The value of our environment – learning from Proctor & Gamble - Wayne Linklater Apr 08

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Proctor & Gamble's Dawn Ultra, New Zealand Springs. Sold in North America. Listed on but unavailable in New Zealand

Proctor & Gamble’s Dawn Ultra, New Zealand Springs. Sold in North America and listed on but unavailable in New Zealand.

New Zealand! The 100% purity and beauty of our freshwaters is an international inspiration…

… for dishwashing liquid.

Dawn Ultra, New Zealand Springs

Dishwashing liquid is an environmental hazard. It adds phosphorous to the environment [1], causes river and lake eutrophication, and contributes to toxic and unsightly algal blooms.

The Environmental Working Group lists Dawn Ultra, New Zealand Springs as scoring its lowest possible grade: F – Highest Concern, and warns of “Potentially significant hazards to health or the environment or poor ingredient disclosure“.

The household products database warns “For external use only. Keep out of the reach of children. If Dawn gets in eyes, rinse thoroughly with water. If swallowed, drink a glass of water to dilute.”

This doesn’t sound like any NZ spring I’d want to swim in.

Corporate duplicity, environmental irony

Dawn Ultra, New Zealand Springs isn’t even the least bad of Proctor & Gamble’s dishwashing liquids. It ranks worse than other products in its range, like Dawn Ultra Mountain Spring: “D – Moderate concern: Some potential for hazards to health or the environment. At least some ingredient disclosure”.

The Environmental Working Group’s main concern about Dawn Utra New Zealand Springs is the “Poor disclosure; May contain ingredients with potential for biodegradation”.

The irony for us, and duplicity by corporates like Proctor & Gamble, is the use of New Zealand’s degrading freshwater environment [2] to sell dishwashing liquid. This is low hanging fruit to an environmentalist.

Dawn Ultra is to freshwater springs, what arsenic is to baby food.

How stupid does Proctor & Gamble thing we are? But then, perhaps we are that stupid. Clearly the product sells*.

Dawn Ultra, NZ Springs, label closeup

Natural environments’ power to sell – protecting their value

More interesting to me, however, is how Dawn Ultra New Zealand Springs illustrates the power of New Zealand’s environment to sell products. It begs the question: Why does our environment not receive a cash injection whenever a business uses it to make money?

Natural environments get used for free by businesses to sell products that degrade the environment. How stupid is that?

Businesses should pay for using natural environments as promotional tools. Those payments would be invested in natural environment protections.

It would be, afterall, for the corporates’ own good – protecting them from themselves by preventing the spoiling of their marketing asset.

Corporates should consider payments for such an environmental service an investment. Instead they get a free ride until, of course, the natural environment is natural no more.

New Zealand’s Department of Conservation or its Regional Councils should get an environmental payment from Proctor & Gamble for profits made from using New Zealand’s springs to sell detergents. Alternatively, Proctor & Gamble should establish a private freshwater protection fund in New Zealand, least it appear to be exploiting our reputation or misrepresenting our nation’s freshwater assets.

Proctor & Gamble’s response

I wrote to Proctor & Gamble asking about why they chose New Zealand and our freshwater springs to market their product. My letter and their response form my next post of this series.



* Proctor & Gamble’s Dawn Ultra, New Zealand Springs. Sold in North America and listed on but unavailable in New Zealand.


1 Comber, S., et al. (2013) Domestic source of phosphorus to sewage treatment works. Environmental Technology 34, 1349-1358.

2 Parliamentary Commission for the Environment (2013). Water quality in New Zealand: Land use and nutrient pollution.


Fat, well-fed cats kill too… and they do it for fun - Wayne Linklater Mar 05

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On our way down to the local corner store for the Saturday morning paper my 5- and 1-year-old daughters and I meet a feline ritual.

At the front gate of a home half-way down, every day without fail stands a generously fed black moggy with white socks and nose, long hair, and an inviting purr. She sits reliably waiting for us – and many others I suspect – to walk by and give her a scratch and a pat. My daughters lavish her with love.

well fed cat with starling

This morning we met her as usual at her gate. She meowed and AJ, my daughter, played with her tail and the cat rubbed her arm in purrrrrfect happiness.

I wondered, while waiting for the mutual love-fest to be over, how often a fat, well-fed cat kills. Perhaps hardly ever? That has been the argument of some. Owned, well fed cats are not the problem* But then, even where that is true, in a community where cats or cat ownership are unregulated, not all cats are well-fed, many stray, and so the cat problem is perpetual.

We left my thoughts and the cat at the gate, retrieved our newspaper, and just this morning a special treat – a small bag of lollies. With our gums and minds engaged with the delights of coconut ice, we passed our favourite cat’s gate again.

