Something 'Entirely' Different

by Dr June McNicholas

No, it's not a Monty Python sketch, it's simply to pose a few questions. What's the difference between an 'entire' ferret and a 'neutered' ferret? Why should someone want to either keep a ferret 'entire' or to 'neuter' them? Do people know what is involved and what it means for their ferret?

In most domestic species, especially pet animals like cats and dogs, the distinction is clear. You either have your animals 'entire' i.e. sexually active and able to breed, or you have them surgically 'altered' (as the Americans would term it) to make sure they cannot reproduce. However, in ferrets, the distinction is a little blurred. Ferrets, like all their mustelid cousins, do not make the same distinction that we do. Bluntly, there is a category that is 'in-between' leaving a ferret totally entire and having him/her surgically sterilised. This can be quite confusing for some ferret owners so I hope this article can help shed some light on the choices that people have to make in keeping their ferrets happy and healthy with regards to their (the ferrets, that is) hormonal activities.

The 'entire' ferret

Quite simply, entire ferrets are those which have not undergone surgery to render them sterile and unable to breed, and usually uninterested in doing so. Hobs will develop very obvious testicles, plus a pungent smell and a propensity to fight other males. They will also be highly motivated during spring and summer to seek out potentially receptive jills. These they court with cave-man tactics consisting of grabbing the jill around the neck and very roughly forcing her to accept his advances. As pets or workers they are not very co-operative at these times of year. If you need a breeding hob, this behaviour is fine. If you want a gentle, playful, odour-free pet, or a co-operative worker, you are onto a loser! He will be driven by thoughts securely situated in his underpants and he will not want to know you at all!

Jills come into season at the time of year when the hours of daylight increase and when the temperature suggests that Spring is in the air. In practical terms, this can mean as early as February. The jills stay in season until mated or when other procedures such as surgery or injections or hormones occur. If a jill is left in season there can be complications to her health. The high levels of oestrogen circulating in a jill's body during her season or 'heat' can lead to a bone marrow disease called aplastic anaemia which carries a high risk of fatality.

If you want to breed from your ferrets then, obviously, you need entire animals but the complexities do not stop here. You need to consider what to do with entire jills which you do not wish to breed from this time round, or even breed from at all. This is where it gets a little complicated, so do please read on.


Entire hobs can stink! It's their hormones at work, although this is of little comfort to their owners. Entire hobs can also become aggressive to other males, disinterested in human companions, and a positive source of sexual harassment to jills. What are the solutions?

If you have no intention to ever breed from your hob then the best solution by far is to have him castrated. This involves the removal of the testes and all internal male plumbing associated with being sexually active. It is a quick and easy procedure, often not even involving a heavy anaesthetic and is usually over in minutes. Hobs generally do not even know what has happened! The result is that they will then lose any pungent pong, become totally disinterested in jills and often develop a better quality of coat. More importantly for pet owners, the hobs are more sociable and playful. It should also be pointed out to those who enjoy working their hobs that castration does not impair working ability. Over the years many of my best workers, including those who have won awards for their working prowess, have been castrated hobs. I should also say that there are no long-term health problems associated with having your hob castrated.

Hobs can be castrated at any time and any age from around five months, although some vets may have preferences as to when the operation is performed. I usually aim to have youngsters done during the Christmas period as this is just before they are likely to become sexually interested in females. Older rescue ferrets are done as and when they have settled in and are healthy. It usually takes between two or three weeks for the 'hobby' smell to subside and for them to start ignoring jills. Castration is a 'one-off' operation and the expense is justified by having a happy, healthy hob who is pong-free and happy to be your companion or worker with no other hormonally-driven distractions.

Vasectomised hobs

An alternative to full castration is to have a hob vasectomised. However, you do need to be aware of what this involves. Again, it is a simple surgical procedure which your ferret will hardly notice, but it does not have the same effect as full castration.

Vasectomisation involves the cutting of the ducts that allow active sperm to be released during the mating process. Bluntly, a vasectomised hob is firing blanks so he cannot make a jill pregnant. However, to all other intents and purposes, he will be an entire hob, retaining his smell, his aggression towards other males, and his over-riding interest in jills, often to the exclusion of his owners and any work you wish him to do!

