I wonder how many coyotes and rattlesnakes trip those?
Actually, about 30 years ago I worked for a company that built airborne night vision equipment. We made a call on US Border Patrol headquarters to show how our stuff could help them. Even then they estimated about 3 million illegals were entering each year. But they had no money to buy our equipment because they had spent their entire hardware budget on leftover seismic sensors built for the Ho Chi Minh trail. Yeah, they knew all about coyotes (4 legged) and armadillos along that stretch of border. So many alarms the system was completely swamped.
None actually.