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.
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.
Human overpopulation is often depicted in the media in one of two ways: as either a catastrophic disaster or an overly-exaggerated concern. Yet the data understood by scientists and researchers is clear. So what is the actual state of our overshoot, and, despite our growing numbers, are we already seeing the signs that the sixth mass extinction is underway?
In a recent episode of The Great Simplification podcast, Nate Hagens was joined by global ecologist Corey Bradshaw to discuss his recent research on the rapid decline in biodiversity, how population and demographics will change in the coming decades, and what both of these will mean for complex global economies currently reliant on a stable environment.
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.
The way that eels migrate along rivers and seas is mesmerising. There has been scientific agreement since the turn of the 20th Century that the Sargasso Sea is the breeding home to the sole European species. But it has taken more than two centuries since Carl Linnaeus gave this snake-shaped fish its scientific name before an adult was discovered in the area where they mate and spawn.
Even among nomadic people, the average human walks no more than a few dozen kilometres in a single trip. In comparison, the animal kingdom is rife with migratory species that traverse continents, oceans, and even the entire planet (1).
The European eel (Anguilla anguilla) is an outstanding example. Adults migrate up to 5000 km from the rivers and coastal wetlands of Europe and northern Africa to reproduce, lay their eggs, and die in the Sargasso Sea — an algae-covered sea delimited by oceanic currents in the North Atlantic.
The European eel (Anguilla Anguilla) is an omnivorous fish that migrates from European and North African rivers to the Sargasso Sea to mate and die (18). Each individual experiences 4 distinct developmental phases, which look so different that they have been described as three distinct species (19): A planktonic, leaf-like larva (ilecocephalus phase) emerges from each egg and takes up to 3 years to cross the Atlantic. Off the Afro-European coasts, the larva transforms into a semi-transparent tiny eel (iiglass phase) that enters wetlands and estuaries, and travels up the rivers as it gains weight and pigment (iiiyellow phase). They remain there for up to 20 years, rarely growing larger than 1 m in length and 4 kg in weight (females are larger than males) — see underwater footage here and here. Sexual maturity ultimately begins to adjust to the migration to the sea: a darker, saltier, and deeper environment than the river. Their back and belly turn bronze and silver (ivsilver phase), respectively, the eyes increase in size and the number of photoreceptors multiplies (function = submarine vision), the stomach shrinks and loses its digestive function, the walls of the swim bladder thicken (function = floating in the water column), and the fat content of tissues increases by up to 30% of body weight (function = fuel for transoceanic travelling). And finally, the reproductive system will gradually develop while eels navigate to the Sargasso Sea — a trip during which they fast. Photos courtesy of Sune Riis Sørensen (2-day embryo raised at www.eel-hatch.dk and leptocephalus from the Sargasso Sea) and Lluís Zamora (Ter River, Girona, Spain: glass eels in Torroella de Montgrí, 70 cm yellow female in Bonmatí, and 40 cm silver male showing eye enlargement in Bescanó). Eggs and sperm are only known from in vitro fertilisation in laboratories and fish farms (20).
As larvae emerge, they drift with the prevailing marine currents over the Atlantic to the European and African coasts (2). The location of the breeding area was unveiled in the early 20th Century as a result of the observation that the size of the larvae caught in research surveys gradually decreased from Afro-European land towards the Sargasso Sea (3, 4). Adult eels had been tracked by telemetry in their migration route converging on the Azores Archipelago (5), but none had been recorded beyond until recently.
Crossing the Atlantic
To complete this piece of the puzzle, Rosalind Wright and collaborators placed transmitters in 21 silver females and released them in the Azores (6). These individuals travelled between 300 and 2300 km, averaging 7 km each day. Five arrived in the Sargasso Sea, and one of them, after a swim of 243 days (from November 2019 to July 2020), reached what for many years had been the hypothetical core of the breeding area (3, 4). It is the first direct record of a European eel ending its reproductive journey.
Eels use the magnetic fields in their way back to the Sargasso Sea and rely on an internal compass that records the route they made as larvae (7). The speed of navigation recorded by Wright is slower than in many long-distance migratory vertebrates like birds, yet it is consistent across the 16 known eel species (8).
