Why do...

Dogs eat grass?

The other day Nona the Wonder Dog was mooching about eating grass. She'd sniff and sniff, tracking back and forth across patches of seemingly identical grass, then having found what she was looking for, tear up a mouthful of greenery, chew it with slobbery delight, and swallow it down.

A little while later she'd throw it up, give it a good sniff, roll in it, then begin the process anew.

Yesterday she was dragging her butt across the ground, which made me say, "shit, she's got worms." Worm pills cost $40 a pop, so I am not a big fan of worms. Though to be fair, parasites gotta make a living too.

Then I noticed that she had a long stem sticking out of her backside. I know that's icky, but so what?

"C'mere," I said, and she wiggled on over to be examined. I grabbed the stem and pulled it out. No, I did not don hazmat gear, nor did I glove up. What I extracted from her colon was a completely (more or less) intact western salsify stem and flower.

Yeah, yeah, yeah. I get it. Icky. Butt (see what I did there? Cue sophomoric giggle) pretty cool if you beat the icky cooties into submission and think it through.

Dogs have a very simple gut compared to humans. It's a carnivore gut, optimized to extract nutrients from flesh and bone and sinew.

So the same gut that can break down big chunks of bone can also leave a stemmed flower intact.

Why is that?

Most likely it's because the canine gut isn't designed to handle plant material, and is probably designed to quickly evict such material if it happens to be ingested.

That's my working hypothesis.

So if dogs are carnivores, why do they eat grass (and flowers)?

You often hear that they do it to purge their gut, and that's certainly a possibility. But it's only a possibility. It's just as likely that grass and other plants contain micronutrients which the dog gut can extract and put to use.

There's a bit of an important lesson about understanding nature here. Sorry to be pedantic, but there's no way to know for certain why dogs eat grass. We could do a big study, analyzing dog guts and plant nutrients, and probably come up with a solid theory matching nutrient to need, and say that we have a good idea about why dogs sometimes hit the salad bar.

But we won't know for sure. We're not dogs, we can't get into their minds, let alone understand their canine drives and thoughts and ideas. We can match things up and find interesting correlations, and with enough rigorous study gain a very good understanding of dog physiology and nutrition and metabolism.

This has been done many times. You can look it up.

But you will never find anything more than a theory (or set of theories) regarding the consumption of plant matter by canines.

As it turns out, we humans are not omniscient. That's a good thing to keep in mind.