Mice are nocturnal animals, live in packs, and enjoy a challenge to appeal to their sense of curiosity and smell. They have great hearing, have poor eyesight, and love to eat almost anything. You can feed a mouse sugary stuff, and they will develop diabetes.
Knowing all of this, you can expect to be very capable of catching, relocating or killing your herd of mice. The control of your pest population is a very patient practice, and you should expect to employ many solutions before you are rid of the black long poops.
Note: if you have longer black poops than 1/8″ of an inch, you may have a rat population. Mice and rats do not get along, and rats will kill mice.
The most common example of a humane rat trap is the tiny mouse cage specifically designed to lure and catch a rodent. Bait is placed inside and a one way door is provided. Once the furry little fellow crawls in, the door shuts and locks. But the rat would not wonder about it as it is too busy nibbling on its bait.