By Alex Paton
When people find out I am studying feral cats, I get hit with a lot of questions and opinions. Well, mostly opinions, and often they are a tad misinformed. I am here to answer the most common questions I get asked about feral cats, supply some facts about their life in Tasmania, and to give some advice on how to help our native wildlife cope with their
presence.
How did cats get to Tasmania?
Cats were brought to Tasmania during European settlement in the 1800s thanks to their skills as mousers aboard transport vessels, and for the comfort and companionship they provided to sailors. Landing in Hobart town and Macquarie Harbor, cats spread into the eastern and western halves of the state. Being a valuable commodity for their perceived ability to ward off rats and rabbits, cats were taken to every settlement that could afford to buy them, meaning that by 1890 cats were widespread across the state.
Felis catus quickly adapted to their new surroundings, learning to hunt the native prey found on the fringes of settlements before pushing out into the bush. Thanks to their preference for fresh meat, the cats were not reliant on direct access to water while searching for habitat, allowing them to occupy pretty much any environment. So long as the cats could find
some form of shelter (hollow logs, dense scrub, rabbit warrens), they spread there. Soon, the cats had established multi-generation, free living populations that had never been exposed to humans. These are what we call feral cats.
Since European settlement, feral cats have probably contributed to 27 (57%) of the 47 extinctions of Australian reptiles, birds, and mammals. However, none of these extinctions occurred in Tasmania, with the state’s only recent extinction being the Thylacine. So what exactly have feral cats been doing in Tasmania?
How do we keep an eye on the cats?
When formulating management plans, it is a good idea to know how many animals you are dealing with, and what damage they might be doing to native wildlife. Until recently, spotlight surveys and track counts have been used to monitor feral cats. These surveys work reasonably well in savannahs and deserts (which is a great deal of Australia), but they fail in
forested environments. Considering Tasmania is around 50% forest, it’s unsurprising that our understanding of feral cat ecology in the state is severely lacking.
To monitor cats, we have needed to employ a new, low effort, low impact technology called camera-trapping. Essentially, ecologists leave a camera out in the environment, which automatically takes a photo when an animal passes it. This gives us an idea of where cats (and other animals) are. The best part is that this technology be used in any habitat, and is well suited for forests.
In my research, I have used a network of camera traps deployed by the DEEP research group to study feral cats throughout Tasmania. The map below shows areas where our team has detected feral cats, with cameras sighting 0.11 cats per day on average. In essence, that means a cat is walking past a camera trap once every ten days. As you can see, feral cats have spread though Tasmania’s western rainforests and are present throughout the state.
Many of these locations are extremely remote, and feral cats are completely isolated from human populace. As such, immigration from pet cats is likely inconsequential for feral cat population size. This idea is supported by the lack of “domestic” coat types seen in our feral cats. The only time I observe white, calico, or long-haired cats on the camera-traps is when they are within five kilometres of a township. Considering the numbers, distribution, and time since establishment, it might be time to admit that feral cats aren’t going anywhere soon...
Why haven’t we gotten rid of cats? The most common methods for controlling feral cats include shooting, poison-baiting, and trapping. Shooting requires high intensity effort, like that seen in the Macquarie Island eradication initiative, making it a costly endeavour for any real hopes of success. If you only shoot cats occasionally, new, younger cats quickly occupy the freed territory of the deceased cat, fighting it out to determine who gets to stay. This increased activity results in a plethora of problems for the native wildlife, with a rapid and intense increase in predation by the competing cats, as well as a potential bout of toxoplasmosis shed by the new arrivals. Eventually, one cat will reign supreme, and the status quo will return to how it was before the original cat was shot.
Poison baiting has shown some success in food-stressed regions of mainland Australia. The most common poison used is 1080, sodium fluoroacetate, which triggers a metabolite called fluorocitric acid. This inhibits key enzymes for cellular respiration, the process by which our body creates energy. Consequently, when an animal ingests 1080, its body cannot create energy and it goes into organ failure. For cats, death takes around 21 hours, with the animal experiencing convulsions, trembling, seizures, and other unpleasant symptoms.
As a result, this poison is illegal in most countries (though Australia and New Zealand are the exceptions). Because sodium fluoroacetate is produced by many native Australian plants, some native herbivores were previously thought to be resistant to its affects. In reality, the majority of Australian animals will experience the same symptoms as cats and other invasive species if they consume a 1080 bait, with death as a likely outcome.
In Australia, our ability to target feral cats has come from the packaging of 1080, as it is kept as a pill at the centre of a juicy meat pellet. Native species are likely to nibble around the pellet, avoiding the poison, while feral cats take up the whole bait indiscriminately. There are obvious problems with this practice in Tasmania though, where carrion-loving Tasmanian devils reside. While one pellet may not contain a lethal dose for a devil, these opportunist scavengers are likely to consume multiple bait, before dying a painful and slow death.
