Cat purring is like people talking with a vocal fry

I'll try and explain the title. The human vocal fry is vocalising in a deep, creaky, breathy voice. I think you hear it quite a lot in advertisements when a man speaks in a vocal fry register to compel people to be attracted to a product.

And it may surprise people to know that a recent study which I believe has been peer-reviewed but which requires follow-up studies, indicates that when a cat purrs it's a simple case of an airflow passing over connective tissue masses within the larynx of the cat. Human vocal fry requires a shortening of the vocal cords.

The study researchers compressed the larynx slightly and then passed air through it and they produced a purring sound. How did they achieve this? They received the consent of owners of cats who had been euthanised because of chronic illness. And they surgically removed the larynxes of the disease cats. They were then able to pass an airflow through the larynx having, I believe, restricted it slightly.

The point is this: it was a very simple test. It only required an airflow going over these tissue masses inside the larynx to create the sound. This is a very low rumbling sound as we know made by animals much larger than the domestic cat. It is therefore a very specialist sound.

It registers with a frequency in between 20-30 Hz as I recall. The study is called: "Domestic cat larynges can produce purring frequencies without neural input."

The referencing the title to "neural input" means that the brain doesn't have to send signals to the throat to constricted and then release it many times a minute which is what the experts originally thought was the process of creating the purr. It was more or less universally thought that in order to create the purring sound the throat had to be constricted and then released rapidly through a nervous system signal. We now know that that isn't the case.

Although, the people who conducted the study say follow-up work would be useful, the lead researcher in the study, Christian Herbst, believes that it should shed some light on animal and human vocal communication. It shows that the cat converts aerodynamic energy which is the flow of air caused by breathing into acoustic energy via the "passive, cyclical oscillation of tissue".

In the early days, many experts were mystified by the domestic cat purr and some proposed that it was created through the flow of blood through the cat's main veins into the heart. When it was increased it caused turbulence and the sound of the turbulence were transmitted to the animal's chest and amplified by the diaphragm. A very complicated and entirely incorrect hypothesis as it happens.

An interesting aspect of the study is that we know that kittens purr while they are drinking their mother's milk. So, cats can purr and drink at the same time. I would like that to be explained to me. There must be a simple explanation for the ability of a cat to do that.

The last point to make is that cats purr when they breathe out and in, which creates this continuous sound.

Claims made by trap-neuter-release (TNR) volunteers are not always true but TNR is effective and humane

TNR volunteer. Great people as far as I am concerned. Image in public domain.

There is a study online dated 2009 (Critical Assessment of Claims Regarding Management of Feral Cats by Trap–Neuter–Return) so it's quite old. I can't read the entire study but I can read the summary which states that the claims that TNR volunteers make are all untrue. These are some of them:

• Feral cats only harm wildlife on islands and not on continents
• Feral cats fill a natural niche and don't contribute to the decline of native species
• Feral cats don't spread disease or they don't act as a reservoir for disease
• TNR eventually reduces the number of feral cats to zero
• TNR managed feral cat colonies "resist invasion by other cats".

Harming wildlife

We know that feral cats harm wildlife. It is common sense. They need to eat and in order to eat they need to kill small mammals, marsupials, insects, birds and reptiles. It depends where they live but there is quite a lot of killing. People who dislike feral cats - and there are many scientists who dislike feral cats - exaggerate the amount of killing by this type of cat. 

They take small sample sizes and work out how many animals the cats kill and then they extrapolate that figure and argue that an entire nation of feral cats kill so many billions of animals. This is liable to produce inaccuracies. 

We can't rely on the numbers disseminated by experts as published in studies on websites such as Google Scholar. We certainly can't rely on the numbers stated by Australian conservationists when arguing that they should exterminate all feral cats on that continent.

But feral cats certainly do not only kill small animals on islands. The reference to islands is there because it is known that on several notorious occasions it is argued that feral cats have made extinct certain small species on islands because those animals had nowhere to escape to. The feral cat dominated the island as a top predator and wiped-out small animal species.

