Tuesday, April 20, 2010
Analyzing the data
Last night we sat down with Chris to have a look at the data we have collected so far. They set out with a question they wanted to answer, developed a method that would give them reliable results, and we are helping them collect data. Answering their question can only happen after data has been collected over a long period of time. Once you collect enough data, the problem is to find out what it tells you. The data doesn't mean anything until you have examined it. He explained their methodology for doing this. One way is called Capture-Mark-Recapture or CMR. This means they count the number of recaptured animals after a few days to estimate how many animals are in an area. There was a very useful math formula we could plug our data into and come up with an estimate: based on the fact that we caught 7 voles, and recaptured 5 of them over 5 days, we can estimate that there are 13 voles in 1 hectare (100m x 100m square) at last week's location. Very cool! Here is Anne checking the new traps we set yesterday. There is some grassland, some forest, and also some hard brush. Malakai, here's what the red fox scat looks like! They are rare around here because they compete with coyote for the same food, and the coyote is much bigger. They also leave scat as a way of marking their territory. They leave it on top of prominent places like big rocks. Can you see all the fur and bones twisted up in it? We only caught one mammal so far at Cooks Lake, it's a meadow vole, as opposed to the red-backed voles we caught last week. Do you see any differences? We saw a rotted tree stump on a walk today, but the core of the tree had decomposed before the branches, so you can see how the branches leave their mark inside of the tree as it grows.