Why does my neutered male mount blankets and toys?

For many younger dogs, mounting and humping is part of a developmental phase, fueled by hormonal changes and normal growth cycles. After your dog is neutered, it usually takes about two months for the hormones to leave his body.

A lot of people mistakenly think neutering will stop all activity and that’s just not so. Mounting and masturbation is a normal sexual activity for both males and females, whether neutered, sprayed or intact and, in fact, a neutered dog can still get erections and ejaculate. Sometimes the behavior is even accompanied by “flirtatious” body language like tail up, ears rotated backward, licking, pawing, play bows, etc.

Mounting and humping isn’t just sexual, and both male and female dogs often mount other animals and people to display social status or control. A dog mounting for this reason may or may not display an erection, but he’s unlikely to ejaculate.
Sometimes, a dog will mount or masturbate also as a response to stress or excitement, such as meeting a new dog or person.
The solution in both cases is to tire the dog out. Take your dog out for at least one long, strenuous walk and play time each day. This will help release any aggression and minimize his stress
Other reasons include:
• Play response: Some dogs, especially poorly socialized ones, become too aroused during play and will mount and thrust; they almost never display erections.
• Compulsive disorders: Masturbating can become a compulsive habit, especially if a dog does it in response to stress. Compulsions like mounting and masturbating can interfere with a dog’s normal functioning.
NOTE: In all cases, see the veterinarian first to rule out any underlying medical issue. In some cases, humping is caused by hormone imbalances that may indicate serious conditions, such as hypothyroidism. If this doesn’t work then your next stop is a canine behavioral specialist, who can train the dog to stop the behavior.