If it goes outside at all ... it doesn't.

We had a cat that didn't eat cat food from May until October, we didn't assume it was a breatharian during that time.

When our cat disappeared (we assume a fox or wolf got her) after almost a decade of this, the farmers to either side of us started having mice and rat problems again :-)

I'm not sure actually. In many videos, he offers it things like fish and chicken and wet cat food but that cat doesn't touch them. It does eat some dry kibbles - maybe that's enough? Now that I think about it, calling it "pure vegetarian" was my mistake because it does eat those kibbles which probably contain non-vegetarian nutrients.

Yes, dry kibble certainly contains meat (fish, poultry or even red meat).

also, unless it is an indoor only cat you cannot determine what it actually eats.

Probably eats mice/birds/etc. or the food of other cats when the owner isn't looking.

I've been told that the cats of a great-grandparent were only fed pastas...

I've always wondered how they could survive on that! But I suspect that since those cats lived mostly outside, they probably ate many other things, including small animals they caught in gardens, sheds, etc.

Can confirm, in rural southern Europe cats were (and still are were I live ATM) fed scraps and leftovers (if any); if they don't like that the fields outside are an excellent training ground for their primal instincts

And it's not just that cats have to eat meat to get nutrients they need. Their systems aren't able to process significant amounts of carbohydrates at all. A cat consuming more than a couple grams of carbs per day will develop kidney disease extremely quickly.

That seems too low a threshold - lots of cheap cat food (esp. chow/kibble) has much higher levels of carbs, and while I am sure they aren't great for cats, there also doesn't seem to be an epidemic of feline kidney failure...

Actually, there is. It's among the most common causes of death for domestic cats ([1] says the second most common). It's been what killed most of the cats I've ever known (notable exceptions being two that got hit by cars and the one who, no kidding, died of mercury poisoning after being fed nothing but canned tuna her entire life).

[1] http://skeptvet.com/Blog/2015/03/longevity-causes-of-death-i...

It seems plausible that those nutrients might be found in certain plants, and could be identified and concentrated. I wouldn't risk it with my cats, but plenty of people do feed their cats veggie kibble and I haven't heard of them dying of malnutrition in droves.

IIRC the nutrient that makes cats obligate carnivores is taurine. Although it can be found in seaweed, or synthesised in a lab, cats and water makes me think this is unlikely in nature. (That said, human edible != cat edible, don’t just feed seaweed to your cat without asking an expert).

https://www.ncbi.nlm.nih.gov/m/pubmed/28849526/

> IIRC the nutrient that makes cats obligate carnivores is taurine.

> That said, human edible != cat edible, don’t just feed seaweed to your cat without asking an expert

Or energy drinks.

My cat refuses to drink Monster, but insists on Red Bull Blueberry.

They are finicky creatures.

Stimulants — or drugs in general, legal or not — should definitely not be assumed safe on a different species.

(Also: not all energy drinks are vegetarian, so wouldn’t always solve the diet puzzle even if you confirmed it as safe).