Rapid loss of top predators ‘a major environmental threat’

Scientists warn that removal from ecosystem of large carnivores like the dingo could be as detrimental as climate change

Dingoes keep kangaroo and fox numbers down, which means less overgrazing and more small native animals. Photograph: AAP

Oliver Milman

The rapid loss of top predators such as dingoes, leopards and lions is causing an environmental threat comparable to climate change, an international group of scientists has warned.

A study by researchers from Australia, the US and Europe found that removing large carnivores, which has happened worldwide in the past 200 years, causes a raft of harmful reactions to cascade through food chains and landscapes.

Small animals are picked off by feral pests, land is denuded of vegetation as herbivore numbers increase and streams and rivers are even diverted as a result of this loss of carnivores, the ecologists found.

“There is now a substantial body of research demonstrating that, alongside climate change, eliminating large carnivores is one of the most significant anthropogenic impacts on nature,” the study states.

The research looked at the ecological impact of the world’s 31 largest mammalian carnivores, with the largest body of information gathered on seven key species – the dingo, grey wolf, lion, leopard, sea otter, lynx and puma.

In Australia the downfall of the dingo, which has been largely pushed out of the country’s eastern and southern states, has had a number of detrimental effects. Dingoes have been culled to prevent them preying on sheep, while inter-breeding with dogs has also had an impact.

Dr Mike Letnic, the report’s co-author and research fellow at the University of NSW, told Guardian Australia that his studies either side of the vast dingo-proof fence showed the consequences of their absence.

“We found there were more small native animals such as poteroos and bilbies where the dingoes were,” he said. “That’s because they [dingoes] suppress foxes, which have given small mammals a really hard time since they were introduced.

“Dingoes also kill kangaroos, so losing them means more kangaroos. That means areas are overgrazed, nutrients are lost from the soil and you risk desertification of areas. More dingoes aren’t ideal for kangaroos, but they are a net benefit to the ecosystem.”

This increase in kangaroo numbers in parts of Australia has had other unintended consequences, with the marsupials targeted by farmers for competing with livestock for prime grazing land. Letnic said they may even be to blame for outbreaks of Ross River fever.

Further afield, researchers found that the reintroduction of wolves to Yellowstone national park in the US caused a reduction in deer numbers, in turn benefiting the park’s trees and plants.

The spread of Lyme disease in the US was partially attributed to booming deer numbers, which host the ticks that carry the disease, while an increase in the number of herbivores grazing is thought to change the flow of local rivers, making them straighter and threatening creatures that dwell in slow-moving waters. Loss of vegetation also removes key carbon storage from the environment.

Letnic said: “A good example is in west Africa, where people removed lions and leopards. They then suffered an outbreak of baboons, which give small animals a hard time but also give people a hard time. They raid crops, which mean that kids don’t go to school because they have to guard the crops all day.

“Overall, we’ve got to find better ways to live with carnivores. They aren’t always easy to live with, but they are an important part of the ecosystem.

“In terms of dingoes, we need to find landscapes where they are left alone or actively promoted. In livestock grazing areas we need to work out what impact they are having and work out a system, perhaps with guard dogs, that we can use to avoid killing them off.”

Source: http://www.theguardian.com/environment/2014/jan/10/rapid-loss-of-top-predators-a-major-environmental-threat

Access to the article by clicking  here

Dingos May Have Outfoxed Tigers

New evidence suggests that thylacines were driven to extinction on the mainland by dingo attacks rather than competition for food, as previously thought.

Thylacines flourished widely until around 3500 years ago. Their disappearance from areas other than Tasmania co­incided with the arrival of the dingo, which never reached Tasmania.

It is common for predators to kill smaller species that might represent competition. However, this was once dismissed as a possible explanation for the thylacine’s mainland disappearance since the Tasmanian tiger was larger than dingos.

Dr Mike Letnic of the University of NSW says this view ignores Bergmann’s Rule – the observation that animals are larger in colder climates – so Letnic and colleagues at the University of Sydney compared the size of thylacine and dingo bones from similar areas. They found a substantial overlap in size, but some adult thylacines were much smaller than any dingoes.

