In narcotics detection, which action can be a primary sign of a dog indicating the presence of drugs?

In narcotics detection, the action that signifies a dog indicating the presence of drugs is alerting. This behavior involves the dog exhibiting a specific response when they detect a scent associated with narcotics. An alert can manifest in various forms, such as sitting, lying down, staying in a particular area, or using their nose to touch the source. This response indicates to the handler that the dog has made a positive identification of the presence of narcotics.

While other actions such as ranging, pacing, and chasing may occur in various contexts, they do not reliably indicate a positive drug detection. Ranging refers to a dog's movement away from the handler to search an area, which can help in locating scents but does not confirm detection. Pacing involves the dog moving back and forth but does not signal an alert to the presence of drugs. Chasing is more related to play or instinctive behavior and is not a specific sign of narcotics detection. Therefore, alerting is the definitive action that dog handlers look for to confirm the presence of narcotics.