AJ yelled ‘Daddy!’ – a cry of amazement and upset together.

I turned to see my daughters’ favourite, fat, well-fed cat walking towards us with large bird in its mouth. But reluctant to bring it to us, the cat instead would place and chase the injured bird around the lawn.

Repeatedly the bird would try to escape and the cat pounce, carry, place, walk away, turn and wait to pounce again.

YouTube Preview ImageIt was a starling – an introduced, exotic bird species the cat had caught. Starlings are not a conservation concern. But it was not possible for me to be unconcerned about the welfare of that startling.
It is disturbing to me that some can claim the mantle of caring about the rights and welfare of their cats but not the animals they kill. The inconsistency, hypocrisy, is because the cat-only lover is an egoist – ultimately selfishly caring only about the animals that they have a relationship with.

well fed cat looking over starling

The starling died – eventually giving up the desire to escape, and then the will to go on.

Fat, well-fed cats can also be killers in our neighbourhoods. Having a well-fed fat cat is not a guarantee that they do not kill. And they do it for pleasure.


*Actually, the evidence suggests differently. Mine and my daughters’ experience is just an anecdote but records by cat-owners of prey their cats bring to them indicate that even some well-fed cats kill [1].

1. Gillies, C. & Clout, M. The prey of domestic cats (Felis catus) in two suburbs of Auckland City, New Zealand. Journal of Zoology (Lond.) 259, 309-315 (2003).

Killing to save, saving to kill – hunting rhino - Wayne Linklater Jan 27

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Resurgent killing for horn that is then traded on the international black market for thousands of dollars a gram threatens to undo two decades of progress recovering the black rhinoceros from near extinction. Countries are mobilising and people are dying protecting rhino from international crime syndicates that out manoeuvre and out gun them. Do not underestimate our situation – we at war for biodiversity and the environment.

In this context the sale of a permit to hunt a black rhino in Namibia for US$350,000 at the Dallas Safari Club created a mad furore. For many, especially of the well-to-do, comfortable, urbanites of the West, conservation hunting is oxymoronic.

Neto - field assistant and rhino ranger - and I shelter behind tree trunks as Alice mock charges. Black rhino, when not frightened away, can be aggressive towards people and so make themsleves as easy, and thrilling, target for hunters.

Neto Pule, field assistant and rhino ranger, and I shelter behind tree truncks as Alice mock charges. Black rhino can be aggressive towards people and so make themselves easy, and thrilling, targets for hunters. See also the video of a rhino charing below.

But we should try to achieve a more considered and carefully articulated response to this event than the one heard from many individuals and groups who claim the mantle of animal rights or conservation in our first-world countries.

Some conservation organisations, like the International Union for the Conservation of Nature, and the US Fish & Wildlife Service, support the hunt. Why would they?

On my way to answering this question, let me begin with my experience of stalking rhino.

Hunting rhino is easy

It is not difficult to shoot a rhinoceros – thousands of successful poachers and the near extinction of the species attest to that. They can be dangerous, of course. Regrettably, I have seen how dangerous rhino can be and I don’t wish to revisit the images seared into my brain that still wake me some nights. But rhino are also very vulnerable to a bullet.

In my work with black rhino I have been close enough to shoot over 100, and I am not a practiced shot. But black rhino make the task easy. They leave their heavy, easily followed, tracks from waterholes where they must drink each day. They are terribly poor sighted – relying on their sense of hearing and smell to detect danger – and so I have routinely stalked rhino to within 30 metres downwind without being detected.

How close can you get?

One of the students in my research group, Roan Plotz, who recently finished his PhD, measured how quickly a black rhino detects a person walking towards it by asking his field ranger and assistant to walk crosswind, without concealment, directly at black rhino. The black rhino failed to detect 77% of approaches before Roan had to call off the approach out of fear for the field ranger’s safety. Even when detected, the field ranger first got to within 23m of the black rhino (59m if there are oxpecker birds on the rhinos back, but that is another story for another time).

YouTube Preview Image

We had been watching this adult female rhino for over 20 minutes undetected. But then she smelt or heard us. I am unsure which. She turned towards us to investigate, paused for what seemed several minutes, but then charged. This was not a mock charge. Snorting as she ran at us, she hit the other side of the tree trunk with her horns and full weight - more than 1 tonne. I felt the tree move and almost droped the camera

Rhinos’ death-wish behaviour

If disturbed by the smell or sound of danger – a snapping twig, a scent of human – rhino lift their heads and turn to face the danger, thus providing the perfect forehead shot. They will flee if they detect people, but not always. Sometimes they will approach to confirm the danger. Sometimes they will charge, but often only to threaten.

