Authors: Thomas M Newsome, Aaron C Greenville, Mike Letnic, Euan G Ritchie and Christopher R Dickman
Published in:Food Webs (early view)
We challenge the arguments of Morgan et al. in regard to the efficacy of dingo reintroductions Image credit: Daryll Bellingham via Flickr
In their paper “Trophic cascades and dingoes in Australia: does the Yellowstone wolf-elk- willow model apply?” Morgan et al. (2016) argue that the case for dingo reintroduction in Australia, based on trophic cascade theory, is “weak”. They conclude that, “because of climate instability, the strong top-down trophic responses reported from the Yellowstone National Park case study are unlikely to apply in arid and semi-arid south-eastern Australia and are speculative at best”.
We agree that dingoes (Canis dingo) are likely to exert different effects on ecological communities in Australia as compared to grey wolves (Canis lupus) in North America. A comparison of body sizes and dietary preferences between these canid species alludes to their functional ecological differences. Differences in the biological communities and climate between Yellowstone National Park and Australia also prevent direct comparisons of trophic cascade-processes between the two regions. These facts should not, however, preclude examination of the efficacy and consequences of dingo reintroductions in Australia.
We contend that Morgan et al. (2016):
misunderstand the circumstances that make trophic cascades important to consider in Australia,
do not acknowledge key reasons why dingo reintroduction has been proposed,
haven’t recognised the different pathways by which dingoes could influence ecosystems via trophic cascades, and
do not fully acknowledge literature and theory relevant to understanding the interplay of bottom-up and top-down processes in Australia.
Our reply is intended to assist managers and decision makers when deciding whether or not to reintroduce dingoes into Australian ecosystems.
Newsome TM, Greenville AC, Letnic M, Ritchie EG, Dickman CR (2017) The case for a dingo reintroduction in Australia remains strong: A reply to Morgan et al., 2016, Food Webs,PDFDOI
Interactions within Mallee ecosystem food chains are out of balance.
The apex predator of the Mallee landscape — the dingo — is on the decline, allowing invasive species in the middle order of the food chain to become overabundant.
Propping up dingo numbers in the region will help control local pest species and problems associated with planned burning.
The war between cat-lovers and bird-lovers may have found its compromise: larger predators. Dingoes may do a far better job than humans of keeping feral cats in check, and without the ethical baggage. In other words, if you want to kill a feral cat, get a wild dog.
That’s the message from Arian Wallech et al. in a recently published piece: Novel trophic cascades: apex predators enable coexistence. Wallach’s paper reinforces my research into the interactions between dingoes and feral cats in Australia. Using native predators to kill or scare off introduced predators could be our best bet; working with nature , not against it.
But can we apply our learnings to other contexts and ecosystems? Stan Gehrt of Ohio State University thinks so: he studies the much-maligned coyote — specifically a thriving urban population in Chicago — which seems to be keeping the local cats at bay.
“There was a plague of them and one night I got approximately 300 which had been poisoned in the garden during night. This went on for two or three years.”
Take a second and have a guess what animal species this quote might be referring to. Here’s a hint, the quote is from western Victoria, Australia, during the 1800s.
What did you guess? A house mouse, or another introduced species like a rabbit?
Australia has the worst rate of mammal extinctions in the world. More than a third have become extinct since European settlement, or are currently threatened with extinction. But what about the survivors? And what can we do to prevent further losses?
A lost world
Few Australians would appreciate just how much our native mammal communities have changed since European arrival more than 200 years ago. Early quotes from books and newspaper articles like the one above, painstakingly collated by researchers, offer some insight.
Early explorers made similar notes about abundant mammals because their dogs were “completely distracted by the numbers of wallabies, paddymelons and kangaroo rats that bounded off on all sides”.
Their poor horses would struggle through the sandy soils that were “full of Wallabi holes”.
Such quotes describe an Australian landscape rich in native wildlife. A landscape that, owing to the decline and extinction of so many mammal species, has radically changed.
The abundant mammals that distracted the dog and made life difficult for the horse probably refer to species long gone. According to researchers, the burrowing bettong, which is now extinct on mainland Australia, was probably the “kangaroo rat” responsible for those pesky holes.
The “paddymelons” and wallabies are probably the eastern hare and/or bridled nailtail wallabies; the former now extinct, the latter now restricted to a few pockets across eastern Australia.
