Occasionally you will see stories about cats trapped in walls or other places for weeks at time and be able to survive. Humans can only manage around 3 days or so without water, how can cats go for so long without water?
Before anyone claims that your premise is completely false, I know that it is true at least to some degree. A very screwed up male friend had an apartment and his one companion was his female cat. He came home one day to find that workmen had come in to do some repairs on a wall and his cat was no where to be found. Obviously, the bastards let her out accidentally. He posted flyers and scoured the neighborhood for a week getting more and more upset. On day 7, he heard a faint noise in the wall at got so distraught that he just took a hammer and destroyed part of it. There she was. She climbed in while they were doing work, hid, and then got sealed in.
This isn’t really a second-hand story because I was there while the search went on and knew right away after she was found again.
I’ve heard several similar stories about cats getting trapped in drywall - every couple of years you hear something like that.
A WAG - they’re desert animals, originally.
Better at concentrating their urine before dumping it into the bladder, in part. They cannot reabsorb fluid from the bladder (IIRC only chelonians, turtles, can), but they may have more nephrons (functional units of the kidney) adapted and better able to concentrate and absorb as much fluid as they can. IIRC, they’re better than dogs (and both of them are better than herbivores) in concentrating their urine.
As for why, they’re better at doing without water:
When my ex-wife’s cat got stuck in a wall for the better part of a week, it was eventually lured out with food. The vet told my ex- that as descendants of desert animals they could survive longer in emergencies than other types of pets without water.
Interesting. I’ve known a few cats that have had kidney problems, and wondered before if they were more susceptible to kidney issues than other animals.
Sounds like the extra concentrating could be related: