Dogs find enough sustenance from eating their own poo.
I don't think that's literally true.
Your comment reminds of the time I interviewed someone for a sales position in our small engineering services company. The candidate said that he had previously worked for Terminix, and he was the only salesman there who had become certified as an exterminator to better know his product.
He added, "Did you know that cockroaches can survive on their own excrement?"
To which I replied, "Doesn't the efficiency of that run down eventually? Isn't there some sort of thermodynamic/entropic limit at play here?"
BTW, we hired him and he was good. But, he didn't answer my question.