Evidence from Tasmania shows that thylacines were highly sexually dimorphic, with the females much smaller than the males. Although it is not possible to identify the sex of most of the fossils, it seems likely that male thylacines were of similar size to dingoes while females were not much larger than foxes.

“Recent studies have shown that foxes are suppressed in areas that have many dingoes, and it appears that the dingoes kill the foxes. Hence we believe that the same mechanism occurred 3500–5000 years ago with dingoes killing thylacines,” says Dr Mathew Crowther of Sydney University’s School of Biological Sciences.

Male thylacines may have been large enough to fight off dingos, but the females would probably have succumbed, leaving the species unable to breed.

In PloS One the researchers argued that direct attacks by dingoes may have wiped out the thylacines. “Recent analysis has found the evidence for competition as a driver of extinction is weak,” Letnic says. “It can have a big effect on abundance, but usually a species can find a location in which it can survive. Direct killing is harder to avoid, particularly with an introduced species, which the smaller animal may lack adaptations to avoid.”

Letnic acknowledges that the theory lacks direct evidence, such as dingo bite marks on thylacine fossils. However, he says finding this would be “like looking for a needle in a haystack”.

The paper also raises the possibility that changes in Aboriginal culture and economy, coinciding with the dingo’s arrival, may have contributed, as might the dingo’s greater tendency to hunt in packs.

Source: http://www.australasianscience.com.au/article/issue-julyaugust-2012/dingos-may-have-outfoxed-tigers.html

Paper conclusion:
Dingoes were similarly sized to male thylacines but were considerably larger than female thylacines on mainland Australia during the Holocene. Small size may have made female thylacines particularly susceptible to direct killing by dingoes and such killing could have driven thylacines to extinction. Due to their lower metabolic rate and convergent morphology, thylacines would have also been susceptible to resource competition with dingoes, but competition is generally thought to be a weaker extinction threat than predation. Our results provide support for the hypothesis that direct killing by larger dingoes contributed to the extinction of the thylacine on mainland Australia. However, attributing the extinction of the thylacine to just one cause is problematic because the arrival of dingoes coincided with another potential extinction driver, the intensification of the human economy.

Access to the paper: http://www.plosone.org/article/fetchObject.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0034877&representation=PDF

Want Dingoes to leave people alone? Cut the junk food

By Thomas M Newsome 

A dingo in the wild.

Dingoes are back in the news, with Prime Minister Tony Abbott raising concerns on ABC radio last week about dingoes in drought-hit areas of Queensland and New South Wales:

I’d learnt some years ago on my Pollie Pedal bike ride that wild dogs were a difficulty in the high country of Victoria, but I now discover that this is a much more widespread problem.

The federal government is close to announcing a new assistance package to help drought-struck areas. Given the Prime Minister’s unprompted remarks, there’s a chance that extra measures to control dingoes will be part of that package.

               Where dingoes are found and are most abundant around Australia.

                                                                                          Queensland and NSW has been particularly hard-hit by rainfall shortages in the past 18 months.

It would be an understandable move, given that dingoes are synonymous with livestock predation and come into conflict with people around some tourist and mining activities.

But while culling to control dingo numbers is one management option, there are other ways to lessen the impacts of dingoes on humans.

Dingoes are opportunistic predators that hunt a wide variety of prey. Consequently, they are especially likely to consume abundant food items. While in many cases this food is likely to be fauna, it can equally be food waste provided by people.

Our research suggests that waste food can be a key resource for dingoes, that has dramatic impacts on the ecology and behaviour of dingo populations. Further, it seems this food subsidy can escalate conflicts between humans and dingoes in all kinds of settings, including on farms, at mines and at tourist attractions.

How do humans change dingoes’ behaviour?

In the Tanami Desert in northern Australia, we compared dingo populations in areas with and without human-provided food. The results demonstrated that access to this food, scavenged from unfenced rubbish tips, altered the diet, weight, movement and social behaviour of dingoes.