Don't contribute to the decline of native species

This is a big argument. I remember, years ago, the Royal Society for the Protection of Birds saying that there was no evidence at that time (about 12 years ago) that feral cats endangered the survival of a species of bird. Yes, feral cats killed birds but not in sufficient numbers to put a particular bird species on the brink of extinction. And I should add that a lot of the birds that feral cats eat are old, dying or dead birds.

It may interest you to think about dead birds. How many dead birds do you see? When you walk in the park or anywhere else, you never see dead birds do you? And yet millions and millions of birds are dying every day. That's because while animals like foxes and feral cats are eating them.

In short, there is no hard evidence as yet that feral cats, preying on birds, jeopardises the survival of a species. And the same applies to any other animal species. Except, as mentioned about island wildlife where there are differences.

I don't want to defend the feral cat unjustifiably. They do kill a lot of animals and this is of great concern to conservationists. But my argument has consistently been that humans kill a lot more animals than feral cats and are doing so as I dictate this because global warming, an indirect consequence of human behaviour, is killing millions of animals every day. 

An example of that would be the massive floods in Australia coupled with the massive wildfires on that continent. It is said that the latter killed over a billion animals often small mammals, marsupials and reptiles, the kind of prey killed by feral cats. That's the point I'm making.

To global warming you can add herbicides and insecticides used by humans in intensive farming which kills many animals. You can add tall buildings and windfarms which kill many birds. All human commercial activity kills animals because it might lead to deforestation for example. There are numerous ways that humans indirectly kill billions of animals. Humankind should stop being hypocritical about wildlife conservation and look to themselves first is the primary destroyer of nature.

Feral cats don't spread disease

Often you hear spokespersons for local authorities saying that feral cats have to be eliminated because they have a negative impact upon the health of residents. There is no hard evidence to prove this. None whatsoever. I've never seen it. If you can refer to an example then please comment. There is exaggeration about feral cats acting as reservoirs of diseases.

It is notable that the Covid-19 pandemic was caused by humans misbehaving in killing wild animals in a wet market in China in an unregulated way. Nothing to do with feral cats. Or the pandemic was caused by the escape of pathogens from a bio lab in Wuhan, China. Once again, a human-created massive problem. Let's look to humans for the cause of the spread of disease first before we criticise the feral cat which is the victim of human carelessness.

TNR reduces a colony of feral cats to zero

If a volunteer says that TNR reduces a feral cat colony to a population of zero, they are wrong. It might happen from time to time but in general TNR doesn't produce a zero population. It stabilises the population and it means that the cats are looked after to a certain extent and therefore it is a humane practice. Sometimes people dump cats and they add to the colony. Numbers are often significantly reduced and the resulting colony size is manageable.

The volunteers are happy in caring for the cats and the residents of the area are usually happy that the feral cats are being managed. Sometimes people argue with volunteers and they hate TNR volunteers and there can be some nasty altercations but by and large the management of feral cat colonies works out well.

Resisting invasion by other cats

I don't think that this is correct. If TNR volunteers are saying that their work helps to resist the invasion of the colony by other cats it is wrong to say that in my opinion. As mentioned above sometimes people see a feral cat colony as an opportunity to get rid of their cat because they know that somebody else will look after him or her. That's immoral and it doesn't help the TNR volunteers.

One last point, if you kill all the feral cats rather than look after them and neuter them, you end up with this well-known condition where you create a vacuum and other feral cats come into that vacuum. Killing feral cats is arguably less effective than gradually reducing their numbers through TNR programs. #

The problem for a lot of authorities is that the processes too gradual. Politicians need to see instant results to satisfy the electorate. That is one reason why the authorities criticise TNR programs sometimes. More enlightened local authorities support TNR programs and praise the work of these wonderful volunteers.

Domestic cats are harder to read than domestic dogs

Although I can't find the actual study, the Mail Online reports on a study led by Prof Daniel Mills from the University of Lincoln, UK which explores how cat and dog owners recognise the emotions of their companion animals through their expressions. The study asked 438 pet owners to state whether their dog or cat displayed a list of 22 different emotions from disappointment, frustration to sadness and joy.

