More species = more resilience

8 01 2014

reef fishWhile still ostensibly ‘on leave’ (side note: Does any scientist really ever take a proper holiday? Perhaps a subject for a future blog post), I cannot resist the temptation to blog about our lab’s latest paper that just came online today. In particular, I am particularly proud of Dr Camille Mellin, lead author of the study and all-round kick-arse quantitative ecologist, who has outdone herself on this one.

Today’s subject is one I’ve touched on before, but to my knowledge, the relationship between ‘diversity’ (simply put, ‘more species’) and ecosystem resilience (i.e., resisting extinction) has never been demonstrated so elegantly. Not only is the study elegant (admission: I am a co-author and therefore my opinion is likely to be biased toward the positive), it demonstrates the biodiversity-stability hypothesis in a natural setting (not experimental) over a range of thousands of kilometres. Finally, there’s an interesting little twist at the end demonstrating yet again that ecology is more complex than rocket science.

Despite a legacy of debate, the so-called diversity-stability hypothesis is now a widely used rule of thumb, and its even implicit in most conservation planning tools (i.e., set aside areas with more species because we assume more is better). Why should ‘more’ be ‘better’? Well, when a lot of species are interacting and competing in an ecosystem, the ‘average’ interactions that any one species experiences are likely to be weaker than in a simpler, less diverse system. When there are a lot of different niches occupied by different species, we also expect different responses to environmental fluctuations among the community, meaning that some species inherently do better than others depending on the specific disturbance. Species-rich systems also tend to have more of what we call ‘functional redundancy‘, meaning that if one species providing an essential ecosystem function (e.g., like predation) goes extinct, there’s another, similar species ready to take its place. Read the rest of this entry »

Don’t blame it on the dingo

21 08 2013

dingo angelOur postdoc, Tom Prowse, has just had one of the slickest set of reviews I’ve ever seen, followed by a quick acceptance of what I think is a pretty sexy paper. Earlier this year his paper in Journal of Animal Ecology showed that thylacine (the badly named ‘Tasmanian tiger‘) was most likely not the victim of some unobserved mystery disease, but instead succumbed to what many large predators have/will: human beings. His latest effort now online in Ecology shows that the thylacine and devil extinctions on the Australian mainland were similarly the result of humans and not the scapegoat dingo. But I’ll let him explain:

‘Regime shifts’ can occur in ecosystems when sometimes even a single component is added or changed. Such additions, of say a new predator, or changes such as a rise in temperature, can fundamentally alter core ecosystem functions and processes, causing the ecosystem to switch to some alternative stable state.

Some of the most striking examples of ecological regime shifts are the mass extinctions of large mammals (‘megafauna’) during human prehistory. In Australia, human arrival and subsequent hunting pressure is implicated in the rapid extinction of about 50 mammal species by around 45 thousand years ago. The ensuing alternative stable state was comprised of a reduced diversity of predators, dominated by humans and two native marsupial predators ‑ the thylacine (also known as the marsupial ‘tiger’ or ‘wolf’) and the devil (which is now restricted to Tasmania and threatened by a debilitating, infectious cancer).

Both thylacines and devils lasted on mainland Australia for over 40 thousand years following the arrival of humans. However, a second regime shift resulted in the extinction of both these predators by about 3 thousand years ago, which was coincidentally just after dingoes were introduced to Australia. Dingoes are descended from early domestic dogs and were introduced to northern Australia from Asia by ancient traders approximately 4 thousand years ago. Today, they are Australia’s only top predator remaining, other than invasive European foxes and feral cats. Since the earliest days of European settlement, dingoes have been persecuted because they prey on livestock. During the 1880s, 5614 km of ‘dingo fence’ was constructed to protect south-east Australia’s grazing rangelands from dingo incursions. The fence is maintained to this day, and dingoes are poisoned and shot both inside and outside this barrier, despite mounting evidence that these predators play a key role in maintaining native ecosystems, largely by suppressing invasive predators.

Perhaps because the public perception of dingoes as ‘sheep-killers’ is so firmly entrenched, it has been commonly assumed that dingoes killed off the thylacines and devils on mainland Australia. People who support this view also point out that thylacines and devils persisted on the island of Tasmania, which was never colonised by dingoes (although thylacines went extinct there too in the early 1900s). To date, most discussion of the mainland thylacine and devil extinctions has focused on the possibility that dingoes disrupted the system by ‘exploitation competition’ (eating the same prey), ‘interference competition’ (wasting the native predators’ precious munching time), as well as ‘direct predation’ (dingoes actually eating devils and thylacines). Read the rest of this entry »

Learning from danger

13 05 2013
Guanaco fleeing
Study vehicle, a group of vicuñas and a guanaco in San Guillermo National Park (San Juan, Argentina) [courtesy of Marco Escudero]. Guanacos and vicuñas are native to South America, and are the ancestors of domesticated llamas and alpacas – which are exploited for their meat, milk and wool. Both species form monotypic genera. They have discontinuous distributions in Argentina, Bolivia, Chile and Peru, with introduced populations in Paraguay (guanaco) and Ecuador (vicuña). Population estimates are > 500,000 (guanaco) and > 300,000 (vicuña), the latter restricted to high-altitude ecosystems. They are ‘Least Concern’ for the IUCN but, given their low population growth rates (fertility = 1 offspring/female/yr), guanacos and vicuñas are targeted by conservation programs in all their native countries.

