Neutering of Small Furries – Yes or No?


It is common practice in the UK to neuter companion cats and dogs that are not intended for breeding purposes, that it is now regarded very much a “routine” procedure. But what about small furry companion animals such as rabbits, guinea pigs and ferrets which are also commonly kept as pets?

Rabbits are naturally a social species, found in large groups in the wild, and so are much happier kept as a group or pair rather than singly. Unrelated females (does) will usually tolerate each other if provided with sufficient space, but can fight, whilst entire males (bucks) will fight and inflict severe injuries. Neutering minimises the risk of conflict as well as preventing unwanted litters. The most stable pairing is a neutered buck and a neutered doe. Rabbits should not be housed with guinea pigs as we have seen on numerous occasions in the past, as bullying by either species can occur, particularly by the rabbit, and these animals have different dietary and husbandry requirements.


Other benefits of neutering in rabbits include reducing the risk of false pregnancies (pseudopregnancy) in females, which can cause undesirable behaviour such as nesting and digging. Adult does (non-spayed) are also at high risk of developing uterine adenocarcinoma (cancer), which can be as high as a 60% risk in some breeds – neutering prevents this and reduces the risk of other reproductive diseases. Neutering rabbits also make them nicer pets – when rabbits reach sexual maturity, they can become territorial, aggressive and destructive. These changes make the pet rabbit more difficult to handle, harder to litter train, and bucks are more likely to spray urine.

Most rabbit breeds reach sexual maturity between 4 to 6 months of age. At Stanhope Park Veterinary Hospital, we routinely recommend neutering of rabbits at 4-5 months of age as they reach sexual maturity, and have been carrying out these procedures on pet rabbits routinely for many years now. Some veterinary practices may still be reluctant to perform elective surgery on small furries such as rabbits, due to the perceived risks associated with general anaesthetic. At Stanhope Park Vets we have highly trained and experienced staff who deal with a variety of species regularly (rabbits are now the 3rd most commonly kept pet in the UK). We are also proud to be able to offer advanced facilities and drug protocols for these patients, keeping all potential risks to a minimum, and we believe that the advantages associated with neutering rabbits, outweigh the potential (and now rare) risks involved.


Guinea Pigs are also a social species, and live a much more contented life in the presence of other guinea pigs (wild guinea pigs live in social groups of 5 to 10 animals). Entire males (boars) can fight, although this is lessoned if reared together from an early age. Females (sows) will often live happily together, and the sexes may be mixed, but castration of males is therefore advisable to prevent unwanted pregnancies.

Cystic ovarian disease (affecting one or both ovaries) is one of the most common reproductive diseases of the sow, with single or multiple serous cysts being identified in 58% to 100% of sows between 3 months to 5 years of age! Ovarian cysts can often be associated with other conditions, and clinical signs include a pear-shaped abdominal distension, anorexia, depression, gastro-intestinal problems and infertility. When functional follicular cysts are present symmetrical alopecia (hair loss) can also be seen on the sow’s flanks due to increased oestrogen production. Behavioural changes such as aggression may also be observed. Spaying is the treatment of choice for ovarian cysts, as recurrence is common.


Mammary gland tumours, as well as uterine and cervical cancer, are also commonly reported in entire sows. Given the high incidence of reproductive disease in female guinea pigs, Stanhope Park Veterinary Hospital routinely advises elective ovariohysterectomy (spaying) in non-breeding pets, with neutering of both sexes performed from 4 months of age. It is important to be aware that sexual maturity is usually reached prior to this age, at around 3-4 months for boars, whilst sows become sexually mature earlier at 2-3 months, although we have seen pregnant sows at a much younger age, so consideration should be given to keep different sexes separate initially to prevent unwanted pregnancy prior to neutering.


Ferrets are extremely social animals, with females generally getting on well together. Male ferrets (hobs) may fight so care should be taken when housing multiples.

Ferrets are quite unique when it comes to reproductive behaviour and prevention of unwanted pregnancies. Female ferrets (jills) will start to some into season (heat) as the days get longer, with the breeding period being between March and September. When a jill comes into heat, this produces a rush of oestrogen which reduces the body’s ability to make red blood cells. The jill’s oestrus will only end if she is mated (inducing ovulation), or the end of the breeding period is reached. A jill may come into heat multiple times throughout the breeding season if mating occurs but does not result in pregnancy. This long period of oestrus can result in a life-threatening anaemia for the jill. Whilst the obvious solution might be to spay the jill, this can also bring with it its own complications….

Surgical neutering of ferrets (both females and males) may make them more likely to develop a condition known as “HYPERADRENOCORTICISM”. Neutering ferrets removes the critical negative feedback on the adrenal glands (an endocrine organ capable of  secreting sex steroid hormones), and this results in constant stimulation of adrenal gland hormones and adrenal disease.

One alternative to prevent unwanted pregnancy, is to mate the jill with a vasectomised hob. This, however will need to happen several times throughout the breeding season, every time the jill comes into heat again, and can lead to false pregnancy which can cause aggression, nesting behaviour and milk production. Vasectomy (surgery to remove a segment of the spermatic cord) of hobs means that testosterone (sex hormone) is still produced, and therefore retains the negative feedback to the adrenal glands so that hyperadrenocorticism is less of a risk, whilst ensuring the male cannot fertilise a female during mating.

Hormone implants (“SUPRELORIN”) are now the most often recommended alternative to surgical neutering of ferrets. They are given as a slow-release capsule, implanted under the skin in the scruff of the neck under a short general anaesthetic. The hormone implant prevents males being able to impregnate females during mating, and can be used “off-licence” in jills to prevent oestrus. The implant will also reduce the smell from both hobs and jills, although this benefit can take over 3 months to develop. The implant can take a few weeks to start to work, so the hob should be kept separate from jills on heat during this time to prevent unwanted pregnancy. The hormone implant works for approximately 16 months in hobs, so subsequent implants are needed at approximately that time period to prevent accidental pregnancy if mated with a jill. The need for subsequent implants should also be based on the increase in testis size and/or increase in plasma testosterone concentrations and return to sexual activity. It is not known if males injected with these implants would be able to be used for breeding at a later date, and so their use should be carefully considered in such circumstances. Hormone implants last for around 18 months for female ferrets, so should take her through 2 breeding seasons, though a short false season may occur shortly after implantation. Hormone implants should be considered a safe, effective alternative to neutering in both hobs and jills.


At Stanhope Park Veterinary Hospital, we treat a vast variety of companion animal species on a daily basis, and have been doing so for many years now. Whilst we recognise that some of these species may pose more of an anaesthetic risk than cats or dogs, it goes without saying that we always use safe and modern drugs and techniques, and keep up-to-date with the ever advancing field of veterinary medicine. When it comes to neutering of small companion animal species, we always advise in the best interest of the patient, and frequently the health and behavioural benefits of neutering far outweigh the risks that may be involved with elective surgery.

As well as the species described above, we have also successfully neutered various other species, such as hedgehogs, gerbils, rats, hamsters and sugar gliders!