Deer advantages

Why are deer so active at sunrise and sunset?

The way I understand it one of the advantages a deer has is its ability to see in the ultraviolet range, which is at a peak in the early morning and late afternoon.

The next generation of my mechanical do it yourself deer deterrent will take into account this trouble window and somehow gear up to a higher noise frequency, but the details are still fuzzy.

Image credit goes to the informative deer management portion of the Fish and Wildlife site for Delaware.