Tag Archives: Plos One

Why Do Zebras Have Stripes?

Quite why zebras have stripes is a question that has long fascinated scientists. Theories abound including the obvious one that they provide the animal some form of camouflage against their natural predators. However, the fly in this particular ointment is that it isn’t particularly effective. Zebras are the prey of choice of lions and other large predators and they seem to get through their fair share of the ungulates, camouflage or no.

It was in the 1930s that the idea of stripes having something to do with controlling the number of flies that land on and bite zebras gained some traction. After all, they live in parts of the world where flies carry deadly disease and where the constant draining of blood can affect the animals’ general well-being. A big step forward was made in 2014 when Tim Caro of the University of California and his colleagues published the results of their research in the journal, Nature Communications in a paper entitled The function of zebra stripes. I will shut my eyes to the fact it was published on April 1st.

They looked at various species of zebras, horses and asses, and sub-species, trying to establish whether the ecology of the area in which they lived had any influence on their propensity to have stripes. The scientists found that where there was a preponderance of inimical insects, particularly the tsetse flies, the equids were more likely to have stripes. Moreover, those areas of the body most vulnerable to attack generally had a greater density of stripes.        

These findings lent some credence to the theory that the zebra’s stripes may have evolved to ward off biting flies. But how? After all, an insect wouldn’t be able to distinguish between a striped animal and a plain one until it was close by. Some further field research was needed to put some flesh on these theoretical bones.

The indefatigable Tim Caro and his team took up the challenge by examining the behaviour of tabanids, horse flies to you and me, on striped zebras and plain horses on a farm in Britain. Their results, published in the journal, Plos One, on February 20, 2019 in an article entitled Benefits of zebra stripes: Behaviour of tabanid flies around zebras and horses, revealed that fewer flies landed on the zebras than the horses although there was no noticeable difference in the number buzzing around them. Interestingly, flies seemed to be surprised to encounter stripes, they were British, after all, and either veered off or were so discombobulated that they were unable to land on the animal’s skin.  

Their research was followed up by a series of ingenious experiments conducted by a team of Japanese scientists, led by Tomoki Kojima. In a paper intriguingly entitled Cows painted with zebra-like striping can avoid biting fly attack, published in Plos One on October 3, 2019, they revealed that they took six pregnant Japanese black cows, painting on two of them white stripes some 4 to 5 centimetres wide. Two they painted black and the other two were left as nature intended them.

The process was repeated twice more so that each cow spent three days striped, painted black or unpainted. The scientists also took high-resolution photographs of the cows at different times of the day, the more easily to count the number of insects that had landed on them. They were also interested to see whether the animals exhibited any behavioural traits suggestive of being bothered by insects, such as flicking their tails or stamping their feet.

When the results were analysed, the scientists found that only 55 flies visited the cows with white stripes, compared with 111 on the black-painted cows and 128 on the plain ones. Behaviours designed to repel flies were deployed less frequently by the white-striped cows than the others, 40 times every thirty minutes compared with 53 and 54 respectively.  

The stripes were not completely fool proof as the ersatz zebras were bitten, perhaps because the flies use other senses such as smell to locate their victims, but the implication is that stripes do have some deterrent effect on flies. Clearly, more research is needed and an efficient way of striping cattle has to be found. It took the scientists around five minutes to paint the stripes on each cow, so it may be some time before we see farmers deploy this technique to give their animals a modicum of respite when flies are at their most active.  

But I will tell you one thing. Since I bought a zebra onesie, there have been no flies on me!

Motivated By Curiosity And A Desire For The Truth – Part Thirty Three

Do woodpeckers suffer brain damage?

One of the distinctive sounds to be heard in the garden of Blogger Towers is the drilling of a woodpecker as it tries to dislodge insects from within the bark of one of the nearby trees. It has always struck me that there must be easier ways for them to get their food. After all, each time they strike the tree their beaks and head undergo forces of between 1,200 and 1,400 G, over fourteen times the force that would give a human concussion.

According to the ever popular journal Plos One, a team of scientists, led by Peter Cummings, from Boston University School of Medicine, carried out some research into the brains of woodpeckers, using exhibits from the Field Museum and Harvard Museum of Natural History. The tell-tale sign for brain damage, in human brains at least, is the build-up of tau protein around our axons. Normally, tau protein wraps around the axons, giving them protection and stability while preserving their flexibility. Too much of it, though, disrupts the ability of the neurons to communicate, causing no end of problems with some of the brain’s functions relating to our emotions, cognitive powers and our ability to move.

In what is thought to have been the first detailed examination of woodpecker brains, the little grey cells were removed from a number of exhibits and the amount of tau protein was compared with that to be found in the brains of Red-winged Blackbirds. Now, of course, the woodpeckers in question may have been particularly stupid, having allowed themselves to be caught and end up in a museum’s glass case, but the researchers found that there was considerably more tau protein in their brains than in the blackbirds.

