Wildlife TV

Learn interesting and funny plant and animal facts with videos and photos

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!




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!


Collecting Urine For Conservation

They may not be the most famous or iconic African animals (they’re not one of the ‘Big 5’, for example) but they have a place in the heart of many safari-goers; the African Wild Dog (Lycaon pictus), or ‘painted dog‘, is a fascinating, beautiful and (sadly) endangered animal.

African Wild Dog (Lycaon pictus)

The African Wild Dog (Lycaon pictus) is a beautiful and unique animal, but it is becoming increasingly endangered. Photo Credits.

Wild dog numbers are dwindling in the wild for a number of complex reasons, but work is under way to help conserve the remaining population and hopefully help them prosper for future generations: recent research efforts have shown that the secret to their salvation may be found in their urine! But why are wild dogs in so much trouble? The reason, almost invariably, is because of conflict with humans. Human farmers do not enjoy sharing land with dogs that hunt and kill their livestock.

African wild dogs are exceptional hunters, perhaps some of the most successful hunters in the animal kingdom. Packs of wild dogs cooperate extremely effectively to coordinate bringing down prey that is often much larger and stronger than themselves and their hunts end in a successful kill 80% of the time. Most predators are very lucky if they can succeed in a hunt half of the time. The effective team-working approach to hunting means that individual wild dogs do not have to be strong and powerful which means that if they come into conflict with a competing predator, such as a lion or spotted hyena, they are unable to put up a fight. Indeed, in the wild, lions and hyenas will drive wild dogs off of their kills and steal it for themselves. Wild dogs are also not particularly fearsome creatures; their peculiar social system is based on submission and non-aggression (for example, in the pack, individuals will never fight over food, but rather compete with begging).

In order to ensure that they don’t end up on the wrong end of a lion, wild dogs hunt over huge areas of land, which helps lower the chances that they’ll run into any competition. Unfortunately, huge, open, wild spaces are becoming more and more rare in Africa and wild dogs are feeling the squeeze, in fact, almost all the nature reserves in Africa are too small to sustain a decently sized pack of wild dogs. One quirk that wild dogs possess is that fences cannot contain them; they are notoriously clever in finding a weakness in a fence and getting through it, and they certainly have reason to.

Wild Dog Pack with a Wildebeest

Wild Dogs are extraordinarily effective hunters, able to bring down prey much larger than themselves, however, they are very social and do not show aggression to each other (most of the time). Photo Credits.

The problem arises when wild dogs break free of their wildlife reserves and go out hunting in the human world beyond, often killing farmers’ livestock. Local farmers have resorted to extreme measures in protecting their livelihoods, often resorting to extermination, including poisoning whole packs of wild dog. Diseases spreading from domestic dogs into the wild has also resulted in wild dog deaths and this, combined with severe habitat loss, is threatening the very existence of the animal. Last century there could have been as many as 500,000 individuals throughout Africa, but now their numbers are down to around 5000; only 1% of the former population. In a previous post, we saw how there are only a handful of individuals remaining in South Africa.

Thankfully, work is under way to save the wild dog. Craig Jackson, a wild dog researcher, has recently completed a thesis on wild dog territorial behaviour for the Norwegian University of Science and Technology, and it seems he might have discovered a key for the conservation of wild dogs. Packs of wild dog hunt in clearly defined territories (that ignore human fences) and these territories are marked by the spraying of urine. The dogs are very respectful of these territorial borders and will rarely cross over into a neighbour’s turf. Jackson found that by collecting the sand onto which they sprayed urine, he could relocate it and create ‘fake’ borders and the dogs were fooled; they respected the transplanted urine trails as if another pack had sprayed them.

Urine collection might seem like an unlikely form of conservation, but strategically placing urine trails around wild dog packs will be much more effective than erecting fences and it will keep wild dogs out of danger from rival predators and disgruntled farmers. Unfortunately, the process of following dogs around and collecting their urine is very time consuming and labour intensive, so the challenge is set to try and synthesis a chemical that replicates wild dog urine and mass produce it. Pioneering wild dog researcher and conservationist John ‘Tico’ McNutt is on the case and is currently experimenting with a range of options.

Hopefully, if this new idea can be implemented, we might see a decline in unnecessary wild dog deaths and we might be able to save the species from extinction. It would be a tragedy to see such a peculiar and fascinating animal disappear, but, with the right science it might not be the case.

Much love,