Many of us might have stumbled twice on the same stone, yet learnt to be wary of future situations of similar risk. Likewise, wild animals can be predisposed to flee when faced with already known predators (or threats in general). The type and magnitude of their evasive response depends on predator distance, speed and body size (1). Regardless, prey need to assess predation risk in a matter of seconds (or even shorter than that), i.e., balancing the benefits and costs of fleeing.

The benefits all boil down to survival, but the costs might include moving away from offspring, loss of access to fresh and abundant food, or spending precious metabolic energy (2). The methods ecologists use to study animal flight behaviour in the wild are rife with nuisances (3), yet they represent a tool for quantifying wildlife stress resulting from a variety of human activities.

Equipped with our modern technological kit (weapons, vehicles, GPS, etc.), humans behave like genuine predators and can trigger the range of flight behaviours displayed by their potential prey. In that context, Emiliano Donadio and Steve Burskirk (4) studied flight behaviour of guanacos (Lama guanicoe) and vicuñas (Vicugna vicugna) in the Argentinean open plains (‘llanos’). They monitored 2 protected areas under weak surveillance and subject to illegal hunting: the Laguna Brava Provincial Reserve and the San Guillermo Biosphere Reserve (treatment = H); and one area free of hunting and only exposed to guided visits with strict entry/exit times: the San Guillermo National Park (treatment = NH). The ecologists did 3 transects per study area. When they encountered a group of camelids, they classified three types of flight behaviour (alert without fleeing, walking away, galloping away), and measured flight time (between vehicle detection and initiation of flight behaviour) and flight distance (between the vehicle and the individuals when initiating flight behaviour). Read the rest of this entry »

No need for disease

7 01 2013

dead or alive thylacineIt’s human nature to abhor admitting an error, and I’d wager that it’s even harder for the average person (psycho- and sociopaths perhaps excepted) to admit being a bastard responsible for the demise of someone, or something else. Examples abound. Think of much of society’s unwillingness to accept responsibility for global climate disruption (how could my trips to work and occasional holiday flight be killing people on the other side of the planet?). Or, how about fishers refusing to believe that they could be responsible for reductions in fish stocks? After all, killing fish couldn’t possibly …er, kill fish? Another one is that bastion of reverse racism maintaining that ancient or traditionally living peoples (‘noble savages’) could never have wiped out other species.

If you’re a rational person driven by evidence rather than hearsay, vested interest or faith, then the above examples probably sound ridiculous. But rest assured, millions of people adhere to these points of view because of the phenomenon mentioned in the first sentence above. With this background then, I introduce a paper that’s almost available online (i.e., we have the DOI, but the online version is yet to appear). Produced by our extremely clever post-doc, Tom Prowse, the paper is entitled: No need for disease: testing extinction hypotheses for the thylacine using multispecies metamodels, and will soon appear in Journal of Animal Ecology.

Of course, I am biased being a co-author, but I think this paper really demonstrates the amazing power of retrospective multi-species systems modelling to provide insight into phenomena that are impossible to test empirically – i.e., questions of prehistoric (and in some cases, even data-poor historic) ecological change. The megafauna die-off controversy is one we’ve covered before here on, and this is a related issue with respect to a charismatic extinction in Australia’s recent history – the loss of the Tasmanian thylacine (‘tiger’, ‘wolf’ or whatever inappropriate eutherian epithet one unfortunately chooses to apply). Read the rest of this entry »

Toothed conflict

1 11 2012

Left: An Anatolian shepherd (a Turkish breed improved in the USA) guiding a herd of boer goats whose flesh is much appreciated by people in Namibia and South Africa. Right: A cheetah carrying a radio-transmitter, within a project assessing range movements of this feline for the Cheetah Conservation Fund. Cheetahs refrain from moving close to the herds when the latter are looked after by the guardian dogs. Photos courtesy of Laurie Marker.

Another corker from Salva. He’s chosen a topic this week that’s near and dear to my brain – the conservation of higher-order predators. As ConBytes readers will know, we’ve talked a lot about human-predator conflict and the inevitable losers in that battle – the (non-human) predators. From dingos to sharks, predator xenophobia is just another way we weaken ecosystems and ultimately harm ourselves.

Rural areas devoted to livestock are part of the natural landscape, so it is inevitable (as well as natural) that predators, livestock and humans interact in such a mosaic of bordering habitats. However, their coexistence remains an unresolved conservation problem. 

When two species, people, political parties, enterprises… want the same thing, they either share it (if possible) or one side eliminates the competitor. The fact that proteins are part of the diet of humans and other carnivore species has resulted in a trophic drama that goes back millennia. Nowadays, predators like eagles, coyotes, lions, wolves and raccoons are credited for attacks on cattle and poultry (and people!) in all continents. This global problem is not only economic, but interlaces culture, emotion, policy and sanitation (1-4). For instance, some carnivores are reservoirs of cattle diseases and contribute to pathogen dispersal (5, 6).

Management options

Managers of natural resources have implemented three strategies to handle these sorts of issues for livestock breeders in general (7). Those strategies can be complementary or exclusive on a case-by-case basis, and are chosen following cost-benefit assessments and depending on the conservation status of the predator species involved. (i) ‘Eradication’ aims to eliminate the predator, which is regarded as noxious and worthless. (ii) ‘Regulation’ allows controlled takes under quota schemes, normally for pre-defined locations, dates and killing methods. ‘Preservation’ is applied in protected areas and/or for rare or endangered species, and often requires monitoring and measures set to prevent illegal harvest or trade. Additionally, many livestock breeders receive money to compensate losses to predators (8).

