I haven't, but my father was one of 12 children, eleven of whom lived and married. My mother was one of seven. Medicine and effective birth control are rather new. Most families before 1900 lost children. Nearly every couple that doesn't use birth control will lose a pregnancy; most of the time this will be called a "late period," but it will be a spontaneous abortion.
As for cats, if you have to ask, you don't know much about cats.
Which is enough to prove that "every single organic being around us may be said to be striving to the utmost to increase in numbers" is false.
my father was one of 12 children, eleven of whom lived and married
Which is enough to refute both Mayr's assertion "all the individuals of a population... are exposed to the adversity of the environment, and almost all of them perish or fail to reproduce" and your assertion: "the process of reproduction creates far more offspring than survive to reproduce."