Is this indicative of brain damage?

Frustratingly, the researchers are not prepared to commit; all Cummings was prepared to say was “We can’t say that these woodpeckers definitely sustained brain injuries, but there is extra tau present in the woodpecker brain.” It is dangerous to assume that what is good for humans must also be the case for other forms of animal life so a bit more research is needed, I guess.

Empirically, though, as woodpeckers have been around for 25 million years and nature evolves – a controversial contention, I know – you would think that they would have developed mechanisms to prevent injurious damage to their bodies. And it seems they have. Researchers have previously established that woodpeckers have particularly thick neck muscles which serve to diffuse the blow when their beak strikes the wood. They also have a third inner eyelid which prevents their eyeballs from popping out.

In 2012 scientists from Beijing’s Beihang University and the Wuhan University of Technology carried out a more detailed examination of the thick bone that surrounds and cushions the woodpecker’s brain, details of which were reported in Science China Life Sciences. It appears that their brains are surrounded by a spongy bone plate made of tiny beams or rods called trabeculae. This provides a protective layer around the brain. Similarly, their beaks contain these same trabeculae. It is thought that the beak deforms during impact, absorbing the impact rather than sending it onwards towards the brain.

So the answer is probably no. Makes sense, I suppose.

If you enjoyed this, why not try Fifty Curious Questions by Martin Fone which is now available via www.martinfone.com

Motivated By Curiosity And A Desire For The Truth – Part Nine


Life is full of seemingly random events which individually don’t seem to make sense but when linked with other random events paint an interesting picture. Take being bitten by a moggy and depression. Thank heavens there are scientists who are prepared to investigate disparate bits of data in the hope of making sense of a bigger picture. Quite why DA Hanauer, N Ramakrishnan and LS Seyfried chose to investigate the linkage between cat bites and depression is anyone’s guess but their findings, published in the ever popular PLOS One journal, are fascinating nonetheless.

Their starting point was the 1.3 million odd electronic health records held by the University of Michigan Health system, dating back to 1998. They isolated the records of some 117,000 patients over the age of 18 whose records showed one of the 26 codes allocated to describe depression. Then they identified the records of all patients over the age of 18 whose records recorded some form of non-venomous animal bites or injuries.

When the researchers correlated the datasets they came up with some astonishing results. 41.3% of patients who had been bitten by cats had also been diagnosed with depression and some 28.7% who had been bitten by pooches had also suffered from the blues. Moreover, 85.5% of those patients who had suffered both a cat bite and depression were women compared with 64.5% who had both been bitten by a dog and were diagnosed as being medically depressed.

If a woman had sustained a bite from a moggy serious enough to trouble the medics there was a 47% of her being diagnosed with depression at some point in her life. There was a 24.2% chance of a man being diagnosed with depression if he had at some point been bitten by a cat. Interestingly, the probability of a depression diagnosis reduced to 35.8% in women if they had been bitten by a dog. The corresponding probability for men was 21.1%.

The study also showed that the majority of the bites inflicted on patients were from the patient’s own moggy. Being bitten by a stray or feral cat was least common although there was a very high incidence of depression amongst women who had been bitten by strays.

What to make of all this? Well, the report draws no firm conclusions save to make a desperate pitch for more funding with the throw-away comment, “while no causative link is known to explain this association, there is growing evidence to suggest that the relationship between cats and human mental illness, such as depression, warrants further investigation”. Quite.

I suppose there are two ways to look at this. If the moggy that you have lavished lots of love and attention on – not to mention money on those expensive vet’s bills and treats – turns round and bites you, you are going to be pretty peed off. For those of a sensitive disposition this might just be enough to tip you over the edge. On the other hand, cats are predators and all predators seek out the weakest amongst their prey – it saves a lot of trouble and effort in the long run. Perhaps the moggy is using some innate hunting instinct to recognise that their owner has some form of vulnerability and pounces. Makes some kind of sense, I suppose.

Best to play safe, though. Preserve your sanity by giving your cat the order of the boot.

Isn’t science wonderful?!

If you enjoyed this why not check out Fifty Curious Questions by Martin Fone. Available now. Just follow any of the links




A New Day Yesterday – Part Four


More news from the pre-tirement frontline.

I have to admit I’m settling down very comfortably into the new routine of only working four days a week – soon to be three – and am finding that I have more than enough to keep me occupied. I’m one of the lucky ones, I know, being sufficiently well-off to make my own decision as to when to head off into the sunset.

What doesn’t help, though, when you have got your head round the idea of no longer being a 9 to 5 wage slave, is reading reports in my favourite medical journal, Plos One, that researchers from Stony Brook University and the International Institute for Applied Systems Analysis in Austria (funded by the European Research Council (natch) otherwise it might have been Stoney Broke) that middle age begins at 60.