Many experts now advocate non-lethal (preventive) measures that modify the behaviour of people, livestock or predators (2, 7). The use of livestock-guarding dogs is one of those preventive measures (9). As an example, Laurie Marker (director of the Cheetah Conservation Fund) et al. (10) studied the use of 117 Anatolian shepherds adopted by Namibian rangers between 1995 and 2002 (Fig. 1). In this African country, cheetahs (Acinonyx jubatus) selectively forage on small-sized cattle and juveniles. Despite this feline being protected nationally, Namibian laws authorise rangers to shoot cheetahs in situations of risk to people and their properties, with more than 6,000 cheetahs having been killed in the 1980s alone (11). Through face-to-face interviews, Marker found that since the arrival of the Anatolian shepherds, > 70 % of the rangers perceived a pronounced reduction in cattle mortality (10). Although, the use of livestock-guarding dogs has worked out fine in many places worldwide, it is no panacea. In many other instances, the dogs dissuade some predator species and not others from harassing the livestock, or are only effective in combination with other measures (7, 9). Read the rest of this entry »

Threats to biodiversity insurance from protected areas

26 07 2012

A red-eyed tree frog (Agalychnis callidryas) from Barro Colorado Island in Panama. This small island, just 1500 ha (3700 acres) in area, is one of the tropical protected areas evaluated in this study (photo © Christian Ziegler <>, Smithsonian Tropical Research Institute). Note: It is prohibited for any third party or agency to use or license this image; any use other then described above shall be subject to usage fees as determined solely by the photographer.

Much of conservation science boils down to good decision making: when, where and how we ‘set aside’ terrestrial or marine areas for specific protection against the ravages of human endeavour. This is the basis for the entire sub-discipline of conservation planning and prioritisation, and features prominantly in most aspects of applied conservation and restoration.

In other words, we do all this science to determine where we should emplace protected areas, lobby for getting more land and sea set aside so that we have ‘representative’ amounts (i.e., to prevent extinctions), and argue over the best way to manage these areas once established.

But what if this pinnacle of conservation achievement is itself under threat? What if many of our protected areas are struggling to insure biodiversity against human consumption? Well, it’d be a scary prospect, to say the least.

Think of it this way. We buy insurance policies to buffer our investments against tragedy; this applies to everything from our houses, worldly possessions, cars, livestock, health, to forest carbon stores. We buy the policies to give us peace of mind that in the event of a disaster, we’ll be bailed out of the mess with a much-needed cash injection. But what if following the disaster we learn that the policy is no good? What if there isn’t enough pay-out to fix the mess?

In biodiversity conservation, our ‘insurance’ is largely provided by protected areas. We believe that come what may, at least in these (relatively) rare places, biodiversity will persist despite our relentless consumerism.

Unfortunately, what we believe isn’t necessarily true.

Today I’m both proud and alarmed to present our latest research on the performance of tropical protected areas around the world. Published online in Nature this morning (evening, for you Europeans) is the 216-author (yes, that is correct – 216 of us) paper entitled “Averting biodiversity collapse in tropical forest protected areas” led by Bill Laurance. Read the rest of this entry »

Empty seas coming to a shore near you

12 07 2012

Last week I had the pleasure of entertaining some old friends and colleagues for a writing workshop in Adelaide (don’t worry – they all came from southern Australia locations, so no massive carbon footprints for overseas travel). I’m happy to report it was a productive (and epicurean) week, but that’s not really the point of today’s post.

One of those participants was long-time colleague, Dr. Rik Buckworth. Rik and I first met in Darwin back in the early 2000s when he was lead fisheries scientist for Northern Territory Fisheries; this collaboration and friendship blossomed into an ARC Linkage Project (with Dr. Mark Meekan of AIMS) on shark fisheries (see some of the scientific outputs from that here, here, here and here). Rik has since moved to CSIRO in Brisbane, but keeps a hand in NT fisheries’ affairs. Incidentally, Rik trained under one of the most well-known fisheries modellers in the world – Carl Walters – when he did his PhD at the University of British Columbia back in the early 1990s.

During our workshop, Rik pointed out a paper he had co-authored back in 2009 in Reviews in Fish Biology and Fisheries that had completely escaped my attention – it’s a frightening and apocalyptic view of the Australasian marine tropics that seems to confirm our predictions about northern Australia’s marine future. Just take a look at the following two figures from their paper (Elasmobranchs in southern Indonesian fisheries: the fisheries, the status of the stocks and management options): Read the rest of this entry »

Can Australia afford the dingo fence?

18 05 2012

I wrote this last night with Euan Ritchie of Deakin University in response to some pretty shoddy journalism that misrepresented my comments (and Euan’s work). Our article appeared first in The Conversation this morning (see original article).

We feel we have to set the record straight after some of our (Bradshaw’s) comments were taken grossly out of context, or not considered at all (Ritchie’s). A bubbling kerfuffle in the media over the last week compels us to establish some facts about dingoes in Australia, and more importantly, about how we as a nation choose to manage them.

