This type of "culvert" trap is used to catch bears that pose a danger to people or property. They are then transported to wilderness areas where they will not conflict with humans.
Using these live traps has almost eliminated the killing of nuisance animals.
Some bears are almost impossible to trap, having learned from previous encounters. Some are quite happy to be caught repeatedly. They have learned that the trap contains a free meal and the trap/people won't harm them.
You have to wonder, too, whether creatures as intelligent as bears may be reading the warning sign posted on the trap door.