The value of a vasectomised hob is simply to mate with jills to bring them out of season as it is the act of mating, rather than conception, that halts their period of season or 'heat'. Other than that the value of a vasectomised hob is debatable as he remains a rather smelly chap with more interest in finding a jill than in you or any work you have lined up for him. Owners should also be aware that Vasectomisation is not always permanent. There have been a growing number of reports of vasectomised hobs becoming fertile again within a couple of years (presumably the sperm ducts have re-grown and rejoined), resulting in a number of unwanted litters of kits. So should you wish to opt for vasectomisation of your hob, it may be wise to discuss with your vet the permanency of this procedure.

An important note is that should you have your hob vasectomised with a view of putting him back with entire jills, please be aware that he may carry viable sperm for up to six weeks after the vasectomisation op. You can still end up with the patter of lots of little paws if you put him back too soon!


Jills are lovely, mercurial little creatures, full of life and mischief, great pets and great workers, but they do need some care from their owner to keep them in good health. Jills come into season early in the year and will stay in season until mated or until they are given hormonal injections or surgically operated on to render them sterile. The onset of her season is clear by the enlargement of her vulva. This is barely visible at other times of the year but will swell to several times normal size when she comes into season.

Sadly, there is still an opinion that jills need to be mated every year. Equally sadly, this means a number of unwanted kits being born, usually even if there are no caring homes waiting for the offspring. Even more sadly, there is an atom of truth in this belief since entire jills need some sort of intervention to prevent them becoming potentially fatally ill through aplastic anaemia. So what can an owner do? The bottom line is that you MUST do something to control your jill's hormonal cycles as she may die prematurely.


For the owner of a pet jill, where there is never any intention to breed from her, do please consider spaying her at around five to six months of age. This is the best age simply because the ferret is young and pre-puberty, but spaying can take place at any age quite safely.

Spaying involves the removal of all reproductive equipment: ovaries, uterus and the connecting 'plumbing'. Basically, it's the equivalent of a hysterectomy. Again, it is a 'one-off' operation which is relatively easy and from which your ferret will quickly recover. My personal recommendations are that a young jill is booked in around Christmas before she comes into season. The only drawback at this time of year is the weather as it can be cold. Post-op jills tend to be a little bit delicate (although not all, as various jills here have demonstrated by bouncing off the walls within a few hours of their ops) and need to be kept in warm surroundings while they work off the anaesthesia. A couple of days in a hutch or small cage until you know they are back on their paws is all that is necessary. The one problem we have noticed is that sometimes a groggy jill will make her way unsteadily to the water bowl or bottle and fall asleep en route. This is not a major problem although you would not want this to happen if it meant she was left exposed in the cold, so bringing a jill into the kitchen or a warm shed or whatever for a day or so until you are really sure she's properly over the anaesthetic is important.

Again, surgery does not impair any working ability, nor does it affect character and personality. It simply frees the jill from the problems of reproduction and all the hormonal upheaval that this involves. It is certainly the procedure recommended for all owners of pet jill ferrets.

It should also be said that some vets are reluctant to spay jills, often citing that small animals/exotics are more difficult to deal with either surgically or anaesthetically. In a few cases this has led to very high prices being quoted to perform a spay operation. This is untrue and unnecessary. Ferrets are hardly little animals and usually sail through surgical procedures with little or no problem. If you do wish your jill to be spayed but are unable to locate a vet willing to perform the operation or who seems to be quoting a high price for the procedure (ops on ferrets should be around the cost of equivalent ops on cats) do please ring the NFWS who may well be able to locate an alternative vet or, as I used to do, people who organise a 'vet run' whereby ferrets are picked up, taken to the vet, operated on, given rest and then returned to their owners, all at a reduced fee.

On the whole, I recommend spaying and have found that they live longer, work longer, and have better overall health. All the jills that come to us (usually several dozen a year via rescue) are spayed before they leave us. We have had no reports of illness or complications arising from the ops. The only exceptions I make are for very elderly jills or those who have particular health problems which may predispose them to complications with anaesthesia, although this would always be fully discussed with the vet.