A small article in the News Ltd. Adelaide Advertiser appeared on 11 May in which one of us (Bradshaw) was quoted as advocating the removal of the dingo fence because it was not “cost effective” (sic). Despite nearly 20 minutes on the telephone explaining to the paper the complexities of feral animal management, the role of dingoes in suppressing feral predators, and the “costs” associated with biodiversity enhancement and feral control, there wasn’t a single mention of any of this background or justification.

Another News Ltd. article denouncing Ritchie’s work on the role of predators in Australian ecosystems appeared in The Weekly Times the day before, to which Ritchie responded in full.

So it’s damage control, and mainly because we want to state categorically that our opinion is ours alone, and not that of our respective universities, schools, institutes or even Biosecurity SA (which some have claimed or insinuated, falsely, that we represent). Biosecurity SA is responsible for, inter alia, the dingo fence in South Australia. Although our opinions differ on its role, we are deeply impressed, grateful and supportive of their work in defending us from biological problems. Read the rest of this entry »

Sharks: the world’s custodians of fisheries

5 05 2012

Today’s post comes from Salvador Herrando-Pérez (who, incidentally, recently submitted his excellent PhD thesis).

Three species co-occurring in the Gulf of Mexico and involved in the trophic cascade examined by Myers et al. (8). [1] Black-tips (Carcharhinus limbatus) are pelagic sharks in warm and tropical waters worldwide; they reach < 3 m in length, 125 kg in weight, with a maximum longevity in the wild of ~ 12 years; a viviparous species, with females delivering up to 10 offspring per parturition. [2] The cownose ray (Rhinoptera bonasus) is a tropical species from the western Atlantic (USA to Brazil); up to 2 m wide, 50 kg in weight, and 18 years of age; gregarious, migratory and viviparous, with one single offspring per litter. [3] The bay scallop (Agropecten irradians) is a protandric (hermaphrodite) mollusc, with sperm being released a few days before the (> 1 million) eggs; commonly associated with seagrasses in the north-western Atlantic; shells can reach up to 10 cm and individuals live for < 2 years. In the photos, a black-tip angled in a bottom long-line off Alabama (USA), a school of cownose rays swimming along Fort Walton Beach (Florida, USA), and a bay scallop among fronds of turtle grass (Thalassia testudinum) off Hernando County (Florida, USA). Photos by Marcus Drymon, Dorothy Birch and Janessa Cobb, respectively.

The hips of John Travolta, the sword of Luke Skywalker, and the teeth of Jaws marked an era. I still get goose pimples with the movie soundtrack (bass, tuba, orchestra… silence) solemnizing each of the big shark’s attacks. The media and cinema have created the myth of man’s worst friend. This partly explains why shark fishing does not trigger the same societal rejection as the hunting of other colossuses such as whales or elephants. Some authors contend that we currently live in the sixth massive extinction event of planet Earth (1) 75 % of which is strongly driven by one species, humans, and characterized by the systematic disappearance of mega-animals in general (e.g., mammoths, Steller’s seacow), and predators in particular, e.g., sharks (2, 3).

The selective extirpation of apex predators, recently coined as ‘trophic downgrading’, is transforming habitat structure and species composition of many ecosystems worldwide (4). In the marine realm, over the last half a century, the main target of the world’s fisheries has turned from (oft-large body-sized) piscivorous to planctivorous fish and invertebrates, indicating that fishery fleets are exploiting a trophic level down to collapse, then harvesting the next lower trophic level (5-7).

Myers et al. (8) illustrate the problem with the fisheries of apex-predator sharks in the northeastern coast of the USA. Those Atlantic waters are rife with many species of shark (> 2 m), whose main prey are smaller chondrichthyans (skates, rays, catsharks, sharks), which in turn prey on bottom fishes and bivalves. Myers et al. (8) found that, over the last three decades, the abundance of seven species of large sharks declined by ~ 90 %, coinciding with the crash of a centenary fishery of bay scallops (Agropecten irradians). Conversely, the abundance of 12 smaller chondrichthyes increased dramatically over the same period of time. In particular, the cownose ray (Rhinoptera bonasus), the principal predator of bay scallops, might today exceed > 40 million individuals in some bays, and consume up to ~ 840,000 tonnes of scallops annually. The obvious hypothesis is that the reduction of apex sharks triggers the boom of small chondrichthyans, hence leading to the break-down of scallop stocks. Read the rest of this entry »

Give way to the invader

25 01 2012

By weird coincidence, Salvador Herrando-Pérez (student blogger extra-ordinaire – see his previous posts on evolution, pollination, bird losses, taxonomic inflation, niche conservatism, historical biogeography, ecological traps and ocean giants) has produced a post this week expanding on the problem of roads. Also weirdly coincidental is that both Salva and I are in his home country of Spain this week.

Australia’s > 800,000-km road network would go 60 times around the equator of our planet. Confined to the boundaries of any one country, roads are a conspicuous component of the landscape, and shape the dispersion, survival and reproduction of many plants and animals in urban and remote areas.

Those who drive (or are driven by) will be familiar with the image of a crushed kangaroo on the roadside (a hedgehog in Europe), or the sticky mosaic of insects smashed against the windscreen after a high-speed run. Mortality by collision is one of the many effects that roads can have on the demography of organisms – including humans. Those effects encompass

  • physical alteration of terrestrial and aquatic habitats,
  • chemical pollution leakage during road construction and maintenance, and from asphalt compounds during storms,
  • alteration of animal behaviour (e.g., change in home range, or in patterns of flight or vocalisation),
  • access to remote areas by hunters, fishermen and gatherers in general, and
  • intense habitat fragmentation1-3.

