Wildlife TV

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Why do people think that ostriches bury their heads in the sand?

You may have found yourself in an argument with someone who is refusing to see sense and listen to you. You may have found yourself saying that they have buried their head in the sand.

It is a common metaphor that is a part of our cultural vocabulary; we use when people are being ignorant of facts, refusing to acknowledge advice or in denial about their situation. It has been commonly used in this way for centuries, since Roman times. But what is the origin of the phrase? It comes from the ancient observations of the behaviour of animals, namely, ostriches. So, why do ostriches bury their heads in the sand? Well the answer is that they don’t.

It has long been believed that ostriches will bury their heads in the sand to avoid predators; that they are so stupid as to believe that by concealing their heads they become invisible to predators. However, the truth is that this is a myth; there has never been any observation of an ostrich burying its head and yet for centuries the idea has stuck with us. There are, however, many behaviours which ostriches perform that might have given rise to this curious myth.

Ostrich Head and Neck (Struthio camelus)

Ostriches (Struthio camelus) are strange and fascinating birds; is it really true that they bury their heads in sand? If not, why do so many people think so? Photo Credits.

The common ostrich (Struthio camelus) is the world’s largest bird (currently alive). It is found across large swathes of sub-Saharan Africa and, historically, North Africa and Arabia. The first recorded occurrence of a belief that they bury their heads comes from Gaius Plinius Secundus, also known as Pliny The Elder (AD 23 – AD 79) a Roman scholar who invented the idea of the encyclopedia. Pliny spent most of his time observing and recording natural phenomena, including the behaviour or wild animals. He was a great author and philosopher who wrote volumes of information about the natural world, however, not all of it turned out to be entirely accurate. So from where did he get his ideas about ostriches? There are several potential explanations.

Gaius Plinius Secundus (aka Pliny the Elder)

Gaius Plinius Secundus (aka Pliny the Elder) was a Roman scholar who wrote about ostriches hiding their heads to evade detection. He was a great naturalist and even invented encyclopedias, but he was wrong on this one issue. Photo Credits.

Ostriches are extremely fast runners. They have long powerful legs that can accelerate them to up to 70 kilometres per hour; clearing 4 or 5 meters in a single bound. Quite rightly, they use their tremendous speed as their first resort when faced with a threat, however, sometimes, they might be trapped or injured or otherwise unable to escape. When they are not able to run, ostriches will lie down as flat as possible, stretching their necks out flat against the ground. Their necks and heads, incidentally, are often the colour of their habitat’s terrain (sandy brown/grey) and so at a casual glance, only their bodies would be visible, perhaps leading to the assumption that they have buried the rest.

Ostriches are omnivorous, eating a wide variety of things, however, they mostly feed on low level vegetable matter such as roots and fallen seeds, as well as invertebrates such as crickets. They also practice geophagia; picking up stones and pebbles from the ground and swallowing them, keeping them in their gizzards to help grind up and digest food. As a result of this diet, ostriches have their heads down at ground level for large amounts of time. Perhaps this has been misinterpreted and has helped propagate the idea of burying their heads.

Male Ostrich (Struthio camelus) Feeding

Ostriches (Struthio camelus) find most of their food on the ground and so have their heads down often. This may have given rise to the idea that they even bury their heads. Photo Credits.

It has also been suggested that ostriches will lower their heads to ground level in order to scan the horizon for threats. They may simply also lower their heads to ground level to be less obvious to prowling predators when they feel nervous. But the idea that they believe that they can conceal themselves completely by hiding their head is unfounded. Pliny the Elder suggested that they also stuck their heads into bushes to achieve the same effect. This notion is born from the idea that ostriches are ‘stupid‘ animals because they have such tiny brains: Ostriches have brains smaller than their own eyeballs (although they do have the largest eyes of any land animal)! In reality, animal cognition is not as simple as saying that a small brain equals a stupid animal. However, their small heads may have contributed to the myth; when their heads are down at ground level, they are so small that they can be difficult to see, this optical illusion may have led people to believe the animals’ heads were in fact buried.