I have stood behind many a tree trunk with a black rhino 2 or 3 car lengths away having halted its charge, and occassionally even within arms-reach as it pounded the other side of the tree with its horn. My field ranger could have rested the loaded barrel of his rifle against the rhinos’ forehead.

All of these behaviours provide the hunter of black rhino ample opportunity for a well-placed bullet. White rhino are even easier to kill. They are social and prefer to eat grass, and so live in small groups and more open habitat with better visibility for the stalker.

Hunting as part-solution

Nevertheless, some find the power and prestige, or mana as we call it in New Zealand, of killing a rhino with modern weaponry an achievement. And, against my experience, I accept their preferences as another example of the diversity of human approaches to our natural world because hunters can play a small but important role in the conservation of endangered species like rhino.

Solutions to the extinction crisis come in many forms. I wager that there are almost as many parts to the solutions as the people contributing to them. I am not a hunter. But I am a rhino conservationist. The evidence leads me to believe that they can sometimes be the same thing.

I’m unlikely to ever want to kill a rhino. But, here – in the following posts of this series – I will defend rhino hunting as an appropriate, useful, and important contribution to species conservation.

It will be a journey in ecology, economics, and social psychology, not of rhino, but of people.


Annihilate, really? – show me the evidence - Wayne Linklater Dec 18

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The nation missed an important opportunity at Raglan. If cats have been removed from the Raglan community then, had we the time beforehand to prepare, we could have tested whether cats were a beneficial urban predator, as claimed here and here.

Cats on evidence. Evidence on cats... adn their relationship with other wildlife in our neighbourhoods.

Cats on evidence. Evidence on cats… and their relationship with other wildlife in our neighbourhoods.

We could have measured the movements and survival of other native and exotic wildlife, like birds, reptiles, and rodents, in the area before and after cats were removed–called our scientific treatment site.

Importantly, we would also have compared the changes, if any, with a similar community where cats have not been removed–called our scientific control site.

Unfortunately, the scientific study has not been done or the measurements made. Nevertheless, this has not stopped some from using the Raglan experience as if it were evidence for cats as a beneficial urban predator. Forgive me for disagreeing. Last time I looked ecology was a science.

We need better evidence–scientific evidence. Current information that is paraded as evidence, like the Raglan experience and Dr. Flux’s cat, is inadequate for deciding government policy or wildlife management, although it is being used as if it is reliable information.

In the absence of a scientific comparison of wildlife before and after cat removal and comparison with a control site, it is premature to conclude that the removal of cats has been detrimental to native wildlife in the Raglan area.

I too think it possible for domestic cats to be a predator that is beneficial to native wildlife. However, I quickly add two important caveats which impose very large uncertainties around the usefulness of the idea:


The role of cats as predators, good or bad for native wildlife, is context dependent and we do not know what those contexts are or how commonly they occur. The killing of native wildlife that rats do is a reason for killing rats, not keeping cats (photo source:

1. It depends… and we do not know when

It is certain that cats will not be beneficial at all times and in all places because what cats kill, native or exotic, is context-dependent.  It depends on the characteristics of the cats, and the cats’ owners, the relative availability of exotic and native prey… and much more besides.

Thus, we should not assume that cats are always and everywhere good. Unfortunately, until the ecological science is done–because it has not yet been done–we do not know under what circumstances cats are beneficial and how common those circumstances are.

2. It is a reason for killing rats, not keeping cats

The benefit of having cats is unlikely to be as great as the benefit of removing all exotic predators of native wildlife–cats and rats.

Thus, the presence of rats killing wildlife is not a reason for having cats, it is a reason for killing rats! We would not need cats to kill rats if we got on top of the rat problem in New Zealand’s towns and cities.

Would the loss of cats in Raglan, assuming the reports are accurate, have been a problem if the community had themselves also been controlling rats?

We should do the experiment

To improve the evidence, and address the uncertainties that surround the idea of cats as beneficial urban predators, we need a community, like that in Raglan, to take part in an experiment, like the one I have outlined above or here and here. They would keep their cats indoors for a year and we would compare the changes in wildlife abundance and movements in their neighbourhoods with those of another community where cats are free to roam.

Until such time as the evidence is improved in this way, we need to implement measures which control ALL exotic predators of our native wildlife, at the same time.

Cats can’t kill it, if it is not there - Wayne Linklater Dec 13


For cats to be a “beneficial urban predator” they must largely kill the exotic predators and competitors of native animals.

Dr. John Flux believes his 17-year record of the prey one cat brought to him [1] proves that cats are good for native wildlife in cities. His belief featured prominently in the media to have a major influence on the public debate about cats and native wildlife.

But John’s assertion depends on the observations of a cat that lived where most potential prey were introduced, exotic animals. What do cats kill when exotic prey is less common or native prey more common?