Like many people, dingoes readily opt for an easy take-away meal. Discarded food scraps comprised 60-70% of the diet of dingoes living close to a rubbish tip, whilst further away, reptiles, especially blue-tongues and goannas, were dingoes’ primary prey.

Dingoes scavenging at a rubbish tip.

Click to enlarge

Our most recent study, which has just been published in the Journal of Mammalogy, confirmed that the eating habits of dingoes around the tip were similar to free-roaming domestic dogs in a nearby township. This is akin to dingoes acting just like man’s best friend.

Eating human-provided food scraps also had consequences for dingoes’ weights. As with over-consumption of other “junk” foods, they got fat: animals living close to the tip were 20% larger than their desert-living counter-parts. Further, these labrador-like dingoes moved only about half as much as dingoes in other areas. One dingo that ate food scraps had a home range size of only two square kilometres. This is dramatically smaller than another dingo, well away from human-provided food, which ranged over 2000 square kilometres. With food provided daily at the tip, dingoes didn’t need to roam over large areas hunting prey.

Contrasting dingo movements: the lines represent movement paths and the circle represents the main area of occupancy. Thomas Newsome, CC BY-NC-ND  Click to enlarge

The reduced dingo movements were also associated with drastically altered social behaviour. Ordinarily, dingoes maintain small family groups and will actively defend their territories to ensure they have access to food and water. Every day at the tip, where there was regularly sufficient food for at least 225 dingoes, we observed 50 to 100 individuals. From the DNA samples we collected from some of the dingoes using the tip, it was apparent that a group of at least 55 closely related individuals were living close by; a five- to ten-fold increase on typical dingo family size. Despite this, little aggression was observed, even towards dingoes visiting from away.

As well as changing the size and behaviour of dingoes, people appear to have also compromised the genetic purity of this remote population. We observed higher rates of cross-breeding between dingoes and domestic dogs around the facility, suggesting it might have been easier for domestic dogs to infiltrate dingo society where food was abundant.

Cutting down on conflict

Our key point is that access to easily available food appeared to drastically alter the way dingoes live and behave. And that could alter how dingoes interact with other predators and prey.

That could have important knock-on effects, because dingoes can help the environment and humans by suppressing overabundant animals that they prey on, including emus and kangaroos and possibly goats and rabbits. In some situations, they may even suppress smaller predators in their area, such as foxes and cats.

Our research found that when humans make food too easily available, it appeared to have mostly negative consequences. That includes sustaining and increasing dingo populations to unnaturally high levels – potentially leading to more conflict with humans.

An example of a properly built predator-proof fence at a rubbish facility. Thomas Newsome,CC BY-NC-ND Click to enlarge

Our findings are important given that people are increasingly making it easier for dingoes to eat our food scraps. Rubbish tips at mine sites, townships, remote communities and tourist areas throughout Australia are often left unfenced, or so poorly fenced that dingoes can freely access food.

Fortunately, addressing this problem is remarkably simple. At large industrial facilities (like mine sites), predator proof fences can be erected around food resources, such as rubbish tips.

At tourist facilities, including campgrounds and picnic areas, predator-proof containers for the storage of food and rubbish will help.

A predator-proof storage container (with bear-proof doors) installed in Yosemite National Park in the US. People and bears co-exist at Yosemite without the need for fencing around the camp ground. Thomas Newsome, CC BY-NC-ND  Click to enlarge

Of course, it would be ideal – and cheaper – if people would simply remove the waste they generate. Doing so would reduce the need for intensive, costly and often controversial management, such as culling or excluding dingoes, to ensure human safety.

Dingoes around a cattle carcass in Ravenshoe QLD. Carcasses attract a plethora of wildlife including dingoes. Graham Wienert and Invasive Animals CRC  Click to enlarge

Although it is difficult to deal with carcasses in pastoral operations, it is worth highlighting that these provide easy, take-away meals for dingoes. Similarly, dumping homestead food waste and carcasses in poorly constructed tips is an open invitation to enterprising predators.

