Black racers are insectivorious as neonates and juveniles. They actually actively forage for crickets and grasshoppers. They raise up the first third of their body and bend over tall grasses to see if anything jumps off, then they chase it down. As they get older, they change from crickets to fence lizards and eventually anything they can find that they can overpower.
"typical" rodent eaters will stay underground a lot, maybe go a month or more before they stumble onto a nest of mice. And not pet trade mice, but species like oldfield mice or deer mice, which vary in size from smaller than a petstore mouse to larger.
I have no hard, fast figures, but Ecological principles say that the larger the clutch size, the high the mortality rate.
And for every hatchling snake, there are hatchling lizards, baby mice, nestling birds etc.
Rome did not build a great empire by having meetings, they did it by killing all who opposed them.