Well, let me think. I have been retired for awhile now, so I have to recondition my brain from working in a grocery store back to aviation. You are correct. The airfield is lined with fencing to protect the taxiways and runways from many different things that may have ventured out onto it, including people, which has also happened.
Did you know that
some of the vehicles that you see driving around on the tarmac have huge magnets under them to pick up any steel lying about that may have fallen off of a vehicle or plane? Most airports do have cameras, but if no one is monitoring the cameras, then it is possible for a big animal like a bear to walk through a weak fence and onto the runway/taxiway. For years, the FAA has considered making airports install sensors above the runways to protect it from outside sources. A few airports have been attempting to use it as a matter of functionality. Check it out.
GTT I am not real familiar with these systems. They were being used in trials mostly when I retired.
This brings to mind the accident with the piece of metal that fell off a Continental Airline's plane taking off in France and then it laid on the runway for the Concorde to run over causing its tires to explode and when the pilots retracted the landing gear back up into the belly, it caused the plane to catch on fire. Terrible, terrible day for aviation. From time to time when you are in the airport and looking out at the planes landing and taking off, you may see a pickup truck or car going up and down the runways. They are checking for debris on the runway.
Personally, I have seen debris on the runway and reported it to the ATC in the tower. When that happens, they stop all traffic using that runway and have it swept.
You seldom hear of runway incursions with animals. The noise seems to keep them at bay. If anyone has ever heard a jet that has landed and then hear the reverse thrusters activated, it would definitely scare anyone, or any animal to get off the runway. Especially, like the old
B-747's with their four engines.
I love aviation and miss it more than anyone will ever know.
Again, sorry for the long post. Now aren't you sorry you asked?