"Alert nature" refers to being awake, attentive, and quick to notice things happening around you. It means being observant and being ready to take action if necessary. Full definition
His high energy levels and alert nature make him ideal watchdog material. (petguide.com)
Both have the same square head, close coat and highly alert nature. (linkroll.com)
On Wednesday County Executive Anthony J. Picente, Jr. announced a new service where people can text 911 to alert the nature of an emergency and its location. (ocgov.net)