The Effects of neutering in Jack Russell Terriers

Whilst in the womb, male and female puppies are exposed to different hormone levels that leads to differences in their brains.

In males at puberty, which occurs at about six months of age, the testes start producing testosterone, the male hormone. This causes changes in their brains and bodies that make them more likely to be successful at passing on their genes. These include:

• Physical changes, such as thicker skin and stronger muscles
• Behaviour designed to pass on genes, such as interest in bitches in season, finding a mate
• Scent marking (frequent leg lifting, stronger smell)
• Mounting
• Inter-male competition.

Neutering can solve the problem provided that it is caused by these male hormones rather than by something else, such as fear or insecurity.

In females, the ovaries begin producing hormones that prepare the body for pregnancy. Seasons occur and the hormones that are produced at this time result in behaviour changes. Neutering can often help with the following problems:

• Behaviour changes at season time, including escaping to find a mate.
• Inter-female competition around and during season time, particularly between bitches that are kept together in the same family.
• Behaviour changes during phantom pregnancies which occur after seasons, especially 'baby' guarding.

Is neutering the answer?

In dogs of either sex, neutering will not help with boisterousness, fear-related or status related aggression and urine marking due to insecurity.

Fighting between entire males

Inter-male competition between entire dogs is normal. If both dogs are well socialised, they are unlikely to fight unless one of them will not back down. Usually, rituals and body posturing are enough to decide who will be the top dog and gain access to bitches. If a dog is not well socialised and meets other entire dogs infrequently, it may start to use aggression to gain the upper hand. If dogs meet regularly in the park, this quickly sets up a situation where they will fight on sight and their owners will have great difficulty in keeping them apart.

Such territorial males will usually pass females, puppies and neutered males without a problem once they have checked them out, and may even play with them. Once territorial males have been neutered, the behaviour may continue for a while as some of the problem behaviour will be learnt. Additional behaviour therapy may be needed, especially in older dogs where the behaviour has been practices for a number of years.