Without context or a complete sentence it's difficult to say. The only thing I can think of is that someone wouldn't even board a gerbil with someone for whatever reason, meaning that someone's facilities for boarding animals (horse stables, dog kennels, etc.) might be so bad that even a gerbil shouldn't be boarded there.

I assume you know what it means to board an animal like a horse or a dog somewhere.

Thanks a lot, dude.

Dude, I honestly don't see how you interpreted that into the sentence fragment we were given - why couldn't it just mean having someone care for a gerbil while the owner is away?

Because I've never heard of anyone boarding a gerbil; have you? The cage a gerbil lives in tends to go along with the gerbil when the owner goes on vacation, doesn't it?

I would suggest it probably just means sending the gerbil somewhere to stay while the owner is on vacation. I've never heard it as an idiomatic expression for anything.