However, some species get around those negative impacts by using the roads as pathways to new territories, thereby eluding barriers like seas, mountains, rivers, dense vegetation, or competition for vital resources with other species. Read the rest of this entry »

Crocodiles, spiders and leeches

11 04 2011

I just wrote a fun little piece for a new section in the journal Frontiers in Ecology and the Environment that they’re calling Trails and Tribulations. The basic idea is that the author recounts a particularly interesting field-related experience through which an ecological concept is woven.

Editor-in-Chief Sue Silver said that I could reproduce my article here as long as I acknowledged Frontiers and the Ecological Society of America. It was fun to write, and I hope you enjoy it too [the PDF of the article is available free of charge here].

“So does each team get a hand gun?”

“No, you get an oar”

“What good is an oar?”

“Listen, mate. When a 3-metre croc jumps out of the swamp at you, there is nothing more natural in the world than to thump him with a big stick. It’s an autonomous response. With a gun, IF you manage to keep it dry, and IF you manage to get it out in time before the croc bites off your head, chances are you’ll just shoot the bloke in front of you anyway. So you get an oar.”

“Fair enough”.

That is an approximate, paraphrased reproduction of the initial conversation I had with renowned Australian crocodile biologist, Grahame Webb, just prior to my first (and as it turns out, only) trip to collect crocodile eggs for his Darwin wildlife park and crocodile farm. I volunteered to take part in the collection because I had recently begun working with Grahame and his team tracking the world’s largest crocodile species – the saltwater or estuarine crocodile Crocodylus porosus – and modelling aspects of its populations (Bradshaw et al. 2006). Having already been out on several occasions to harpoon and satellite-tag animals (some measuring > 4 m) on the Mary River, and cage-trap others in Kakadu National Park, I thought a little egg collection would be a proverbial walk in the park. Little did I know that it would end up being one of my more memorable experiences.

Let me walk you through the process. First, you wait until the height of the wet season and drive out as far as you can toward the breeding swamp of interest (in this case, Melacca Swamp in the Adelaide River flood plain, about one hour’s drive from Darwin). Then you and two other loonies pile into a small helicopter equipped with landing pontoons which ferries you to one of many previously identified crocodile nests. Because there is usually too much vegetation around the nest itself, the helicopter must land about 100-300 m away. Clothed only in long pants, a long-sleeved shirt and cotton gloves to protect your skin from the slicing blade grass, you jump off the helicopter’s pontoons into impenetrably murky, chest-deep water. One of the team drags an esky (chiller box into which eggs will be placed) and another carries an oar. As the noise of the departing helicopter becomes a faint buzz, you suddenly realise via the rapid expansion of your terminal sphincter that you are in the middle of a crocodile-filled swamp – and you are holding an oar. Read the rest of this entry »

Global erosion of ecosystem services

14 09 2010

A few months ago I was asked to give a lecture about erosion of ecosystem services to students in the University of Adelaide‘s Issues in Sustainable Environments unit. I gave that lecture last week and just uploaded a slidecast of the presentation (with audio) today.

I’ve reproduced the lecture here for your viewing pleasure. I hope you find the 45-minute presentation useful. Note that the first few minutes cover me referring to the Biodiversity film short that I posted not too long ago.

CJA Bradshaw

Student opportunities with Australian Wildlife Conservancy

8 09 2010

A colleague of mine, Dr. Matt Hayward of the Australian Wildlife Conservancy (AWC), asked me to circulate some Honours, MSc and PhD student project opportunities. I thought this would be best done by publishing the call as a blog post.

The AWC is a non-government, non-profit organisation dedicated to the conservation of Australia’s wildlife and their habitats. AWC’s south-east region has a team of 7 ecologists who work closely with the land managers to carry out AWC’s Conservation and Science Program. The Science Program includes strategic research designed to help us manage threatened species more effectively. Several of these research projects are suitable for Honours, Masters or PhD projects.

This prospectus provides an outline of the student projects that are currently on offer in the south-east region. The majority of the projects are based on one sanctuary, although some aspects of the research may be done on other AWC sanctuaries and/or government conservation areas.

AWC will partially support these projects with equipment, staff time and expertise, and accommodation. In some cases, AWC may also provide some vehicle use and office facilities onsite at The Scotia Field Research Centre. We anticipate these projects will be collaborative efforts with input from students, academics and AWC staff, with appropriate acknowledgement for all involved. These projects are offered on a first in, first approved basis and have been offered to multiple universities.

More details on the sanctuaries and AWC are available here. If you are keen do one of these projects, please contact Matt Hayward and we will then formulate a research proposal and research agreement. Eight project descriptions follow. Read the rest of this entry »

Classics: Mesopredator Release

17 03 2010

© J. Short

Although popularised by Crooks & Soulé (1999), Soulé et al. (1988) first gave us the term that described how entire ecosystems can become unbalanced by a reduction of a higher trophic-level predator exerting so-called ‘top-down’ control on the abundance of species occupying lower trophic levels.

The idea had theoretical support in ecology (Wright et al. 1994; Litvaitis & Villafuerte 1996), but it was not until Soulé and colleagues described how the decline of dominant predators combines with habitat fragmentation to release top-down pressure on smaller predators, thereby increasing predation rates on prey lower down the trophic web.

