You mean they been actin' so smart 'cause they're so stupid?

Burt Gummer:

I knew it. Infrared. It doesn't hear us; It doesn't actually see us; it senses the heat of our bodies. See that? The thing that rises up must be the heat sensor. You feel that? Gives off a lot of heat when it screams. Kate (White) Reilly:
That's it. I bet that's the way they communicate. The sound doesn't matter. I mean they make noise, but they signal each other with their body heat. Earl Bassett:
It only sees heat? Kate (White) Reilly:
Yes, that's not so weird. A rattlesnake strikes at body heat. Earl Bassett:
Well that's why they tore up the cars-- because the engines were hot. They thought it was food. Kate (White) Reilly:
And the same thing with the radio tower. That electronic gear puts off all kinds of heat. Burt Gummer:
So basically, they bite anything that's warm. Grady:
You mean they been actin' so smart 'cause they're so stupid?