I use detect life A LOT because I stealth around and it is really really useful if you are a stealth kind of guy. Aggressive enemies always show up red. Non-aggressive things like dudes in town and calm people show up blue.
Rabbits don't actually attack but they ALWAYS show up red.
I believe it is the hatred that makes aggressive things red and this just proves rabbits are made of pure hatred.
I will kill every rabbit in the land of skyrim for this.