On the one hand, that’s good news. After all, having a ticket to freedom at the onset of middle age means many more years to enjoy myself when I can enjoy the qualitative aspects of life, not just the quantitative. But on the other hand, there is this guilt thing going on – have I thrown in the towel too soon and what if I live so long that my financial resources run dry? And this kind of research isn’t helpful in these times of pressures on public funding. Budget slashers will seize on this sort of thing to move the holy grails that keep us over-sixties focused, such as free bus passes, heating allowances and a state pension, further into the distance.

The crux of this research is the argument that those who are described as having reached old age and of being elderly should be those who only have a few years left to live. At the moment the average life expectancy in the UK is 79 for chaps and 82 for chapesses and there are signs that life expectancy is increasing significantly. Figures produced by the Office of National Statistics suggest that death rates amongst the over 65s are falling and that a newborn baby boy born in London can expect to live 6.7 years longer than if it was born 20 years ago. So it makes sense, intuitively, that the start of old age should be further down the chronological spectrum.

But there is the body and mind thing going on. I find the mind is embracing the new definition of middle age more eagerly and quickly than the body. I want to do things and, physically, I find I can still do them – it just takes longer to recover. It is that mix of the physical and the mental that the statistical analysis doesn’t take account of.

Still, the phone has begun ringing and intriguing e-mails have started coming in suggesting that some people somewhere think I may have something still to contribute should I care to. The good thing is that it would be on my terms. But it has left me wondering whether I am perceived as having some skills which are only needed from time to time but when they are, they command a premium.

Take safe-cracking. The inexorable march towards a cashless society has meant that the old-fashioned bank hold-up or safe job is pretty much a thing of the past. And so when one is being planned, those with the necessary skills are thin on the ground. The fascinating thing about the Hatton Garden jewellery heist (and as matters are sub-judicial I have to be careful here) is the age of some of the alleged suspects. Three who have had their collar felt were in their seventies but they may well have plugged a skills gap. Having watched a reconstruction of the raid which involved abseiling down a lift shaft, I’m sure it was a mind over body decision to get involved and I bet they ached the next day!

Pumpkins are doing well and are now outside in their grow bags. Each transplanting has engendered a level of anxiety I have not experienced for some time. I remain in hope.

The Meaning Of Life – Part Thirty Six Of Forty Two


Why do knuckles crack?

I have to admit it but one of the most irritating things someone can do in my presence is crack their knuckles. I long for the moment – it will be delicious when it arrives – when they have dislocated one or more of their digits in the process. Until then, I will just have to grin and bear it.

A recent exhibition of knuckle cracking in my proximity led me to wonder why this happens and why, alas, the perpetrator is able to put them back without any apparent harm. I was astonished to find, reading a report in the ever popular journal, Plos One, that whilst the phenomenon was acknowledged, the cause had not been the subject of detailed scientific investigation until a team of Canadian scientists from the University of Alberta under the leadership of Professor Greg Kawchuk cracked their grey cells on the matter.

It was back in 1938 that Nordheim, a German physician, demonstrated that most joints in healthy people can be made to pop when pulled – research, I’m sure, the Gestapo made good use of. The why, he never addressed.

In 1947 a couple of doctors at St Thomas’ Hospital in London conducted their own research into the knotty problem. They found volunteers – there is always one – tied a cord round their fingers and told them to tug until the joint popped. The docs captured what happened on a series of X-ray images and concluded that a tension of around 7 kilogrammes was required to make the bones in the knuckle separate by about half a centimetre.

As to why, they thought that the crack sounded when the joint surfaces were wrenched apart, causing a sudden drop in pressure in the synovial fluid around the joint and the formation of a bubble. Gratifyingly, once cracked, the same knuckle wouldn’t crack again for around 20 minutes.

For anyone who cared about such things this was the commonly accepted explanation until, in 1971, scientists from Leeds University repeated the St Thomas experiments and concluded that the crack came from the swift collapse of the bubble, not its formation.

And there matters stood until the Canadian scientists came along and videoed, using a MRI scanner, what exactly happened internally when knuckles were cracked. They discovered that every crack occurred precisely when the joints suddenly separated and a gas-filled pocket appeared in the synovial fluid which lubricates the joint. As the pressure in the fluid drops, the bubble comes from the gas in the fluid. The natural reaction of the joint is to resist the pulling but at some point, probably when the tension is some 7 kilogrammes, it will suddenly give way with a crack.

So, it seems that the London doctors were right and one of life’s many little mysteries has been solved. Rather desperately in trying to find an application for this discovery, rather than just glorying in putting a thorny problem to rest, Kawchuk suggests that the regular monitoring of the ability of those who can crack their knuckles will give a clue as to the health of the joints. Get out of here!

So now we know!