Bait, birdfeeders and bias

You may have heard that Snapshot Wisconsin researchers ask volunteers to place cameras at least 100 yards (~100 m) away from bait and feed. Bait and feed are materials placed outdoors to intentionally attract wild animals, and may include food, scent materials, salt, minerals, grains, birdfeeders, and carcasses. Bait and feed attract really interesting animals that we love to see on camera, so why do we ask our trail camera hosts to avoid them?

The main reason is to avoid bias in the animal data we get from the project. It is okay that there are naturally occurring areas of the landscape that are more attractive to animals than others (and, indeed, we encourage camera placement near water that attracts all kinds of animals) – but we want to make sure that some camera sites aren’t disproportionately attracting one kind of animal. We also don’t want some camera sites to be so attractive that animals forgo natural movements within their range in favor of spending time at certain sites. Rather than intervene in natural animal movements, our goal is to act as an “innocent bystander” and passively observe where animals go.

With that said, there are some projects that work in the exact opposite way. For example, the AppalachianEagles project uses carcasses to attract carnivores and scavengers to their camera sites. This project differs from Snapshot Wisconsin in a few key ways that make this strategy make sense for them: 1) They are interested in carnivores and scavengers specifically (whereas we are interested in all animals) and 2) they have far fewer cameras spread over a far larger area. With cameras so spread out, the sites need to be attractive to get a sense of what is in the area.

It is good to compare different scientific projects and ask how different methods might affect the type of data collected and the conclusions that come out of the study. In the case of Snapshot Wisconsin, we’re going for a fairly dense network of cameras observing animal distributions as they naturally occur, with as little human interference as possible.