is a major concern for all ecological systems.
I’m very chuffed today to signal the publication of what I think is one of the most important contributions to the persistent conundrum surrounding the downfall of Australia’s megafauna many tens of millennia ago.
Sure, I’m obviously biased in that assessment because it’s a paper from our lab and I’m a co-author, but if readers had any inkling of the work that went into this paper, I think they might consider adopting my position. In addition, the injection of some actual ecology into the polemic should be viewed as fresh and exciting.
Having waded into the murky waters of the ‘megafauna debate’ for about a decade now, I’ve become a little sensitive to even a whiff of binary polemic surrounding their disappearance in Australia. Acolytes of the climate-change prophet still beat their drums, screaming for the smoking gun of a spear sticking out of a Diprotodon‘s skull before they even entertain the notion that people might have had something to do with it — but we’ll probably never find one given the antiquity of the event (> 40,000 years ago). On the other side are the blitzkriegers who declaim that human hunting single-handedly wiped out the lot.
Well, as it is for nearly all extinctions, it’s actually much more complicated than that. In the case of Sahul’s megafauna disappearances, both drivers likely contributed, but the degree to which both components played a part depends on where and when you look — Fred Saltrédemonstrated that elegantly a few years ago.
So, why does the polemic persist? In my view, it’s because we have largely depended on the crude comparison of relative dates to draw our conclusions. That is, we look to see if some climate-change proxy shifted in any notable way either before or after an inferred extinction date. If a particular study claims evidence that a shift happened before, then it concludes climate change was the sole driver. If a study presents evidence that a shift happened after, then humans did it. Biases in geochronological inference (e.g., spatial, contamination), incorrect application of climate proxies, poor taxonomic resolution, and not accounting for the Signor-Lipps effect all contribute unnecessarily to the debate because small errors or biases can flip relative chronologies on their head and push conclusions toward uncritical binary outcomes. The ‘debate’ has been almost entirely grounded on this simplistically silly notion.
This all means that the actual ecology has been either ignored or merely made up based on whichever pet notion of the day is being proffered. Sure, there are a few good ecological inferences out there from some damn good modellers and ecologists, but these have all been greatly simplified themselves. This is where our new paper finally takes the ecology part of the problem to the next level.
Back in June of this year I wrote (whinged) about the disappointment of writing a lot of ecological models that were rarely used to assist real-world wildlife management. However, I did hint that another model I wrote had assistance one government agency with pig management on Kangaroo Island.
Modelling by the Flinders UniversityGlobal Ecology Laboratory shows the likelihood and feasibility of feral pig eradication under different funding and eradication scenarios. With enough funding, feral pigs could be eradicated from Kangaroo Island in 2 years.
This basically means that because of the model, PIRSA was successful in obtaining enough funding to pretty much ensure that the eradication of feral pigs from Kangaroo Island will be feasible!
Why is this important to get rid of feral pigs? They are a major pest on the Island, causing severe economic and environmental impacts both to farms and native ecosystems. On the agricultural side of things, they prey on newborn lambs, eat crops, and compete with livestock for pasture. Feral pigs damage natural habitats by up-rooting vegetation and fouling waterholes. They can also spread weeds and damage infrastructure, as well as act as hosts of parasites and diseases (e.g., leptospirosis, tuberculosis, foot-and-mouth disease) that pose serious threats to industry, wildlife, and even humans.
Shamefully, Australia has one of the highest extinction rates in the world. And the number one threat to our species is invasive or “alien” plants and animals.
But invasive species don’t just cause extinctions and biodiversity loss – they also create a serious economic burden. Our research, published today, reveals invasive species have cost the Australian economy at least A$390 billion in the last 60 years alone.
Our paper – the most detailed assessment of its type ever published in this country – also reveals feral cats are the worst invasive species in terms of total costs, followed by rabbits and fire ants.
Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.
Feral cats are Australia’s costliest invasive species. Source: Adobe Stock/240188862
Huge economic burden
Invasive species are those not native to a particular ecosystem. They are introduced either by accident or on purpose and become pests.
Some costs involve direct damage to agriculture, such as insects or fungi destroying fruit. Other examples include measures to control invasive species like feral cats and cane toads, such as paying field staff and buying fuel, ammunition, traps and poisons.
Our previous research put the global cost of invasive species at A$1.7 trillion. But this is most certainly a gross underestimate because so many data are missing.
As a wealthy nation, Australia has accumulated more reliable cost data than most other regions. These costs have increased exponentially over time – up to sixfold each decade since the 1970s.
I’m pleased to announce the publication of a paper led by Kathryn Venning (KV) that was derived from her Honours work in the lab. Although she’s well into her PhD on an entirely different topic, I’m overjoyed that she persevered and saw this work to publication.
Feral cats occupy every habitat in the country, from the high tropics to the deserts, and from the mountains to the sea. They adapt to the cold just as easily as they adapt to the extreme heat, and they can eat just about anything that moves, from invertebrates to the carcases of much larger animals that they scavenge.