Frustrated cat? The facial expression is perfect for a frustrated cat showing anger. But we know how a feline's facial expression can mislead us. Often it is due to the cat's anatomy e.g. Grumpy Cat. I am yet to be completely convinced that domestic cats can feel the emotion of frustration. I think they find a way around it by substituting what frustrates them with something else.

Unsurprisingly, dog owners were better able to recognise their companion animal's emotions than cat owners. I don't think this study really advances our knowledge of cats and dogs that much because we know that cats are less facially expressive than dogs because they are essentially a solitary animal whereas dogs are a pack animal looking up to their alpha male leader for guidance and interacting with other members of the pack which requires communication including body language which in turn includes facial expressions.

In the study, on average, 65% of dog owners compared to 58% of cat owners believed that their companion animal can express a certain emotion.

Based on the study's findings, dogs are more able to express subtle emotions such as guilt and empathy. There probably has to be a word of warning here in that sometimes dog owners project their feelings onto their dog companion and believe something which doesn't actually exist.

It appears that, according to cat owners, cats excel at demonstrating anger! Around 85% of cat owners said that their cat can express anger compared to less than 60% of dog owners. Comment: there may be a misconception here. It may be that people are not relating to their cats properly and are inadvertently provoking them into being defensively aggressive perhaps. This might encourage cat owners to regard their cat as demonstrating anger more commonly than dogs do so with their owners. It is not uncommon, for example, for people to pet their cats too much or in a way which can cause scratches or bites. This may colour their perception of their cat's aggressive nature when the root cause of the issue is how people interact with their companion cat.

Another factor which coloured the study findings would be that cats are less predisposed to looking directly at their owner whereas dogs are more likely to do this as they look for guidance from their alpha male leader which would be the human owner.

In fact, it is said that people should not stare at their cat because they find it intimidating. That is not entirely true nowadays because domestic cats are very well integrated into the human environment but it is probably fair to say that cats are less likely to look into the eyes of their human owner than pet dogs which would mean that the owner is less likely to spot facial expressions indicating an underlying emotion.

Prof Daniel Mills said, "When cats turn on their owners and scratch them, it can be because owners miss subtle signs suggesting it is time to stop touching or patching them. So, it's important to understand our pets, but these results suggest we may not be as in tune with cats as we are with dogs. This could be because dogs may have been bred to have more expressive faces than cats."

He adds, "But unfortunately we still don't know whether cats and dogs generally show different emotions, or whether people project more emotions onto dogs and cats, because we often work more closely with dogs so need better communication."

The research is published in the journal Animals. The researchers questioned people who had lived with their pets for at least two years and therefore knew them well. They asked the owners whether they had seen six central animal emotions in their companion animal: anger, disgust, fear, joy, sadness and surprise. And they asked them how they were expressed through facial expressions and general posture and eye contact.

The owners said that they were better able to recognise anxiety, boredom, confusion, and the, frustration, guilt, shame, pain and positive anticipation in dogs compared to cats.

Myopic Australian researchers say that invasive species are the number one threat to Australia's wildlife

Research by Australia's national science agency and the Centre for Invasive Species Solutions states that invasive species to that continent are the number one threat to wildlife. They refer to plants and animals. Animals often cited are feral cats, rabbits, and foxes but there are others. Of these the feral cat is perhaps the most hated by the authorities.

Myopic Aussies. Pic: Pixabay - modified.

I read this news online in The Guardian newspaper online. I don't see any reference in that article to habitat loss due to human activity. In general, across the globe, habitat loss due to human population growth and therefore increased human activity, is the single biggest destroyer of wildlife. Why should this be any different in Australia? It probably isn't.

RELATED: Feral cats are a non-native species in Australia but will they become native?

