Pest control – extermination vs. neutering or relocation

Like the population issue, the topic of pest control stirs up a lot of strong reactions as to how it should be handled.

Prevention being better than cure aside, when the pest has invaded our homes, businesses and farms – what should be done?

When it comes to creatures such as snails, slugs, flies, termites, mosquitos and bedbugs; many people find extermination is acceptable; but whack fur or feathers on a creature and the situation often changes.

Often part of the justification is that insects are not considered to be sentient beings, but it turns out these creatures may experience emotions after all. However, I doubt this will change people’s perceptions in the short to medium term.

When it comes to vertebrates, some believe these pests should be relocated or otherwise dealt with rather than exterminated.

In relation to non-native invasive species; I lean toward eradication in most cases – for environmental reasons as much as anything. 

While I certainly feel hypocritical in being judge, jury and executioner as I am a member of an “invasive species” myself; and it saddens me to destroy a creature simply for existing in the “wrong” place (often as a result of human action), some invasive species just shouldn’t be relocated as wherever they are relocated to, they’ll continue to cause problems – or it’s simply not feasible to do so.

Here are some examples – I’ve chosen these as I have a degree of familiarity with these particular problem species.

Feral cats

Cats are incredible killing machines. I was surprised to learn in some countries that they have neutering programs for feral cats. It’s a noble gesture, but one that is misguided I feel. While the cat won’t breed, it will go on killing to survive and for sport. A single cat can kill many birds and lizards over its lifespan whether it’s neutered or not. It could be the difference between a species surviving and becoming extinct. I feel the money spent on programs neutering feral cats could be better spent on other environmental projects.

Pack dogs/wild dogs

I look at my much-cherished Niki The Wonder Dog peacefully sleeping near my feet and I could never really imagine her teaming up with other dogs and then going out on the prowl – killing for fun during the night and returning in the morning. Some domestic dogs don’t return and basically return to their wild roots very quickly; breeding a new generation of wild dogs.

It does happen here in Australia and I assume in other places. If Niki should stray onto a neighbouring farmer’s property and is shot, I can hardly hold it against the farmer for taking such an action – the fault lies squarely with me. The farmer can’t afford to just hope that Niki is a domesticated dog that has strayed; for his or her own safety as much as anything.
The thought of shooting a dog I find totally repulsive, but in some cases it is necessary. It’s not just livestock that feral dogs prey on; it’s native species as well and like other invasive species, they can carry parasites and disease.

European carp

In the town I grew up in, I watched a very nice lake turn into a muddy mess thanks to the introduction of European carp. European carp dig up the bottom and in doing so can turn an aquatic habitat into a hostile environment for other native creatures. 

The problem was so bad a law was introduced to ban the return of captured carp to the lake and each year a major fishing competition was held to try and help thin the numbers. It’s been nearly 30 years since I last lived in that town and as far as I know, the problem persists today. 

Once an invasive species has a foothold, they can be incredibly difficult to control.

Mice and rats

I like house mice – I think they are incredibly cute critters and I admire their agility and ability to adapt. However, I would never, ever relocate a captured mouse. Mice are prolific breeders. A female mouse can have up to 12 young in a litter and do that multiple times a year. When you consider a mouse can start breeding when it’s just a couple of months old; a single pair of mice can turn into hundreds of mice over a year. Mice and rats can also carry a number of diseases and be hosts to various parasites. 

We’re in the midst of a mouse plague here in Australia with concentrations of well over 500 per acre not uncommon. Crops are being wiped out and property and habitats are being damaged. While these mice can also become food for other creatures such as birds of prey, it sets up a boom and bust cycle where predator populations increase greatly very quickly and when the plague is over, they too become victims as suddenly a major food source has gone – or other species that those predators then have to turn their attention to. While there can be short term winners as the result of the boom in another species’ population, longer term things mightn’t be so rosy.

Relocating a single house mouse you catch in your home to outdoors may seem like a kind act, but that action can have very negative ramifications.

European starlings

European starlings aren’t native to my country and were brought here to deal with other pests – but became one; as was often the case when we began tinkering with biological controls. European starlings destroy orchards, eat and foul food and water meant for stock and have a habit of nesting in gutters; which in turn can cause water damage in buildings. They also compete with native birds for food and nesting sources and play a major role in weed distribution.


Another animal I greatly admire for their survival abilities. Unfortunately, feral goats in Australia’s outback breed very well, compete with native species for food and water and also cause a great deal of erosion. Goats will eat an incredible range of materials, so they also have an impact on plants that are not usually food sources for other animals.

I really could go on – we have so many feral species here in Australia – rabbits, foxes, pigs; horses, cattle, even camels – all of which do so much damage, not just to human interests but to our native creatures. Relocation just isn’t a viable option and neutering through any means just allows more time for damage to occur.

While nature has its own series of checks and balances and can address these problems – it can be quite cruel in how it deals with a population that has grown out of hand and it can take some time before those controls kick in; making rehabilitation of the affected area quite a lengthy process.
The big picture
It concerns me when I see uproar from environmental groups about the destruction of non-native animals as it can sometimes be a knee jerk reaction that whips up a frenzy among people who may have good intentions, but who do not understand the scale of the problem the animal in question, or its numbers, presents. 
I’ve never seen an action take place about killing millions of houseflies or termites unless there was another non-target species at risk. The presence of a backbone shouldn’t make that much difference in people’s attitudes if the problem is effectively the same.
Some environmental problems aren’t as cut and dried as they seem. While no-kill seems to go hand-in-hand with green living; it’s not always a straightforward issue and we need to understand the bigger picture before forming an opinion and lobbying.
By not despatching with creatures that have become a major problem, instead of helping the environment we may be working against it.

However, methods of extermination need to be effective and not involve a high risk of collateral damage. Where possible, we should also use the animals – for example, carp can be turned into fertiliser and feral goats can be used for human or pet food.
Equally as important – once the problem is under control, then we need to look at what caused it to hopefully prevent it from happening again – as so often humans have a hand in the imbalance occurring in the first place when it occurs outside of natural cycles within a given environment.