Ostrich Chick (Struthio camelus)

Adult ostriches (Struthio camelus) grow to be the largest birds on the planet, but the start life as very cute chicks! Photo Credits.

Ultimately we have seen that an ancient misconception has turned into a common metaphor for human behaviour and it has been hard to separate the popular myth from the scientific truth ever since. There are many reasons that might explain why Pliny the Elder first wrote about the idea, but ultimately, we may never know where it came from originally.

Much love,

-Nick

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Tom and Jerry: Fatal attraction or something else?

How many of us grew up watching Tom the cat and Jerry the mouse constantly fighting and teasing each other to our own amusement? This show created in 1940 has been a source of entertainment for millions of children worldwide for decades. It shows us the reality of the animosity between cats and mice, but how real is it?
Do cats and mice really hate each other? Do they fight? Do naughty mice track down, tease and get cats in trouble?
The answer to all these questions might be slightly different than you think.

Domestic cats and urban mice are natural enemies the same way that lions and zebras are. One is the predator and one is the prey and while the former does whatever it takes to track down and hunt the other, the latter would do all it can to avoid that fate. They don’t exactly hate or fight each other for their own entertainment, they just do what they need to do to in order to survive.

Tom the cat chasing Jerry the mouse. From Warner Bros

Tom and Jerry   © Warner Bros

So why does Jerry keep on trying to chase and annoy Tom? Wouldn’t he just leave him alone and try to be sneaky and quiet as a mouse to the best of his abilities as that would be the difference between survival and being a snack?
Scientifically speaking there is one very good explanation to why Jerry does this (apart from the fact that they are clearly just cartoons and not realistic interpretations of cat-mouse interactions).

There’s a very well known parasite called Toxoplasma gondii that is the source of one of the most feared diseases for pregnant women, toxoplasmosis. While in humans it can cause life long damage if passed from pregnant mother to fetus, in mice the consequences are quite different.

Mice have evolved a healthy avoidance of predators, especially cats, for millions of years. They can detect signs of the presence of felines and alter their behaviour in order to avoid crossing its path. If it wasn’t for this trait passed from generation to generation we wouldn’t have mice nowadays.

But this is nothing special. All living beings strive for survival and that doesn’t exclude the parasitic protozoan, Toxoplasma gondii. Our friend gondii, even though it is able to live inside almost any warm blooded animal, has a thing for cats. They live their lives either inside a cat or doing whatever they can to convince another animal to get inside one. Over millions of years of evolution they have perfected their technique.

 

This is a conversation I imagined went between gondii pals:

  • “Hey Steve have you seen Carlos recently? Ever since he met that cat he’s doing well in his life. He can even reproduce sexually now!”
  • “No way Andre! I thought we could only reproduce asexuality. I must try this cat technique. How does this cat thing work?”
  • “It seems that we need to get ourselves inside a cat’s stomach and once we’re there it’s like heaven or something. That’s what Carlos told me though but he tends to overreact, you know that.”
  • “I must try this anyway. The problem is that we are inside a mouse now and they hate cats. How can we make this work?”
  • “Hum.. I know it! Let’s just make this mouse think that cats’ smell is the best smell in the world. Instead of avoiding it, it must get so excited about it that it will do its best to find the cat. Once it finds it we know what happens.. the cat will just eat our host, the mouse, and we end up in the cat’s stomach just as planned!”
  • “Dude, you’re a genius. Let’s do this!”

 

And this is pretty much what happens (with some creativity from my part). Toxoplasma gondii is capable of permanently changing the mouse host’s behaviour for its own benefit. This parasite increases the activity of the limbic regions of the mouse’s brain to react to a cat’s urine with sexual attraction instead of fear, forcing the mouse to seek the sexy company of the cat instead of hiding and escaping it.

