Jills are induced ovulators, meaning that they remain in heat (estrus) indefinitely unless ovulation is induced by breeding. All female pet ferrets should be spayed to avoid the following health problems caused by side effects of being in heat for more than 3 weeks:
Spaying is removal of both the ovaries and uterus of the female. The surgery can be done any time after weaning. Ferrets tolerate anesthetics well and are fast healers.
Unneutered males (hobs) have a very strong body odor and greasy skin secretion during the breeding season (early spring to mid-summer). Few pet owners would choose to tolerate the smell of a male ferret in breeding condition in their homes.
Hobs are rarely aggressive with human beings. However, they will usually attack other intact (uncastrated) or neutered male ferrets, biting them around the head and neck. These skirmishes rarely do serious harm, but will leave sore spots where the hobs bite and hang on to the neck and ears. The wounds take a long time to heal, the hair may never grow normally again, and the ferret may be left with cauliflower ears.
Intact males should always be housed individually. Male ferrets become sexually mature at 7 to 8 months of age, and by then have reached their full stature, but not their full weight. Depending on the season of the year, mature hobs try to breed any females that they encounter, in heat or not, and fight with other intact or neutered males. Because of this behavior, you may choose to have them neutered a bit earlier than 8 months of age.
Neutering (castration) is removal of both testicles, which are the source of the male hormones that stimulate the production of the ferret odor. The side effects of neutering a male ferret include loss of greasy skin secretion and odor, slimming of the head and neck area, and behavioral changes. Ferrets castrated before sexual maturity do not grow as large as animals neutered later in life. Much of the difference in size between male and female ferrets is due to the growth-stimulating effect of male hormones.