Arguably, if is possible to assess it accurately enough, humans are the number one threat to Australia's wildlife. And non-native species are the second most important threat. But humans are writing the report. They are myopic when it comes to their behaviour. They are biased. They are suffering from an acute attack of speciesism.

Perhaps the problem is this: humans cannot change their ways and therefore they simply do not consider what they might do to minimise their impact on Australia's wildlife. And it is much easier to blame animals and to kill them in order to curb their predatory activities.

Of course, it is very difficult to get rid of feral cats in Australia. This is been proved time and again despite the ingenious and sinister methods that Australian ploy to slaughter feral cats in large numbers.

RELATED: Australian cutting-edge program to poison feral cats could kill pet dogs too.

One underlying aspect is climate change. Humankind is the author of its own problems in this regard. It isn't just habitat loss because of the building of human settlements and commercial enterprises which destroys the homes of wild species. It is also the destruction of habitat due to fires and the heating up of the environment which makes life on earth untenable for wild species.

I am convinced that when you combine habitat loss and climate change, both of which are caused by people, you have to conclude that the greatest threat to Australia's wildlife is Australians.

Having come to that conclusion I'll add a few details about this report. They say that the problem of invasive species is costing Australia AU$25 billion annually. They argue that more than 80% of nationally listed threatened plants, animals and habitats are affected by alien species. They want urgent development of new technologies to eradicate and prevent invasive pests.

They think it's important to get on top of the problem now. Yet they've been struggling with this problem for decades it seems to me. Every 6-12 months they come up with a new toy which is designed to poison as many animals as possible using 1080 poison which is very painful. They don't care if the animals die a painful death or not. It's irrelevant in their equation.

Australians need to look themselves in the mirror and do much more themselves to help save their precious native species. The most vulnerable are small mammals living in the brush and undergrowth. Billions of animals were killed by the recent devastating forest fires which it is believed were caused by climate change or at least the extent of the fires was greatly exaggerated by climate change.

Do hungry domestic cats hunt more than well fed ones?

There is or was a belief that a domestic cat's desire to hunt is divorced from his hunger or lack of it. In other words whether a cat is well fed or not does not affect his desire to hunt prey animals as the desire or motivation to hunt in innate. It is instinctive and the feline will always do it when the prey is available.

This article refers to a study on cat food ingredients and hunting desire but before you read that it has to be common sense that a hungry cat will be a more committed hunter for the simple reason they need to eat to survive. They will kill and eat what they need to survive.

And on the other side of the coin a well-fed cat is less likely to hunt provided the food is balanced and contains all the nutrients but a fed cat will still hunt instinctively with the caveat that each cat has their own desire to hunt. Some cats just don't want to do it. I lived with a female cat who was disinterested for instance.

High quality wet cat food which is grain-free plus play will curb your cat's desire to hunt. Graphic provided by the scientist conducting the study. 

There is no doubt that there is some truth in this but a recent study  might be considered to undermine the theory or perhaps it supports the theory? The scientists found that complete diet cat food as described i.e. wet cat food which is considered by the manufacturers to totally complete, might not be quite so complete as expected as it might be omitting some micronutrients (unspecified). Domestic cats instinctively sense this and hunt mice to make up the deficit.

The scientists decided this because when they fed cats grain-free wet cat food their hunting behaviour diminished by 36 percent. Playing with your cat can reduce hunting by 25 percent.

Martina Cecchetti, a PhD student also of Exeter University who conducted the trial said: 

"Some cat foods contain protein from plant sources and it is possible these foods leave some cats deficient in one or more micronutrients, prompting them to hunt."

So there is some potential deficiency in 'complete cat food' which contains grain. Perhaps the presence of the grain in some of these foods triggers a message in the brain of cats to tell them that the food is not quite up to scratch and drives them to hunt for the real thing: a small rodent, their preferred prey animal.

Play also helps to deter feline hunting. This indicates that when a cat has hunted he pauses because he has satisfied his desire to hunt. This is the likely conclusion because playing with a domestic cat is a hunting substitute for the cat. All cat play is play-hunting.

