Problem is obviously vampires. They mistook your red tomatoes for blood-sacks.

Snakes don't eat vegetation.

It sounds like bird pecks or animal bites to me. Are there always two holes the same distance apart?

If you want to save some ripe maters for yourself, why don't you cover them with a plastic bag draped over them? That apparently deters some of the larger fruit snitchers and destroyers, bird and animal.

Sarah,

I had the exact same problem when I planted my very first garden years ago. I had just moved into a house that never had a garden and the yard was overgrown. I found the problem to be mice! Mice love to take a bite and run, they also climb so you may find the bite marks on tomatoes high and low. Those mice later got so bold that they would come out while I was weeding!!! I later found the neighbor on the other side of the fence had an old shed that was infested with the rodents. Try setting a couple of mouse traps, using peanut butter, out in your garden. I know it may sound ridiculous, but I trapped over 40 mice that first year. After that, the bite marks disappeared!!