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.

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..

That’s all folks!

~Sofia.

Posted in Articles, Behaviour, Mammals, Microorganisms

Tags: cartoons, cat, cats and mice, microorganisms, mouse, nature, research, science, tom & jerry, tom and jerry, toxoplasma gondii, toxoplasmosis, Warner Bros