Worms, maybe? I'm not familiar with the native worms down there, so I can't tell you what kind of piles they produce. Our worms make teeny little piles of round pills of soil. They appear next to holes in the ground where the worm either lives or passed by temporarily.

morpheusa is right.
Worms.
Thats a good thing.

If worms then yes, that's a very good thing. They gently aerate your soil, feed the lawn by processing off organics, and are fun to watch in rain.

Not only is no intervention required, none is recommended. High worm populations are a great thing for lawns and gardens. I've spent a fair bit of time, money, and energy getting my worm populations up.

Agree with worms. If you had golf greens, then it would be worm damage. Since you don't, then it is worm help.

As for the grass problems...
1. How often and how long do you water?
2. When were the last two times you used fertilizer and what did you use?
3. Have you used a herbicide, insecticide, or fungicide this year?