This leads to the fifth reason why John’s logic and conclusion are flawed:

5. Cats can only kill what is available …

Silvereyes were the most common native bird killed by Dr. John Flux's cat. They were also the most common native bird in John's garden. What would John's cat have killed if native animals were more common, and exotic species less common, in John's garden? If we aspire to have more native species in our cities, and fewer exotic species, then what John's cat brought to him is not informative.

Silvereyes, like the one pictured after its encounter with a cat, were the most common native bird killed by Dr. John Flux’s cat. They were also the most common native bird in John’s garden, although exotic bird species were more common still and more commonly killed. What would John’s cat have killed if exotic species were less common and native animals more common in his garden? If we aspire to have more native species in our cities, and fewer exotic species, then what John’s cat brought to him is not informative (image by Dr. Phil Garnock-Jones).

The science of ecology established very long ago that the availability of prey to a predator has a large influence on what it kills. Domestic cats are primarily opportunistic hunters first and choosey only secondarily [2].

John and his cat lived in a highly modified, impacted semi-rural landscape [1]. Their small half-hectare property was surrounded by paddocks of grass for domestic livestock with scattered patches of scrub that was mostly gorse, and a pine tree plantation. The pine plantation’s understory, and about half John’s garden, was regenerating native bush but the rest of his garden was a grassed orchard.

The most common animals in John’s garden, therefore, were introduced exotics [1], especially mice, rats, hares and rabbits, two species of sparrows and blackbirds, starlings, song thrushes, and three finch species, and yellowhammer. The only native bird that was similarly common was the silvereye and so it is no surprise that they were also the native bird mosts killed by John’s cat.

What do cats kill where exotic prey is less common?

Not all places are good habitat for exotic animals. The density of exotic prey for cats will vary across the urban landscape because of variation in the availability of resources like food and water, and variation in the risks of death, like busy roads.

Moreover, on our farms, and in our towns and cities, people control many introduced animals already because they are threats to health, property, and income. Mice and rats are common targets for control. Thus, the availability of exotic prey for cats can be depressed in some places. Where exotic animals are less common, cats will turn their attention to killing something else.

I expect that where exotic prey is less common cats will kill more native prey.

… and we are restoring native animals.

The communities of New Zealand’s cities are making extraordinary progress at bringing our native species back to the places we live, work, and play–largely because we are controlling their predators, especially rats and possums [3].

It is also very common for people to plant their backyards, or put out food and water, to attract native wildlife. Ms. Kerry Charles, who this year completed her Master of Science degree on the topic from the Centre for Biodiversity and Restoration Ecology at Victoria University, found that in Wellington City people are extraordinarily active at encouraging native wildlife:

-          56% of suburban residents planted their properties to encourage birdlife,

-          34% put food or water out for birds and a third of those targeted native species,

-          25% of residents did both.


Where exotic prey are less common, cats will kill something else. In cities, towns, and on farms where our communities are successfully restoring native wildlife, that ‘something else’ is more likely to be native species (image source:

What do cats kill where native prey are more common?

Native wildlife is becoming increasingly common in our neighbourhoods.

In the future our farms, towns and cities are going to be more populated with native species–we want them there. As native animals become more common, cats will kill more of them. Do we want our good work undone?

5 reasons Dr. Flux’s cat is not evidence

In my original post I listed five reasons why what Dr. Flux’s cat dragged in is not reliable evidence for cats being good for urban wildlife. I addressed the first four in consecutive posts: cats bring only a small and biased sample of what they actually kill, the persistence of native species in John’s backyard might be because killed wildlife are replaced by animals recolonizing from elsewhere, and there is more than one cat in each neighbourhood and they each kill differently. I have now added the final reason:

-          cats will kill more natives if and when they are available.

Cats that live where native prey is more common will kill more native animals. Cats that live where exotic prey is uncommon will kill more native animals. In the future, when our cities are home to more native species, cats will kill more native prey.

Improving the environment for our children, grandchildren, and beyond depends on thinking into the future, not the pest-infested past. What one cat killed from a landscape infested with exotic animals is not necessarily what cats kill in other healthier landscapes–the city landscapes of the future.

Let us think ahead, not backwards.


1. Flux JEC. 2007. Seventeen years of predation by one suburban cat in New Zealand. New Zealand Journal of Zoology, 34:289-296.

2. Barratt DG. 1997. Predation by house cats, Felis catus (L), in Canberra, Australia .1. Prey composition and preference. Wildlife Research, 24:263-277.

3. Miskelly C, Empson R, Wright K. 2005. Forest birds recolonising Wellington. Notornis, 52:21-26.

4. Charles K. 2013. Urban human-wildlife conflict: North Island kākā (Nestor meridionalis septentrionalis) in Wellington City. Victoria University of Wellington, School of Biological Sciences, M.Sc. Thesis.

