I rely quite heavily on my two providing "security" for me. Have provided them access (stairs/ramps) where they can view out the first and second floor windows. But, when they are outside and just "hanging around", they have their noses up in the air, sniffing constantly, and can detect the Postman a block away.
Frequently they alarm (bark) and rush to the fence which in most places one can not see through. I've given up looking (over the fence) because every time I have, there has been a Cat, someone walking by or something else, which is an "authorized" alert, and they've done that totally on scent. And the "intruder" doesn't have to be very close at all.
Also, they have a "level" of alarm, which is more apparent to them, than it is me. I can "sorta" tell just what level of threat they are placing it at.
Like for a Cat, it won't be as intense, like just a moderate call to the other, to say "look there's a Cat out here, come look".
Then, there's the biggie, where they see or smell someone at night. That's a lot more intense and I always check that one out.
