Monday, December 14, 2009

Counting Polies

Well, our experiment with Polytopia has run its course. Quick summary: my daughter did a science fair experiment examining which of four habitats roly polies would like the best: Dry potting soil, moist potting soil, moist local canyon dirt or moist wood chips and leaves. We released 200 polies into the habitat about two weeks ago and yesterday she counted the ones she could find.

As an aside, it's rained like crazy here in San Diego for the last week and although the Polytburo did it's best to put a tarpolyn over Polytopia, everything ended up wet. Having said that, the dry potting soil had stayed dry for a few days after the release of the polies and we hypothesize that the polies crawled around for only a few hours before curling up and going dormant due to the cold weather.

Polytopia's protective shield.

In the end, the count was quite conclusive. She found 50 of the original 200, distributed thusly:
  1. Woodchips: 38
  2. Moist canyon soil: 10
  3. Moist potting soil: 1
  4. Dry potting soil: 1
It looks like the polies headed straight for cover, burrowed in and snoozed. I wasn't too surprised that she only found 50 of them - most of our population were tiny youngsters and given the muddy soil conditions and the visual clutter of the woodchips and leaves, it was pretty hard to find them.

As for the sub-preference of the canyon soil over the potting soil, I think that they chose it because of the decaying wood in the canyon soil. We collected that dirt in an area where workers had been cutting down scrub brush for fire prevention and there was plenty of finely ground wood mixed in with the soil.

1 comment:

tim eisele said...

That looks pretty conclusive, all right!

Of course, if she wants to go whole-hog on this, she could try making an estimate of the relative difficulty of finding roly-polies in the different substrates:

1. Get together four groups of, say, 20 roly-polies each
2. Mix one of the groups of 20 into about a gallon of the soil or woodchips to be tested.
3. See how many can be found immediately afterwards.

Although, I doubt it would turn out to be 10 times easier to find them in canyon soil than in potting soil, or over 30 times easier to find them in woodchips, so it probably isn't necessary to go overboard here.