Better and more consistent management of food scraps would contribute to a reduction in human-dingo conflict. It may even decrease rates of cross-breeding between dingoes and domestic dogs, a process that may permanently change the characteristics of Australia’s dingo.

Importantly, removing human food would enable the dingo to fulfil its natural ecological roles, including keeping a check on other animals like kangaroos. In the long-run, that will create benefits for all of us – including farmers.

Source: http://theconversation.com/want-dingoes-to-leave-people-alone-cut-the-junk-food-23436?

Is the Dingo Special Enough to Save?

• By LEIGH DAYTON

A startling discovery: Commonly believed to be a breed of wild dog, scientists now consider the dingo to be a species in its own right. Photo: Neil Newitt

When you look at the picture above, what do you see? A wild dog? A strangely colored wolf? Or something entirely different: a dingo? For centuries, scientists have debated whether Australia’s native canine is its own species or merely a type of wolf or dog. Now, based on physical and genetic evidence, a team of scientists is making the case that the dingo is a unique species that deserves protection under Australia’s federal conservation laws. If they can’t convince governments and landholders, the dingo may be doomed.

Wild dingoes live across Australia, in grasslands, deserts, and even wetlands and forests. Archaeological evidence suggests that the animal arrived on the continent at least 3500 years ago as people sailed back and forth from Asia, where it first appeared, then continued to evolve in isolation until the arrival of Europeans and their dogs in the late 18th century. The European naturalists who first heard descriptions of the dingo believed it represented a new species of canine and gave it a species name to match: Canis dingo. Domesticated dogs, on the other hand, are known as Canis lupus familiaris, indicating that they are a subspecies of wolf (Canis lupus).

But over the next 300 years, scientists began to argue about what to call the dingo, given the lack of early physical specimens and the fact that the original classifications were based on nothing more than a painting and description given by Australia’s first governor, Arthur Phillip. Dingoes have continued to change as they bred with settler dogs. Today, Australia’s native canine is most often referred to by scientists as C. lupus dingo, relegating it to a subspecies of wolf based on a notion that dingoes evolved from wolves in Asia. Recent studies suggest that dingoes, dogs, and wolves are cousins, all descended from a distant ancestor.

That classification left University of Sydney wildlife biologist Mathew Crowther unsatisfied, given his experience studying wild dingoes. He believed that conservation and management decisions were not being based on firm evidence. “A dingo is a distinctive thing in Australia,” identifiable by its erect ears, bushy tail, and neck that can arc backward into prime howling position, he says. Still, it’s difficult to tell a dingo from a dingo-dog hybrid, or even a feral dog, because natural variation within dingoes is poorly understood and mating with wild dogs may have altered the genome of living dingoes, Crowther explains.

Being able to define what a dingo is—and isn’t—is increasingly important in Australia. While some scientists argue that dingoes with no dog DNA fill the important niche of apex predator in Australia’s ecosystem by eating feral cats and foxes, ranchers lump dingoes, feral dogs, and dingo-dog hybrids into the category of pests that attack and kill valuable livestock. Current policies in some jurisdictions of Australia aim to exterminate dingo-dog hybrids while conserving dingoes. But without a clear definition of what distinguishes a dingo, it’s hard to manage wild dingoes, dingo-dog hybrids, and free-roaming domestic dogs, says Damian Morrant, an ecologist with James Cook University, Cairns, who was not involved in the new study. He says the work is a “baseline” for developing clear guidelines for identifying dingoes in the wild.

To begin sorting dingo from nondingo, Crowther and his colleagues at the universities of Sydney, New South Wales, and Western Sydney reviewed genetic work conducted by other researchers and began tracking down pre-1900 dingo specimens, which would allow them to study the species before it encountered—and mated with—domestic dogs brought by European settlers. “One of our colleagues went to all the European [natural history] museums: London, Paris, Germany, Oslo,” Crowther explains. The team discovered a range of coat colors on dingoes preserved in the museums: yellow, brown, ginger/red, black, and white. That indicated that these colors are not the product of recent mating with dogs, and that animals boasting them today can be considered pure dingoes.

