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.

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.