Crooks & Soulé (1999) described an example where the decline in coyotes (Canis latrans) in combination with urbanisation-driven habitat fragmentation led to an increase in cat (Felis catus) densities and the subsequent decline in scrub-breeding birds. More recent examples attest to the importance of the mesopredator release phenomenon: Myers et al. (2007) described how the decline in large coastal shark species has allowed mesopredator cownose rays (Rhinoptera bonasus) to increase, leading to a reduction in commercially important shellfish densities; and Johnson et al. (2007) showed how dingoes (Canis lupus dingo) in Australia suppress populations of exotic predators such as cats and foxes, leading to more locally abundant populations of native marsupials (see previous post).

Conservation biologists have benefited from this knowledge because we’ve realised that top-order predators affect far more than their immediate prey. These examples really hit home how a fully functional community is required for ecosystem stability, so we should strive to preserve complete complements of communities, not just our favourite species.

CJA Bradshaw

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Can we solve Australia’s mammal extinction crisis?

3 09 2009

© F. O'Connor

© F. O'Connor

This ‘In DepthScience Opinion piece from the ABC couldn’t have come at a better time. Written by Ian Gordon of the CSIRO, this opinion piece was written off the back of the special session on mammalian extinctions held at the recent International Congress of Ecology in Brisbane. Three previous blogs in August (here, here and here) were devoted to specific talks at the Congress, including one about John Woinarksi’s gloomy tale of dwindling mammal populations in the Top End (which is especially frightening considering its also going on in our so-called ‘protected’ areas such as Kakadu, Litchfield and Garig Gunak Barlu National Parks!).

So, I recommend you have a read of my blog post on the shocking continued loss of Australian mammals, then read Ian’s piece copied below. Bottom lines – stop burning the shit out of our forests and encourage dingo population recovery and expansion.

Australia leads the world in mammal extinctions.

Over the last two hundred years 22 mammal species have become extinct, and over 100 are now on the threatened and endangered species list, compiled as part of the federal government’s Environment Protection and Biodiversity Conservation Act.

Evidence suggests Australia is on the cusp of another wave of mammal extinctions with a reduction in the abundance of some species and alarmingly, their range.

This is undoubtedly one of the major biodiversity conservation issues affecting Australia. It’s crucial we focus on the management solutions required to stop these species falling into extinction.

A South American success story

Working as a zoologist has allowed me to be involved in projects across the globe, looking at species at risk of extinction due to over-exploitation by humans.

Earlier this year I edited a book on the South American vicuña‘s comeback from the brink of extinction. Once abundant in the Andes, this wild relative of the llama suffered a sharp population drop in the 1960s due to international demand for its fleece.

An international moratorium on the sale of vicuña fleece in 1969 saw populations recover enough by 1987 for Andean communities to be able to harvest the fibre in a sustainable way. Population numbers of vicuña have remained healthy ever since, making it one of the few success stories of wildlife conservation worldwide.

Australia’s mammal extinction crisis

However Australia’s medium-sized mammals have had to deal with a different range of issues to the vicuña: the introduction of feral animals, particularly cats and foxes; increased grazing pressure; altered fire regimes; the clearing of habitat for development and production; and now, the effects of climate change.

It isn’t that any of these pressures are particularly important by themselves, but the fact that many of them act in concert has had a significant impact on causing the crashes in population numbers, and increasing the risk of species becoming extinct.

For example, the crescent nailtail wallaby was once an abundant and widespread macropod of central and western Australia. The pressures of feral cats and foxes coupled with clearing for agriculture and grazing, and altered fire regimes pushed this little species over the edge and it is now classified as extinct.

The problem is also more far-reaching than we first assumed. Many people may think that animals are becoming extinct in the south of Australia where habitat destruction is quite evident.

But the populations of iconic species in the north of Australia such as the northern quoll, golden bandicoot and the Carpentarian rock-rat are also collapsing. In our lifetime populations of some species have greatly reduced in number, and others have completely disappeared in landscapes that are considered to be in excellent condition.

The golden bandicoot, listed as a vulnerable species, used to be found across much of the north of Australia. It is now only found in very small populations in the Northern Territory and on the isolated Burrow Island off the coast of Western Australia.

Time to bring back the dingo?

Further research on the impacts of fire, grazing, invasive species and climate change on Australian mammals would be extremely valuable, but ecologists recognise that crucial management decisions need to be made now.

We’ve found ourselves in a position where we have identified the threats to Australian mammal species and documented the loss of these species, the role of science must turn more directly to identifying the opportunities for assisting the survival of these mammals.

In August I chaired a panel with Professor Chris Johnson from James Cook University at the International Congress of Ecology, to discuss what management could be put in place now to help beleaguered populations of small mammals recover.

Johnson’s main focus is to bring back the top-order predator.

He believes there is now good evidence that a stable population of dingoes suppresses the numbers and activity of foxes and cats, and some other feral animal species as well.

He argues that the effect of using a top predator like the dingo to hold down populations of foxes and cats is that the total intensity of predation on smaller native mammals can be reduced.

Bringing back the dingo has many sheep and cattle farmers raising their eyebrows because the wild dogs are known to kill stock. But guardian sheepdogs can protect stock herds by fighting off dingoes if they come too close. This still allows the dingoes to have a beneficial effect in the ecosystem.

Current trials of Maremma dogs, a type of sheepdog, at Dunluce sheep station in northwest Queensland demonstrate that they can be effective dingo deterrents in a pastoral zone.