Telemetry (6) and fisheries (14) of European eel (Anguilla anguilla). Eel silhouettes indicate the release point of 21 silver females in Azores in 2018 (orange) and 2019 (yellow), the circles show the position where their transmitters stopped sending signals, and the grey background darkens with water depth. The diagrams display the distance travelled and the speed per eel, where the circle with bold border represents the female that reached the centre of the hypothetical spawning area in the Sargasso Sea (dashed lines in the map) (3). Blue, green and pink symbols indicate the final location of eels equipped with teletransmitters in previous studies, finding no individual giving location signals beyond the Azores Archipelago (6). The barplot shows commercial catches (1978-2021) of yellow+silver eels in those European countries with historical landings exceeding 30,000 t (no data available for France prior to 1986), plus Spain (6120 t from 1951) — excluding recreational fishery and farming which, in 2020, totalled 300 and 4600 t, respectively (14). Red circles represent glass-eel catches added up for France (> 90% of all-country landings), Great Britain, Portugal, and Spain. Catches have kept declining since the 1980s. One kg of glass eels contains some 3000 individuals, so the glass-eel fishery has a far greater impact on stocks than the adult fishery.
Wright claimed that, instead of swiftly migrating for early spawning, eels engage in a protracted migration at depth. This behaviour serves to conserve their energy and minimises the risk of dying (6). The delay also allows them to reach full reproductive potential since, during migration, eels stop eating and mobilise all their resources to swim and reproduce (9).
Other studies have revealed that adults move in deep waters in daylight but in shallow waters at night, and that some individuals are faster than others (3 to 47 km per day) (5). Considering that (i) this fish departs Europe and Africa between August and December and (ii) spawning occurs in the Sargasso Sea from December to May, it is unknown whether different individuals might breed 1 or 2 years after they begin their oceanic migration.
Management as complex as life itself
The European eel started showing the first signs of decline at the end of the 19th Century (10, 11). In 2008, the species was listed as Critically Endangered by the IUCN, and its conservation status has since remained in that category — worse than that of the giant panda (Ailuropoda melanoleuca) or the Iberian lynx (Lynx pardinus).
Thanks to the collaborative and evidence-driven foresight of my colleagues at PIRSA Biosecurity and Landscape Boards, I was recently involved in more research examining the most efficient, cost-effective, and humane ways to cull feral dear in South Australia. The resulting paper is now in review in NeoBiota, but we have also posted a pre-print of the article.
Feral deer are a real problem in Australia, and South Australia is no exception. With six species of feral deer in the country already (fallowDama dama, redCervus elaphus, hogAxis porcinus, chitalA. axis), rusaC. timorensis, and sambarRusa unicolor deer), fallow deer are the most abundant and widespread. These species are responsible for severe damage to native plants, competition with native animals, economic losses to primary industries (crops, pastures, horticulture, plantations), and human safety risks from vehicle collisions. Feral deer are also reservoirs and vectors of endemic animal diseases and have the potential to transmit exotic animal diseases such as foot-and-mouth. If left uncontrolled, within 30 years the economic impacts of feral deer could reach billions of dollars annually.
I’ll preface this post with a caveat — the data herein are a few years old (certainly pre-COVID), so things have likely changed a bit. Still, I think the main message holds.
That last observation is important because there are really two main ways to quantify a country’s environmental performance. First, there is its relative environmental damage, which essentially means what proportion of its own resources a country has pilfered or damaged. This type of measure standardises the metrics to account for the different areas of countries (e.g., Russia versus Singapore) and how much of, say, forests, they had to start with, and what proportion of them they have thus far destroyed.
Looking at it this way, small countries with few large-scale industries came out in the lead as the least-damaged environmentally — the least environmentally damaged country according this metric is Cape Verde (followed by Central African Republic, Swaziland, Niger, and Djibouti).
However, another way to look at it is how much of the overall contribution to the world’s environmental damage each country is responsible, which of course implies that the countries with the highest amounts of resources damaged in absolute terms (i.e., the biggest, most populous ones) disproportionately contribute more to global environmental damage.
