Mink are inquisitive, and research has shown that they find it hard to resist investigating a tunnel, especially if the tunnel is floating on a raft. If a cage trap is placed in the tunnel, any visiting mink is likely to go inside and be caught when the trap door closes. The traps are equipped with an electronic alarm unit which immediately alerts nominated people (usually conservation-minded volunteers) to the fact that the trap requires an urgent visit. One advantage of this capture method is that the animal in the trap is unharmed, and can be quickly released if it is anything except a mink. If a mink has triggered the trap, it is instantly and humanely dispatched with an air gun.