I am seeing scratch like marks on bottoms of my tomatoes. What is causing this? Possibly chipmunks? I have tried eight solutions with no results.
You are likely seeing either stretch marks from the fruits swelling, which is normal, or flower scars on the underside, which are very apparent on large tomatoes as thin, brown lines which criss-cross or star on the bottom of the fruit.
Neither of these drastically affects fruit quality, and are untreatable. Almost all large tomatoes have these marks.
Can you better describe the scratch marks? Do they go through the skin into the fruit or are they just surface, cosmetic damage only? Are they two parallel gouges or scratches, or multiple lines of scratches? How large are the scratches? If you are seeing two parallel gouge-type scratches that go into the fruit, you are almost assuredly looking at rodent damage. It could be anything from voles, to chipmunks or squirrels, or woodchucks, or field mice or rats, depending on what you have wild there and how big the scratches are.
Birds will also attack ripening tomatoes, but the damage they do is usually more along the lines of making holes in the fruit, rather than just creating scratches.
If the damage is cosmetic only, confined to the bottom of the fruits and does not penetrate to the inside, then you are probably looking at the stretch marks mentioned in the other post. Some varieties of tomatoes are more prone to those than others are as they mature, especially in the summer when the heat makes the skins tougher. When it rains or the garden is watered, the fruit will soak up the extra moisture, but because the skin is tough, it will cause minor cracks and marks due to a lack of elasticity to hold the expansion of the "meat" of the fruit inside. Sometimes the fruit will even crack open for the same reason.
Pictures would definitely help all of us do a better job of guessing what you are dealing with.