Cats are Australia’s bane, but you can’t help but be at least a little impressed with their resilience.
Still, we have to try our best to get rid of them where we can, or at least reduce their densities to the point where their ecological damage is limited.
Typically, the only efficient and cost-effective way to do that is via lethal control, but by using various means. These can include direct shooting, trapping, aerial poison-baiting, and a new ‘smart’ method of targeted poison delivery via a prototype device known as a Felixer™️. The latter are particularly useful for passive control in areas where ground-shooting access is difficult.
A live Felixer™️ deployed on Kangaroo Island (photo: CJA Bradshaw 2020)
A few years back the federal government committed what might seem like a sizeable amount of money to ‘eradicate’ cats from Australia. Yeah, good luck with that, although the money has been allocated to several places where cat reduction and perhaps even eradication is feasible. Namely, on islands.
They’re one of the most damaging environmental forces on Earth. They’ve colonised pretty much every place humans have set foot on the planet. Yet you might not even know they exist.
We’re talking about alien species. Not little green extraterrestrials, but invasive plants and animals not native to an ecosystem and which become pests. They might be plants from South America, starfish from Africa, insects from Europe or birds from Asia.
These species can threaten the health of plants and animals, including humans. And they cause huge economic harm. Our research, recently published in the journal Nature, puts a figure on that damage. We found that globally, invasive species cost US$1.3 trillion (A$1.7 trillion) in money lost or spent between 1970 and 2017.
The cost is increasing exponentially over time. And troublingly, most of the cost relates to the damage and losses invasive species cause. Meanwhile, far cheaper control and prevention measures are often ignored.
Yellow crazy ants, such as these attacking a gecko, are among thousands of invasive species causing ecological and economic havoc. Dinakarr, CC0, Wikimedia Commons
An expansive toll
Invasive species have been invading foreign territories for centuries. They hail from habitats as diverse as tropical forests, dry savannas, temperate lakes and cold oceans.
They arrived because we brought them — as pets, ornamental plants or as stowaways on our holidays or via commercial trade.
For many years I’ve been interested in modelling the extinction dynamics of megafauna. Apart from co-authoring a few demographically simplified (or largely demographically free) models about how megafauna species could have gone extinct, I have never really tried to capture the full nuances of long-extinct species within a fully structured demographic framework.
That is, until now.
But how do you get the life-history data of an extinct animal that was never directly measured. Surely, things like survival, reproductive output, longevity and even environmental carrying capacity are impossible to discern, and aren’t these necessary for a stage-structured demographic model?
The answer to the first part of that question “it’s possible”, and to the second, it’s “yes”. The most important bit of information we palaeo modellers need to construct something that’s ecologically plausible for an extinct species is an estimate of body mass. Thankfully, palaeontologists are very good at estimating the mass of the things they dig up (with the associated caveats, of course). From such estimates, we can reconstruct everything from equilibrium densities, maximum rate of population growth, age at first breeding, and longevity.
But it’s more complicated than that, of course. In Australia anyway, we’re largely dealing with marsupials (and some monotremes), and they have a rather different life-history mode than most placentals. We therefore have to ‘correct’ the life-history estimates derived from living placental species. Thankfully, evolutionary biologists and ecologists have ways to do that too.
The Pleistocene kangaroo Procoptodon goliah, the largest and most heavily built of the short-faced kangaroos, was the largest and most heavily built kangaroo known. It had an unusually short, flat face and forwardly directed eyes, with a single large toe on each foot (reduced from the more normal count of four). Each forelimb had two long, clawed fingers that would have been used to bring leafy branches within reach.
So with a battery of ecological, demographic, and evolutionary tools, we can now create reasonable stochastic-demographic models for long-gone species, like wombat-like creatures as big as cars, birds more than two metres tall, and lizards more than seven metres long that once roamed the Australian continent.
Ancient clues, in the shape of fossils and archaeological evidence of varying quality scattered across Australia, have formed the basis of several hypotheses about the fate of megafauna that vanished during a peak about 42,000 years ago from the ancient continent of Sahul, comprising mainland Australia, Tasmania, New Guinea and neighbouring islands.
There is a growing consensus that multiple factors were at play, including climate change, the impact of people on the environment, and access to freshwater sources.
Just published in the open-access journal eLife, our latest CABAH paper applies these approaches to assess how susceptible different species were to extinction – and what it means for the survival of species today.
Using various characteristics such as body size, weight, lifespan, survival rate, and fertility, we (Chris Johnson, John Llewelyn, Vera Weisbecker, Giovanni Strona, Frédérik Saltré & me) created population simulation models to predict the likelihood of these species surviving under different types of environmental disturbance.
We compared the results to what we know about the timing of extinction for different megafauna species derived from dated fossil records. We expected to confirm that the most extinction-prone species were the first species to go extinct – but that wasn’t necessarily the case.
