Tag Archives: fox

The Conversation: Killing cats, rats and foxes is no silver bullet for saving wildlife

By Tim Doherty (Edith Cowan University), Chris Dickman (University of Sydney), Dale Nimmo (Charles Sturt University) and Euan Ritchie (Deakin University). 

Cats, rats and foxes have wrought havoc on Australian wildlife and ecosystems. Image credit Paul Hocksenar, Jude, Paul Hocksenar via Flickr.

Cats, rats and foxes have wrought havoc on Australian wildlife and ecosystems. Known as “invasive mammalian predators”, these are species that have established populations outside their native range.

Responsible for numerous extinctions across the globe, this group of species also includes American mink in Europe, stoats and ferrets in New Zealand, and mongooses on many islands.

One common solution is to kill these predators. However, research published this week in the journal Biological Conservation shows it’s much more complicated than that. Killing invasive predators often doesn’t work and is sometimes actually worse for native wildlife.

Killing for conservation

Management of the threats to biodiversity posed by invasive predators has focused on reducing their populations using lethal control. This includes poison baiting, trapping and shooting.

These programs have at times been successful at local scales and on islands. However, they are extremely costly and they often fail to stop declines of native fauna at larger scales.

Such management programs often occur with little regard for how they might interact with other threats that are impacting ecosystems. This has led to unpredictable outcomes of invasive predator control. Sometimes it doesn’t work or, worse, it results in a negative outcome for wildlife.

Key disturbances

We identified six disturbances with strong potential to increase the impacts of invasive predators: fire, grazing by large herbivores, land clearing, altered prey populations, the decline of top predators and resource subsidies from humans (such as increased food or shelter availability).

These disturbances interact with invasive predators in three main ways.

First, disturbances such as fire, grazing and land clearing result in a loss of vegetation cover, which makes prey more vulnerable to predation.

For example, small mammals in the Kimberley region of northern Western Australia experienced more predation by feral cats in an intensely burnt area, compared with patchily burnt and unburnt areas. Grazing by livestock similarly removes protective cover. Research shows that feral cats prefer to hunt in these areas because of the improved hunting success.

Second, increases in food or declines of competing top predators can allow populations of invasive predators to increase, thereby increasing their impact on native species.

For example, introduced prey species, such as rabbits in Australia, can support larger predator populations. This can lead to increased predation pressure on native species – a process termed “hyperpredation”.

The extinction of the Macquarie Island parakeet was attributed to this process. The parakeet co-existed with feral cats for more than 60 years, but declined rapidly to extinction following the introduction of rabbits to the island in 1879. Resource subsidies, such as garbage or hunters’ carcass dumps, can also support larger predator populations, leading to greater predation pressure.

Third, many of these disturbances also have a direct impact on native species, which is exacerbated by invasive predators. For example, habitat fragmentation reduces population sizes of many native species due to habitat loss. Increased predation by invasive predators can therefore make a bad situation much worse.

Getting it right

Our synthesis shows that management of invasive predators is likely to benefit from employing more integrated approaches.

Maintaining habitat complexity and refuges for prey species is one way that invasive predator impacts can be reduced. This includes improved management of fire and grazing. Lower-intensity fires that retain patchiness could reduce the predation-related impacts of fire on native species. Such approaches may be the best option where no effective predator control method exists, such as for cats in northern Australia.

Native top predators such as wolves in Europe and North America or dingoes in Australia can have suppressive effects on invasive predators. “Rewilding” is an option in some places where these species have declined. Where native predators conflict with livestock producers, guardian animals can often protect livestock from predation instead of lethal control.

Reducing resource subsidies is a simple way of reducing food resources for invasive predator populations.

If lethal control is used, it should be applied with caution. Selectively removing individual pest species from ecosystems can do more harm than good. Multi-species approaches are the best way to avoid such surprises and the order in which species are removed is an important consideration.

Rather than focusing on single processes, conservation managers should consider the multiple disturbances operating in stressed ecosystems and use management actions that address these threats in unison. Such integrated approaches are essential if further extinctions are to be avoided.

The paper is free to download until 30 July 2015.The Conversation

This article was originally published on The Conversation. Read the original article online, including reader comments.

The Conversation

 

Interspecific and Geographic Variation in the Diets of Sympatric Carnivores: Dingoes/Wild Dogs and Red Foxes in South-Eastern Australia

Authors: Naomi E Davis, David M Forsyth, Barbara Triggs, Charlie Pascoe, Joe Benshemesh, Alan Robley, Jenny Lawrence, Euan G Ritchie, Dale G Nimmo and Lindy F Lumsden.

