From Gareth Morgan’s call for more responsible cat ownership, to a recent news item that the Auckland Council plans to put down any stray cats that have not been micro-chipped, it’s been a tough year for felines. Much is made of the impacts that cats can have on our indigenous wildlife, and this has driven debate on where cats might fit into any strategy to reduce or eradicate predators from New Zealand.
It may come as a surprise to the reader, but like many folk, some of our ecologists have cats as pets. The tensions surrounding cat management are not lost on us!
As ecologists working with our clients, such as when applying for resource consent for new subdivision or land development, we are sometimes asked: ‘Should cats be banned?’
The answer is not clear cut; and the plot thickens when we consider domestic cats versus feral cats.
It is well understood that feral cats hunt to obtain sufficient food, and thus have much larger home ranges than domestic cats. Even in the steep country of the Orongorongo Valley, recorded ranges of feral cats averaged up to 6.3 km for males and 3.8 km for females.
On the other hand, research has found that domestic cats generally range over smaller distances than feral cats. In part, the distance that cats roam is dependent on prey availability, which will differ between urban and rural areas.
Studies that radio-tracked domestic cats found the distances they move from their homes ranged from a maximum of 276 m in urban environments to 1.2 km for cats at urban-fringe sites.
This suggests that to be effective, cat-exclusion zones would need to be at least 1.2 km wide in urban-fringe habitats; and perhaps at least twice this distance in rural areas.
“But surely,” we might ask ourselves, “how much a domestic cat hunts will depend on how much they are fed at home?” Research has shown that this is not the case: the amount of food a cat is fed is unlikely to affect the likelihood of them hunting. So, we cannot assume that a well-fed, domestic cat is less likely to hunt.
Information on exactly what a cat eats is not easy to find; cats are, after all, hunters by stealth and secretive in their movements.
Again, we might think, “My cats bring home their prey, so surely we can pretty accurately document what domestic cats hunt?”
A recent study from Wellington recorded what a single cat caught or brought into the house over a 17-year period. The study found that both native and introduced birds formed about one third of the prey, and that rodents formed a large part of the diet, including rodent kills not brought to the house.
An American study of 55 free-roaming cats used cameras, and found that 44% of domestic cats hunted wildlife (reptiles, mammals and invertebrates), but only 23% of prey was taken back to the house; while 49% was left where it was caught, and just 28% was eaten.
This suggests that we cannot rely on information based on prey that domestic cats bring back to the home.
Any decision-making on banning or excluding cats needs to be based on well-founded behavioural studies. Research shows that domestic cat prey in New Zealand is broad. In some studies, cat diet was dominated by invertebrates and lizards with no birds or mammals recorded; whilst in others the prey was dominated by native and exotic birds.
And while we’re considering the prey question: many argue that domestic cats play an important role in reducing rodent numbers, and thus contribute to a ‘predator-free New Zealand’!
What we might take from this, and what may appear as bias to some, is that the effects of domestic cats on New Zealand’s indigenous fauna does need some critical research. There is also a need for an educational programme to demonstrate what influence cats have on our wildlife. Neither of these will be easy to achieve; studying cats is difficult given the influence of place in their lives, and their often elusive behaviour. One thing that is clear is that community attitudes are often set in favour of the cat as a domestic pet.
Even so, the question remains: are cat-exclusion zones effective, or would other management techniques achieve the same goal (i.e., reducing the predatory impact of cats on New Zealand’s indigenous wildlife)?
A variety of methods are available for the management of feral and domestic cats.
These range from lethal management of feral cats, to a mix of de-sexing, micro-chipping, night curfews and cat-free zones for domestic cats.
A recent survey of community attitudes to cat management from Melbourne, Australia (where the role of cats in wildlife management is equally controversial) highlighted some interesting results.
The level of agreement for lethal management of feral cats was high, as was agreement with traditional domestic cat regulations (de-sexing, micro-chipping and night curfews). There was also overwhelming support for cat-free zones in areas with high conservation value.
So far, all well and good, but tensions emerged as the respondents were less certain and less convinced of the impacts of domestic cats on wildlife.
Consequently, there was resistance to management methods, such as 24-hour cat curfews and lethal control of roaming stray cats. Perhaps this explains the controversy over Auckland Council’s announcement to put down any stray cats that have not been micro-chipped.
So, do cats have a future in New Zealand? The short answer is yes, for the time being.
But there are extended claws ahead, as Councils and decision makers take up the challenge to reduce the impact that cats have on our indigenous fauna. As with most things, the answer lies somewhere in the middle ground, with the merits of excluding cats in any specific location and situation being the important consideration. And, in some circumstances in some locations, the answer will be an emphatic yes – exclude cats!
One factor yet to be fully considered is the changing role of technology. The technology behind pest eradication is moving fast. Our ecology and biodiversity teams – including the cat owners and cat lovers amongst them – are keeping abreast of new research findings regarding cats, and the success and failures of methods to manage cats. We’ll continue to advise our clients and to advocate for conservation outcomes as we work together to understand the future of cats in New Zealand.
18 January 2018