While we did find that slower-growing species with lower fertility, like the rhino-sized wombat relative Diprotodon, were generally more susceptible to extinction than more-fecund species like the marsupial ‘tiger’ thylacine, the relative susceptibility rank across species did not match the timing of their extinctions recorded in the fossil record.
Indeed, we found no clear relationship between a species’ inherent vulnerability to extinction — such as being slower and heavier and/or slower to reproduce — and the timing of its extinction in the fossil record.
In fact, we found that most of the living species used for comparison — such as short-beaked echidnas, emus, brush turkeys, and common wombats — were more susceptible on average than their now-extinct counterparts.
Let’s step back to 2015. In a former life when I was at another institution, I had the immense fortune and pleasure to spend six months on sabbatical in a little village just south of Paris working with my friend and colleague, Franck Courchamp, at Université Paris-Sud (now Université Paris-Saclay).
Sure, I felt a bit jammy living there with my daughter in a beautiful house just down the street from two mouth-watering pâtisseries and three different open marchés. We ate well. We picked mushrooms on the weekends or visited local châteaux. We went into the city and visited overwhelmingly beautiful museums at our leisure. We drank good champagne (well, I did, not my eight-year old). We had communal raclettes.
But of course, I was primarily there to do research with Franck and his lab, despite the obvious perks.
While I busied myself with several tasks while there, one of our main outputs was to put together the world’s first global database of the costs of invasive insects, which we subsequently published in 2016.
But that was only the beginning. With funding that started off the process with insects, Franck persevered and hired postdocs and took on more students to build the most comprehensive database of all invasive species ever compiled — InvaCost.
I cannot stress enough how massive an undertaking this was. It’s not simply a big list of all the cost estimates in existence, it’s also a detailed assessment of cost reliability, standardisation, and contextualisation. I’m not sure I would have had the courage to do this myself.
Herein we described how the economic costs of invasive alien species accumulated since 1970 are tremendous, and that they have been steadily increasing over time.
Easy. Don’t go swimming/surfing/snorkelling/diving in the ocean.
“Oh, shit”
Sure, that’s true, but if you’re like many Australians, the sea is not just a beautiful thing to look at from the window, it’s a way of life. Trying telling a surfer not to surf, or a diver not to dive. Good luck with that.
It turns out that many of the deterrents we tested failed to show any reduction in the probability of a shark biting, with only one type of electronic deterrent showing any effect at all (~ 60% reduction).
Great. But what might that mean in terms of how many people could be saved by wearing such electronic deterrents? While the probability of being bitten by a shark is low globally, even in Australia (despite public perceptions), we wondered if the number of lives saved and injuries avoided was substantial.
In a new paper just published today in Royal Society Open Science, we attempted to answer that question.
To predict how many people could avoid shark bites if they were using properly donned electronic deterrents that demonstrate some capacity to dissuade sharks from biting, we examined the century-scale time series of shark bites on humans in Australia. This database — the ‘Australian Shark Attack File‘ — is one of the most comprehensive databases of its kind.
In some African countries, lion trophy hunting is legal. Riaan van den Berg
In sub-Saharan Africa, almost 1,400,000 km² of land spread across many countries — from Kenya to South Africa — is dedicated to “trophy” (recreational) hunting. This type of hunting can occur on communal, private, and state lands.
The hunters – mainly foreign “tourists” from North America and Europe – target a wide variety of species, including lions, leopards, antelopes, buffalo, elephants, zebras, hippopotamus and giraffes.
Debates centred on the role of recreational hunting in supporting nature conservation and local people’s livelihoods are among the most polarising in conservation today.
On one hand, people argue that recreational hunting generates funding that can support livelihoods and nature conservation. It’s estimated to generate US$200 million annually in sub-Saharan Africa, although others dispute the magnitude of this contribution.
On the other hand, hunting is heavily criticised on ethical and moral grounds and as a potential threat to some species.
Evidence for taking a particular side in the debate is still unfortunately thin. In our recently published research, we reviewed the large body of scientific literature on recreational hunting from around the world, which meant we read and analysed more than 1000 peer-reviewed papers.
Many animals avoid contact with people. In protected areas of the African savanna, mammals flee more intensely upon hearing human conversations than when they hear lions or sounds associated with hunting. This fear of humans affects how species use and move in their habitat. Throughout our lives, we interact with hundreds of wildlife species without…
Deep-sea sharks include some of the longest-lived vertebrates known. The record holder is the Greenland shark, with a recently estimated maximum age of nearly 400 years. Their slow life cycle makes them vulnerable to fisheries. Humans rarely live longer than 100 years. But many other animals and plants can live for several centuries or even millennia, particularly…
Procreating with a relative is taboo in most human societies for many reasons, but they all stem from avoiding one thing in particular — inbreeding increases the risk of genetic disorders that can seriously compromise a child’s health, life prospects, and survival. While we all inherit potentially harmful mutations from our parents, the effects of…
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