If a young dog is spooky or shy, will it grow out of it?
Maybe, maybe not. If a pup is abnormally reactive to everyday things or situations, do the best you can with positive socialization. However, if the behavior does not improve it is wise to seek help from a trainer specializing in behavioral issues. If the dog cannot learn to react appropriately to normal situations as it matures it would be better not to breed it.
Can extreme noise sensitivity shorten a dog’s lifespan?
Not directly, but in some cases it might contribute. Longevity for a given dog would probably depend on how much chronic stress the dog’s phobia caused it and what other health conditions it might have. A dog with severe anxiety issues will be under a lot of stress; chronic stress impacts immune system function and exacerbates some diseases.
Sometimes a dog that is sound sensitive will panic so badly it breaks out of its home or enclosure. A loose, panicked dog could get killed running into a road or other dangerous situation. The cause of death, strictly speaking, would be an accident but the panic would be a major contributing factor. To the extent that this happens, sound sensitivity (or other panic or anxiety behaviors) can shorten longevity.
Is fighting inherited?
Fighting behavior can be learned or inherited and may be a combination of the two. Early in the breed’s history some lines were more prone to fighting than others. This is likely still true today, though to a lesser degree. When dogs live in remote rural areas where guarding property from predators or strangers is needed, a scrappy disposition can be an asset. In the suburbs and cities it’s an invitation to a lawsuit. Over the past few decades breeders have been selecting for the less pugilistic dispositions, so Aussies with an inherent urge to fight are uncommon. You should not assume that fighting is in your dog’s genes. Consult a qualified trainer or behaviorist and follow up on their advice. However, if the behavior cannot be modified significantly, inheritance is a possible factor. An incorrigible fighter must be kept away from situations that may lead to a fight and should not be used for breeding.
Is fighting with other dogs caused by thyroid disease?
In most cases fights between dogs have strictly behavioral causes (though some of those may be influenced by genetics). However, autoimmune thyroiditis occasionally causes affected dogs to exhibit aggressive behavior. But if the cause is thyroiditis or any other non-behavioral issue you should be seeing other signs that indicate something else is wrong in addition to the aggressive behavior.
What is rage syndrome?
Also called sudden onset aggression, rage syndrome is a neurological disorder, not a temperament defect or training/socialization problem. Affected dogs go into a kind of seizure that makes them attack anyone or anything that happens to be in the vicinity. The dogs are fine one moment but launch a violent attach without warning the next. After an episode, the dog may be briefly disoriented but it soon returns to normal behavior, unaware of what it has done. You cannot predict rage attacks. Medication may help but requires a veterinarian who specializes in behavioral abnormalities.
Rage can be to some extent hereditary. It was first identified in Springer Spaniels and was originally called “Springer Rage” until it became apparent that it occurred in other breeds as well. It sometimes occurs in Aussies but is, thankfully, very rare. Dogs with rage syndrome should not be bred.