Sudden Aggression in Boston Terrier

Question
QUESTION: I have a three dog household which consists of a 10 year old Terrier mix (male), a 10 year old Pug/Chihuahua mix (female) and a 6 year old male Boston Terrier.  Within the past month, the Boston Terrier has started attacking the male terrier mix.  At first, it was only during playtime, feeding time or when one of us came home.  The Boston has recently been diagnosed with hypothyroidism, but has shown no improvement with aggression towards the terrier mix.  The terrier mix is totally submissive and has never challenged the Boston.  In fact, since being on the medication for hypothyroidism, his aggression has been worse.  He seems obsessed with the terrier mix and watches his every move.  As a result, we have been keeping the Boston on his leash and away from the terrier mix at all times.  We have been using our behavioral training manual from a prior in-home 6 week session with a professional trainer and re-instituting this training but it has not seemed to help.  Should we consult our vet for some other type of medication to help with his behavior?  Are we driving the Boston's interest in the terrier mix by keeping him on the leash?  Any help you can provide is GREATLY appreciated.  Thank you.

ANSWER: Your house tab (indoor leash) is essential and you should keep using it.  BUT you really DO have to go back to the veterinarian with this dog as it appears the medication is worsening his problem.  If steroids are being used (and they probably are) this is seriously affecting his temperament.  You need to have blood levels checked (and frequently) as this medication can cause life threatening problems, not merely behavioral, and even a tiny amount over his physiological needs can worsen behavioral problems.  A beta blocker might assist in reducing the Boston's aggression toward the older dog but your veterinarian might not be willing to prescribe it.  See what the veterinarian has to offer and keep the Boston on house tab regimen.  Repost after your vet visit with details regarding the contents of this behavioral training regimen you are using.  It might not be up to speed for this problem.

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QUESTION: Thank you for your answer.  We just had his blood levels re-checked and his thyroid levels are lower than at first.  The vet increased his dosage.  If his aggression does not improve over the next 2-3 weeks, we will be taking him back to vet to inquire about additional medication.  As far as behavioral training, we are making the Boston work for everything.  He has to sit to go out, get his food or treats.  We do evening regimens with sit, wait, watch me, and downs.  Any other suggestions are certainly appreciated!

Answer
It's possible that your Boston is observing the physical decline of the older male in your household.  It is also possible that you are promoting the older dog because he is NOT being made to earn everything.  I suggest you put all dogs on your Nothing in Life Is Free regimen, even the female.  Observe the interaction between the males very closely.  Because the older dog has not overtly challenged the Boston does not mean there isn't a rank issue going on right in front of you which you might be missing.  Body language, including eye movement, is essential.  If you perceive the older dog attempting to assert rank, you need to clearly make the statement to your pack that this is not appropriate.  This is done by putting the Boston first...greeting, feeding, going in/out, etc.  It's most likely best to do this in any case as the older male is naturally losing his "edge".  This might assist in reducing the problem.  But most importantly, ALL dogs must see YOU as "alpha" and respond to your simple command to 'cut it out' with no hesitance.