NOGALES, Ariz. -- Border Patrol agents say nighttime is the busiest time along the U.S.-Mexico divide, but they have some high-tech tools to keep smugglers and illegal immigrants at bay.

Watch: Border Patrol: Cover Of Night

One such tool is a mobile surveillance system equipped with radar, thermal imaging capabilities, lasers and a global positioning system.

The military-like tool can detect people, vehicles and even jackrabbits up to 10 miles away, allowing agents to track border-crossers walking in remote areas that are nearly impossible to travel through.

Agents can tell the difference between an animal and a person using several methods. For one, animals are smaller and tend to walk or graze in circles; people, on the other hand, tend to cross the desert in a straight line.

Once agents spot a group, they strap on bulletproof vests -- shootings are not unheard of -- and use night-vision goggles and GPS coordinates to follow it.

Using the mobile surveillance system, the patrol can also tell whether border-crossers are illegal immigrants or drug smugglers, and whether they have weapons or backpacks full of drugs.

Nevertheless, despite the patrol's high-tech tools, crossing the border is a way of life for many of those caught -- they'll likely make the trek again.