The last option is trapping cats. This option doesn’t leave us with much wiggle room. Like shooting, this is a high-intensity practice requiring plenty of time and money. Cats are extremely trap shy, and so cage-trapping is only effective for capturing young and naive cats. This method will not help remove “problem” individuals. Leg-hold traps are more effective in capturing feral cats, but they are illegal in Tasmania due to the risks they pose to native wildlife. It might be time that we think outside the box on dealing with feral cats, instead of jumping the gun.
What can we do? As far as dealing with feral cats goes, a few new technologies are being developed. Creating more feral cat exclusion zones (maintaining fenced areas that provide sanctuary for at-risk species) is a great step towards preserving vulnerable species. This way, we can create an “artificial island” where cat eradication is more plausible.
The Felixer is also currently being trialled throughout Tasmania. This machine is equipped with sensors that detect the height and shape of a passing animal to determine if it is a cat. When a cat is detected, a “paint-ball” of 1080 poison is fired into the cat’s fur. Cats, as groomers, will later lick off the poison and die. This machine can still only target cats that pass it, and isn’t yet 100% accurate in its targeting in Tasmania, (yet), but nonetheless it may help control populations in problem areas.
Ultimately, there is not much we can do about the wild free-living feral cats in Tasmania just yet, but maybe it is time we shifted our focus to our own doorsteps. It is estimated that pet cats predate 28-52x more wildlife than feral cats living in the wilderness, due to their density and abundance of resources available to them. Really, it is not surprising that five cats living on the same block, all with unlimited food and shelter, can kill more wildlife than one cat occupying an equivalent area fighting tooth and nail to survive in the wilderness. Hence, encouraging responsible cat ownership through desexing and keeping cats indoors will make a huge contribution towards keeping our local wildlife safe.
The Tasmanian government has shown promise with its new feral cat management initiative. All cats in a cat management facility must be microchipped and desexed, meaning that a cat brought into a shelter can be desexed without the owner’s permission. More changes are intended to be rolled out in 2022, including mandatory desexing for all cats over four months old, and a multiple cat permit for households owning more than four felines.
If you have strong opinions about cats in Tasmania, and want to have a tangible positive impact on our native wildlife, here are some ways you can help:
Volunteer (or donate) at your local cat shelter. You will be contributing to an organisation that deal with feral cats, desexes strays, rehomes cats that may otherwise become feral, educates the public regarding responsible cat ownership, and ensures management is undertaken in an ethical manner.
Volunteer for the new “Edu-cat” program being run by 10-lives, or encourage your local school to take-part. This educational initiative sends volunteers to schools to teach them about responsible cat ownership and the impact of feral cats on wildlife (https://tenlives.com.au/educate/).
Encourage friends and family to keep their cats indoors. (https://kb.rspca.org.au/knowledge-base/how-can-i-be-a-responsible-cat-owner/)
Put up bird-boxes and grow native plants (https://www.abc.net.au/news/2019-01-26/what-to-plant-to-help-local-wildlife-survive/10723870). Help fight the negative impact of feral cats by having a positive impact yourself!
For advice on feral cat management in Tasmania, contact the Invasive Species Branch on 03 6165 3777 or visit DPIPWE's Cat Management in Tasmania website (https://dpipwe.tas.gov.au/invasive-species/cat-management-in-tasmania).
All posts are personal reflections of the blog-post author and do not necessarily reflect the views of all other DEEP members
References:
Bengsen, A, Butler, J, Masters, P (2012) Estimating and indexing feral cat population abundances using camera traps.Wildlife Research 38, 732-739.
Lazenby, BT, Mooney, NJ, Dickman, CR (2015) Effects of low-level culling of feral cats in open populations: a case study from the forests of southern Tasmania. Wildlife Research 41, 407-420.
McIlroy, J (1986) The sensitivity of Australian animals to 1080 poison. 9. Comparisons between the major groups of animals, and the potential danger non-target species face from 1080 poisoning campaigns. Wildlife Research 13, 39-48.
Read, JL, Bowden, T, Hodgens, P, Hess, M, McGregor, H, Moseby, K (2019) Target specificity of the Felixer grooming “trap”. Wildlife Society Bulletin 43, 112-120.
Travouillon, KJ, Phillips, MJ (2018) Total evidence analysis of the phylogenetic relationships of bandicoots and bilbies (Marsupialia: Peramelemorphia): reassessment of two species and description of a new species. Zootaxa 4378, 224-256.
Woinarski, JC, Legge, SM, Dickman, CR, (2019) 'Cats in Australia: companion and killer'. CSIRO Publishing.