Sexual maturity in ferrets usually comes between 4 and 8 months of age and begins in the first spring after their birth, as the days grow longer.
In females it is essential to interrupt the heat if they are not being mated and giving birth at each one, because their physiology keeps them almost constantly in heat throughout the breeding season. The prolonged, constantly high level of female sex hormones — oestrogens — harms the animal’s health (it suppresses bone marrow function, leading to anaemia).
There are several options for stopping heat in ferrets:
- neutering, in which the ovaries and uterus / the testes are removed
- hormonal therapy by injection
- subcutaneous implantation of a chip releasing a synthetic hormone, which stops heat for up to 18 months in females and up to 16 months in males.
For females there are two further options:
- mating with a vasectomised male at every heat, which may be repeated several times in one breeding season
- mating with an intact male and giving birth at every heat.
Neutering stops the heat in both sexes and reduces the odour of the skin glands. During the operation the anal glands, which secrete a sharp-smelling substance, can also be removed.
The surgical intervention is performed under full anaesthesia; inhalation (gas) anaesthesia is recommended because of the increased risk of complications when sedating ferrets.
The possible late side effects of neutering in both sexes are the development of hyperadrenocorticism — overactivity of the adrenal glands, which also secrete sex hormones. Skin problems, weight loss, increased thirst and signs of heat may appear. The condition is controlled with a hormonal implant. There are theories that longer light exposure contributes to adrenal overactivity in ferrets, so it is recommended to keep them in rooms with limited light, restrict artificial light exposure, and give them places to hide in the dark.