This is just one potential solution that may work in some areas. Reinstating mosaic fire regimes, where patches of land are burnt at different times to allow the land to recover in stages, and controlling grazing around sensitive habitat of endangered mammals are other potential solutions that are currently under trial in various parts of the country.

Working together

Even though science doesn’t have all the answers I believe that it is more important than ever for land managers and scientists to work together to put new management regimes on the ground.

Our scientific knowledge can provide guidelines for land managers to reduce the pressures on our biodiversity. Through monitoring how species and ecosystems respond to on-ground management we can then learn and adapt our advice to meet future challenges facing Australia’s threatened species.

We need to act now: the international community is watching Australia and we have an opportunity to show how we can apply science through collaborative agreements with land managers to reduce the threats and protect endangered species.

We’ll then be able to add Australian animals to the short list of species, like the vicuña, that have been brought back from the brink of extinction.

CJA Bradshaw

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June Issue of Conservation Letters

6 06 2009

Quick off the mark this month is the new issue of Conservation Letters. There are some exciting new papers (listed below). I encourage readers to have a look:

Policy Perspectives


CJA Bradshaw

Protein mining the world’s oceans

31 03 2009

Last month David Agnew and colleagues published a paper in PLoS One examining the global extent of illegal, unreported and unregulated (IUU) fishing (Estimating the worldwide extent of illegal fishing), estimating its value from US$10-23.5 billion and representing between 11 and 26 million tonnes of fish annually. The value is roughly the same as that lost from illegal logging each year. Wow.

Of perhaps most interest is that Agnew and colleagues found evidence for a negative relationship between IUU fishing as a proportion of total catch and an international (World Bank) governance quality index. This suggests that improving governance and eradicating corruption may be the best way to curtail the extent of the illegal harvest.

We have just published a paper online in Fish and Fisheries about the extent and impact of IUU fishing in northern Australia. Entitled Protein mining the world’s oceans: Australasia as an example of illegal expansion-and-displacement fishing, the paper by Iain Field and colleagues advocates a multi-lateral response to a problem that has grown out of control in recent decades.

IUU fishing is devastating delicate ecosystems and fish breeding grounds in waters to Australia’s north, and can no longer be managed effectively by individual nations. The problem now requires an urgent regional solution if food security into the future is to be maintained.

The paper is the first big-picture account of the problem from Australia’s perspective. Although there had been a decline in IUU fishing in Australian waters over the past two years, possibly linked to large Australian government expenditure on enforcement and rising fuel prices, the forces driving illegal fishing have not gone away and are likely to resurface in our waters.

We expect that the small-scale illegal fishers will be back to prey on other species such as snapper, trochus and trepang as soon as it is economically viable for them to do so. To date, these IUU fishers have focused mostly on high-value sharks mainly for the fin trade, to the extent that the abundance of some shark species has dropped precipitously. IUU fishing, which has devastated fish resources and their associated ecosystems throughout Southeast Asian waters, is driven by deep economic and societal forces. For example, the Asian economic crisis in the late 1990s drove a large number of people out of cities and into illegal fishing.

It is not enough to maintain just a national response as the problem crosses national maritime zones, and it poses one of the biggest threats known to marine ecosystems throughout the region. These IUU fishers are mining protein, and there is no suggestion of sustainability or factoring in fish breeding or ecosystem protection into the equation. They just come into a fishing area and strip-mine it, leaving it bare.

Illegal fishing in Australian waters started increasing steeply about 10 years ago, largely because of over-exploitation of waters farther north, peaking in 2005-06 then falling away just as steeply. There are three factors behind the recent downturn: Australian government enforcement measures estimated to have cost at least AU$240 million since 2006; the high price of fuel for the fishing boats; and, most importantly, the fact that the high-value species may have been fished out and are now economically and ecologically extinct.

The $240 million has funded surveillance, apprehension, transportation, processing and accommodation of the several thousand illegal foreign fishermen detained each year since 2006. These activities have been successful, but it is doubtful whether they can hold back the IUU tide indefinitely – the benefits to the illegal fishers of their activities far outweigh the penalties if caught.

With increasing human populations in the region, the pressure to fish illegally is likely to increase. Regional responses are required to deter and monitor the illegal over-exploitation of fisheries resources, which is critical to secure ecosystem stability as climate change and other destructive human activities threaten food security.

CJA Bradshaw (with IC Field, MG Meekan and RC Buckworth)

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Man bites shark

7 01 2009
© RG Harcourt

© RG Harcourt

Yesterday I had a comment piece of the same title posted on the ABC‘s Unleashed site. I have permission to reproduce it here on

The silly season is upon us again, and I don’t mean the commercial frenzy, the bizarre fascination with a white-bearded man or a Middle-Eastern baby, the over-indulgence at the barbie or hangovers persisting several days into the New Year. I mean it’s the time of year when beach-goers, surfers, and municipal and state policy makers go a bit ga-ga over sharks.

There are few more polite pleasures than heading down to the beach during the holidays for a surf, quick dip or just a laze under the brolly. Some would argue it’s an inalienable Australian right and that anything getting in our way should be condemned to no less than severe retribution. Well, in the case of sharks, that’s exactly what’s happened.