Using this absolute metric, the countries with the greatest overall damage are Brazil (largely due to the destruction of the Amazon and its other forests), the USA (for its greenhouse-gas emissions and conversion of its prairies to farmland), and China (for its water pollution, deforestation, and carbon emissions). On the flip side, this means that the smallest countries with the fewest people are ranked ‘better’ because of their lower absolute contribution to the world’s total environmental damage.
Looking more closely at how countries do relative to each other using different and more specific measures of environmental performance, the best-known and most-reported metric is the ecological footprint. This measures the ecological ‘assets’ that any particular population of people requires to produce the natural resources it consumes and to absorb its wastes.
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.
Mounting evidence is pointing to the world having entered a sixth mass extinction. If the current rate of extinction continues we could lose most species by 2200. The implication for human health and wellbeing is dire, but not inevitable.
In the timeline of fossil evidence going right back to the first inkling of any life on Earth — over 3.5 billion years ago — almost 99 percent of all species that have ever existed are now extinct. That means that as species evolve over time — a process known as ‘speciation’ — they replace other species that go extinct.
Extinctions and speciations do not happen at uniform rates through time; instead, they tend to occur in large pulses interspersed by long periods of relative stability. These extinction pulses are what scientists refer to as mass extinction events.
The Cambrian explosion was a burst of speciation some 540 million years ago. Since then, at least five mass extinction events have been identified in the fossil record (and probably scores of smaller ones). Arguably the most infamous of these was when a giant asteroid smashed into Earth about 66 million years ago in what is now the Gulf of Mexico. The collision vapourised species immediately within the blast zone. Later, species were killed off by climate change arising from pulverised particulates suspended in the atmosphere, as well as intense volcano activity stimulated by the buckling of the Earth’s crust from the asteroid’s impact. Together, about 76 percent of all species around at the time went extinct, of which the disappearance of the dinosaurs is most well-known. But dinosaurs didn’t disappear altogether — the survivors just evolved into birds.
No matter most people’s best intentions, poaching of species in Sub-Saharan Africa for horn and ivory continues unabated. Despite decades of policies, restrictions, interventions, protections, and incentives, many species of elephant and rhino are still hurtling toward extinction primarily because of poaching.
Clearly, we’re doing something heinously wrong.
Collectively, we have to take a long, hard look in the conservation mirror and ask ourselves some difficult questions. Why haven’t we been able to put any real dent in the illegal trade of poached elephant ivory and rhino horn? How many millions (billions?) of dollars have we spent seemingly to little avail? Why haven’t trade bans and intensive security measures done the trick?
The reasons are many, but they boil down to two main culprits:
neo-colonial sentiments driven by the best intentions of mainly overseas NGOs have inadvertently created the ideal conditions for the poaching economy — what we term poachernomics — to thrive by ensuring the continued restriction of legal supply of wildlife products; and
shutting off conservation areas to local people and directing the bulk of ecotourism profits away from source communities have maintained steady poaching incentives in the absence of other non-destructive livelihoods.
The logic of money contradicts the logic of species conservation and human health. As illegal trade has driven pangolins to near extinction, their hunting and market value has kept increasing ― even when we have known that they act as coronavirus reservoirs in the middle of the Covid-19 pandemic.
Sunda pangolin (Manis javanica) in a monsoon forest (Sumba Island, Indonesia). With adult weights up to 10 kg and body lengths around half a metre, these animals are mostly solitary and nocturnal, feed on ants and termites, and love tree climbing using bark hollows to shelter and give birth to singletons. The species occurs across mainland and islands of South East Asia, and became ‘Endangered’ in 2008 and ‘Critically Endangered’ in 2014, following a 80% decline in the last 20 years due to hunting and poaching. It has been the most heavily trafficked Asian species, and the IUCN’s assessment states: “… the incentives for harvesting and illegally trading in the species are universally high based on the high financial value of pangolin parts and derivatives”. Captive breeding is unlikely to deter wild collection because (among other reasons) farming costs are high (more so on a large scale) and, even if the species could be traded legally, wild versus farmed pangolin products and individuals are difficult to distinguish (23). Photo courtesy of Michael Pitts
Urbanites are attracted to exotic species, materials, and places. Our purchasing power seems to give us the right to buy any ‘object’ that we can pay for, no matter how exotic the object might be. In such a capitalist rationale, it is no surprise that > 150 thousand illegal cargos with wild animals and plants have been confiscated in 149 countries over the last two decades, moving some 6000 species from one place of the planet to another (1).