5. Brockie R, Duncan C. 2012. Long term trends in Wellington City bird counts: 1969-2006. Notornis, 59:1-6.

There is always more than one cat - Wayne Linklater Dec 07


Cats might be a “beneficial urban predator” according to Dr. John Flux and his conclusion featured prominently in the media to have a major influence on the public debate about cats and native wildlife. But Dr. Flux’s conclusion has relied heavily for evidence from just one cat [1].

Dr. John Flux on TV3 II

Dr. John Flux, and the 17-year record of what his cat dragged in, featured prominently in the media during the debate about cats and native wildlife. But the evidence from one cat is not good enough to conclude that cats are “a beneficial urban predator” (Source:

There are five reasons why what John’s cat dragged in is not reliable evidence for cats being good for urban wildlife. I addressed the first three in my previous posts: cats bring only a small and biased sample of what they actually kill, and the persistence of native species in John’s backyard might be because killed wildlife are replaced by animals recolonizing from elsewhere.

One cat

John’s conclusion also depended on his observation of one cat, where he thought there were no others – before his cat “only a few stray cats were seen” [1]. Actually, John doesn’t know the density of feral, stray and other domestic cats in his neighbourhood and their kill-rate – he didn’t measure it.

This leads to the fourth reason why John’s logic and conclusion is flawed:

4. There is never only one cat … 

In an urban or suburban landscape cats share habitat. Free-ranging domestic cats are our most common companion animal [2]. They live in our towns and cities in extraordinary numbers.

New Zealanders own 1.4 million cats – the highest ownershp rate in the world. Almost half our households have at least one cat. Our 25 largest cities have about 1.6 cats per hectare (photo source:

New Zealand is home to about 1.4 million domestic cats. Almost half (48%) of our households own an average of almost 2 cats each (1.8 per household with cats). One in every five households own two or more cats – the highest rate of cat ownership in the world. Only 23% of Australian, 19% of UK, and 33% of USA households own a cat [2].

1.6 domestic cats per hectare

In New Zealand’s 25 main cities there are from 36 to 829 households per square kilometre or 188 households per km2 overall. With our high levels of cat ownership, that translates into up to 7 cats per hectare (a hectare is about one rugby football field or soccer pitch) and at least 1 cat per 3 hectares.

Overall, New Zealand’s cities average 1.6 domestic cats per hectare – an extraordinary density for an urban predator that typically ranges over about 1 to 10 hectares or up to 1.2 km from their home [3].

… and they each kill differently -

Importantly, cats have idiosyncratic hunting preferences – some favour birds, others mice [4]. Some cats are lethal, others less so.  Animals, like cats, are adaptable, learning creatures whose hunting preferences develop and change with experience and circumstances.  Lethal cats can become harmless, and harmless cats lethal, during their lifetimes. Some will target native animals more than others.

Stray cat colonies, variously cared for and neglected, occur in their hundreds in NZ cities in addtion to the extrordinary densities of domestic cats (Source:

Cats are super-dense in New Zealand’s cities. And that is without also considering the hundreds – yes hundreds – of stray cat colonies [5]  in our cities, or feral cats in and around the city that are continually replenished with neglected domestic cats. The enormous scale of the cat population and variation in their killing is missed by John in reaching his conclusion.

Science measures variation in cat populations, not one cat

John recorded just one cat that he reports was the only hunter in the vicinity of his home. In the wider world, however, the landscape of our cities, towns, farms and wild places are filled with more than one cat and they are each killing differently. Given the extraordinary density of cats in NZ cities, it is possible that many neighbourhoods will have at least one catastrophic killer of native wildlife.

John was careful to write that his cat’s killing was “not necessarily representative of cats in general”  but he would have more accurately said that the information from his one cat cannot possibly represent the killing by all the cats in our towns and cities. The record from one cat is not population or ecological science.



1. Flux JEC. 2007. Seventeen years of predation by one suburban cat in New Zealand. New Zealand Journal of Zoology, 34:289-296.

2. MacKay J. 2011. Companion Animals in New Zealand. pp. 62: New Zealand Companion Animal Council Inc.

3. Metsers EM, Seddon PJ, van Heezik YM. 2010. Cat-exclusion zones in rural and urban-fringe landscapes: how large would they have to be? Wildlife Research, 37:47-56.

4. van Heezik Y, Smyth A, Adams A, Gordon J. 2010. Do domestic cats impose an unsustainable harvest on urban bird populations? Biological Conservation 2010, 143:121-130.

5. Aguilar GD, Farnworth MJ: Distribution characteristics of unmanaged cat colonies over a 20 year period in Auckland, New Zealand. Applied Geography 2013, 37:160-167.

