If he's biting her on the back, it sounds like it resembles the way a male cat will grab a female during the mating process. - I assume your male is neutered but if not he needs to be.
Without seeing your cats I dont' know if this is the case, or if your male is trying to play or being aggressive.
At any rate, you need to find someone to help you with this because your 17 year old cat shouldn't be harrassed like that - she's too old and that sort of thing is too stressful for her - if it is happening frequently it is decreasing her quality of life and the stress can also affect her health.
Separate the cats if necessary, or even consider installing an indoor, magnetic cat door to a spare bedroom for example, so that your older cat can wear a collar that releases the magnet. This will allow her to get into a room and escape your male because he won't be able to follow her.
We have a DVD on Helping Kitties Coexist that also provides LOTS of info about helping cats get along. You'll find it at www.HelpingKitty.com
Copyright 1994-2016 MedHelp International. All rights reserved.
MedHelp is a division of Aptus Health.
This site complies with the HONcode standard for trustworthy health information.
The Content on this Site is presented in a summary fashion, and is intended to be used for educational and entertainment purposes only. It is not intended to be and should not be interpreted as medical advice or a diagnosis of any health or fitness problem, condition or disease; or a recommendation for a specific test, doctor, care provider, procedure, treatment plan, product, or course of action. Med Help International, Inc. is not a medical or healthcare provider and your use of this Site does not create a doctor / patient relationship. We disclaim all responsibility for the professional qualifications and licensing of, and services provided by, any physician or other health providers posting on or otherwise referred to on this Site and/or any Third Party Site. Never disregard the medical advice of your physician or health professional, or delay in seeking such advice, because of something you read on this Site. We offer this Site AS IS and without any warranties. By using this Site you agree to the following Terms and Conditions. If you think you may have a medical emergency, call your physician or 911 immediately.