Social networks show people interacting with all kinds of fauna, creating the illusion that any animal can become a pet (2). And there’s a multi-$billion market of wildlife for a diverse array of uses including collecting, food, ornamentation, leisure, clothing and medicine (3-5). The paradox is that the rarer a species is, the higher its market value runs and the more lucrative selling it turns out to be, leading to more exploitation and rocketing extinction risk (6).
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.
South Australian legislation requires that all landholders cull feral deer on their properties. Despite this, feral deer abundance and distribution are increasing across South Australia. This arises because culling by land managers and government organisations is not keeping pace with rates of population growth, and some landholders are harbouring deer for hunting, whereas some deer escape from deer farms.
There are an estimated 40,000 feral deer in South Australia, and state government agencies are working to ramp up programs to cull feral deer before their numbers reach a point where control is no longer feasible.
Planning such large-scale and costly programs requires that government agencies engage economists to measure the economic impacts of feral deer, and to predict the value of these impacts in the future. That modelling is done regularly by governments, and in the case of pest-control programs, the modelling draws on models of feral deer population growth, farmer surveys about the economic, social, and environmental impacts of feral deer, and analyses of culling programs and trials of new culling techniques.
The economic models predict and compare both the current and future costs of:
deer impacts on pastures, crops, native plants, and social values (including illegal hunting)
culling programs that achieve different objectives (e.g., contain vs. reduce vs. eradicate)
The outputs of the models also inform whether there are sufficient public benefits from the investment of public funds into the culling of feral deer.
This PhD project will collate published and unpublished data to refine models of feral deer distribution and abundance under various culling scenarios. This project will drive both high-impact publications and, because this project builds extensive collaborations with government agencies, the results will inform the management of feral deer in South Australia.
As someone who writes a lot of models — many for applied questions in conservation management (e.g., harvest quotas, eradication targets, minimum viable population sizes, etc.), and supervises people writing even more of them, I’ve had many different experiences with their uptake and implementation by management authorities.
Some of those experiences have involved catastrophic failures to influence any management or policy. One particularly painful memory relates to a model we wrote to assist with optimising approaches to eradicate (or at least, reduce the densities of) feral animals in Kakadu National Park. We even wrote the bloody thing in Visual Basic (horrible coding language) so people could run the module in Excel. As far as I’m aware, no one ever used it.
Others have been accepted more readily, such as a shark-harvest model, which (I think, but have no evidence to support) has been used to justify fishing quotas, and one we’ve done recently for the eradication of feral pigs on Kangaroo Island (as yet unpublished) has led directly to increased funding to the agency responsible for the programme.
According to Altmetrics (and the online tool I developed to get paper-level Altmetric information quickly), only 3 of the 16 of what I’d call my most ‘applied modelling’ papers have been cited in policy documents:
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.
While some of us still might imagine the conservationist as a fancy explorer discovering new species in a remote corner of the world, or collecting samples while drowning in mud, a growing portion of conservation science nowadays consists of asking people about their ideas and behaviours.
Needless to say, this approach produces a fair share of awkward, if not dangerous, situations. After all, who likes the idea of completing a questionnaire from the fisheries office, asking about compliance with harvest limitations or licence fees? Or, even worse, who fancies being asked about the possession of illegally traded wildlife?
Many conservationists would really like to have this valuable information, but at the same time it is clear that these questions put people at great discomfort. This leads to biased estimates of important behaviours affecting conservation. This is where specialised questioning techniques can help.
Specialised questioning techniques aim to prevent researchers, or anyone else, to trace back individual answers. Many do so by adding noise with a known distribution to individual answers. Then, when all answers are pooled, this noise is ruled out with statistical approaches. Noise can come from a randomising device (e.g. a die), like in the randomised response technique:
Individual answers can also be masked by asking respondents not to indicate if they engaged in a certain behaviour, but by asking them, out of a list of sensitive and non-sensitive behaviours, to indicate the number in which they engaged. This is the case of the unmatched count technique (a.k.a list experiments):
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.
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.
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