Abstract

Dingoes/wild dogs (Canis dingo/familiaris) and red foxes (Vulpes vulpes) are widespread carnivores in southern Australia and are controlled to reduce predation on domestic livestock and native fauna.

We used the occurrence of food items in 5875 dingo/wild dog scats and 11,569 fox scats to evaluate interspecific and geographic differences in the diets of these species within nine regions of Victoria, south-eastern Australia.

The nine regions encompass a wide variety of ecosystems. Diet overlap between dingoes/wild dogs and foxes varied among regions, from low to near complete overlap. The diet of foxes was broader than dingoes/wild dogs in all but three regions, with the former usually containing more insects, reptiles and plant material. By contrast, dingoes/wild dogs more regularly consumed larger mammals, supporting the hypothesis that niche partitioning occurs on the basis of mammalian prey size.

The key mammalian food items for dingoes/wild dogs across all regions were black wallaby (Wallabia bicolor), brushtail possum species (Trichosurus spp.), common wombat (Vombatus ursinus), sambar deer (Rusa unicolor), cattle (Bos taurus) and European rabbit (Oryctolagus cuniculus). The key mammalian food items for foxes across all regions were European rabbit, sheep (Ovis aries) and house mouse (Mus musculus).

Foxes consumed 6.1 times the number of individuals of threatened Critical Weight Range native mammal species than did dingoes/wild dogs. The occurrence of intraguild predation was asymmetrical; dingoes/wild dogs consumed greater biomass of the smaller fox.

The substantial geographic variation in diet indicates that dingoes/wild dogs and foxes alter their diet in accordance with changing food availability.

We provide checklists of taxa recorded in the diets of dingoes/wild dogs and foxes as a resource for managers and researchers wishing to understand the potential impacts of policy and management decisions on dingoes/wild dogs, foxes and the food resources they interact with.

Davis NE, Forsyth DM, Triggs B, Pascoe C, Benshemesh J, Davis NE, Forsyth DM, Triggs B, Pascoe C, Benshemesh J, Robley A, Lawrence J, Nimmo DG, Ritchie EG, Lumsden LF (2015) Interspecific and Geographic Variation in the Diets of Sympatric Carnivores: Dingoes/Wild Dogs and Red Foxes in South-Eastern Australia. PLoS ONE 10(3): e0120975. PDF DOI

Does fire influence the landscape-scale distribution of an invasive mesopredator?

Authors: Catherine J Payne, Euan G Ritchie, Luke T Kelly and Dale G Nimmo.

Abstract

Predation and fire shape the structure and function of ecosystems globally. However, studies exploring interactions between these two processes are rare, especially at large spatial scales. This knowledge gap is significant not only for ecological theory, but also in an applied context, because it limits the ability of landscape managers to predict the outcomes of manipulating fire and predators.

We examined the influence of fire on the occurrence of an introduced and widespread mesopredator, the red fox (Vulpes vulpes), in semi-arid Australia. We used two extensive and complimentary datasets collected at two spatial scales.

We examined the influence of fire on the distribution of introduced red foxes in semi-arid Australia. Image credit Area51Bel [CC-BY-SA 3.0] via Wikimedia Commons.

We examined the influence of fire on the distribution of introduced red foxes in semi-arid Australia. Image credit Area51Bel [CC-BY-SA 3.0] via Wikimedia Commons.

At the landscape-scale, we surveyed red foxes using sand-plots within 28 study landscapes — which incorporated variation in the diversity and proportional extent of fire-age classes — located across a 104 000 km² study area. At the site-scale, we surveyed red foxes using camera traps at 108 sites stratified along a century-long post-fire chronosequence (0–105 years) within a 6630 km² study area.

Red foxes were widespread both at the landscape and site-scale. Fire did not influence fox distribution at either spatial scale, nor did other environmental variables that we measured.
Our results show that red foxes exploit a broad range of environmental conditions within semi-arid Australia.

The presence of red foxes throughout much of the landscape is likely to have significant implications for native fauna, particularly in recently burnt habitats where reduced cover may increase prey species’ predation risk.

Payne CJ, Ritchie EG, Kelly LT, Nimmo DG (2014) Does Fire Influence the Landscape-Scale Distribution of an Invasive Mesopredator? PLoS ONE 9(10): e107862 PDF DOI