Bats activate tripwire, while it is intended* that they don't activate tripwire nor pressure plates, they are just for environmental and atmosphere reasons. Pressureplates is difficult to test, since bats always fly, unless they hang on the ceiling, but then the pressureplate has to be on top, which is not possible.
Evidence: https://www.youtube.com/watch?v=zyMvbA1s1cQ&t=2m05s
http://minecraft.gamepedia.com/Bat#History see 12w42a
Comments 5
Okay, fine, a reliable source https://mojang.com/2012/10/minecraft-snapshot-12w42a/
Okay, when I am back home I'll compare 1.4.2 with 1.8.1, if bats activate tripwire in 1.4.2, ot is WAI, if they don't it is definately a bug.
Also I will post a video of that here, if it is a bug. I keep you up to date with the progress.
The Wiki isn't considered a reliable source.