The funny thing is that studies even show that this fatal attraction doesn’t happen with other species, only between cats and mice. It takes a Tom and Jerry for this scene to happen and all the other normal behaviours, senses and general health of the mouse remain unaltered. They just seem to suddenly feel extremely attracted to sexy cats..

That would explain why Jerry is so obsessed with Tom; always trying to get him in trouble, tease him and being naughty in general. He’s just a mouse in love..

 

Jerry the mouse kissing Tom the cat. From Warner Bros

Tom and Jerry   © Warner Bros

That’s all folks!

~Sofia.

 

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Callithrix kuhlii, you are NOT the father!

As a little guilty pleasure of mine, sometimes I enjoy watching tv shows where there’s a dispute of paternity involved. You know what kind of shows I’m talking about: those where the host proclaims “Trevor, you are NOT the father” and within a split second the audience is shouting, howling and/or clapping and the presumable “father” is doing something that resembles Dr. Zoiberg’s happy dance.


But how do paternity tests work?

The entire premise is quite simple; the man will provide a sample of his DNA by swabbing the inside of his cheek to collect epithelial cells and his genetic information will be compared to the one from the child. If they are around 50% similar to each other then the laboratory can attest that both parties are related.

When babies are formed they get 50% of the nucleic DNA from each parent to achieve the 100% they need to develop properly so if baby Trevor Jr. doesn’t have close to a 50% match of his DNA with Trevor Sr. then we can assume that they are not related.

However, what if I told you that there is a species in which the male that mated with the female and produced the baby was not the father? Even better, his brother (the baby’s uncle) is the father even though he never even met the mother!
This is so crazy but I can assure it’s true!

And if you are thinking that it must be some barely known species of fish or invertebrate you couldn’t be more wrong. It’s a small New World monkey, the Wied’s marmoset (Callithrix kuhlii) that lives in the tropical forests of Brazil.

A shy Wied's Marmoset (Callithrix kuhlii) hides behind a tree branch

A shy Wied’s Marmoset (Callithrix kuhlii) hides behind a tree branch.
Photo Credit


How is this possible?

The reason is simple; you see, in nature there are some very special individuals that have more than one DNA set. These individuals are called “chimeras”. The name came from the Greek mythology where the chimera was a creature that was made up of parts of several others animals.
While in Greek mythology chimeras looked quite crazy with part lion, part snake and part deer (or other variations), the real life chimeras existing on our planet are less easy to spot but equality exciting and the Wied’s marmoset is a great example of it.

These South American small monkeys are very well known for almost always giving birth to fraternal twins. As embryos in the womb of their mother, the twins’ placentas get fused together from an early stage in the development thus allowing stem cells the freedom to be transferred between both siblings. These stem cells are the ones that will eventually set up groups of cells and developing specific parts of the body.


So now follow me in this situation:

  • Marmoset A(ndre) and B(runo) are twin brothers and both chimera (as in, they both have sets of DNA from their twin brother).
  • Because of them being chimeras, when they were born, Andre ended up with his DNA in most parts of his body (such as the brain, muscles, liver, etc) but his testicles developed using Bruno’s DNA that got transferred through stem cells while they were in the womb.
  • This means that when Andre’s testicles produce sperm, the genetic information contained in this sperm will in fact be Bruno’s DNA.
  • Andre and Bruno were living in a Zoo and before they reached maturity, Bruno got transferred and Andre stayed behind.
  • Eventually they both reached sexual maturity and Andre got a female (C)arla pregnant.
  • When the babies were born the Zoo wanted to check out who the father was and tested the babies.
  • Because Andre’s testicles were producing sperm with Bruno’s DNA, their dad, Andre was technically and genetically not the dad.
  • This is how Bruno managed to father some babies even though he never even met Carla!


Nature can be so complex and crazy that sometimes I wonder if I’m reading a scientific article or watching a Mexican soap opera.

In case you want to know more about this very interesting topic feel free to read the (very detailed) article published by the Proceedings of the National Academy of Sciences.


Até à próxima!
~Sofia.


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