Most cat owners who allow their cats free access to the outside would wish to curb their cat's hunting. Some find it disgusting, others accept it but dislike it. Here are two things that can be done to curb it. Select grain-free wet cat food and play with your cat a lot more.

Click here to read the study.

Australian scientist claims that diseases transmitted by cats to people cost the Australian economy AU$6 billion annually

I find this extraordinary. Unfortunately I don't have access to the full article by Donna Lu on the newscientist.com website because you have to subscribe to the site and I don't want to do that (but see update below please). But the opening paragraphs state that diseases transmitted by the domestic cat to people, including cat scratch disease, cost the Australian economy more than AU$6 billion per year (4.2 US dollars). The costings are based upon the impact on human health and livestock production. Clearly they are inferring that domestic cat spread disease to livestock as well or is it that people are incapacitated and therefore can't farm? They may be referring to toxoplasmosis. No doubt they are because this disease always comes up in these sorts of discussions. The author emphasises cat scratch disease and bites.

Prof Sarah Legge. Photo: Australian National University.

Well, there you are. I will have to speculate as to how they have calculated this cost. But they must be saying is that cat owners and non-cat owners are being bitten or scratched by domestic and stray cats which removes them from the workplace for a day or two while they recover. Or perhaps they go to hospital but this is normally extremely rare.

99% of cat bites and scratches do pretty well nothing in terms of interfering with one's day-to-day living. That's my personal experience. Toxoplasmosis is almost always asymptomatic in people i.e. no symptoms. Cat scratch disease is rare in people. Certainly, cats can cause it but I would speculate that one in 500 or 1000 scratches results in cat scratch disease. It needs to be treated. Bites are not uncommon but most often are irritations more than injuries that need to be dealt with immediately. That said when bitten by a cat you have to be vigilant and watch the area where you were bitten. As soon as it looks as if it's becoming infected you must take antibiotics as prescribed by a doctor to ensure that they are the right antibiotics. This is an absolute must as stated. Because if you let an infection caused by a cat bite get worse it can cause a serious injury and it can lead to hospitalisation.

Zoonotic diseases transmitted by cats to people are on the whole pretty rare and therefore have difficulty in understanding how they arrive at a AU$6 billion cost.

Update

I have found an article on a Chinese website which discusses the research by Prof Sarah Legge of the Australian National University and the University of Queensland. She argues that annually over 500 people die in Australia and there are 11,000 hospitalisations due do diseases transmitted by cats to people. The costs include medical treatment, reasonable relevant expenses, lost income et cetera.

She refers to toxoplasmosis as mentioned, roundworm and cat scratch disease. Of these toxoplasmosis has the biggest negative impact on the Australian economy. She claims that it has possible long-term effects on behaviour and mental health. Note, the word "possible". She doesn't know and therefore how can she make calculations on the back of it.

She claims that the parasite that causes toxoplasmosis causes 200 deaths and 6,500 hospitalisations due to car accidents which could be avoided in Australia annually. She believes that the disease causes mental health disorders which I presume are translated into poor driving! She claims that one in five cases of schizophrenia and one in 10 cases of suicide were caused by toxoplasmosis. She wants domestic cats to be kept indoors all the time in Australia and for people to wash their hands thoroughly after handling cat litter or gardening. This is to stop transmission of toxoplasma gondii oocysts in the soil or faeces in the litter tray to the hands and from the hands to the mouth and therefore ingested.

She also claims that feral cats around towns are a reservoir for disease.

Human behavior

We have to discuss human behaviour in this equation. Most cases of toxoplasmosis are caused by mishandling of raw foods in the kitchen. That's due to careless human behaviour. Being scratched or bitten by cat is often put down to careless human behaviour. Contracting toxoplasmosis through mishandling of cat litter or when gardening, once again, can be put down at least in part two careless human behaviour. Therefore this vast economic loss to the economy in Australia as stated is in large part due to human behaviour. It is unreasonable to blame the cat exclusively as this professor is.