The researchers also compared the skulls of the dingo specimens with those of wolves and similar-looking domestic dogs such as Australian cattle dogs and collies. While there were overlaps, the dingoes had wider and shorter skulls and no hind leg dewclaws, vestigial toes that don’t touch the ground, which are common among dogs and wolves, the team reported online this week in the Journal of Zoology. Based on these physical and genetic differences, the researchers propose changing the dingo’s scientific name back to Canis dingo, once again classifying it as its own species.

Given the contentious attitudes about dingoes as either top predators or pests, as well as the uncertainty among scientists about their evolutionary past, the paper will “inflame passions across the board,” says Christopher Dickman, a conservation ecologist at the University of Sydney who is not part of the team. And so it has. Although J. William Ballard, an evolutionary geneticist at the University of New South Wales in Sydney, says the study provides a “road map for the debate,” he believes the methodology is weak and the data unconvincing. Still, dingo specialists such as Christopher Johnson, a conservation biologist and ecologist at the University of Tasmania, Sandy Bay Campus, welcome the work. “It places the dingo on firmer biological ground as a distinct [group],” he says.

Crowther and his colleagues acknowledge that they’ve not yet identified “consistent and clear diagnostic features” that characterize all members of C. dingo, but they claim they’ve set limits on physical traits of the species. And for conservation and land managers that’s a start, says Euan Ritchie, an ecologist at Deakin University, Melbourne Burwood. “If it looks like a dingo, smells like a dingo, and acts like a dingo, is that enough” to count it as a dingo?

Sources:

http://news.sciencemag.org/biology/2014/03/dingo-special-enough-save

http://www.smh.com.au/environment/animals/dog-gone-scientists-confirm-the-dingo-is-a-unique-species-20140328-35onp.html#ixzz2xWWMjaAz

Access to the paper: http://onlinelibrary.wiley.com/doi/10.1111/jzo.12134/abstract

THE UNWANTED SIDE EFFECTS OF POISONING DINGOES

Image © Kitch Bain | Shutterstock

In parts of Australia, people drop poisoned meat from airplanes or helicopters or leave it along dirt roads to keep dingo numbers under control. The justification is that dingoes attack livestock and need to be suppressed. But dingo poisoning has set off a cascade of ecosystem changes that affect other wildlife: according to a new study, small mammals are taking a hit too.

Figuring out what happens when you get rid of top predators is tough. It’s impractical to do a large-scale experiment in which predators are removed from an ecosystem, and such studies would often be illegal or ethically questionable anyway.

But the study authors had the chance to follow a “natural experiment”. In New South Wales, Australia, they identified seven pairs of sites with different levels of dingo control. Within each pair, dingoes had been regularly poisoned at one site for the last five years; at the other site, less than 50 kilometers away, people hadn’t made much of an effort to control dingoes.

The researchers monitored kangaroos, wallabies, foxes, cats, possums, and small mammals such as rodents at each site. They searched for the animals by identifying footprints, scanning the area while driving, or setting traps with peanut butter, oats, and honey.

At the sites with frequent poisoning, the authors found more kangaroos and wallabies and more signs of fox activity, presumably because fewer dingoes were hunting or harassing those animals. Since kangaroos and wallabies are herbivores, the density of understory plants went down. And the number of small mammals, which take cover among plants and are preyed on by foxes, also dropped.

“Dingo control programmes in conservation reserves may be counter-productive from a biodiversity conservation perspective,” the authors write in Proceedings of the Royal Society B. Managers will need to find a way to keep dingo numbers up and farm animals safe at the same time. — Roberta Kwok | 13 March 2014

Sources:

http://conservationmagazine.org/2014/03/unwanted-side-effects-poisoning-dingoes/

Colman, N.J. et al. 2014. Lethal control of an apex predator has unintended cascading effects on forest mammal assemblages. Proceedings of the Royal Society B doi: 10.1098/rspb.2013.3094