Veterinary Handbook Disease Finder



Other Names

  • Buller Syndrome
  • Bullying
  • Dominance Behaviour
  • Mounting Behavior
  • Riding



This is a problem of excessive riding behaviour. In cattle it can involve animals regardless of age, sex, pregnancy status or stage of the oestrous cycle.

It is a more common and serious problem in groups of bulls or steers. In sheep and goats it is more common in groups of entire or castrated males. The term for animals being ridden is bullers, the term for animals performing the mounting is riders. Riders persistently follow and mount bullers. Causes are unclear but may include sexual stimulation, establishing social hierarchy and relieving boredom.

Bullying can be a serious problem in shipments of male animals, particularly feral bucks.

Bullying may begin immediately after animals are penned and is a greater problem in pens with higher stocking densities. A buller may be relentlessly mounted by the rider(s). The problem worsens in groups of animals implanted with hormones or when pen densities increase. Bullers tend to be animals that are smaller, sick, look different (such as having a different coat colour), adopt the injured stance of a buller or are newly added to a pen. Usually one or a few animals in a pen are being mounted frequently by most of the others.

Pregnant heifers may display mounting behaviour at levels less likely to cause problems, though it may cause disputes with importers who think the animals are in oestrus and therefore not pregnant.

Clinical Signs and Diagnosis

Observation of behaviour will detect this condition. Bullers are readily identified as the animals being pursued and mounted by pen mates.

The bullers may suffer bruising, wounds, weight loss and are predisposed to pneumonia and other infections. They may have hair loss and swelling on the rump and tail head from bruising, and blood around the rectum. Their sides may be coated in manure from recumbency after falling or escaping. Animals may suffer partial paralysis associated with sciatic nerve damage, fractures and dislocations. In some cases animals may be so exhausted that they become recumbent. The riders may suffer heat stress or injuries from mismounting.

Riders that become injured or heat stressed may become bullers if pen mates sense an opportunity to change the social hierarchy. Affected animals may either die or require euthanasia.


Remove bullers to a hospital pen and examine and treat for concurrent diseases or conditions. Haematomas and oedema should be left alone to heal.

Pulled animals can be reintroduced to the pen after they recover or after three days (whichever is longer), as pen mates often no longer find them attractive.
However, they should be monitored in case of relapse.

Removing bullers does not always fix the problem because sometimes others replace this role. Be aware that if a number of bullers are placed in a hospital pen, they may begin riding each other.


Match animals in pens on size and looks, and maintain animals in their original social groups if possible.

Avoid high stocking densities. Regularly check for and remove bullers. Don't place females near pens of entire males.

Installing overhead barriers to prevent mounting may be considered.