Should Tom have defecated near Jerry?

A small brown mouse peers tentatively from its nest. As it emerges – confidence growing – a creak in the wooden floor beneath its paws betrays its presence.

The animal stops dead. Within a heart beat a gently slumbering feline has awoken and torn onto the scene, claws brandished and teeth shining through a growing grin. It’s all over. It must be. But hark, a plank of wood – at least 10 times its size – has been lifted aloft by the mouse and brought smashing down onto the head of its captor. So violent is the impact, the plank now has upon it an imprinted outline of the cats cranium. Jerry escapes to taunt another day, while around Tom’s head stars gather and bumps rise.

Bloodthirsty, barbaric and haunting; this is, for a whole generation of people, their first introduction to the predator/ prey relationship. Perhaps the most famous predator/prey relationship there is. Cats and mice; the former, of course, hunts the later.

Yet, even casual viewers will have noted that in the cartoon, the cat never wins. He is sharper of claw, pointier of teeth and more savage of temperament. So why then could the mouse afford the breezy air of a participant who knew he’d always win? We think we know, and from his indifference and apparent over confidence we think Jerry knew as well. Not once did Tom pass biological waste products.

Seriously…not once did urine or faeces make an appearance on any of the horrendously violent dioramas that unfolded before our innocent eyes. Not a sneaky stain or suspicious pile anywhere to be seen.

Would this really have tipped the balance? Most certainly, you see it turns out that in reality the ‘simple’ cat and mouse predator/prey relationship is by no means simple at all. Not content with a physical advantage, evolution has given the cat some rather incredible secret weapons which, frankly, give mice little chance. Recent work has shown that several complex factors – rooted in feline waste products – may cause mice to actually lose the best amour they have against their age-old foe…their fear.

Back in 2013 Wendy Ingram and colleagues at the University of California, Berkeley found that a known response to Toxoplasma gondii in mice might actually be more profound. When infected with the parasite, mice were known to exhibit a reduced aversion to cats – but Ingram found that even when the infection is cleared the reduced aversion to cats remained. It is if in some way the infection causes a permanent change to their brains rendering them putty in a playful cat’s paws. Or indeed dinner in a hungry cat’s jaws. How does this parasite get into a mouse in the first place? It is contracted from eating cat faeces.

Hmmm – so far so scatologically manipulative. But that isn’t all. In July of this year research was presented at the Society for Experimental Biology’s annual meeting in Prague suggesting cats also bring to bear anti-mouse weapons in their urine. A team from the AN Severtov Institute of Ecology and Evolution in Moscow, found that when baby mice are exposed to felinine – a chemical in cat urine – they are less likely to avoid the scent of cats later in life.

Now, ordinarily when smelling felinine, a mouse will become agitated with increased stress hormones. Not so, it seems, for young mice exposed at a critical moment in their development. The team exposed one-month-old mice to the chemical over two weeks. No prizes for guessing that when they were tested later for their reaction they were much less likely to flee the same scent.

And so there you have it, a complexity buried deep in biological relationships always underpins the seemingly simple exterior. With a blade sharpened to perfection by evolution, Nature is almost always more manipulative, brutal and surprising than fiction. Even cartoon fiction.

How different Tom and Jerry’s relationship might have been then if only Tom occasionally answered the call of nature. If he were allowed to bring to bear the full force of the pheromonic and parasitical weaponry at his disposal then perhaps the most famous relationship in all of children’s entertainment would have been even more gruesome.