If you have a cat — and I’m thinking at least, what, 2 or 3 Daily Kos users have cats, right? — you know what happens when they get a hold of a toy with catnip in it. They don’t just act happy; they rub their faces on it, they grab it with their front paws and kick it with their hind legs, they lick it, they roll on it, and so forth.
It seems strange that smelling this one particular plant should have such an effect on them. Did they evolve this for some reason, or is it just an accident, a coincidence? And if they did, how on Earth does it help them? How does flopping around on your belly in the wild help you survive or procreate?
Now researchers in Japan and the UK, led by Masao Miyazaki, have explained what they believe to be the solution, in Science Advances on January 20. Even your cat can be forgiven for missing this article, as there were a few other things going on that day.
Most of us with cats don’t get to see them interact with whole catnip plants, but when they do, the response is very similar. They like to rub their faces on it and chew on it...
And if they catch a whole bush, as their ancestors would have in the wild, they will get on top of it and roll on it…
So they are more than merely attracted to it; their specific reactions are conducive to a lot of contact with the plant, and that seems to be the important part.
Many big cats will do the same things; here is a leopard who’s been given a handful of dried catnip:
The catnip plant looks like this, and you can certainly order seeds and plant it in your yard:
There are a few other plants that also have this effect on cats, such as silver vine:
It’s been known for a while that the active ingredient (as far as cats are concerned) in catnip is nepetalactone. Miyazaki and coworkers found that the active ingredient in silver vine is the very similar nepetalactol.
These compounds belong to the same family of plant-made chemicals that includes menthol (mint flavor), limonene (orange zest flavor), pinene (essentially turpentine), and lots of other flavor and fragrance compounds.
It’s also been known for a while that nepetalactone has insect repellent activity, but that isn’t shocking: Almost all plants make chemicals of some sort that protect them from pests. After all, plants can’t run away or roll up a newspaper. So, while cats’ behavior around these plants may not be easy to understand, it’s pretty clear why catnip and silver vine evolved these things:
Most likely, the adaptive function of nepetalactones in Nepeta is to protect against herbivorous insects, not to stimulate cats; notably, nepetalactones can repel insects with efficiencies comparable to the synthetic repellent N,N-diethyl-meta-toluamide (DEET).
After demonstrating that nepetalactol triggers the opioid response in cats — in other words, the HOW — they then endeavored to find out the WHY.
First, they put small amounts of nepetalactol into a little side room adjacent to a cage with lots of mosquitoes in it. Two milligrams was enough to keep almost all the mosquitoes out. But the control, with only the solvent that the nepetalactol was dissolved in, had no repellent effect at all.
Next, they demonstrated that even 200 micrograms of nepetalactol on a piece of paper was enough for cats to notice, rub their faces on, and by doing so transfer a detectable amount onto their faces and heads.
But then finally, the REAL test: Would cats that had been given silver vine leaves to face-rub against actually be protected from disease-carrying mosquitoes? The answer was YES. The number of mosquitoes landing on the heads of cats who had face-rubbed silver vine leaves was cut in half, with 98% statistical confidence.
So you can just imagine what rolling in a whole catnip bush will do for you. Cat bug spray! I am totally trying this before my next hike in the spring. The neighbors already think I’m weird.
Miyazaki and company conclude:
The rubbing and rolling response transfers nepetalactol from the plant leaves onto the cat’s face and head where it acts as a mosquito repellent, finally revealing the likely biological significance of this enigmatic feline behavior, first [recorded] more than 300 years ago.
So the next time your cat rolls around on a catnip toy, he’s not just being a goofball. He’s showing you what his ancestors did in the wild, millions of years ago.