Tiny black flies in cage litter tray.

Question
(I tried a search but couldn't come up with anything pertinent!)

The last time I cleaned out my mini rex's cage, I noticed that there were teeny tiny black insects jumping around her waste.  They would fly/jump up and land quickly.

I did a good clean, lots of vinegar, disinfected it, and put it back.  I went to clean it out again a few days later (the bugs put me on alert), and there are still some more there.

Any idea what these are?  I don't think they are flies; you can't even see them fly or see any wings.  And it looks like they are just hopping from place to place.

I did a good check on all the buns (three) and their booties look okay.  Should I be looking anywhere else?  And is there *anything* that can get rid of these?

Thanks in advance!

Answer
Dear Stephanie,

They could be little fruit flies (Drosophila), some species of which are attracted to the smell and moisture of ammonia from decomposing waste.  They won't harm the bunnies, but if there's enough smell to attract Drosophila, you might want to clean the litter more often OR switch to a pelleted sawdust litter that's better at absorbing odor and liquid.  We use Feline Pine (or similar product), and it's fantastic.  No odor, no wetness, no bugs!

Hope that helps.

Dana