Presence of native species, not evidence all is hunky-dory - Wayne Linklater Nov 26


Just because native species persist in our backyards despite being hunted by predators, like cats, it does not mean their populations are healthy. Our backyard can be a sink-hole for native species. Each killed is replaced by recolonisers who are themsleves be killed (photo source:

Cats might be a “beneficial urban predator” according to Dr. John Flux. His conclusion and its representation in media, however, has relied heavily on the 17-year record of prey John’s cat, Peng You, brought to him.

But there are five reasons why John’s record cannot be used to conclude that cats are a beneficial urban predator. I addressed the first two in my previous post: cats bring only a small and biased sample of what they actually kill.

John’s conclusion also depends on his observation that native species, like fantails and skinks, persisted in his backyard even though his cat killed them. This, John asserts, is evidence that his cat had no impact but also leads to the third reason why John’s logic and conclusion are flawed:

3. Native animals re-colonise the homes of their killed neighbours

Native animals killed by cats in our backyards are often replaced by animals from other backyards and natural habitats. Young animals, for example, disperse from their parent’s habitat to establish their own breeding territories or home ranges as adults. They will colonise where there is unoccupied habitat and space for them. If a cat, and other backyard predators, are making space available by killing, other native animals may re-colonise that space only to themselves be killed and eventually also replaced.

John’s backyard could have been an all-you-can-eat buffet for his cat – depleting the wider landscape of native animals. Our backyards with cats can be like a sink-hole for native animals. John makes the mistake of assuming that just because he can see the same native species in his backyard for 17 years of killing by his cat that the wider population of natives is not impacted. On the contrary native populations could still be in a cat-induced decline or not increasing as fast as they could without cats.

Our backyards can be breeding-grounds for native animals that grow to recolonise the backyards of our neighbours and the landscapes natural places if, as well as planting native species, we control the predators of native animals in our back yards too. That includes keeping our cats indoors or choosing not to have one in your home (Photo source:

Reversing the sink-hole

We can also turn this process around to consider generating a positive outcome. Without exotic predators, like his cat and rats, John ‘s backyard could have been a place producing more native animals that dispersed to colonise his neighbours’ backyards and the wider landscape.

All John needed to do was control his cat and trap for other predators like rats. How wonderful would that be!

John’s backyard could have contributed to the restoration of native animals in his area, but instead he had a cat, and let the rats be.

When concluding that his cat was a beneficial urban predator, John forgot to think outside his own property to his neighbours’ properties and farther afield. What happens in our backyards has consequences beyond the boundaries of our own properties – for better and worse, depending on whether we support and tolerate exotic predators where we live.

Is your backyard predator-free?

It could be.

Dr. Flux’s cat misleads us - Wayne Linklater Nov 18


Our cats bring us only a fraction, less than half, of their prey and we are less likely to see the small, more palatable prey, like small reptiles and nestlings (Source:

Cats are a “beneficial urban predator” according to Dr. John Flux and his conclusion featured prominently in the media to have a major influence on the public debate about cats and native wildlife.

What John describes is possible but the evidence is scant. John’s conclusion and its representation in media has relied heavily on the 17-year record of prey John’s cat, Peng You, brought to him.

There are five reasons why this record cannot be used to conclude that cats are a beneficial urban predator. Here are the first two:

1. Cats kill more prey than they show us

Cats only bring a fraction of prey to their owner. As few as only 1 in every 5 prey killed by a domestic cat is brought to the owner [1]. Other studies report about 30% of prey [2], and the smallest estimate of undetected prey that I could find is 50% [3]. Most prey is undetected because it is eaten or left where it is not discovered. John assumes that his cat brought him most of her prey but he has no evidence that this is true. The evidence from other studies is that this assumption is flawed .

2. Cats present us with a biased selection of their kills

Some species of prey are more likely to be seen because their parts are unpalatable or they are large. Smaller prey is more likely to be completely consumed [1]. Thus, studies like John’s are likely to under-estimate the number of, for example, reptiles and nestlings killed. John concludes the “effect of our cat on reptiles was insignificant” [4] but he has no evidence that this is true.

Knowing the real and total hunting tally of cats requires that we put tracking devices on them, like radio transmitters or cameras, that enable us to monitor them continuously. Fortunately, such studies are being done [1]. We should rely on their results when making decisions about the impacts of cats on our farms and in our towns and cities, not studies of what one cat brings its owner. Cats kill more than we know about.


1. Loyd KAT, Hernandez SM, Carroll JP, Abernathy KJ, Marshall GJ. 2013. Quantifying free-roaming domestic cat predation using animal-borne video cameras. Biological Conservation, 160: 183-189.

