Beagles tend not to be the most aggressive dog. That being said, under specific sets of circumstances all dogs are going to be aggressive. This mentality has a few different causes, most of which are easily corrected with enough time and attention. Your canine is a complex combination of biology, psychology, and external factors and that is always going to be a hurdle that needs to be overcome. But while proper training and attention can curb these behaviors to a degree, it isn't cure-all. So, what types of factors may be provoking disobediences and agression in your animal? Should there be cause for alarm?
The Root of the Behavior
In most canine breeds, there exist two types of aggressive behavior: human-directed aggression and animal-directed aggression. These are very different types of behaviors, and the more troublesome of the two will almost always tend to be human-directed aggression. This is an aggression that tends to show itself when a canine in a household begins to view itself at the top of the hierarchy. Pack mentality is still very strong in domesticated animals like dogs and can take a negative path if not treated with reverence. Make sure that in these situations you don't continue to "humanize" your dog by associating its behaviors with human emotions and thoughts. This tends to only make things more confusing and difficult in the long term. Your canine will always have very different motivations from you. What's critical here is your dog's perception of you. They're not going to attempt to maintain aggression towards another member of the pack if they feel comfortable in the current hierarchy. If you notice their aggression building, there are almost certainly specific behaviors you've engaged in that have provoked this new series of responses.
Canines aren't usually looking to fill the role of pack leader, so they do so only when they feel pushed into the behavior. You can almost think of your dog's aggression in these instances as "corrective behaviors" meant to push you back into your normal position as pack leader. A real common behavior associated with Beagle aggression is guarding of the food bowl. Children in dog rearing families are constantly being warned about not bothering the dog while it eats, and usually this is for good reason. Your Beagle doesn't think about food the way you do, nor does any canine. They have a lot of trouble leaving food "for later" because to them, later doesn't really factor into their cognitive processes. They simply eat when food is present and available. This means that when most individuals reach for what their consuming, your dog assumes it's a "now or never" situation. They need to hold on to what they have, because it's their only chance to finish it.
Encouraging the Behavior
If your Beagle is especially defensive, make sure to keep unaware children out of the mix. It is a fairly common situation for children to be playing with a dog and not understand the boundaries that they should respect. Beagles were bred to be hunting dogs. Because of this, certain forms of aggression come "stock" within your Beagles DNA. This makes them often prone to hunting behaviors that can be sometimes misconstrued as aggression towards humans. This makes it especially important to pay attention to the body language that your dog is putting out.
Play behaviors are always easy to see. Your dog will inevitably put the front part of its body close to the ground, with its butt up. Their tail should be wagging from side to side. If you're not seeing these movements when you're fearing aggression, take care. It could be a sign of something deeper and less friendly. One way to curb aggression is by neutering your Beagle. Testosterone is the number one hormonal provider of aggression, and cutting this problem off at its source is a surefire way to help the situation. Keep in mind, however that testosterone itself will not cure any confusion that may exist regarding the hierarchy of dominance in your household.
Other Solutions and Considerations
A great solution for curbing aggression from your Beagle is training. A lot of animal behaviorists agree that most behaviors related to dominance can be rectified via intensive training programs and behavior modification therapies. If this is something you're looking to involve your canine in, your vet will almost certainly have suggestions on programs in your area. If your dog is a puppy, this is another consideration you need to make. Beagles that have yet to reach adulthood are hardly ever that well-behaved. In fact, more often than not the aggression you are perceiving may just be your puppy being playful.
So, if your Beagle is presenting the types of negative aggression written about above, there are some clear cut solutions that can quite easily curb these types of behaviors. At the end of the day, if comes down to understanding your animal and the types of communication they're sending you. Beagles are generally not that aggressive, and with the right types of training they can be an "un-Beagle-able" addition to your household!