Bitches vs cats in heat

Same word, two different stories🐶🐱

Although they share many characteristics as female mammals, dogs and cats have notable differences in their reproductive cycles, and these go far beyond the biological. In consultation, it is not uncommon for guardians to be surprised to discover that the behaviour of heat is not the same in both species: what in a dog may go almost unnoticed, in a cat can become a concert of nocturnal meowing.

Understanding these particularities not only helps to prevent unwanted litters, but is also essential for avoiding stressful situations at home, improving coexistence and deciding on the most appropriate time for sterilisation. Good information allows us to make responsible decisions that promote the long-term well-being of our pets.

The ‘hormonal GPS’: what is the oestrous cycle and what do dogs and cats have in common?

The oestrous cycle is controlled by the hypothalamic-pituitary-gonadal axis (in human terms: a ‘switchboard’ that coordinates the brain and ovaries). The hypothalamus sends signals, the pituitary gland responds by releasing hormones (such as LH, luteinising hormone, and FSH, follicle-stimulating hormone) and the ovaries adjust the rest by producing mainly oestrogen and progesterone. This hormonal choreography explains behavioural changes, attraction to males and, in dogs, even bleeding.

What they do have in common (although they express it differently)

Both species alternate between a “follicular” phase (dominated by oestrogen, with growing follicles) and a “luteal” phase (with high progesterone after ovulation). In practical terms, this means that during the fertile phase, the female may be receptive and attract males, and that hormonal changes may then occur that influence behaviour, appetite and mammary glands, even without pregnancy.

Here, a key and frequently consulted concept arises: pseudopregnancy (also called pseudocyesis or “psychological pregnancy” when there are clinical signs). In bitches, it is relatively common to see maternal behaviour and mammary changes in the period after heat; in cats, as ovulation usually depends on mating, it is less “automatic”, but it can occur if ovulation occurred without pregnancy.

Normal signs vs warning signs (the red line)

Changes do not necessarily mean illness, but there are symptoms that warrant immediate consultation: marked lethargy, fever, abdominal pain, foul-smelling discharge, vomiting, excessive thirst or a sudden worsening after heat. The reason is simple (and not very poetic): certain reproductive tract pathologies, such as pyometra (uterine infection), can occur when the uterus is under the influence of progesterone.

Clash of the champions: dogs go into heat ‘seasonally’, cats ‘repeatedly’ (if you let them)

The bitch: more predictable… and usually more “visible”

Bitches are usually monoestrous, meaning they do not go into heat every few weeks. Many bitches go into heat once or twice a year, although there is individual variability and breed, age and environment all have an influence.

As a guide, canine heat is usually divided into pro-oestrus (when bloody discharge and vulvar oedema may occur), oestrus (receptive phase) and subsequent phases where the body returns to ‘maintenance mode’.

An important point for owners to note: bleeding during heat is not menstruation as in humans. In bitches, the endometrium is not ‘eliminated’ as such; what is observed is a consequence of local changes in the reproductive system during the cycle.

Did you know? 🧠

In female dogs, oestrus bleeding is not a ‘period’ as in humans. It is more of a ‘side effect’ of changes in the reproductive system during proestrus. Your dog is not menstruating: she is in canine biology mode.

Useful veterinary tools (and why they matter): in canine reproduction, measuring serum progesterone or performing a vaginal cytology helps to estimate the time of ovulation and fertile window much more accurately, especially if there is an intention to breed or doubts about fertility.

The cat: seasonally polyestrous and with an “ovulation button”

Cats are typically seasonal polyestrous: their reproductive activity intensifies with more hours of daylight. This explains why some cats “activate” at certain times of the year and why, in homes with prolonged lighting, heat can seem almost continuous.

And here is the difference that often drives families (and sometimes the neighbourhood) crazy: if the cat does not ovulate, heat can recur at relatively short intervals. In practice, typical recurrences every 14–21 days during the fertile season are described when ovulation is not triggered (Little, 2011). In other words, it’s not that she “can’t get over it”… it’s that her biology is designed to persist.

The physiological key is this: cats are usually induced ovulators. This means that ovulation does not occur ‘on schedule’ as in many bitches, but is triggered by stimuli associated with copulation. And, to complicate matters further, it is not always a binary switch: it has been reported that the LH surge (the hormonal signal that triggers ovulation) can be more potent when there are multiple copulations; for example, higher peaks were observed when cats mated 8–12 times in a few hours, compared to fewer matings (Concannon et al., 1980; Biology of Reproduction). Therefore, from a clinical and management point of view, a cat can enter a cycle of repeated heat if ovulation does not occur.

Quick clinical comparison (without losing common sense)

Comparison helps, but always with one foot in reality: every animal is unique.

Appearance	Bitch	Cat
Type of cycle	More spaced out	More repetitive during season
Ovulation	Generally spontaneous	Generally induced
Typical signs	Bleeding, enlarged vulva, behavioural changes	Vocalisation, lordosis, rubbing; there is usually little or no bleeding
“Typical problem” at home	Males following the female, escapes	Repeated heat cycles, night-time meowing, marking

Coexistence, prevention and sterilisation: the practical side (no magic, just science)

How to manage heat at home without your flat looking like a reality show

In female dogs, the main objective is to avoid unwanted mating and escapes. In female cats, it is also important to avoid the “cycle” of repeated heat.

The basics work surprisingly well when applied consistently: walks on a leash and less crowded routes, no “impromptu encounters” with intact males, surveillance at doors and terraces, and in cats, minimising stimuli and preventing access to males (a determined cat is an engineering project… and she usually wins).

Pseudopregnancy: when the body creates a movie and the dog acts in it

Pseudopregnancy can include maternal behaviour, protection of imaginary “babies”, nervousness and even aggression, with or without mammary changes. It is not “stubbornness”: it is endocrinology applied to behaviour.

At home, it helps not to reinforce the maternal role (for example, by removing ‘adopted’ objects if the behaviour is obsessive), to maintain a routine and to consult your vet if there is breast pain, fever or discharge. And if the symptoms recur with intensity, it is a good time to talk about medium-term prevention.

Sterilisation: it is not just about ‘not having puppies’; it is well-planned preventive medicine

Sterilisation (ovariectomy or ovariohysterectomy, depending on the case) reduces unwanted pregnancies and can reduce or eliminate significant risks to the reproductive system, especially in bitches at risk of uterine pathology. Regarding mammary tumours, the honest message is: the later the sterilisation, the less “protective effect” it seems to have, although the exact size of the effect varies between studies and populations.

There is no single formula for “when”. The decision is made based on species, age, size, lifestyle, orthopaedic risks, behaviour and medical context. Good prevention is tailored to the actual patient, not the average animal in a book.

When to make an appointment without hesitation

Lethargy, fever, vomiting, abdominal pain, increased thirst, foul-smelling discharge, or a sudden worsening after heat are not things to “watch for a few days.” They are reasonable grounds for consultation and examination.