2. Kays RW, DeWan AA. 2004. Ecological impact of inside/outside house cats around a suburban nature preserve. Animal Conservation 2004, 7: 273-283.

3. George WG. 1974. Domestic cats as predators and factors in winter shortages of raptor prey. Wilson Bulletin 1974, 86: 384-396.

4.  Flux JEC: Seventeen years of predation by one suburban cat in New Zealand. New Zealand Journal of Zoology 2007, 34:289-296.

Dr. Flux’s cat and science communication - Wayne Linklater Nov 12


In the heat of public debate about cats and their impact on native wildlife, what scientific evidence did the media most use to inform?

Mostly they used Dr. John Flux’s article [1] about one cat published in the New Zealand Journal of Zoology in 2007.

Dr. John Flux's cat, Peng You, who brought home some of the many prey she killed over 17 years, 1988-2005 (Source: ).

Dr. John Flux’s cat, Peng You, who brought home some of the many prey she killed over 17 years, 1988-2005 (Source: Peng You – a fascinating predator – Hans Anderson:

Dr. John Flux’s 17-year record of what his cat, Peng You, brought to him made it onto TV3’s Campbell Live, into the print media – like the Listenerseveral newspaper articleseditorials, and commentary, and, of course, specialist weblogs.

John was invited to give a public talk to describe his work at New Zealand’s National Museum.

John concluded publicly that cats are a “beneficial urban predator” and that “…they are probably okay in NZ bush since, on balance, their positive effect in suppressing rodents far outweighs their negative effects on bird predation.”

5 flaws in John’s data

I wouldn’t usually single out a colleague’s work for critique in this forum, especially when it is the record from just one cat, but the use of John’s article in the media and John’s public conclusions during the debate make such critique inevitable and necessary.

There are five reasons why what John’s cat dragged in cannot be used as evidence for low cat impact or that cats are a benefit to native animals:

The New Zealand Journal of Zoology - publishing zoological science from New Zealand, and particularly conservation biology,  and pest control.

The New Zealand Journal of Zoology – publishing zoological science from New Zealand, particularly conservation biology and pest control topics.

1. prey that cats bring to their owners is a fraction of all the prey killed,

2. cats bring a biased sample of prey species to their owners,

3. the native animals killed will be replaced (recolonisation),

4. where there is more than one cat there will be more killing, and

5. John’s cat hunted from a largely exotic, non-native fauna.

I will explain each of these reasons in turn and in detail in my next four posts to reveal that John’s data cannot be used to reach the conclusions he has. For the moment, however, I address the problem of science communication that the use of John’s article illustrates.

Science communication bias

A recurrent complaint about the media in public debates that can be informed by science is that the wrong type, or the poorer quality science, often gets attention. This occurs, in part, because the media seeks to generate an adversarial discourse. Scientific adversaries and contradictions in scientific information are sought, even where none exist.

Such is the case over the #catstogo debate. Although John’s data and conclusion about the benefits of cats for native wildlife has five serious flaws, his was the single most reported science in the debate about cats and native wildlife.

What John’s cat brought to him received as much media attention as all the other NZ science and scientists on the topic combined. Better quality science from research groups at UniTec Institute of Technology [2], Otago University [3], and Auckland University [4], to name just a few amongst many others [5], received much less attention.

Peng You huting from a tree (Source: Flux, J 2010, New Zealand Journal of Zoology)

Peng You huting from a tree (Source: Flux, J 2010, New Zealand Journal of Zoology)

The media failed to consider the better data and conclusions of colleagues because John and what his cat dragged in is a cute story and his scientific article was ‘low hanging fruit’.

John’s article became the New Zealand Journal of Zoology’s most downloaded article. I suspect that if John’s article had not been published better science would have been represented by the media during the debate and NZ’s public would have been better informed.

The media is not expert in interpreting science and we should not expect it to be. Thus, the onus is also on us, scientists, to improve the standards of what is published in New Zealand’s scientific journals.

Science publication standards

The importance of the relationship between science and the media, and the potential for the media to get it wrong, raises the issue of whether or not John’s article should have been published by a scientific journal at all.

The article is just a detailed anecdote about one cat and, in my opinion, should not have found its way into one of New Zealand’s peer-reviewed scientific journals. It would have been better as a story in a local magazine for a special interest group. The New Zealand Journal of Zoology should have been more discerning.

When cutesy science like John’s is published in scientific journals it is made to appear credible to the media and can be used to manufacture adversarial discourse rather than to generate solutions-focused debate. Apparent disagreements amongst scientists and scientific data frequently result in policy inertia where none should, and progress is stymied.


1. Flux JEC: Seventeen years of predation by one suburban cat in New Zealand. New Zealand Journal of Zoology 2007, 34:289-296.