Apart from a good number of adrenalin-addicted surfers and mad marine scientists, most people are scared shitless by the prospect of even seeing a shark near the beach, let alone being bitten or eaten by one. I won’t bore you with some ill-advised, pseudo-psycho-analytical rant about how it’s all the fault of some dodgy 1970s film featuring a hypertrophied American shark; the simple fact is that putative prey don’t relish the thought of becoming a predator’s dinner.

So, Australia is famous for its nearly 100-year-old pioneering attempt to protect marine bathers from shark attack by setting an elaborate array of shark nets around the country’s more frequented beaches. Great, you say? Well, it’s actually not that nice.

Between December 1990 and April 2005, nearly 3500 sharks and rays were caught in NSW beach nets alone, of which 72 per cent were found dead. Shark spearing was a favourite past-time in the 1960s and 1970s, with at least one high-profile species, the grey nurse shark, gaining the dubious classification of Critically Endangered as a result. Over-fishing of reef sharks has absolutely hammered two formerly common species in the Great Barrier Reef, the whitetip and grey reef sharks (See the Ongoing Collapse of Coral-Reef Shark Populations report). And illegal Indonesian fishing in northern Australia is slowly depleting many shark species in a wave of protein mining that has now penetrated the Australian Exclusive Economic Zone.

Despite the gloomy outlook for sharks, I’m happy to say today that we are a little more aware of their plight and are making baby steps toward addressing the problems. Australia has generally fared better in shark conservation than most other parts of the world, even though we still have a lot of educating to do at home. Over 50 per cent of all chondrichthyans (i.e., sharks, rays and chimaeras) are threatened worldwide, with some of the largest and most wide-ranging species being hardest hit, including white sharks. The most common threat is over-fishing, but this is largely seen by the lay person as of little import simply because of the persistent attitude that “the only good shark is a dead shark”.

The attitude is, however, based on a complete furphy. I’m sure many readers would have seen some statistics like the following before, but let’s go through the motions just to be clear. Dying from or even being injured by a shark is utterly negligible. Based on the International Shark Attack File data for Australia, there were 110 confirmed (unprovoked) shark attacks in Australian waters between 1990 and 2007, of which 19 were fatal. Using Australian Bureau of Statistics human population data over the same period, this equates to an average of 0.032 attacks and 0.006 fatalities per 100,000 people, with no apparent trend over the last two decades.

Now let’s contrast. I won’t patronise you with strange comparative statistics like the probability of being killed by a (provoked) vending machine or by being hit by a bus, they are both substantially greater, but I will relate these figures to water-based activities. Drowning statistics for Australia (1992-1997) show that there were around 1.44 deaths per 100,000 people per year, or approximately 0.95 if just marine-related drownings are considered. These values are 240 (158 for marine-only) times higher than those arising from shark attack.

It’s just plainly, and mathematically, ridiculous to be worried about being eaten by a shark when swimming in Australia, whether or not there’s a beach net in place. The effort made, money spent and anxiety arising from the illogical fear that a shark will consider your sunburnt flesh a tasty alternative to its fishier sustenance is not only regrettable, it’s an outright crime against marine biodiversity. Of course, if you see a big shark lurking around your favourite beach, I wouldn’t recommend swimming over and giving it a friendly pat on the dorsal fin, but I wouldn’t recommend screaming that the marine equivalent of the apocalypse has just arrived either.

You may not be fussed either way, but consider this – the massive reduction in sharks worldwide is having a cascading effect on many of the ocean’s complex marine ecosystems. Being largely carnivorous, sharks are the ecological equivalent of community planners. Without them, herbivorous or coral-eating fish can quickly get out of control and literally destroy the food web. A great example comes from the Gulf of Mexico where the serial depletion of 14 species of large sharks has caused an explosion of the smaller cownose ray that formerly was kept in check by its bigger and hungrier cousins. The result: commercially harvested scallops in the region have now collapsed because of the hordes of shellfish-eating rays.

The day you fail to find sharks cruising your favourite beach is the day you should really start to worry.

CJA Bradshaw

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Feral predators – ‘super’ cats, foxes and dingoes

3 07 2008

Here’s one to get us going. A recent news item on ABC News discusses the prospect of importing so-called ‘super cats’ (‘savannah cats’ = domestic cat x African serval) into Australia. Although most of the items and people commenting on the subject deplore the very notion, I cannot believe that there was the legal capacity to import these things in the first place! Or indeed, that the company attempting to commit the heinous conservation crime has the right even to exist in this country. You’d think we’d learn after swamp buffalo, cane toads, foxes and a host of other alien nasties have caused Australian fauna to experience some of the higher rates of extinction known in the modern context. Indeed, it is my opinion that all cats (domestic and otherwise) should be declared illegal in Australia and destroyed. This is where it gets interesting though. One for the ‘papers to watch’ categories is by a mate and colleague of mine, Professor Chris Johnson of James Cook University in Townsville. He and his colleagues last year published a paper in Proc. R. Soc. B. called ‘Rarity of a top predator triggers continent-wide collapse of mammal prey: dingoes and marsupials in Australia‘.

© J. Edwards, National Geographic

© J. Edwards, National Geographic

Here, they showed how dingoes (themselves ‘alien species’, but from some time ago) actually appear to suppress the populations of more recent alien predator arrivals (e.g., cats and foxes). The upshot is that more dingoes = fewer cats/foxes = more native fauna. Brilliant! I hope we can say in a few years how the careful management of dingoes and promotion of their conservation has benefitted an array of threatened marsupials in Australia. Well done Chris and colleagues.

CJA Bradshaw


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