'But I don't want to spay my jill'

If you decide against spaying you will still need to think about other methods of making sure that your jill recovers from her period of being in season. I am constantly concerned about articles in various journals which have stated that there is no need to do anything with your jill when she comes in season. These articles tend to be based on the author's lack of experience of any problem with his/her jills. Well, that's great for them, but ask any vet or ferret welfare about the problems they've encountered with jills that have been left in season and it's a different story. The bottom line is that jills can die if left in season. They can over time develop a bone marrow disease due to the high level of oestrogens circulating in the body. Vets estimate that about 50% of all jills are at risk of this disease. Sadly, once the jill develops aplastic anaemia, there is little hope of successful treatment.

So, if you do not want to spay your jill for whatever reason, what can you do?

'Jill Jabs'

These are hormonal injections given by your vet that will prevent or halt a jill's season. Ideally, they should be given before a jill comes into season but since jills do not give advance notice they are frequently given at the onset of a season. The jabs can last for a whole summer but may need topping up if they wear off before Autumn. As an alternative to spaying, they are effective in that they prevent a jill from becoming fertile and therefore prevent pregnancy. A drawback is that some jills appear to lose condition and some of their 'bounce', becoming a little more sleepy and less alert for a few weeks. This does not happen to all jills; many simply carry on as normal with no outward sign of anything having been done to them. In either case, it is a better scenario than an unwanted pregnancy.

Sometimes jill-jabs are given to jills who are booked in to be spayed but who are in season at the time or look as if they are about to come into season. This is a routine procedure in some practices and the spay op can proceed around six weeks later with no additional risks or side effects.

My personal preference is to only use jill-jabs on jills who cannot be spayed, but then I do not breed from our ferrets so my main concern is to prevent problems arising from extended hormonal periods. For breeders and those who do not wish to embark on the permanent course of spaying, the use of a jill-jab is very useful.

Vasectomised hobs to bring jills out of season

A jill's season is ended by the act of mating, not by conception, so a vasectomised hob can be used to mate jills without them becoming pregnant. To all intents and purposes, this is just like the mating of two entire animals since the hob has no knowledge that he is infertile. Mating can be a rough business for the jill, so be prepared for scarred and bitten necks. Sadly, the hob ferret has little idea of romance! The good news is that the jill will come out of season within a week or so. The bad news is that this will only last six weeks. During this time the jill may develop a phantom pregnancy and believe herself to have given birth. This is bad news for all the ferrets in her pen! She will identify them as her babies and even the heftiest hob may find himself dragged off to bed by an insistent 'mother'! This behaviour lasts only a short time, much to the relief of any cage mates. However, after a couple of weeks of phantom motherhood, the jill will need to be returned to the vasectomised hob as she will come back in season.

Vasectomise hobs do play an important role in preventing unwanted pregnancies, but there are some caveats. If you 'borrow' a vasectomised hob, do please make sure that he is coming from healthy stock and from a clean, disease-free environment. The last thing you want is to introduce illness from a visiting ferret. You also need to be aware that repeated use of a vasectomised hob may predispose a jill to pyometra, an infection of the womb. The only treatment for pyometra is an emergency spay operation which is more risky than a spay op under normal circumstances when the jill is not sick or infected. So, if you think you do not want to breed from your jill at all, or not in the foreseeable future, it may be a good idea to consider spaying in the first place

I'm not a great fan of vasectomised hobs but this a personal opinion, possibly based on the fact that most of our jills are spayed as soon as practicable, and those that cannot be spayed are given jill-jabs which I buy in at cost (approx 1 a shot). However, I do appreciate that a vasectomised hob can be a great saving in vet fees given that charges for jill-jabs can vary from a few pounds to over thirty pounds per jill. He can do sterling service (and smile at the same time!) for years and save you a great deal of money should you not wish to opt for permanent sterilisation of your jills

So, the choice is yours. You just need to know what you are paying for, and what that treatment does, and for how long. For owners of purely pet ferrets I would personally advise castration of hobs and spaying of jills. Get all the hassle out of the way once and for all! Your ferret will be just as happy, perhaps even more so.

If for some reason you do not wish to go for such a permanent measure, do please make sure you are aware of the benefits and drawbacks of vasectomisation, jill-jabs and so forth.

The bottom line is that you do need to do something for your ferret and his/her hormones. His/her health and happiness (not to mention your peace of mind or your sense of smell!) may depend on your correct choices.

First Published in NFWS News #81 May 2008

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