Why Do Dogs Try To Catch Flies

You’ve probably seen it at least once before: a dog sitting outside in the sunshine, occasionally snapping at a passing insect buzzing by. Some dogs may even be more persistent about it, chasing the fly around the yard, determined to eat it. Others may only snap a time or two as the offending bug swoops by. And occasionally, dogs may even snap at insects that aren’t there.
Why do dogs snap at flies or other flying critters? And if you don’t see any bugs nearby, exactly what are they snapping at? Does your dog obsess about flies or other bugs? Is it healthy or normal, or should you be concerned?

Also called fly-biting or fly-snapping, this strange behavior may be caused by several different things. Some dogs, particularly hunting or sporting breeds, may be more inclined to chase and pursue bugs that annoy them. Chasing flies can also become an obsession or compulsion. Other obsessive behaviors may include tail chasing, pacing, toy fixation, light chasing, chewing or licking, and nonstop barking. If you have a dog that does something compulsively and can’t stop, this fly chasing may just be another one of those compulsions. Veterinarians don’t yet agree on the root cause of these compulsive actions. Possible causes include genetics, neurological or digestive problems, or epilepsy.
If your dog compulsively snaps at flies that aren’t there, they may be experiencing a mild form of seizure. When you hear the term “seizure,” you might be picturing muscle spasms, drooling, and uncontrolled movements. There are other seizures, called complex partial seizures or focal seizures, which, in humans, may manifest hallucinations. There is very little evidence to prove or disprove this theory as of yet. Epilepsy is hard to diagnose in dogs without proper equipment monitoring brain activity during one of these fits.
In one of these fly-biting episodes, dogs may snap repeatedly at nothing, as though surrounded by a swarm of flies. They may also compulsively lick their forelegs. During one of these episodes, they may generally appear conscious, alert, and undisturbed or emotionless. Although occasionally, dogs may growl during fly-biting or appear upset by them, coming to their owners for comfort. They may even “snap out” of the episode by being called by name or distracted with a toy.
Eye problems may be another possible cause of fly-biting. Sometimes, the eye has small pieces of debris in the eye fluid. These are called “vitreous floaters.” These are usually detectable with the right kind of examination. It is also possible that visual hallucinations stemming from neurological effects, like migraines, or other conditions, might cause dogs to snap at bugs that aren’t there.
In a recent study conducted at the University of Montreal Veterinary Teaching Hospital with seven dogs who experience fly-snapping episodes, five of the subjects all had the same gastrointestinal (GI) condition. After receiving treatment for their GI disease, the fly-biting resolved.

If your dog tries to catch the occasional fly, there’s really nothing to worry about. Sometimes, they may chase bees instead, and suffer the consequences of a sting to the face or mouth. In these cases, other than a little pain or discomfort, your dog should be fine. Just keep an eye out for any concerning side-effects.
You can always discourage snapping at bugs by engaging your dog in other activities or exercise. Distraction is a great way to keep your dog from chasing bugs.
If your dog compulsively chases bugs, there may be other underlying conditions causing the obsessive-compulsive behavior. Consult a vet to rule out other disorders.
You can also discourage obsessive behaviors by working on more mental stimulation. Dogs who tend to become obsessive often need more rigorous training. Breeds like Border Collies, for example, require adequate mental training during puppyhood to avoid later compulsivity. Teaching more tricks and practicing them often may help reduce the number or severity of compulsive behaviors since the more intelligent dog breeds require more mental stimulation.
If your dog has fits or episodes where they are snapping repeatedly at things that aren’t there, you should consult a vet for a thorough examination to rule out other disorders or diseases. And you can help by snapping your dog out of it during one of these fits with a toy or calling their name.

A good way to help stop one of these fly-biting episodes is to distract your dog with something else. Even just calling their name may snap them out of the fit. You can also try giving your dog additional mental and physical stimulation, which may help reduce the frequency of these episodes. Working on an additional trick, going for longer walks, or using more stimulating toys are all good ways to keep your dog engaged and occupied. And, even though the research is limited so far, trying higher quality food should help keep your dog’s digestive system working better. Cheap or nutritionally deficient dog foods have been linked to a number of problems in dogs. Feeding them high-quality food is a good way to keep them healthy. Consult your vet for advice on the best food for your dog, and to rule out digestive issues.

Catching flies can be an innocuous habit or a symptom of a more serious condition, depending on your dog’s specific behavior. If you’re concerned, discuss it with your vet. But whether it floats like a butterfly or stings like a bee, chasing bugs might just be a fun game your dog employs to stave off boredom.