On the bright side
Even with the sad loss of so many native mammals, Australia retains a suite of truly fascinating species, many of which occur right among us.
In Melbourne’s suburb of Cranbourne, populations of southern brown bandicoots persist, fossicking in people’s gardens and dining from dog’s bowls by night.
Species of flying fox survive in our inner cities and darken the dusk sky as they leave their colony for their nightly foraging.
In most major capitals, some possum species are so common as to be an annoyance to many as they bound over roofs and devour prized roses.
A diverse array of kangaroo species still bound through rural landscapes, sharing paddocks with wombats, echidnas, dingoes and koalas. Platypuses fish for yabbies in farm dams nearby.
Australia is still blessed with spectacular and globally unique mammals. But we can do better.
Australia’s native mammals will undoubtedly be a focus of the hub, as many species are on the brink of extinction.
However, one thing our history of mammal extinctions has taught us is that complacency is our worst enemy. Common species go extinct, and can do so rapidly.
On the other hand, species that are regionally extinct should not be forgotten when assessing how our conservation dollar is best spent. This is particularly true for species that perform important functional roles that benefit other species (or entire ecosystems), such as native predators. Just as complacency is to be avoided, an aversion to taking calculated risks and trying new approaches in conservation also jeopardises our species’ chances of survival. We urgently need to go further and be bold if our landscapes are to be restored.
The revival of apex predators across Europe, species such as wolves, bears and lynx, demonstrates that biodiversity change is not a one way street. Indeed, few would have predicted a predator renaissance in Europe 50 years ago. Yet, European society has deemed that predators are important to conserve and they are actively restoring them.
There are emerging signs that Australians are up to the task too.
The western quoll, a species that once occurred in every mainland state (now restricted to southwestern Western Australia), has been reintroduced to the Flinders Ranges, and is reproducing.
There is growing support for ambitious projects such as the reintroduction of Tasmanian Devils onto mainland Australia, both for their own conservation and to help control invasive predators, such as red foxes and feral cats. The eastern quoll also persists in Tasmania and so their reintroduction to mainland Australia remains a possibility.
Organisations are being assembled to specifically promote and support the recovery of many of our iconic apex predators.
It is time for the public, governments and non-government organisations to capitalise on this momentum and support audacious projects that seek to rewild Australia and restore its natural glory.
Let us hope that a future not so far away will see our landscapes reinvigorated by a resurgent mammal fauna.
Authors: Fabrizio Sergio, Oswald J Schmitz, Charles J Krebs, Robert D Holt, Michael R Heithaus, Aaron J Wirsing, William J Ripple, Euan G Ritchie, David Ainley, Daniel Oro, Yadvendradev Jhala, Fernando Hiraldo and Erkki Korpimäki.
Abstract
Research on the ecology of top predators — upper trophic level consumers that are relatively free from predation once they reach adult size — has provided regular contributions to general ecology and is a rapidly expanding and increasingly experimental, multidisciplinary and technological endeavour.
Yet, an exponentially expanding literature coupled with rapid disintegration into specialized, disconnected subfields for study (e.g. vertebrate predators versus invertebrate predators, community ecology versus biological control, etc.) increasingly means that we are losing a coherent, integrated understating of the role and importance of these species in ecosystems.
This process of canalization is likely to hinder sharing of scientific discovery and continued progress, especially as there is a growing need to understand the generality of the top–down forcing, as demonstrated for some members of this group.
Here, we propose ways to facilitate synthesis by promoting changes in mentality and awareness among specialists through increased debate and collaboration, conceptual reviews and a series of exemplary case studies.
The strategy will rely on the collective contribution by all scientists in the field and will strive to consolidate and formalise top-order predation as a holistic, cohesive, cross-taxonomical field of research studying the ecology, evolution and behaviour of apex predators and their capability to exert top–down forcing on lower trophic levels.
Sergio F, Schmitz OJ, Krebs CJ, Holt RD, Heithaus MR, Wirsing AJ, Ripple WJ, Ritchie EG, Ainley D, Oro D, Jhala Y, Hiraldo F, Korpimäki E (2014) Towards a cohesive, holistic view of top predation: a definition, synthesis and perspective. OikosDOIPDF
Applied ecology and conservation research group 
