If a Jack Russell Terrier exhibits aggressive behavior, what should a handler do?

Consulting a professional trainer or behaviorist is the most appropriate course of action when a Jack Russell Terrier exhibits aggressive behavior. This choice is correct because experienced trainers or behaviorists have the expertise to assess the root cause of aggression and develop a tailored behavior modification plan. Aggression in dogs can stem from various issues, including fear, territorial instincts, or past traumas. Professionals can evaluate the dog's behavior in context and provide strategies that are safe and effective, ensuring not only the safety of the dog but also the people and animals around it.

In contrast, ignoring the behavior could allow the aggression to persist or worsen, as the underlying issues remain unaddressed. Attempting to discipline the dog immediately is often counterproductive, as it may exacerbate fear or anxiety, leading to further aggression. Changing the dog's diet typically does not address behavioral issues directly related to aggression, and while nutrition is essential for overall health, it is not a solution to behavioral problems. Therefore, seeking guidance from a professional is the best step a handler can take in these situations.