2. Aguilar GD, Farnworth MJ: Stray cats in Auckland, New Zealand: Discovering geographic information for exploratory spatial analysis. Applied Geography 2012, 34:230-238.

3. van Heezik Y, Smyth A, Adams A, Gordon J: Do domestic cats impose an unsustainable harvest on urban bird populations? Biological Conservation 2010, 143:121-130.

4. Gillies C, Clout M: The prey of domestic cats (Felis catus) in two suburbs of Auckland City, New Zealand. Journal of Zoology (Lond) 2003, 259:309-315.

5. Langham NPE: Feral Cats (Felis-Catus L) On New-Zealand Farmland. 2. Seasonal Activity. Wildlife Research 1992, 19:707-720.


Academic profiling – unwise, unfair, unethical, but common? - Wayne Linklater Oct 29


University rankings can be useful. They can also be used inappropriately to discriminate inaccurately and unjustly.

Dr. Mark Hauser at Harvard University – consistently amongst the world’s highest ranked universities – was found guilty of scientific miscounduct, fraudulent science in 2012 – an example of why the university a person is employed at is a poor metric of their credibility or future performance (source:

To students making enrolment decisions, or governments deciding how to invest in institutions, a university’s rank represents the relative and average quality of its measured parts – staff or student achievement, research output and influence, teaching quality, or resources. It is a population- or institution-level metric only, not a measure of any of its individuals – duh, right?!

But I have observed a rise in academic profiling – university ranks sometimes also being used to discriminate amongst individuals.

The differences between the ranks of universities are small compared to the range in the quality of their parts. Some departments, staff, and students perform poorly while others outperform at all institutions. A university’s rank, therefore, is a poor measure or predictor of the quality of any individual that works or studies there.

Why, then, have I developed the impression that university rankings are increasingly being used to evaluate the merits of individuals and the value of their supporting referees by committees awarding scholarships to students, or sabbatical leave and promotion to academics?

Sir Paul Callaghan GNZM FRS FRSNZ (1947 – 2012) had his DPhil from Oxford University – ranked 2nd in the world – but chose to work in New Zealand at Victoria University. Victoria University’s world ranking dropped 28 places this year to 265th. Amazing people choose to work in much less ‘amazing’ universities.

At first encounter this practice seemed reasonable. Highly ranked universities generally employ and enrol more talented staff and students, are better funded, and maintain better reputations. It seems useful, therefore, to value individuals at or from those institutions relatively highly.

BUT… using a university’s rank to evaluate an individual’s application or support is like racial or sexual profiling (see text box below).

A person can be at a lower ranked university but be an international leader. Academics at some of the world’s best universities do some very bad work. Many graduates from the world’s top universities perform poorly, despite their greater opportunities. Some very talented people graduate from the world’s lowest ranked universities.

Sir Don McKinnon ONZ GCVO – alumni of one of New Zealand’s lowest ranked universities (Valuation and Farm Management, Lincoln University,1960-61) but also previously Nobel Peace Prize nominee, Secretary-General of the Commonwealth, and Deputy Prime Minister of New Zealand. How unimportant is the rank of one’s university?

Most people choose to work or study at a university largely for reasons other than the institution’s rank. Many choose universities near their families, or in their communities or home countries. People all over the world move from higher to lower ranked universities – actively choosing, for example, to make a contribution to the future of their country or community of birth, or raise their families in places familiar. Many choose or return to lower ranked universities because they aspire to achieve in ways that cannot be measured by the rank of the institution they work or study at.

I understand that committees formed to award student scholarships or academic promotion have a difficult job. They are deciding the winners and losers with far-reaching consequences for individuals. Using a rank of the university that a referee is writing from, or student graduated from, to judge their value simplifies their decision. The contemporary Performance-based Research Fund, amongst other ranking systems, and the competitive culture developing amongst institutions encourages the practice.

But using an institutional address to evaluate an individual is academic profiling. Academic profiling is not a reliable predictor of individual performance, and it is unethical. It is also bizarre, or perhaps just laziness, because applicants provide an extraordinary level of individual detail for committees to evaluate their suitability and merit. The university address they, or their references, come from is rendered redundant.

I hope my impression that academic profiling is on the increase is incorrect or, at least, exceptional. I’d be interested in hearing from colleagues about how often they encounter it. I have encountered two examples in as many months.

Next time someone says to you an applicant’s university isn’t good enough, or a reference less valuable because it comes from someone at a lower-ranked university, suggest politely that they do their job and evaluate people, not their address.

profiling text box

Postscript - written from the university ranked 8th in the world while on sabbatical from the university ranked 265th. I look forward to returning to my home university at the end of my sabbatical for reasons unrelated to its rank.



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